ScholarBank@NUShttps://scholarbank.nus.edu.sgThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Wed, 21 Aug 2019 10:03:15 GMT2019-08-21T10:03:15Z501821- Effects of incidence and afterbody shape on flow past bluff cylindershttps://scholarbank.nus.edu.sg/handle/10635/58226Title: Effects of incidence and afterbody shape on flow past bluff cylinders
Authors: Luo, S.C.; Yazdani, Md.G.; Chew, Y.T.; Lee, T.S.
Abstract: In the present paper the effects of the afterbody shape and the angle of incidence on the structure of the flow past a prismatic body are experimentally investigated, both quantitatively in the form of wind tunnel measurement and qualitatively in the form of water tunnel flow visualization. Four cross-sectional shapes with identical upstream facing side and streamwise dimension were chosen in the present investigation. They were a square, two trapeziums, and a triangle. By studying the structure of the flow associated with the above-mentioned shapes, a systematic investigation in which the effects of the afterbody are gradually reduced can be carried out. From the measured magnitude and frequency of the fluctuating aerodynamic forces, the main effect of differences in afterbody shape is the proximity of the two separated shear layers to each other and to their corresponding side faces. This proximity difference, in turn, results in differences in the normal force, the gradient of its variation with the angle of incidence, and, hence, the susceptibility of the shape (with respect) to flow-induced oscillation. Also, due to the difference in interaction between the separated shear layers and the sides of the prismatic structure, the vortex formation length, the base pressure and, hence, the axial force, the rate at which vortices are shed and, hence, the frequency of the aerodynamic loading on the structure and the longitudinal vortex spacing also vary. Changes in the angle of incidence can be viewed as similar to changes in the afterbody shape and, hence, its effects are similar to those caused by changing the afterbody shape. Experiments show that no cross-sectional shape is absolutely stable to galloping oscillation because a shape that is stable to galloping oscillation at a certain mean angle of incidence may become unstable at a different mean angle of incidence. By idealising the vortex wake as two parallel rows of vortices, various vortex street parameters, including the vortex spacing ratio and the strength of each vortex in the wake, are estimated. They show a dependence on the afterbody shape and the angle of incidence. © 1994.
Thu, 01 Dec 1994 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/582261994-12-01T00:00:00Z
- Experimental studies on hydrodynamic resistance and flow pattern of a narrow flow channel with dimples on the wallhttps://scholarbank.nus.edu.sg/handle/10635/85968Title: Experimental studies on hydrodynamic resistance and flow pattern of a narrow flow channel with dimples on the wall
Authors: Zhao, J.B.; Chew, Y.T.; Khoo, B.C.
Abstract: A systematic flow visualization study on flow structures inside dimples with different relative depths (h/d) and with round or sharp edges is carried out in the first part of this investigation; three flat test plates are made and each one has two dimples with the same print diameter (d) at 40 mm and the same h/d, which is set at 4%, 20% and 50% respectively. Then friction factor is measured on a test channel with two types of test plates. One has dimples array with h/d at 4% and round edge and the second is a flat plate used as reference; surface roughness can be changed for both test plates by painting and covering with water-proof paper. Flow visualization is also done on a dimple located at the center of the plate in the channel. Results show that shallow dimple (h/d=4%) produces non-separated flows at Reynolds number Re δ1500. Dimple with h/d at 20% produces two symmetric vortices at Reδ1700. Round edged dimple changes its fl pattern at different Reynolds number comparing to its sharp edged counterpart. For the dimple with h/d at 50%, at Reδ 1800, it is unstable with its rotating direction changing frequently. In this part of preliminary work, dimpled plate with roughness reduces the friction factor by at least 2% in the flow channel comparing to the reference plate at Reynolds number Re Dh≈8,500-24,000. The friction factor curve of the channel with roughened dimpled plate approaches a hydraulically smooth channel with the increase of Reynolds number. No increase in friction factor is observed on the channel with dimpled plate having smooth surface in the comparison to the reference channel without dimples. Copyright © 2004 by ASME.
Thu, 01 Jan 2004 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/859682004-01-01T00:00:00Z
- Effects of transverse curvature on oscillatory flow along a circular cylinderhttps://scholarbank.nus.edu.sg/handle/10635/58240Title: Effects of transverse curvature on oscillatory flow along a circular cylinder
Authors: Chew, Y.T.; Liu, C.Y.
Abstract: Oscillatory flows with zero mean velocity can be found in a variety of natural phenomena. The classic example of oscillatory flows in unbounded stagnant fluid is that over an infinite flat plate executing periodic sinusoidal motion along its plane. This was solved by Stokes and is often referred to in the literature as Stokes flow. Some characteristic features of this flow are that, although the flow oscillates at the same frequency as the plate, it lags behind the plate, and the phase lag is proportional to the distance from the plate. The layer of oscillatory flow also is referred to in the literature as 'Stokes layer'. In the present paper a general oscillatory Stokes flow including the transverse curvature effect is presented.
Tue, 01 Aug 1989 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/582401989-08-01T00:00:00Z
- EXPLICIT NON-REAL TIME DATA REDUCTION METHOD OF TRIPLE SENSORS HOT-WIRE ANEMOMETER IN THREE-DIMENSIONAL FLOW.https://scholarbank.nus.edu.sg/handle/10635/58272Title: EXPLICIT NON-REAL TIME DATA REDUCTION METHOD OF TRIPLE SENSORS HOT-WIRE ANEMOMETER IN THREE-DIMENSIONAL FLOW.
Authors: Chew, Y.T.; Simpson, R.L.
Abstract: An explicit non-real time method of reducing triple sensor hot-wire anenometer data to obtain the three mean velocity components and six Reynolds stresses, as well as their turbulence spectra in three-dimensional flow is proposed. Equations which relate explicitly the mean velocity components and Reynolds stresses in laboratory coordinates to the mean and mean square sensors output voltages in three stages are derived. The method was verified satisfactorily by comparison with single sensor hot-wire anemometer measurements in a zero pressure gradient incompressible turbulent boundary layer flow. It is simple and requires much lesser computation time when compared to other implicit non-real time method.
Wed, 01 Jun 1988 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/582721988-06-01T00:00:00Z
- Numerical Flow Visualization of Stall Suppression of a Symmetrical Aerofoil by Leading-edge Moving Surfacehttps://scholarbank.nus.edu.sg/handle/10635/92752Title: Numerical Flow Visualization of Stall Suppression of a Symmetrical Aerofoil by Leading-edge Moving Surface
Authors: Chew, Y.T.; Lee, T.S.; Li, W.P.; Pan, L.S.; Ng, Y.T.
