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

Symmetry ◽  
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).

Numerical investigation of the vibration effect of a flexible membrane on the flow behaviour around a circular cylinder

2018 ◽  
Vol 81 (2) ◽  
pp. 21101
Author(s):  
Nabaouia Maktouf ◽  
Ali Ben Moussa ◽  
Saïd Turki
Keyword(s):  
Circular Cylinder ◽  
Strouhal Number ◽  
Bluff Body ◽  
Numerical Study ◽  
Rear Side ◽  
Ansys Fluent ◽  
Flexible Membrane ◽  
Drag And Lift Coefficients ◽  
Vibration Effect ◽  
Drag And Lift

Active control of the flow behind a bluff body is obtained by integrating a vibrating membrane. A numerical study has been conducted to investigate the effect of the vibration of a flexible membrane, stuck to the rear side of a circular cylinder, on the global flow parameters such as the Strouhal number, the drag and lift coefficients. The shape of the membrane is evolving as a vibrating chord using a dynamic mesh. The governing equations of 2D and laminar flow have been solved using ANSYS Fluent 16.0 as a solver and the Gambit as a modeler. The motion of the membrane is managed by two parameters: frequency f and amplitude A. The effect of the flexible membrane motion is studied for the range of conditions as 0.1 Hz ≤ f ≤ 6 Hz and 5 × 10−4 m ≤ A ≤ 10−3 m at a fixed Reynolds number, Re = 150. Three different sizes of the flexible membrane have been studied. Results show that a beat phenomenon affects the drag coefficient. The amplitude does not affect significantly the Strouhal number as well as drag and lift coefficients. By increasing the size of the flexible membrane, we show a lift enhancement by a growth rate equal to 39.15% comparing to the uncontrolled case.

Interaction of a Steady Approach Flow and a Circular Cylinder Undergoing Forced Oscillation

1997 ◽  
Vol 119 (4) ◽  
pp. 808-813 ◽  
Author(s):  
Jianfeng Zhang ◽  
Charles Dalton
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Stokes Equations ◽  
Numerical Study ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Large Eddy Simulation Model ◽  
Drag And Lift Coefficients ◽  
Eddy Simulation ◽  
Drag And Lift

This paper presents a numerical study on the interaction of a steady approach flow and the forced transverse oscillation of a circular cylinder. The two-dimensional stream-function/vorticity formulation of the Navier-Stokes equations is solved by a semi-implicit finite-difference scheme. Calculations for flows with different amplitude (a) and frequency (fc) of the oscillation of the cylinder show a strong effect of the oscillation when fc is close to fso, the vortex shedding frequency, of the stationary cylinder. Lock-on of vortex shedding, distinct flow patterns, and increase in both drag and lift coefficients from those of a stationary cylinder are observed for Reynolds number Re = 200, a/R (R is the radius of the cylinder) from 1.0 to 2.0, fc/fso from 0.85 to 1.7. For Re = 855, a/R = 0.26, a large eddy simulation model for turbulent flow is used. The results at Re = 855 and a/R = 0.26 show that lock-on has occurred for fc/fso ≥ 0.85. The behavior of the drag and lift coefficients is seen to be influenced by the lock-on phenomenon.

scholarly journals Computational Analysis of Fluid Forces on an Obstacle in a Channel Driven Cavity: Viscoplastic Material Based Characteristics

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 529
Author(s):  
Rashid Mahmood ◽  
Afraz Hussain Majeed ◽  
Qurrat ul Ain ◽  
Jan Awrejcewicz ◽  
Imran Siddique ◽  
...  
Keyword(s):  
Computational Grids ◽  
Neumann Condition ◽  
Viscoplastic Material ◽  
Driven Cavity ◽  
Drag And Lift Coefficients ◽  
Fluid Forces ◽  
Bingham Number ◽  
Element Approach ◽  
Drag And Lift ◽  
Velocity Pressure

