Reattachment Point Research Articles

Duct Height Effect on Terminal Shock/Boundary-Layer Interaction in a Generic Supersonic Inlet

A generic external-compression inlet model was tested to investigate the effect of duct height on terminal shock/boundary-layer interactions, with special sidewall arrangements to eliminate corner separations. Experimental results showed that the separation length significantly decreased by 41% as the duct height was reduced from 60 mm to 40 mm . To obtain the influence of the duct height in a wider range of values, Reynolds-averaged Navier–Stokes simulations were further performed. The scales of the -shock structure and separation region decrease as the duct height decreases. Shrinkage of the scale of the λ-shock structure results from a decrease in separation length. The downstream shift in the separation point and the upstream shift in the reattachment point both contribute to this decrease, but the upstream shift in the reattachment point is a dominant reason. The underlying mechanisms of the variation in the reattachment position as the duct height decreases include two aspects. The first is the stronger pressure gradient in the wall-normal direction immediately behind the shock system, which produces a stronger radial pressure gradient above the bumplike separation bubble, quickly turning the streamlines toward the bottom wall and enclosing the bubble. The second results from the postshock acceleration of the irrotational flow above the separated layer as the duct height decreases. An accelerating mainstream with a favorable pressure gradient above the separated layer increases the mixing strength and momentum exchange between the low-speed layer near the wall and high-speed flow above the separated layer.

Experimental analysis of the impact of an acoustic excitation on a separated boundary layer behaviour

The paper examines the effect of acoustic excitation at broadband frequency range (100 - 650 Hz) on separated boundary layer developing on a flat plate subjected to an adverse pressure gradient. The experiment was conducted with a low inlet turbulence intensity level (Tu < 1%) in order to provide a cleaner environment that magnifies the effects of the excitation frequency. It was shown that acoustic excitation at sound pressure levels: SPL=125 and 135 dB, can lead to a more rapid increase in flow instability followed by an earlier laminar-turbulent (l-t) transition. The boundary layer reattachment point was shifted upstream and the size of the separation bubble was reduced in the flow with the acoustic excitation active.

Correspondence between the number of no-slip critical points and nature of rear stagnation point of a symmetric object

For flow around an isolated object, the points of zero vorticity/shear stress located at fluid–solid interface, i.e., the separation, reattachment points inclusive of forward and rear stagnation points are refered to as no-slip critical points. The total number, n (≥2), of such points is an even number. For flow past a diamond-section object, it is shown here that a change of the value of n by 2 alters the nature of its rear stagnation point. The rear stagnation point acts as a separation point for n = 2, 6, 10, etc. and as an attachment point for n = 4, 8, 12, etc. A pair of hypothetical mean wakes is proposed and their viability discussed with reference to results available in literature. Concerning flow past two in-line diamond cylinders, the formation of an “anti-wake” at the leading edge of the downstream cylinder renders its forward stagnation point to act as a separation point, which, otherwise for an isolated object, invariably serves as an attachment point. The forebody and afterbody of a symmetric object act as independent entities in influencing the nature of no-slip stagnation points.

Flow-induced rotation modes and wake characteristics of a circular cylinder attached with a splitter plate at low Reynolds numbers

In this paper, the flow past a freely rotating cylinder-plate body is numerically investigated within a laminar flow region. The effects of Reynolds number and plate length on the rotary oscillation, wake flow, and hydrodynamic characteristics are examined. Numerical results indicated that the bifurcation phenomenon, i.e., the equilibrium position of the rotary oscillation deflects to a position which is not parallel to the free stream, is found in most cases. According to the variations of equilibrium position and root-mean-squared rotary angle (the root-mean-squared value of rotary oscillation obtained from sufficient stable rotary periods) against Reynolds number, three different rotation modes are identified: non-bifurcation regime without rotary oscillations (mode I), bifurcation regime with tiny rotary oscillations (mode II), and bifurcation regime with large rotary oscillations (mode III). Both the equilibrium position and root-mean-squared rotary angle increase first and then converge to a nearly unchanged value as Reynolds number increases. The splitter plate length has significant impacts on rotary oscillation responses. Generally, the cylinder with longer splitter plates possesses smaller deflection but larger root-mean-squared rotary angle. Moreover, a longer plate will push downstream the shear layer interaction, leading to a longer recirculation region and thus a smaller lift force. Due to the deflection, the upper and lower separation points of the rotatable cylinder-plate body are not symmetrical. The 2S vortex shedding pattern is recognized when the structure rotates, where two vortices are shed from the tip and the lower side of the plate, respectively. Additionally, three different reattachment behaviors are identified according to the position of the reattachment points: symmetrical reattachment (SR), asymmetrical tip-reattachment (ATR), and asymmetrical side-reattachment behavior (ASR). As compared with a bare cylinder, the rotatable splitter plate is helpful to reduce the drag and lift forces and meanwhile suppress vortex shedding.