Abstract: This paper applies the numerical simulation techniques based on the generalized conservation of circulation (GCC) method to investigate the effects of momentum injection by a leading-edge moving surface on flow past a two-dimensional aerofoil at a Reynolds number of 1000. The stream function and vorticity contours obtained together with the animated flow visualization show that the stall flow region is highly unsteady and consist mainly of large vortices being shed alternately. They are confined to a narrow region near the upper surface of aerofoil as Cu (the ratio of the speed of the moving surface to the free stream velocity) is raised. The proximity of vortices to the upper surface of aerofoil at high Cu is caused by the ability of free stream to negotiate around the leading edge since the leading-edge moving surface suppresses the growth of boundary layer by reducing the relative between the inviscid flow and the wall. As well-formed large scale vortices are associated with low pressure regions, their proximity to the aerofoil leads to increase in lift as speed ratio increases.
Sat, 01 Jan 2000 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/927522000-01-01T00:00:00Z
- Numerical simulation of the effect of a moving wall on separation of flow past a symmetrical aerofoilhttps://scholarbank.nus.edu.sg/handle/10635/92753Title: Numerical simulation of the effect of a moving wall on separation of flow past a symmetrical aerofoil
Authors: Chew, Y.T.; Pan, L.S.; Lee, T.S.
Abstract: This paper applies the numerical simulation technique based on the generalized conservation of circulation (GCC) method to investigate the effects of a leading-edge rotating circular cylinder on the suppression of stall flow past a symmetrical Joukowski aerofoil. The variables investigated were the angle of attack α and the ratio of the surface velocity of the cylinder to freestream velocity, C U. The Reynolds number based on chord length is 1.43 × 10 5. It was found that the separation point on the upper surface of the aerofoil shifts downstream with increasing C U and stall flow can be significantly suppressed even at α up to 30° when C U = 4. The lift coefficient C L increases and the drag coefficient C d decreases with increasing C U and the optimum C L/C d occurs at a = 8°. The maximum C L/C d obtained is about 60 at C U = 4. © IMechE 1998.
Thu, 01 Jan 1998 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/927531998-01-01T00:00:00Z
- On near-wall hot-wire measurementshttps://scholarbank.nus.edu.sg/handle/10635/92760Title: On near-wall hot-wire measurements
Authors: Khoo, B.C.; Chew, Y.T.; Teo, C.J.
Abstract: A specially constructed hot-wire probe was used to obtain very near-wall velocity measurements in both a fully developed turbulent channel flow and flat plate boundary layer flow. The near-wall hot-wire probe, having been calibrated in a specially constructed laminar flow calibration rig, was used to measure the mean streamwise velocity profile, distributions of streamwise and spanwise intensities of turbulence and turbulence kinetic energy k in the viscous sublayer and beyond; these distributions compare very favorably with available DNS results obtained for channel flow. While low Reynolds number effects were clearly evident for the channel flow, these effects are much less distinct for the boundary layer flow. By assuming the dissipating range of eddy sizes to be statistically isotropic and the validity of Taylor's hypothesis, the dissipation rate εiso in the very near-wall viscous sublayer region and beyond was determined for both the channel and boundary layer flows. It was found that if the convective velocity Uc in Taylor's hypothesis was assumed to be equal to the mean velocity Ū at the point of measurement, the value of (εiso +)1 thus obtained agrees well with that of (ε+)DNS for y+ ≥ 80 for channel flow; this suggests the validity of assuming Uc = Ū and local isotropy for large values of y+. However, if Uc was assumed to be 10.6uτ, the value of (εiso +)2 thus obtained was found to compare reasonably well with the distribution of (εiso +)DNS for y+ ≤ 15.
Wed, 01 Nov 2000 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/927602000-11-01T00:00:00Z
- On the numerical near-wall corrections of single hot-wire measurementshttps://scholarbank.nus.edu.sg/handle/10635/92762Title: On the numerical near-wall corrections of single hot-wire measurements
Authors: Chew, Y.T.; Shi, S.X.; Khoo, B.C.
Abstract: The present paper numerically investigates the near-wall correction of velocity readings when using hot wires to measure the flows very close to walls. It is found that the near-wall correction is necessary not only for the conducting wall but also for the adiabatic wall. For an infinitely long 5-μm diameter hot wire, measurement error begins to appear at Y+ < 5 for an infinitely conducting wall and at Y+ < 2 for an adiabatic wall. In addition to the distance from wall, the wire diameter also exerts significant influence on the velocity measurements. However, provided the flow is two-dimensional (2-D), the effect of operating overheat ratio seems to be insignificant. © 1995.
Fri, 01 Dec 1995 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/927621995-12-01T00:00:00Z
- The directional sensitivities of crossed and triple hot-wire probeshttps://scholarbank.nus.edu.sg/handle/10635/92796Title: The directional sensitivities of crossed and triple hot-wire probes
Authors: Chew, Y.T.; Ha, S.M.
Abstract: The directional sensitivities of the DISA Type 55P61 crossed-wire probe and DISA Type 55P91 gold-plated triple-wire probe were investigated using a modified calibration set-up with three very accurate orthogonal axes of rotation. The yaw factor kT and pitch factor kN which account for the cooling effects of tangential and binormal velocity components respectively were determined at different yaw angle a and pitch angle theta at velocities of 6 m s-1, 11 m s-1 and 19 m s-1. Based on these measured values, the relative errors in the calculated flow velocity were computed with constant values of kT and kN at alpha and theta =60 degrees , 90 degrees and kT=0, k N=1. The effects of kT and kN cannot be neglected, especially at high alpha and theta . For the DISA Type 55P61 crossed-wire probe, the suitable values are kT=0.30 and k N=1.14. For the DISA Type 55P91 triple-wire probe, they are k T=0.20 and kN=1.01.
Fri, 01 Jan 1988 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/927961988-01-01T00:00:00Z
- Streamwise oscillation of a cylinder at large reduced velocityhttps://scholarbank.nus.edu.sg/handle/10635/92787Title: Streamwise oscillation of a cylinder at large reduced velocity
Authors: Low, H.T.; Chew, Y.T.; Tan, K.T.
Abstract: An experimental study was carried out on a cylinder undergoing harmonic oscillation in line with an indident flow at Reynolds numbers of 27×103 and 54×103. Measurements were obtained of the ensemble-averaged cyclic pressure distribution, from which the cyclic in-line force was determined. It was found that the cyclic force could be approximated by a simple empirical relation based on a quasi-steady consideration of the flow. The quasi-steady drag coefficient was determined for various amplitude to diamater ratios from 0.4 to 2.4, and for a reduced velocity of up to 200. The base pressure coefficient was found to increase with the oscillation amplitude. © 1990.