In the current work, an investigation has been carried out for the Bingham fluid flow in a channel-driven cavity with a square obstacle installed near the inlet. A square cavity is placed in a channel to accomplish the desired results. The flow has been induced using a fully developed parabolic velocity at the inlet and Neumann condition at the outlet, with zero no-slip conditions given to the other boundaries. Three computational grids, C1, C2, and C3, are created by altering the position of an obstacle of square shape in the channel. Fundamental conservation and rheological law for viscoplastic Bingham fluids are enforced in mathematical modeling. Due to the complexity of the representative equations, an effective computing strategy based on the finite element approach is used. At an extra-fine level, a hybrid computational grid is created; a very refined level is used to obtain results with higher accuracy. The solution has been approximated using P2 − P1 elements based on the shape functions of the second and first-order polynomial polynomials. The parametric variables are ornamented against graphical trends. In addition, velocity, pressure plots, and line graphs have been provided for a better physical understanding of the situation Furthermore, the hydrodynamic benchmark quantities such as pressure drop, drag, and lift coefficients are assessed in a tabular manner around the external surface of the obstacle. The research predicts the effects of Bingham number (Bn) on the drag and lift coefficients on all three grids C1, C2, and C3, showing that the drag has lower values on the obstacle in the C2 grid compared with C1 and C3 for all values of Bn. Plug zone dominates in the channel downstream of the obstacle with augmentation in Bn, limiting the shear zone in the vicinity of the obstacle.

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

2017 ◽  
Vol 14 (12) ◽  
pp. 5872-5881
Author(s):  
Shams-ul-Islam ◽  
Raheela Manzoor ◽  
Tahira Mengal ◽  
Asma Naeem ◽  
Sajida Parveen ◽  
...  
Keyword(s):  
Drag Reduction ◽  
Passive Control ◽  
Control Method ◽  
Numerical Study ◽  
Square Cylinder ◽  
Flow Past ◽  
Gap Spacing

scholarly journals Numerical Study of Flow Past Three Rectangular Rods at Unequal Gap Spacing

2019 ◽  
Vol 12 (32) ◽  
pp. 1-13
Author(s):  
S. Ul. Islam ◽  
R. Manzoor ◽  
M. Zahid ◽  
S. Kulsoom ◽  
U. Kausar ◽  
...  
Keyword(s):  
Numerical Study ◽  
Flow Past ◽  
Gap Spacing

Identification of flow states around three staggered square cylinders at two symmetrical arrangements by a numerical investigation

2020 ◽  
Vol 31 (11) ◽  
pp. 2050151
Author(s):  
Salwa Fezai ◽  
Fakher Oueslati ◽  
Brahim Ben-Beya
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Strouhal Number ◽  
Physical Parameters ◽  
Steady Regime ◽  
Drag And Lift Coefficients ◽  
Square Cylinders ◽  
Drag And Lift ◽  
Lift And Drag ◽  
Obstacle Geometry

The fluid flow over three staggered square cylinders at two symmetrical arrangements has been numerically investigated in this study. The numerical calculations are carried out for several values of the Reynolds number (Re) ranging from 1 to 180. The results are presented in the form of vorticity contours and temporal histories of drag and lift coefficients. Furthermore, the physical parameters, namely, the average drag and lift coefficients and Strouhal number are presented as a function of Re. Two different states of flow are found in this work by systematically varying Re: steady and unsteady states. The transition to unsteady state regime is exhibited via Hopf bifurcation first in the second configuration followed consequently by the first one with critical Reynolds number of Re[Formula: see text] and Re[Formula: see text], respectively. It is observed that the bifurcation point of the steady regime to the unsteady one is very much influenced by the change in the geometry of the obstacle. The unsteady periodic wake is characterized by the Strouhal number, which varies with the Reynolds number and the obstacle geometry. Hence, the values of vortex shedding frequencies are estimated for both the considered configurations. Computations obtained also reveal that the spacing in the wake leads to reducing the pressure and enhancing the fluid flow velocity for both arrangements by monotonically strengthening the Reynolds number value. Furthermore, the drag and lift coefficients are determined, which allowed determining; the best configuration in terms of both lift and drag. It is observed that the drag force is dependent on the obstacle geometry and strengthens while lowering the Reynolds number. On the other hand, an opposite trend of the lift drag evolutions is observed for both configurations and considerably affected by the arrangements shape.