Direct numerical simulation of supersonic bump flow with shock impingement

Direct numerical simulations are carried out to identify the effects of shock impingement on the behavior of bump flow at freestream Mach number of 2.25. Two cosine-shaped bump cases, with and without an impinging oblique shock at an angle of 33.2°, are compared. The shock impingement exhibits a remarkable influence on the pattern of the shock system and on the size of the separation region. A spectral analysis finds that low-frequency unsteadiness is significantly enhanced by the impingement interaction, and the proper orthogonal decomposition highlights the low-frequency breathing motion of the separation bubble, which is accurately reconstructed using only the first ten low-order modes. Downstream of the bump, both the Reynolds stress components and the turbulence kinetic energy exhibit a general amplification, with the peaks reoccurring at outer wall-normal locations. A turbulent kinetic energy budget analysis shows the greatly increased production in the outer layer which is balanced by turbulent transport and dissipation. An anisotropy-invariant map analysis identifies enhanced isotropic turbulence in the vicinity of the bump, which is qualitatively modified into a two-component axisymmetric state around the reattachment point. In addition, the mean skin friction decomposition suggests that the shock impingement has little influence on the predominant contribution of turbulence kinetic energy production, apart from the spatial growth dominance at the bump summit in the absence of the impinging shock. Interestingly, a scale-decomposed analysis quantitatively demonstrates that the contributions of small-scale structures are attenuated, but those of large-scale ones are relatively increased, with a contribution of more than 80% with shock impingement.

Experimental investigation of tubing collar's influence on hydrodynamic behavior of annular duct flow

Tubing collars’ influence on hydrodynamic behavior of annular duct flow has been investigated using Particle Image Velocity (PIV) technology. PIV has become an efficient method for complex transient flows visualization. A water flow loop with two replaceable variable cross-sections (VCS), 75–90 mm and 90–110 mm, in a 129 mm inner diameter (ID) pipe was used. The whole field of the variable cross-section annulus (VCSA) was visualized, including forward-facing step (FFS), narrow annulus (NA), and backward-facing step (BFS) flow. The VCSA ratio and Reynolds (Re) number influence on streamline distribution, velocity distribution, and turbulence intensity were discussed. Results showed that the recirculation is easier to form in BFS than FFS flow under the same condition. The VCSA ratio affects the formation of recirculation zones and the location of the reattachment point. Reynolds number mainly affects BFS flow by influencing the main velocity component - axial velocity. The turbulence intensity is relatively high in BFS than FFS flow and is larger at y/h>1.0 than y/h<1.0. Furthermore, the streamwise coherent structures reveal that the first two modes are predominant and represent the main characteristics of the flow by proper orthogonal decomposition (POD) method.

Quantification of Reynolds-averaged-Navier–Stokes model-form uncertainty in transitional boundary layer and airfoil flows

It is well known that the Boussinesq turbulent-viscosity hypothesis can introduce uncertainty in predictions for complex flow features such as separation, reattachment, and laminar-turbulent transition. This study adopts a recent physics-based uncertainty quantification (UQ) approach to address such model-form uncertainty in Reynolds-averaged Naiver–Stokes (RANS) simulations. Thus far, almost all UQ studies have focused on quantifying the model-form uncertainty in turbulent flow scenarios. The focus of the study is to advance our understanding of the performance of the UQ approach on two different transitional flow scenarios: a flat plate and a SD7003 airfoil, to close this gap. For the T3A (flat-plate) flow, most of the model-form uncertainty is concentrated in the laminar-turbulent transition region. For the SD7003 airfoil flow, the eigenvalue perturbations reveal a decrease as well as an increase in the length of the separation bubble. As a consequence, the uncertainty bounds successfully encompass the reattachment point. Likewise, the region of reverse flow that appears in the separation bubble is either suppressed or bolstered by the eigenvalue perturbations. This is the first successful RANS UQ study for transitional flows.