Sun, 01 Apr 1990 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/927871990-04-01T00:00:00Z
- A proposed intermittency measurement method for transitional boundary layer flowshttps://scholarbank.nus.edu.sg/handle/10635/54742Title: A proposed intermittency measurement method for transitional boundary layer flows
Authors: Zhang, D.H.; Chew, Y.T.; Winoto, S.H.
Abstract: A new turbulent intermittency detector method, based on the Turbulent Energy Recognition Algorithm (TERA), has been proposed. Its performance was compared with two other available methods using the data obtained from hot-wire measurements in a developing boundary layer flow on a concave surface with constant radius of curvature of 2 m. Comparisons show that this new method is better than the other two as a turbulent detector under the same flow conditions, especially in the near-wall and in the outer and outside regions of the boundary layer. © 1995 Springer-Verlag.
Sun, 01 Oct 1995 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/547421995-10-01T00:00:00Z
- Galloping of prismatic bodies with different afterbody shapeshttps://scholarbank.nus.edu.sg/handle/10635/92827Title: Galloping of prismatic bodies with different afterbody shapes
Authors: Lee, T.S.; Luo, S.C.; Chew, Y.T.; Yazdani, M.G.
Abstract: Many offshore and polar structures consists of slender prismatic bodies with different cross-sectional shapes. In an ISOPE-93 article by Yazdani et. al (1993) it was shown that at a mean angle of attack [ α ] of zero degrees square cylinder become unstable to galloping oscillation. However, at this same condition, trapezoidal and triangular cylinders exhibit a stable and neutrally stable condition to galloping oscillation respectively. In the present paper, the conditions of galloping stability of cylinders with the same three shapes are examined experimentally at both zero and non zero α. All the experiments were carried out in an open loop wind tunnel. At the experimental wind speed the level of turbulence in the tunnel was no more than 0.5%, which is considered equivalent to a calm sea-state. Dynamic tests, where the cylinder was forced to oscillate in a direction that is transverse to the free stream, were also carried out at amplitude [ a], oscillation frequency [fN] and free stream velocity [UINF]. While a/d (d = cylinder cross-stream dimension) was kept constant at a value of 1 in the experiment, fN and UINF were varied over the range of 1 Hz to 3 Hz and 5 m/s to 20 m/s respectively. The reduced velocity [Ur=UINF/(fNd)] and Reynolds number therefore varied in the range of 33.34 to 400 and 1.5 × 104 to 6.0 × 104 respectively. Dynamic tests were carried out at α of 5°, 10°, 14°, 20° and 30° for the trapezoidal and at α = 5°, 10°, 15°, 22° and 35° for the triangular cylinder. By analyzing the normal force [CN] versus α curves and in particular the sign and magnitude of ∂CN/∂α at different α, it was observed that there exists several ranges of α within which galloping instability for these three shapes becomes possible.
Sat, 01 Jan 1994 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/928271994-01-01T00:00:00Z
- Unsteady fluid force acting on oscillating square-section cylinderhttps://scholarbank.nus.edu.sg/handle/10635/92812Title: Unsteady fluid force acting on oscillating square-section cylinder
Authors: Luo, S.C.; Chew, Y.T.; Goh, E.Y.
Abstract: The difference between experimentally measured lift forces under dynamic condition and quasi-steady condition is termed as an unsteady force, in this technical note. Analysis shows the magnitude of the unsteady force increases with the maximum angle of incidence, αmax encountered by the square cylinder during a cycle of transverse oscillation in a fairly anticipated manner; the phase between the unsteady force and the cylinder displacement only deviates significantly from zero over the range of 8°≤αmax≤16°. In this (αmax) range the unsteady force contributes strongly to the driving force for transverse galloping and cannot be neglected. An attempt had been made to incorporate the unsteady force term into the quasi-steady theory; preliminary results show this leads to an improvement in the agreement between theory and other independent experimental measurements.
Sun, 01 Jan 1995 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/928121995-01-01T00:00:00Z
- A flow visualization study of acceleration effect on the Taylor-Couette flowhttps://scholarbank.nus.edu.sg/handle/10635/92818Title: A flow visualization study of acceleration effect on the Taylor-Couette flow
Authors: Xiao, Q.; Lim, T.T.; Chew, Y.T.
Abstract: The acceleration effect on the Taylor-vortex and later developed wavy vortices was investigated from flow visualization techniques in circular Couette system (with the inner cylinder rotating and outer cylinder at rest) as a function of Reynolds number Re. Our results show that when the acceleration is higher than a critical value of about 2.2 s-1, there exists a new flow regime in which the flow pattern shows remarkable resemblance to the regular Taylor vortex flow with shorter axial wavelength. One of the most surprising aspects of this flow is that it occurs in the range of Reynolds number in which the wavy vortex flow is supposed to occur.
Thu, 01 Jan 1998 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/928181998-01-01T00:00:00Z
- Transition in boundary layers on a concave surfacehttps://scholarbank.nus.edu.sg/handle/10635/58854Title: Transition in boundary layers on a concave surface
Authors: Winoto, S.H.; Zhang, D.H.; Chew, Y.T.
Abstract: Transition from laminar to turbulent flow has been investigated in boundary layers along a concave surface of 2.0 m radius of curvature for a freestream velocity range of 6.0-15.0 m/s. Velocity and turbulent intermittency measurements were made using a single sensor hot-wire anemometer. Intermittency profiles at the so-called upwash and downwash regions were obtained at some streamwise positions to help determine the transition starts and ends at the regions. The experimental results show that, at both upwash and downwash regions for all of the free-stream velocities tested, the intermittency profiles at different transition stages exhibit similar behaviors. The difference between the upwash and downwash intermittency profiles obtained at the same streamwise locations decreases with increasing freestream velocity. For all of the freestream velocities, transition starts and ends earlier at the upwash regions than at the downwash regions. The transition lengths in the upwash regions are slightly longer than those in the downwash regions and decrease with increasing freestream velocity. The starts of transition at the upwash regions agree well with the transition prediction Goertler number of 6, whereas at the ends of transition for both upwash and downwash regions, the Goertler number ranges front 7.90 to 9.30.
Sat, 01 Jul 2000 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/588542000-07-01T00:00:00Z
- Triple-region structure for turbulent flow in a square duct: A finite element approachhttps://scholarbank.nus.edu.sg/handle/10635/58863Title: Triple-region structure for turbulent flow in a square duct: A finite element approach
Authors: Wang, F.M.; Khoo, B.C.; Chew, Y.T.; Yeo, K.S.
