Numerical Study of Drag Reduction for Flow Past a Square Cylinder Through Passive Control Method at Various Gap Spacing

Laminar flow past a circular cylinder has been studied numerically at low Reynolds number. The upstream and downstream rods have been used as passive control in order to reduce hydrodynamics forces acting on the cylinder. Both the upstream and downstream rods significantly contribute in reduction of drag and fluctuating lift compared to single cylinder without the rods. More detail, the upstream installation rod is more dominant in drag reduction than the downstream one. On the contrary, the downstream rod has suppressed the magnitude of the fluctuating lift almost twice that of the upstream configuration. Placing the two rods together as the upstream and downstream passive control in tandem arrangement has given more hydrodynamics forces reduction than the single rod configurations.Keywords:circular cylinder, passive control, tandem, drag, lift.

Download Full-text

A NUMERICAL STUDY OF OPTIMAL DRAG REDUCTION FOR TURBULENT TRANSONIC PROJECTILES USING A PASSIVE CONTROL

International Journal of Computational Fluid Dynamics ◽

10.1080/10618569408904510 ◽

1994 ◽

Vol 3 (3-4) ◽

pp. 251-264

Author(s):

JAN-KAUNG FU ◽

SHEN-MIN LIANG

Keyword(s):

Drag Reduction ◽

Passive Control ◽

Numerical Study

Download Full-text

Numerical Analysis of Fluid Forces for Flow Past a Square Rod with Detached Dual Control Rods at Various Gap Spacing

Symmetry ◽

10.3390/sym12010159 ◽

2020 ◽

Vol 12 (1) ◽

pp. 159

Author(s):

Raheela Manzoor ◽

Abdul Ghaffar ◽

Dumitru Baleanu ◽

Kottakkaran Sooppy Nisar

Keyword(s):

Strouhal Number ◽

Numerical Study ◽

Control Rod ◽

Drag And Lift Coefficients ◽

Fluid Forces ◽

Flow Past ◽

Upstream Direction ◽

Drag And Lift ◽

Gap Spacing ◽

Control Rods

A two-dimensional numerical study was conducted for flow past a square rod in the presence of two control rods. One is placed vertically in the upstream direction and the second one is placed horizontally in the downstream direction of the square rod. The influence of gap spacing was studied by taking g1 = 1–5 and g2 = 0.5–5 (where g1 is the gap between the upstream control rod and the main rod, and g2 is the space between the main rod and the downstream control rod) at Re = 160. The simulation results were obtained in the form of vorticity contour, drag and lift coefficients, Strouhal number, and force statistics. Under the effect of gap spacing, three different flow modes were found and named according to their behavior. It was found that the mean drag coefficient showed decreasing behavior by increasing the value of g2 continually at a fixed value of g1. The largest value of C d m e a n was found at (g1, g2) = (1, 1) and the greatest percentage reduction in C d m e a n was obtained at (g1, g2) = (1, 3), which is 139.72%. The effect of thrust was also noticed for all selected values of g1 and g2. Furthermore, it was noticed that the Strouhal number and the root mean square values of the drag and lift coefficients smaller values than the single rod values, except for the Clrms value of (g1, g2) = (1, 3) and (1, 4).

Download Full-text

Numerical study on flow past 2D square cylinder by Large Eddy Simulation: Comparison between 2D and 3D computations

Journal of Wind Engineering and Industrial Aerodynamics ◽

10.1016/0167-6105(93)90061-r ◽

1993 ◽

Vol 50 ◽

pp. 61-68 ◽

Cited By ~ 18

Author(s):

Shigehiro Sakamoto ◽

Shuzo Murakami ◽

Akashi Mochida

Keyword(s):

Large Eddy Simulation ◽

Numerical Study ◽

Square Cylinder ◽

Eddy Simulation ◽

Flow Past ◽

Large Eddy ◽

2D And 3D

Download Full-text

Large-eddy simulation of the compressible flow past a wavy cylinder

Journal of Fluid Mechanics ◽

10.1017/s0022112010003927 ◽

2010 ◽

Vol 665 ◽

pp. 238-273 ◽

Cited By ~ 69

Author(s):

CHANG-YUE XU ◽

LI-WEI CHEN ◽

XI-YUN LU

Keyword(s):

Circular Cylinder ◽

Drag Reduction ◽

Shear Layer ◽

Compressible Flow ◽

Passive Control ◽

Three Dimensional ◽

Eddy Simulation ◽

Separated Shear Layer ◽

Flow Past ◽

Cylinder Flow

Numerical investigation of the compressible flow past a wavy cylinder was carried out using large-eddy simulation for a free-stream Mach number M∞ = 0.75 and a Reynolds number based on the mean diameter Re = 2 × 105. The flow past a corresponding circular cylinder was also calculated for comparison and validation against experimental data. Various fundamental mechanisms dictating the intricate flow phenomena, including drag reduction and fluctuating force suppression, shock and shocklet elimination, and three-dimensional separation and separated shear-layer instability, have been studied systematically. Because of the passive control of the flow over a wavy cylinder, the mean drag coefficient of the wavy cylinder is less than that of the circular cylinder with a drag reduction up to 26%, and the fluctuating force coefficients are significantly suppressed to be nearly zero. The vortical structures near the base region of the wavy cylinder are much less vigorous than those of the circular cylinder. The three-dimensional shear-layer shed from the wavy cylinder is more stable than that from the circular cylinder. The vortex roll up of the shear layer from the wavy cylinder is delayed to a further downstream location, leading to a higher-base-pressure distribution. The spanwise pressure gradient and the baroclinic effect play an important role in generating an oblique vortical perturbation at the separated shear layer, which may moderate the increase of the fluctuations at the shear layer and reduce the growth rate of the shear layer. The analysis of the convective Mach number indicates that the instability processes in the shear-layer evolution are derived from oblique modes and bi-dimensional instability modes and their competition. The two-layer structures of the shear layer are captured using the instantaneous Lamb vector divergence, and the underlying dynamical processes associated with the drag reduction are clarified. Moreover, some phenomena relevant to the compressible effect, such as shock waves, shocklets and shock/turbulence interaction, are analysed. It is found that the shocks and shocklets which exist in the circular cylinder flow are eliminated for the wavy cylinder flow and the wavy surface provides an effective way of shock control. As the shock/turbulence interaction is avoided, a significant drop of the turbulent fluctuations around the wavy cylinder occurs. The results obtained in this study provide physical insight into the understanding of the mechanisms relevant to the passive control of the compressible flow past a wavy surface.

Download Full-text