Flow characteristics on the leeside of a geotextile mattress with floating plate

The Geotextile Mattress with Floating Plate (GMFP) is a novel scour prevention structure. This paper provides an insight into the effects on the flow pattern near the GMFP to better understand the GMFP working mechanism. The GMFP design parameters were emphasized, including the sloping angle, the height of the floating plate, and the opening ratio. In most cases, the bottom vortex is located immediately downstream to the GMFP. The near bottom velocity downstream to the bottom vortex is remarkably lower than the undisturbed value. The location variation of the bottom vortex reattachment point with the GMFP design parameters was studied. Within the range of hydrodynamic parameters tested, the reattachment point moves upstream when the opening ratio increases over 0.231, which agrees with previous studies. With the increase of the obstruction height of the floating plate, the reattachment point tends to move downstream when the relative obstruction height is below 0.2, and then retreats to the upstream side, which may be attributed to the variation in the water surface profile and the enhanced flow through the sand-pass gap due to the intensified blockage effect. An equation was proposed to predict the location of the reattachment based on the GMFP obstruction height.

Energy analysis of magnetite nanofluid flowing in newly designed sudden expansion tube retrofitted with dimpled fin

Sudden expansion geometry plays an important role in the design of many engineering applications such as heat exchangers to avoid thermal stress on welded joints. While the heat transfer in these geometries is maximized at the reattachment points, it decreases to a minimum in the recirculation regions created by the fluid. To prevent this situation and improve the performance of the expansion tubes, nanofluid, and expanded surfaces can be used. For this purpose, forced convection of magnetite nanofluid flow in various expansion ratios has been investigated numerically in this study. Analyses have been performed on Reynolds (Re) numbers ranging from 100 to 2000, constant and uniform heat flux at 600 W/m2, and volume concentrations (1.0≤φ≤2.0 vol.%). The result showed that while the Nu number increases with increasing Re number, the most efficient case is Dimpled Tube (DT) 9, and the highest value of performance evaluation criteria (PEC) has been obtained at φ=2.0 vol.%. Compared with the water, the highest Nu number value has been obtained as 3.34% increased at Re=2000 and φ=2.0 vol.%. When compared to the DT9 and Smooth Tube (ST) 1 where water was used as the working fluid at Re=2000 and φ=2.0 vol.%, the PEC value increased by 8.66% and 110.31%, respectively. In addition, the bottom wall of the DT9 case performs higher convective heat transfer rate than the top wall.

Reynolds number and submergence ratio effects on turbulence structures in the shallow wake of a horizontal pipe located on a rough bed

The effects of Reynolds number and submergence ratio on mean velocity, separation length, Reynolds shear stresses (RSS), correlation coefficient, anisotropy, and turbulent kinetic energy (TKE) are evaluated by modifying the free-stream velocity and pipe diameter to understand the fluid–structure interaction in the presence of a rough channel bed. Acoustic Doppler velocimetry is used to acquire three-dimensional velocity data in the experiments. The experimental data demonstrate that the non-dimensional separation length is linearly varying with the Reynolds number up to a critical Reynolds number, and after that, it becomes independent of the Reynolds number. The vertical profiles of the mean velocity, RSS, correlation coefficient, anisotropy, and TKE are not affected by the Reynolds number; however, their profiles are affected by the submergence ratio. The RSS and TKE are found to be larger for the higher submergence ratio below the top level of the pipe throughout the wake region. The reattachment point is found to be the most turbulent as the most pronounced peaks of RSS and TKE are occurring at this point. The quadrant analysis reveals that the RSS contribution of ejection events is higher for a lower submergence ratio, whereas the RSS contribution of the sweep events is higher for a higher submergence ratio. In conclusion, this study provides an in-depth understanding of the turbulent flow characteristics in the wake region of a bed-mounted horizontal circular pipe located on a fixed sand bed, especially the modification of the turbulence properties due to changes in the Reynolds number and submergence ratio.