Abstract: The Reynolds-averaged Navier-Stokes equations for describing the turbulent flow in a straight square duct are formulated with two different turbulence models. The governing equations are then expanded as a multi-deck structure in a plane perpendicular to the streamwise direction, with each deck characterized by its dominant physical forces as commonly carried out in analytical work using triple-deck expansion. The resulting equations are numerically integrated using higher polynomial (H-P) finite element technique for each cross-sectional plane to be followed by finite difference representation in the streamwise direction until a fully developed state is reached. The computed results using the two different turbulence models show fair agreement with each other, and concur with the vast body of available experimental data. There is also general agreement between our results and the recent numerical works anisotropic κ-ε{lunate} turbulence model. © 1994.
Thu, 01 Dec 1994 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/588631994-12-01T00:00:00Z
- Effects of imperfect spatial resolution on turbulence measurements in the very near-wall viscous sublayer regionhttps://scholarbank.nus.edu.sg/handle/10635/92692Title: Effects of imperfect spatial resolution on turbulence measurements in the very near-wall viscous sublayer region
Authors: Khoo, B.C.; Chew, Y.T.; Li, G.L.
Abstract: Experiments were carried out to study the effects of imperfect spatial resolution on turbulence measurements in the very near-wall region using hot wires of different lengths, l+ (in wall units). Previous works have indicated that the distributions of the longitudinal velocity rms value, skewness and flatness factors are independent of l+ in the buffer region and beyond provided l+
Sat, 01 Feb 1997 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/926921997-02-01T00:00:00Z
- Discrete vortex simulation of the separated flow around a rotating circular cylinder at high Reynolds numberhttps://scholarbank.nus.edu.sg/handle/10635/92681Title: Discrete vortex simulation of the separated flow around a rotating circular cylinder at high Reynolds number
Authors: Cheng, M.; Chew, Y.T.; Luo, S.C.
Abstract: The separated flow around a rotating circular cylinder is investigated by the discrete vortex method combined with the boundary layer theory. The Keller Box method is used to solve the laminar boundary layer in order to determine the separation points on the upper and the lower sides of the rotating circular cylinder. The nascent vortices are then introduced near the separation points. A discrete circular vortex blob model, which has uniform vorticity distribution, is adopted to simulate the unsteady wake. Numerical experiments are conducted to investigate the cases in which the ratio of the speed at the cylinder surface to the speed at infinity is varied from 0 to 0.3 at a Reynolds number of 6 × 103. The calculated values of the separation positions, the drag and lift force coefficients, the velocuty and the pressure distribution on the cylinder surface are found to agree well with the published experimental data. © 1994.
Thu, 01 Dec 1994 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/926811994-12-01T00:00:00Z
- A new flow regime in a Taylor-Couette flowhttps://scholarbank.nus.edu.sg/handle/10635/92651Title: A new flow regime in a Taylor-Couette flow
Authors: Lim, T.T.; Chew, Y.T.; Xiao, Q.
Abstract: In this Brief Communication, we report a new finding on a Taylor-Couette flow in which the outer cylinder is stationary and the inner cylinder is accelerated linearly from rest to a desired speed. The results show that when the acceleration (dRe/dt) is higher than a critical value of about 2.2s-1, there exists a new flow regime in which the flow pattern shows remarkable resemblance to regular Taylor vortex flow but is of shorter wavelength. However, when the acceleration is lower than 2.2 s-1, a wavy flow is found to occur for the same Reynolds number range. To our knowledge, this is probably the first time that such a phenomenon has been observed. For completeness, the case of a decelerating cylinder is also investigated, and the results are found to be almost the same. © 1998 American Institute of Physics.
Thu, 01 Jan 1998 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/926511998-01-01T00:00:00Z
- Skin Friction following BLADE manipulation in a turbulent pipe flowhttps://scholarbank.nus.edu.sg/handle/10635/58699Title: Skin Friction following BLADE manipulation in a turbulent pipe flow
Authors: Khoo, B.C.; Chew, Y.T.; Mah, Y.A.
Abstract: This study attempts to analyze the measured wall shear stress distribution downstream of single and tandem BLADEs in fully developed pipe flow. Previous works have indicated the adverse effect of overall drag increase with the single BLADE in both channel and pipe flows, and an even larger drag increase with the tandem BLADES. This is contrary to that observed for external boundary layer flow. Extensive comparisons are then made to the wall shear stress distribution following BLADEs in boundary layer flow, leading to the conclusion of little or no potential in the application of BLADEs alone to pipe flow. © 1993 Springer-Verlag.
Wed, 01 Sep 1993 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/586991993-09-01T00:00:00Z
- Steady flow velocity field and turbulent stress mappings downstream of a porcine bioprosthetic aortic valve in vitrohttps://scholarbank.nus.edu.sg/handle/10635/58730Title: Steady flow velocity field and turbulent stress mappings downstream of a porcine bioprosthetic aortic valve in vitro
Authors: Lim, W.L.; Chew, Y.T.; Chew, T.C.; Low, H.T.
Abstract: Velocity profiles and Reynolds stresses downstream of heart valve prostheses are vital parameters in the study of hemolysis and thrombus formation associated with these valves. These parameters have previously been evaluated using single-point measurement techniques such as laser Doppler anemometry (LDA). The purpose of this study is to map the velocity vector fields and Reynolds stresses downstream of a porcine bioprosthetic heart valve in the aortic root region with particle image velocimetry (PIV) techniques in vitro under steady flow conditions. PIV is essentially a multipoint measurement technique that allows full-field measurement of instantaneous velocity vectors in a flow field, thus allowing us to map the entire velocity or stress field over the aortic root (where single-point measurements are difficult). Coupled with flow visualization techniques, the hydrodynamic consequences of introducing a porcine bioprosthetic heart valve into the aortic root was examined, and compared with data obtained from an empty aortic root and an aortic root with the valve mounting ring alone. From our velocity and stress mappings, we found that the valve mounting ring effectively diminishes the central orifice area, giving rise to a higher central axial flow with strong recirculating regions and a corresponding large pressure drop. This in turn produces an intermixing zone between the central jet and recirculating region further downstream from the valve, which contributes to the high-stress zone measured. The development of the flow is further restricted by the valve stents, giving rise to stagnation regions and wakes. High-velocity gradients were also measured at the interface of the jet and recirculating region in the sinus cavity. The overall view of the velocity and stress mappings helps to identify regions of flow disturbances that otherwise may be lost with single-point measuring systems. Although the PIV measurements may lack the accuracy of single-point measuring systems, the overall view of the flow in the aortic root region compensates for the shortcoming.