Influence of Corner Radius on Flow Past Square Cylinder With Tandem Arrangements

2019 ◽  
Author(s):  
Sajjad Miran ◽  
Furqan Ahmad ◽  
Waseem Arif ◽  
Kamran Nazir
Keyword(s):  
Reynolds Number ◽  
Flow Visualization ◽  
Aerodynamic Characteristics ◽  
Diameter Ratio ◽  
Square Cylinder ◽  
Total Drag ◽  
Flow Past ◽  
Corner Radius ◽  
Drag And Lift ◽  
Gap Spacing

Abstract The Flow Past square cylinder with tandem arrangement is numerically analyzed using Commercial Finite volume code. The fixed Reynolds number (Re.) 100 is selected for the present study. However, corner radius to diameter ratio, R/D = 0 to 0.5 and L/D = 1.5 to 7.5 spacing between two cylinders is used as a varying parameter. The flow visualization parameters, the drag and lift coefficients are comprehensively presented and compared for different cases in order to reveal the effect of corner radius and gap spacing on the behavior of the flow. The obtained results have shown that flow aerodynamic characteristics are strongly influenced by cylinders rounded corners and spacing. It was also found that the total drag force can be reduced for the downstream cylinder when cylinders are placed within L/D ≤ 4.5.

Prediction of wake structure and aerodynamic characteristics of flow around square cylinders at different arrangements

2019 ◽  
Vol 30 (02n03) ◽  
pp. 1950015 ◽  
Author(s):  
Salwa Fezai ◽  
Fakher Oueslati ◽  
Nader Ben-Cheikh ◽  
Brahim Ben-Beya
Keyword(s):  
Reynolds Number ◽  
Strouhal Number ◽  
Vortex Shedding ◽  
Aerodynamic Characteristics ◽  
Physical Parameters ◽  
Drag And Lift Coefficients ◽  
Square Cylinders ◽  
Drag And Lift ◽  
Incompressible Fluid Flows ◽  
Obstacle Geometry

Two-dimensional incompressible fluid flows around square cylinders at different arrangements have been numerically analyzed in the present work. The calculations are carried out for several values of Reynolds number (Re) ranging from 20 to 180. The results are presented in the form of vorticity contours and temporal histories of drag and lift coefficients. Besides, the physical parameters, namely, the average drag and lift coefficients and Strouhal number, are evaluated as a function of Re. Two different states of flow are predicted in the current investigation by systematically varying Re for steady and unsteady regimes. Vortex shedding is studied at different arrangements of the square cylinders allowing the investigation of three possible configurations. Special attention is paid to compute the drag and lift forces acting on the different obstacles, which allowed determining the optimal configuration in terms of both drags and lifts. The unsteady periodic wake is characterized by the Strouhal number, which varies with the Reynolds number and the obstacle geometry. The values of vortex shedding frequencies are consequently calculated in this study.

Flow features of three side-by-side rectangular cylinders under the effect of aspect ratios and Reynolds numbers

2020 ◽  
pp. 2150034
Author(s):  
Hamid Rahman ◽  
Waqas Sarwar Abbasi ◽  
Shams-ul-Islam ◽  
Raees Khan ◽  
Muhammad Uzair Khan
Keyword(s):  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Physical Parameters ◽  
Drag And Lift Coefficients ◽  
Fluid Forces ◽  
Aspect Ratios ◽  
Flow Features ◽  
Drag And Lift ◽  
Boltzmann Method ◽  
Rectangular Cylinders

This study focuses on the characteristics of flow past three side-by-side rectangular cylinders under the effect of aspect ratios (AR) and Reynolds numbers (Re) at two different gap ratios ([Formula: see text]) using the lattice Boltzmann method. For this purpose, AR is varied in the range of 0.25–4, the Re values are 100, 140 and 180 and the two different values of [Formula: see text] taken into account are [Formula: see text] and 3. The results are presented in the form of vorticity contours, temporal histories of drag and lift coefficients and power spectrum of lift coefficients. Also, the variation of physical parameters like mean drag coefficient, Strouhal number and the root-mean-square values of drag and lift coefficients with Re and AR is presented for [Formula: see text] and 3. The current numerical computations yield that for both gap ratios and all Re, there exist four different flow regimes depending on AR: (a) steady flow, (b) modulated flow, (c) symmetric flow and (d) periodic flow. At narrow gap ratios, the jet flow emerging within the gaps of cylinders altered the flow structures and fluid forces abruptly. The aspect ratio is found to have more influence on the flow characteristics of cylinders as compared to the Reynolds numbers at large gap ratios.

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