Turbulent separations beneath semi-submerged bluff bodies with smooth and rough undersurfaces

The spatio-temporal characteristics of turbulent separations beneath semi-submerged bluff bodies with different undersurface roughness conditions are studied using a time-resolved particle image velocimetry. The Reynolds number based on the free-stream velocity and submergence depth was fixed to 14 400. Three different undersurface conditions – smooth, sandpaper roughness and cube roughness – were examined. The results showed that wall roughness reduces the mean reattachment length, and suppresses the Reynolds stresses in the second half of the mean separation bubble. The Kelvin–Helmholtz instability is observed at the leading edge of the smooth bluff body, but is bypassed in the rough cases. In the first half of the mean separation bubble, the frequencies in the separated shear layer migrate to lower values in a discrete manner through the vortex pairing mechanism. Consequently, multiple vortex shedding motions at different frequencies are nested in the separated shear layer, and the cores of shed vortices are aligned near the isopleth of free-stream velocity. The shed vortex is accompanied with multiple vortices along the edge of mean flow reversal in the upstream locations. These vortices are influenced significantly by wall roughness. A low-frequency flapping motion manifests as enlargement/shrinkage of reverse flow areas in the first half of the mean separation bubble. The frequencies of flapping motion in the smooth and sandpaper cases are similar, but are relatively lower than that in the cube roughness case. This flapping motion is associated with an extremely large vortex shed from the mean reattachment point to the free-stream region.

LES study on variation of flow pattern around a 4:1 rectangular cylinder and corresponding wind load during VIV

Vortex-induced vibration (VIV) is one of the typical flow-induced large amplitude vibrations. In this study, large eddy simulation (LES) is carried out to investigate the whole VIV process of a rectangular cylinder with aspect ratio 4. The flow fields and wind loads for rigid and elastic models are examined and compared to clarify the crucial flow characteristics during VIV. Results show that the time-averaged reattachment point of separated shear layer moves towards upstream direction with the increase of response amplitude. The mean negative pressure is consequently increased near leading edge of side face. For dynamic flow and wind load, in initial branch, the reattachment point of the separated shear layer, corresponding to the instant of largest side face wind load, gradually moves towards downstream with the increase of response amplitude. Meanwhile, the fluctuating lift coefficient and span-wise wind load correlation increase accordingly. In upper branch, the separated shear layer temporally separates from the side face, which leads to a sharp reduction of fluctuating lift coefficient and span-wise wind load correlation. The response amplitude, however, does not change apparently. In desynchronization, the response amplitude starts to decrease, as the vibration can no longer capture the shedding frequency of shape-induced vortex. The characteristics of the motion-induced wind loads corresponding to different wind speeds are also discussed in this study.

Modeling of Turbulent Heat-Transfer Augmentation in Gas-Droplet Non-Boiling Flow in Diverging and Converging Axisymmetric Ducts with Sudden Expansion

The effect of positive (adverse) and negative (favorable) longitudinal pressure gradients on the structure and heat transfer of gas-droplet (air and water) flow in axisymmetric duct with sudden expansion are examined. The superimposed pressure gradient has a large influence on the flow structure and heat transfer in a two-phase mist flow in both a confuser and a diffuser. A narrowing of the confuser angle leads to significant suppression of flow turbulence (more than four times that of the gas-drop flow after sudden pipe expansion without a pressure gradient at φ = 0°). Recirculation zone length decreases significantly compared to the gas-droplet flow without a longitudinal pressure gradient (by up to 30%), and the locus of the heat-transfer maximum shifts slightly downstream, and roughly aligns with the reattachment point of the two-phase flow. Growth of the diffuser opening angle leads to additional production of kinetic energy of gas flow turbulence (almost twice as much as gas-droplet flow after a sudden pipe expansion at φ = 0°). The length of the flow recirculating region in the diffuser increases significantly compared to the separated gas-droplet flow without a pressure gradient (φ = 0°), and the location of maximum heat transfer shifts downstream in the diffuser.

Effects of wall temperature on separation structures in supersonic flow over a semi-circular cavity

The influence of wall temperature on the vortex structure and flow characteristics of flow in semi-circular cavities is numerically investigated in this paper. The results show that the separation and reattachment points move downstream, and the secondary vortex increases with increases in wall temperature. In the secondary vortex section, normalized wall shear stress in the polar map has good consistency at different wall temperatures, and the flow properties of the three extreme points on the map are similar to Couette flow. In addition, the secondary vortex region can be regarded as an isobaric high-pressure region, while the pressure gradients slowly vary as the wall temperature increases. We confirm the independence of separation pressure for the wall temperature using pressure distribution and find that the peak and inflection points are at the reattachment points and separation points, respectively. Moreover, using a series of numerical calculations of the positions of the vortex center at different wall temperatures, explicit empirical formulas for estimating the positions of the primary vortex center are put forward. Using a topological mapping method, cavity flow is converted into quasi-one-dimensional steady-state compressible viscous flow through a variable cross-section pipe, and the flow parameter distribution, including the Mach number and pressure, conforms to the rule of quasi-one-dimensional flow.