Wed, 01 Jan 1997 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/587301997-01-01T00:00:00Z
- Steady flow dynamics of prosthetic aortic heart valves: A comparative evaluation with PIV techniqueshttps://scholarbank.nus.edu.sg/handle/10635/58729Title: Steady flow dynamics of prosthetic aortic heart valves: A comparative evaluation with PIV techniques
Authors: Lim, W.L.; Chew, Y.T.; Chew, T.C.; Low, H.T.
Abstract: Particle Image Velocimetry (PIV), capable of providing full-field measurement of velocities and flow stresses, has become an invaluable tool in studying flow behaviour in prosthetic heart valves. This method was used to evaluate the performances of four prosthetic heart valves: a porcine bioprostheses, a caged ball valve, and two single leaflet tilting disc valves with different opening angles. Flow visualization techniques, combined with velocity vector fields and Reynolds stresses mappings in the aortic root obtained from PIV, and pressure measurements were used to give an overall picture of the flow field of the prosthetic heart valves under steady flow conditions. The porcine bioprostheses exhibited the highest pressure loss and Reynolds stresses of all the valves tested. This was mainly due to the reduction in orifice area caused by the valve mounting ring and the valve stents. For the tilting disc valves, a larger opening angle resulted in a smoother flow profile, and thus lower Reynolds stresses and pressure drops. The St. Vincent valve exhibited the lowest pressure drop and Reynolds stresses.
Fri, 01 May 1998 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/587291998-05-01T00:00:00Z
- Solutions of three-dimensional boundary layer equations by global methods of generalized differential-integral quadraturehttps://scholarbank.nus.edu.sg/handle/10635/58709Title: Solutions of three-dimensional boundary layer equations by global methods of generalized differential-integral quadrature
Authors: Shu, C.; Chew, Y.T.; Khoo, B.C.; Yeo, K.S.
Abstract: The global methods of generalized differential quadrature (GDQ) and generalized integral quadrature (GIQ) are applied to solve three-dimensional, incompressible, laminar boundary layer equations. The streamwise and crosswise velocity components are taken as the dependent variables. The normal velocity is obtained by integrating the continuity equation along the normal direction where the integral is approximated by GIQ approach with high order of accuracy. All the spatial derivatives are discretized by a GDQ scheme. After spatial discretization, the resultant ordinary differential equations are solved by the 4-stage Runge-Katta scheme. Application of GDQ-GIQ approach to a test problem demonstrated that accurate numerical results can be obtained using just a few grid points.
Fri, 01 Mar 1996 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/587091996-03-01T00:00:00Z
- Stability to translational galloping vibration of cylinders at different mean angles of attackhttps://scholarbank.nus.edu.sg/handle/10635/58722Title: Stability to translational galloping vibration of cylinders at different mean angles of attack
Authors: Luo, S.C.; Chew, Y.T.; Lee, T.S.; Yazdani, M.G.
Thu, 03 Sep 1998 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/587221998-09-03T00:00:00Z
- Unsteady pressure-flow behaviour in collapsible tubeshttps://scholarbank.nus.edu.sg/handle/10635/75092Title: Unsteady pressure-flow behaviour in collapsible tubes
Authors: Low, Hong T.; Chew, Yong T.; Wang, Jian W.
Abstract: An experimental investigation has been made on the unsteady pressure-flow behaviour of collapsible tubes, particularly the effects due to downstream resistance and reservoir head. The mean pressure-flow characteristics as well as pressure and flow waveforms were obtained. It has been found that different pressure and flow waveforms may be obtained depending on the downstream reservoir head and resistance even though the tube's mean pressure and flow rate are similar.
Sun, 01 Jan 1995 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/750921995-01-01T00:00:00Z
- Application of multi-domain GDQ method to analysis of waveguides with rectangular boundarieshttps://scholarbank.nus.edu.sg/handle/10635/57928Title: Application of multi-domain GDQ method to analysis of waveguides with rectangular boundaries
Authors: Shu, C.; Chew, Y.T.
Abstract: A multi-domain GDQ approach is presented in this paper for the analysis of various hollow conducting waveguides with rectangular boundaries. The present approach first decomposes the whole computational domain into several subdomains. Then in each subdomain, the GDQ method is applied to discretize the derivatives in the Helmholtz equation. The resultant eigenvalue equation system is solved by the standard eigenvalue solver. It is demonstrated in this work that accurate cutoff wavenumbers can be simultaneously computed by multi-domain GDQ approach using just a few grid points. As a consequence, the required computational effort is tiny. The multi-domain GDQ results agree very well with available data in the literature. No spurious modes are found in present study.
Fri, 01 Jan 1999 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/579281999-01-01T00:00:00Z
- Application of GDQ scheme to simulate natural convection in a square cavityhttps://scholarbank.nus.edu.sg/handle/10635/57925Title: Application of GDQ scheme to simulate natural convection in a square cavity
Authors: Shu, C.; Khoo, B.C.; Yeo, K.S.; Chew, Y.T.
Abstract: The global method of generalized differential quadrature (GDQ) was applied to simulate the natural convection in a square cavity. Numerical results demonstrated that accurate solutions can be obtained using just a few grid points and requiring much less computational effort and storage. © 1994.
Tue, 01 Nov 1994 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/579251994-11-01T00:00:00Z
- Unsteady wake-source model for flow past an oscillating bodyhttps://scholarbank.nus.edu.sg/handle/10635/75093Title: Unsteady wake-source model for flow past an oscillating body
Authors: Wond, S.C.; Chew, Y.T.; Low, H.T.; Tan, K.T.
Abstract: A potential-flow model of flow past an oscillating body with separated wake is developed based on the Parkinson and Jandall's wake-source model for steady flow. The results show that Morison's equation is in some cases a satisfactory model in the study of unsteady bluff body aerodynamics. The two-dimensional incompressible potential-flow model simulates the effect of flow separation in unsteady flow by placing surface sources, with time-dependent strengths ad angular positions on the rear wetted surface of the body, and downstream sinks to form a closed wake model in the transformed plane. The unsteady Bernoulli equation is used to obtain the time-dependent pressure distributions over the front wetted surface, from which the in-line force coefficients are obtained through integration. The in-line force equation obtained from the present model is shown to comprise of uncoupled drag and inertia terms.