Experimental study of self-sustained spanwise streaks and turbulent mixing in separated shear flow

The self-sustained streaks in turbulent backward-facing step flow are experimentally studied at a step height Reynolds number of 1.0 × 103. As one of the featured dynamic behaviors, evolution of the spanwise streaks plays an important role in the large-scale, aperiodic and vertical flapping motions of the separated/reattaching shear layer. By time-resolved particle image velocimetry, we measure the velocity vector fields in the streamwise-spanwise and streamwise-vertical planes downstream of a two-dimensional backward-facing step. The two cross-sectional velocity fields show that the shear layer remains two-dimensional along the span in the initial half of the shear layer, and then three-dimensional structures start to evolve in the latter half, leading to an unsteady reattaching shear layer and a shifting reattachment point on the downstream wall. By analyzing the finite-time Lyapunov exponent in the spanwise field of view, we find that low-speed fluid elements are vertically entrained upwards into the shear layer. As a result, the entrained fluid elements produce transient and localized low-speed fluid patches in the streamwise-spanwise plane, which move and decay downstream with strong straining and stretching motions along their boundaries. Furthermore, the large-scale streak-type and flap-type flows are clearly extracted and reconstructed by the energy-containing proper orthogonal decomposition modes.

Particle image velocimetry measurements of turbulent flows in rotating square ribbed ducts

This paper investigates the flow characteristics along a ribbed square duct using time-resolved particle image velocimetry. The Reynolds number, defined by the main flow velocity (1.82 m/s) and the hydraulic diameter (80 mm), is 10 000. The rotation numbers are 0, 0.13, 0.26, 0.39, and 0.52. The blockage and aspect ratios of the ribbed square duct are 0.1 and 1, respectively. As the rotation number increases, the recirculation zone on the suction side becomes larger, and the reattachment point moves downstream. The opposite behavior is observed on the pressure side, and this trend develops along the duct. Furthermore, the flow characteristics between different pairs of ribs along the duct vary greatly at the same rotation number. For the downstream ribs, the main stream velocity pattern is deflected more to the pressure side, where both the recirculation zone and the extreme region of Reynolds shear stress are larger than on the suction side.

Investigation of Snow Deposition on the Railway Cuttings During the Snowdrift

This study confirmed a mixture multiphase model based on the Euler–Euler method to predict snow deposition in road cuttings. A scaled model experiment was conducted in the Mayitas region of Xinjiang to verify the numerical simulation accuracy, which revealed a good agreement. Regarding the formation mechanism of drifting snow disasters in road cuttings, the wind speed in the simulation results was analyzed in detail. The results indicated that the low-wind speed area is positively correlated with the vortex size and that snow deposition occurs between the vortex separation point and vortex reattachment point. The appearance and disappearance of the secondary vortex can divide the snow cover process into three stages, and the second phase after secondary vortex emergence represents the period of a rapid increase in the snow thickness. Snow cornices are the leading emergence cause of secondary vortex. The related critical snow storage capacity should also be considered to measure the snow storage capacity of road cutting types.

Hypersonic drag and heat reduction mechanism of a new hybrid method of spike, multi-row discs and opposing jets aerodynamic configuration

In this study, the drag force and aerodynamic heating reduction capacity of a novel combined spike root jet and multi-row disk (SRJ-MRD) model consisting of a blunt body, a spike, four aerodisks, and a counterflow jet was compared with geometric reported proposed in other studies. The proposed geometric model was numerically simulated using Reynolds-Averaged Navier–Stokes (RANS) equations with second-order spatial accuracy and the SST k-ω turbulence model. The flow was steady, compressible, and axisymmetric at Mach number 6. The primary attention of the present study has been focused on investigating the effect of the novel configuration on the flow field, shock-shock interaction, location of reattachment shock wave, and intensity of shock wave at the reattachment point. Besides, the effect of these parameters on the specifications of lift force and aerodynamic heating has been studied. Results showed that the existence of four aerodynamic discs (one conical aero disc and three smooth aerodisks) in the proposed model would guide the shear layer and separation shock wave upward, which causes the reattachment shock wave to occur on the blunt nose near the shoulder. Furthermore, the shock-shock interaction does not occur near the nose wall. In addition, the intensity of reattachment shock wave is reduced by the root opposing jet, and the low-temperature outlet will directly cool the front part of the blunt nose. It was found that the spatial location of maximum heat flux on the conical nose's wall is 68.90˚, denoting the positive effect of the proposed configuration on the reattachment shock wave, separation shock wave, and shock-sock interaction. To evaluate the new proposed configuration, the obtained results were compared with nine designs simulated by other researchers which used the same flow conditions and configuration (i.e., diameter, blunt body type, spike length, aerodisks diameter, location, and pressure ratio) but different control approaches. The results revealed that the drag coefficient and maximum heat flux were 0.2619 and 25.13 kw/m2, respectively. Compared to the results of the best design proposed by other researchers, i.e., spike configuration by applying lateral jet and spike tip, the present configuration shows a reduction in total drag coefficient (Cd,all) and maximum heat flux (Qmax) by 7.9% and 10.05%, respectively.

Computational analysis of compressibility effect on flow field and aerodynamics at low Reynolds numbers

The flow around the wing of exploration aircraft flying in the very dilute Martian atmosphere experiences very specific low-Reynolds-number compressible flows. A fundamental understanding of compressibility effects, especially on a separation bubble, is an important issue in the aerodynamic wing design. We investigated the effect of compressibility on the laminar separation bubbles and aerodynamic properties of a blunt flat plate with a thickness of 5% of the chord length in unsteady two-dimensional laminar and large-eddy simulations at chord-based Reynolds numbers (Re) of 6100 and 11 000 in the Mach number (M) range from M = 0.1 to 0.8. In the incompressible flow below M = 0.2 at Re = 11 000, the separated shear layer rolled up due to the Kelvin–Helmholtz (KH) instability reattaches to the surface with turbulent transition and then forms a laminar separation bubble. In contrast, with increasing Mach number, the transition and reattachment are delayed, and the separation bubble is stretched. In particular, at M = 0.8, the rolled-up vortex is not distorted in the span direction and advects downstream with a strong spanwise two-dimensionality. This is due to the compressibility effect that suppresses the KH instability. On the other hand, at Re = 6100, the separated shear layer is stable without spanwise distortion even in the incompressible flow due to the stronger influence of viscous forces. With increasing Mach number, such stable separated shear layer reattaches without rolling up further downstream, and the Strouhal number of the vortex also gradually decreases. This leads that the large lift oscillation owing to periodic and two-dimensional spanwise vortex shedding is significantly suppressed with an increasing Mach number. This is also due to the weakening of the KH instability due to the compressibility effects. However, at Re = 11 000, the reattachment points move downstream more significantly with the increasing Mach number, indicating that the suppression of the KH instability due to the compressibility effect is more pronounced at Re = 11 000 than at Re = 6100. Consequently, the negative skin friction shear stress owing to the reverse flow inside the expanded separation bubble becomes relatively large, decreasing the total drag with the increasing Mach number.

Parametric investigation of spatio-temporal variability of submerged body hydrodynamics

The spatio-temporal dynamics of the flow around a wall-mounted bluff body immersed in a turbulent boundary layer is investigated numerically, on a 2D vertical plane using ANSYS-Fluent, over a wide parameter ranges. The submergence ratios (SR) considered for the study are 1.5–10, that covers the entire regime of low, intermediate, and high SR. The Reynolds numbers (Reh) considered are 8,400−56,000, that falls within the turbulent regime. The steady and fluctuating flow fields are investigated as a response to varying SR and Reh. It is demonstrated that in the Reynolds numbers range considered, there exists an optimum SR up to which normalized mean reattachment length is proportionate to SR and beyond that optimum value, normalized mean reattachment length is inversely proportionate to SR. In general, the maximum reattachment length over the entire SR range considered, does not show any coherent variability with Reh. Maxima and minima of the normalized mean velocity fields are found to be inveresly proportionate to SR (with varying degree) and independent of Reh. The skin friction coefficient, Cf is proportional to Reh and inversely proportional to SR on all three edges of the obstacle. The maximum Reynolds shear stress seems to occur approximately at the reattachment point. The general observation is: the time-averaged kinematic fields are asymmetrically more influenced by SR over Reh, whereas time dependent fluctuating fields show much higher dependence on Reh compared to SR.