Fri, 01 Jan 1993 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/750931993-01-01T00:00:00Z
- Application of gdq scheme to simulate incompressible viscous flows around complex geometrieshttps://scholarbank.nus.edu.sg/handle/10635/57924Title: Application of gdq scheme to simulate incompressible viscous flows around complex geometries
Authors: Shu, C.; Chew, Y.T.; Khoo, B.C.; Yeo, K.S.
Sat, 01 Jul 1995 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/579241995-07-01T00:00:00Z
- Aerodynamic stability of square , trapezoidal and triangular cylindershttps://scholarbank.nus.edu.sg/handle/10635/74955Title: Aerodynamic stability of square , trapezoidal and triangular cylinders
Authors: Yazdani, M.G.; Luo, S.C.; Lee, T.S.; Chew, Y.T.
Abstract: The objective of the present study is to investigate the galloping stability of prismatic bodies with different cross-sectional shape ( a square, a trapezium and a triangle) but with the same streamwise and cross-stream wise dimensions, so that the effects of shape can be investigated in isolation.The square cylinder is included in the investigation as a mean of calibrating the entire set-up as there are large numbers of square cylinder data available in the literature.
Fri, 01 Jan 1993 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/749551993-01-01T00:00:00Z
- Application of GDQ scheme to solve incompressible navier-stokes equations in the curvilinear coordinate systemhttps://scholarbank.nus.edu.sg/handle/10635/74960Title: Application of GDQ scheme to solve incompressible navier-stokes equations in the curvilinear coordinate system
Authors: Shu, C.; Chew, Y.T.
Abstract: In this paper, a global method of generalized differential quadrature (GDQ) is applied to solve the two-dimensional incompressible Navier-Stokes equations in the curvilinear coordinate system. The vorticity-stream function formulation was used. Numerical results for a smooth expansion channel flow demonstrated that accurate numerical results can be obtained using a considerably small number of grid points.
Sat, 01 Jan 1994 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/749601994-01-01T00:00:00Z
- Response of flush-mounted hot-wire and hot-film wall shear stress probeshttps://scholarbank.nus.edu.sg/handle/10635/75074Title: Response of flush-mounted hot-wire and hot-film wall shear stress probes
Authors: Chew, Y.T.; Khoo, B.C.; Lim, C.P.
Abstract: The present study continues the preliminary work of Khoo et al (1997) using the apparatus designed for generating a known near-wall fluctuating flow field to quantify the dynamic response of a flush-mounted hot-element wall shear stress gauge. Two different types of wall shear stress gauges were used in our experiment: a flush-mounted hot-wire in contact with the wall substrate and commercially-available quartz substrate hot-film gauges with different thickness of quartz coating. The flush-mounted hot-wire gauge was found to have a much higher dynamic response compared to the quartz substrate gauges although it is still lower than the marginally elevated hot-wire configuration. This may suggest the possible use of a marginally-elevated hot-wire as a wall shear stress gauge to ensure sufficient responsiveness for time-resolved wall shear stress measurements.
Wed, 01 Jan 1997 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/750741997-01-01T00:00:00Z
- Response of a near-wall hot-wire anemometer for velocity measurementshttps://scholarbank.nus.edu.sg/handle/10635/75073Title: Response of a near-wall hot-wire anemometer for velocity measurements
Authors: Khoo, B.C.; Chew, Y.T.; Lim, C.P.
Abstract: A known near-wall fluctuating flow field was imposed on a marginally-elevated hot-wire probe to quantify its dynamic response. In this preliminary work, it is found that the dynamic response of a given near-wall hot-wire configuration is dependent on the amplitude of imposed velocity change of the fluctuating flow field. With a constant amplitude of imposed velocity change, the dynamic response of the hot wire is shown to decrease with smaller height (h) above the wall substrate. This is consistent with numerous previous studies on wall corrections of near-wall hot-wire measurements about the increase influence of wall effect with decreasing h.
Wed, 01 Jan 1997 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/750731997-01-01T00:00:00Z
- Effects of riblets on transitional characteristics of a boundary layerhttps://scholarbank.nus.edu.sg/handle/10635/74990Title: Effects of riblets on transitional characteristics of a boundary layer
Authors: Shah, D.A.; Chew, Y.T.; Wan, J.
Abstract: Experimental study has been carried out using a single hot-wire to investigate the effects of riblets on the transition characteristics of a naturally developing low-speed boundary layer. The detailed measurements were carried out across the boundary layer at several streamwise locations for the smooth and riblet surfaces. The semicircular riblets have height h = 1.0 mm and spacing s = 2.2 mm and corresponds to 8 and 18 respectively when normalized with wall variables corresponding to freestream test velocity of 2.8 m/s. The results indicate that the presence of riblets hastens the onset of transition. However, the development of turbulence is slower and the length of the transition is slightly increased in case of riblet flow. At the same turbulence development stage, there are no significant differences in the normal distribution of turbulence intermittency factor over the two surfaces. The frequency of occurrence of turbulence spots is decreased over the riblets in the early stage of transition, and turbulence spot is found to maintain itself for a longer duration over a riblet surface.
Wed, 01 Jan 1997 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/749901997-01-01T00:00:00Z
- Global method for solving incompressible Navier-Stokes equations in the general coordinate systemhttps://scholarbank.nus.edu.sg/handle/10635/75009Title: Global method for solving incompressible Navier-Stokes equations in the general coordinate system
Authors: Shu, C.; Chew, Y.T.; Khoo, B.C.; Yeo, K.S.
Abstract: For the efficient numerical solutions of incompressible Navier-Stokes equations in the general coordinate system, this paper applies a global method of generalized differential quadrature (GDQ) to discretize the spatial derivatives, and a first order Euler implicit finite difference scheme to discretize the time derivative. After numerical discretization, the resultant algebraic equations are solved implicitly. The vorticity-stream function formulation was chosen as the governing equations. Numerical results for a smooth expansion channel flow demonstrated that accurate numerical results can be obtained using just a few grid points.
Sat, 01 Jan 1994 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/750091994-01-01T00:00:00Z
- Pressure-flow characteristics of collapsible tubeshttps://scholarbank.nus.edu.sg/handle/10635/75071Title: Pressure-flow characteristics of collapsible tubes
Authors: Low, Hong T.; Chew, Yong T.; Wang, Jian W.
Abstract: An experimental investigation has been made on the pressure-flow behaviour of collapsible tubes, particularly the effects due to upstream pressure and downstream reservoir-head. These and other experimental parameters were systematically varied to determined the pressure-drop versus flow characteristics. Pressure and flow waveforms were also obtained, showing pressure surges downstream of the collapsible tube. It has been found that different pressure-flow characteristics may be obtained depending on the downstream reservoir-head, even though the tube's pressure parameters were maintained similar.
Sat, 01 Jan 1994 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/750711994-01-01T00:00:00Z
- An experimental technique for distribution of dynamic wind loads on tall buildingshttps://scholarbank.nus.edu.sg/handle/10635/57884Title: An experimental technique for distribution of dynamic wind loads on tall buildings
Authors: Cheong, H.F.; Balendra, T.; Chew, Y.T.; Lee, T.S.; Lee, S.L.
Abstract: An experimental technique to determine the distribution of wind loads along the height of a slender and tall building has been presented using an aeroelastic model which simulates the correct mode shape of the prototype. The dynamic pressures acting on the model have been measured simultaneously from two pressure tappings at a time to compute the auto and cross power spectral densities, from which the modal force and, hence, the acceleration at any height is computed to determine the distribution of dynamic shear and moment. The technique could also be implemented using a rigid model when the motion of the building is not expected to modify the pressure distribution significantly. Since simultaneous measurements of pressures from all the tappings are not required, the proposed technique can be easily implemented in any wind tunnel laboratory. © 1992.
Wed, 01 Jan 1992 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/578841992-01-01T00:00:00Z
- An efficient approach for numerical simulation of flows in Czochralski crystal growthhttps://scholarbank.nus.edu.sg/handle/10635/57879Title: An efficient approach for numerical simulation of flows in Czochralski crystal growth
Authors: Shu, C.; Chew, Y.T.; Liu, Y.
Abstract: The global method of generalized differential quadrature (GDQ) is applied to simulate the flows in Czochralski crystal-growth configuration. The GDQ solver is validated by its application to the benchmark problem suggested by Wheeler. It is demonstrated in this study that the GDQ method can obtain accurate numerical solutions using just a few points and needing small computational resources.
Sat, 01 Nov 1997 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/578791997-11-01T00:00:00Z
- Numerical simulation of blade-vortex interaction in two-dimensional viscous flowhttps://scholarbank.nus.edu.sg/handle/10635/75052Title: Numerical simulation of blade-vortex interaction in two-dimensional viscous flow
Authors: Dong, B.; Chew, Y.-T.; Khoo, B.-C.; Mook, D.T.
Abstract: A numerical approach based on a finite element method has been developed to simulate the two-dimensional blade-vortex interaction in viscous flows. In the scheme, the incompressible Navier-Stokes equations in the vorticity-stream form are used. When the passing vortex is approaching the airfoil from upstream, two different models for the vortex are used. Firstly, the vortex is modeled as an ivicsid vortex convecting at the speed of the local fluid, and the total flow is the superposition of the vortex-induced flow and the viscous flow. Secondly, when the vortex is close to the airfoil, it is distributed in a weighted manner at the nodes of the element where it is located, and then the total flow is governed by the Navier-Stokes equations. Some numerical results are presented, and the potential of the present work is discussed.
Sat, 01 Jan 1994 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/750521994-01-01T00:00:00Z
- Simulation of flows around a rotating cylinder by a diffusing vortex schemehttps://scholarbank.nus.edu.sg/handle/10635/75081Title: Simulation of flows around a rotating cylinder by a diffusing vortex scheme
Authors: Chew, Y.T.; Cheng, M.; Luo, S.C.
Abstract: The flow development past a rotating circular cylinder in a viscous fluid in investigated. A new diffusion-vortex method is employed and extended to calculate the flow problem. The variations with time of the pressure vorticity distribution, the lift and drag forces exerted by the fluid on the cylinder surface, are determined for the selected values of the Reynolds number and rotation rate, and compared with the published experimental results. The results show a variety of unusual and complex flow patterns around the rotating cylinder.
Fri, 01 Jan 1993 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/750811993-01-01T00:00:00Z
- An efficient wavy microchannel heat sink for electronic deviceshttps://scholarbank.nus.edu.sg/handle/10635/51560Title: An efficient wavy microchannel heat sink for electronic devices
Authors: Sui, Y.; Teo, C.J.; Lee, P.S.; Chew, Y.T.; Shu, C.
Abstract: In this paper, we have designed a compact and efficient liquid-cooled heat sink for mini-sized electronic devices, particularly for very-large-scale integrated (VLSI) circuits. The heat sink can either be an integral part of the silicon (or metal) substrate, or a separate part attached onto the substrate. The heat sink consists of several wavy microchannels, with hydraulic diameter on the order of 100 μm, microfabricated on a silicon or metal substrate. The fluid flow and heat transfer performance of the heat sink are studied using numerical simulations in the steady laminar flow region and the dynamical system technique using Poincaré sections is employed to analyze the fluid mixing. It is found that when the liquid coolant flows through the wavy microchannel, Dean vortices can develop. The quantity and location of the Dean vortices may change along the flow direction, which can lead to laminar chaos. The chaotic advection greatly enhances the fluid mixing, and thus the heat transfer performance of the present heat sink is much more superior than previous designs which employed straight microchannels. It is also found that the pressure drop penalty is much smaller that the heat transfer enhancement for the present heat sink. Furthermore, the relative wavy amplitude (wavy amplitude/wavelength) of the channels can be varied along the flow direction for various purposes, without compromising the compactness and efficiency of the heat sink. The relative waviness can be increased along the flow direction, which results in higher heat transfer coefficients and renders the temperature for the devices much more uniform. The relative waviness can also be designed to be higher in regions of high heat flux for hot spot mitigation purposes. Copyright © 2009 by ASME.
Thu, 01 Jan 2009 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/515602009-01-01T00:00:00Z
- Simulation of Czochralski Crystal Growth by Using Lattice Boltzmann Methodhttps://scholarbank.nus.edu.sg/handle/10635/73850Title: Simulation of Czochralski Crystal Growth by Using Lattice Boltzmann Method
Authors: Peng, Y.; Shu, C.; Chew, Y.T.
Abstract: The single crystals form the foundation of the modern technology. They are needed for the scientific appraisal of crystallography, topography and tensor properties of all crystalline materials. The Czochralski technique is one of the widely used prototypical systems for melt-crystal growth. The modeling and understanding of the heat and mass transfer have become an important issue in the optimization of Czochralski technique to grow more uniform and better-quality crystals. In this paper, an alternative new method, Lattice Boltzmann Method (LBM), was used for the simulation of flows in CZ crystal growth. However, the standard LBM can only be used in the Cartesian coordinate system. By inserting the position, time and particle velocity dependent source terms into the evolution equation, the standard LBM can be transformed to be used in the cylindrical coordinate system. We extended this idea to solve the axisymmetric benchmark problem suggested by Wheeler for CZ crystal growth, avoiding the use of 3D standard LBM. The results compared well with available data in the literature.
Wed, 01 Jan 2003 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/738502003-01-01T00:00:00Z
- Tissue engineered tri-leaflet heart valve - preliminary fabrication of biodegradable polymer scaffoldshttps://scholarbank.nus.edu.sg/handle/10635/29490Title: Tissue engineered tri-leaflet heart valve - preliminary fabrication of biodegradable polymer scaffolds
Authors: Teoh, S.H.; Lau, C.Y.; Ranawake, M.; Hutmacher, D.W.; Chew, Y.T.; Sim, K.W.
Fri, 01 Jan 1999 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/294901999-01-01T00:00:00Z
- Performance evaluation of prosthetic heart valves using laser doppler anemometerhttps://scholarbank.nus.edu.sg/handle/10635/29491Title: Performance evaluation of prosthetic heart valves using laser doppler anemometer
Authors: Chew, Y.T.; Low, H.T.; Lee, C.N.; Kwa, S.S.
Tue, 01 Jan 1991 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/294911991-01-01T00:00:00Z
- Lattice kinetic scheme for the incompressible viscous thermal flows on arbitrary mesheshttps://scholarbank.nus.edu.sg/handle/10635/60640Title: Lattice kinetic scheme for the incompressible viscous thermal flows on arbitrary meshes
Authors: Peng, Y.; Shu, C.; Chew, Y.T.; Inamuro, T.
Abstract: The development of lattice kinetic scheme for incompressible viscous thermal flows following the Taylor-series expansion- and least-square-based lattice Boltzmann method (TLLBM) on arbitrary meshes was described. The lattice kinetic scheme saved the computer memory when compared with lattice Boltzmann method. The boundary condition was implemented directly which was similar to coventional Navier-Stokes solvers. The lattice kinetic scheme used on arbitrary meshes was validated by numerical simulations of natural convention in square cavity.
Thu, 01 Jan 2004 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/606402004-01-01T00:00:00Z
- Least-squares-based lattice Boltzmann method: A meshless approach for simulation of flows with complex geometryhttps://scholarbank.nus.edu.sg/handle/10635/60645Title: Least-squares-based lattice Boltzmann method: A meshless approach for simulation of flows with complex geometry
Authors: Shu, C.; Chew, Y.T.; Niu, X.D.
Abstract: A new version of lattice Boltzmann method (LBM) which was derived from the standard LBM was discussed using Taylor series expansion and optimized by the least squares method. The method is basically meshless, and can be applied to any complex geometry and nonuniform grids. The results showed that the proposed method is an efficient approach for simulation of flows involving complex geometry.
Mon, 01 Oct 2001 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/606452001-10-01T00:00:00Z
- Numerical and Theoretical Study of a Micro Tube Flowhttps://scholarbank.nus.edu.sg/handle/10635/60921Title: Numerical and Theoretical Study of a Micro Tube Flow
Authors: Mao, X.; Shu, C.; Chew, Y.T.
Abstract: The 3-D axisymmetric, steady flow in a micro-tube with Kn number in the 'slip flow' regime is investigated by analytical method and DSMC (direct simulation Monte Carlo) approach. The analytical formulations are derived by dimensional analysis and mass conservation law. Under different pressure ratios of the inlet to outlet, the streamwise velocity, nonlinear pressure distributions and volumetric flow rates along the streamwise direction are obtained analytically, which are compared with those given from DSMC computation. Good agreement was achieved. The causes of deviation in pressure distributions between analytical and DSMC results are discussed in terms of compressibility and rarefaction effects.
Wed, 01 Jan 2003 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/609212003-01-01T00:00:00Z
- A reliable and robust method to study flow-induced deformation of three-dimensional red blood cellshttps://scholarbank.nus.edu.sg/handle/10635/73089Title: A reliable and robust method to study flow-induced deformation of three-dimensional red blood cells
Authors: Yi, S.; Chew, Y.T.; Low, H.T.; Roy, P.
Abstract: A hybrid method is proposed to study the transient deformation of capsules in general and red blood cells in particular under flow. In this method, the immersed boundary concept is introduced into the framework of lattice Boltzmann method, and the multi-block strategy is employed to refine the mesh near the capsule to increase the accuracy and efficiency of computation. A finite element model is employed to obtain the forces acting on the membrane nodes of the three-dimensional red blood cell which is discretized into flat triangular elements. The method was validated by studying the deformation of initially spherical capsules under shear flow. The versatility of the present method was demonstrated by studying the effects of inertia on the deformation of capsules, and the deformation of capsules with complex shape like the biconcave discoid. © 2008 Springer-Verlag.
Tue, 01 Jan 2008 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/730892008-01-01T00:00:00Z
- Simulation of natural convection by Taylor series expansion- and least square-based LBMhttps://scholarbank.nus.edu.sg/handle/10635/73855Title: Simulation of natural convection by Taylor series expansion- and least square-based LBM
Authors: Peng, Y.; Shu, C.; Chew, Y.T.
Abstract: The Taylor series expansion- and least squares- based lattice Boltzmann method (TLLBM) is used in this paper to extend the internal energy density distribution function (IEDDF) thermal model to be used on the arbitrary geometry in order to solve practical thermo-hydrodynamics in incompressible limit. The TLLBM essentially has no limitation on the mesh structure and the lattice model. Its use in the thermal model was validated by the numerical simulation of natural convection in a square cavity. Then its application on the curved boundary, natural convection in concentric annuli, was carried out. Favorable results were obtained and compared well with the benchmark data.
Mon, 20 Jan 2003 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/738552003-01-20T00:00:00Z
- Simulation of thermal flows by taylor series expansion- and least square-based Lattice Boltzmann method coupling with macroscopic thermal equationhttps://scholarbank.nus.edu.sg/handle/10635/73857Title: Simulation of thermal flows by taylor series expansion- and least square-based Lattice Boltzmann method coupling with macroscopic thermal equation
Authors: Niu, X.D.; Shu, C.; Chew, Y.T.
Abstract: In this paper we use the Taylor series expansion- and least square-based lattice Boltzmann method to solve thermal flows. By introducing the "thermal source" into the isothermal lattice Boltzmann equation, and coupling with an explicit evaluatipn of temperature from the macroscopic thermal equation, the macroscopic property of the thermal flows can be obtained. To show the effectiveness of the method presented, the nature convection in the annulus between concentric horizontal circular and square cylinders was simulated and good results were obtained.
Mon, 20 Jan 2003 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/738572003-01-20T00:00:00Z