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.

Numerical study of the rounded corners effect on flow past a square cylinder

2015 ◽  
Vol 25 (4) ◽  
pp. 686-702 ◽  
Author(s):  
Sajjad Miran ◽  
Chang Hyun Sohn
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Strouhal Number ◽  
Lift Coefficient ◽  
Numerical Results ◽  
The Body ◽  
Square Cylinder ◽  
Content Type ◽  
Flow Past ◽  
Corner Radius

Purpose – The purpose of this paper is to numerically investigate the influence of corner radius on flow past a square cylinder at a Reynolds number 500. Design/methodology/approach – Six models were studied, for R/D=0 (square cylinder), 0.1, 0.2, 0.3, 0.4, and 0.5 (circular cylinder), where R is the corner radius and D is the characteristic dimension of the body. The transient two-dimensional (2D) laminar and large eddy simulations (LES) models were employed using finite volume code. The Strouhal number, mean drag coefficient (CD), and root mean square (RMS) value of lift coefficient (CL,RMS), for different R/D values, were computed and compared with experimental and other numerical results. Findings – The computational results showed good agreement with previously published results for a Reynolds number, Re=500. It was found that the corner effect on a square cylinder greatly influences the flow characteristics around the cylinder. Results indicate that, as the corner radius ratio, R/D, increases, the Strouhal number increases rapidly for R/D=0-0.2, and then gradually rises between R/D=0.2 and 0.5. The minimum values of the mean drag coefficient and the RMS value of lift coefficient were found around R/D=0.2, which is verified by the time averaged streamwise velocity deficit profile. Originality/value – On the basis of the numerical results, it is concluded that rounded corners on a square cylinder are useful in reducing the drag and lift forces generated behind a cylinder. Finally, it is suggested that with a rounded corner ratio of around R/D=0.2, the drag and oscillation of the cylinder can be greatly reduced, as compared to circular and square cylinders.

Pressure-driven flow past spheres moving in a circular tube

2007 ◽  
Vol 592 ◽  
pp. 233-262 ◽  
Author(s):  
G. J. SHEARD ◽  
K. RYAN
Keyword(s):  
Reynolds Number ◽  
Pressure Gradient ◽  
Axial Force ◽  
Flow Rate ◽  
Circular Tube ◽  
Reynolds Numbers ◽  
Diameter Ratio ◽  
Tube Diameter ◽  
Flow Past ◽  
Pressure Driven Flow

A computational investigation, supported by a theoretical analysis, is performed to investigate a pressure-driven flow around a line of equispaced spheres moving at a prescribed velocity along the axis of a circular tube. This fundamental study underpins a range of applications including physiological circulation research. A spectral-element formulation in cylindrical coordinates is employed to solve for the incompressible fluid flow past the spheres, and the flows are computed in the reference frame of the translating spheres.Both the volume flow rate relative to the spheres and the forces acting on each sphere are computed for specific sphere-to-tube diameter ratios and sphere spacing ratios. Conditions at which zero axial force on the spheres are identified, and a region of unsteady flow is detected at higher Reynolds numbers (based on tube diameter and sphere velocity). A regular perturbation analysis and the reciprocal theorem are employed to predict flow rate and drag coefficient trends at low Reynolds numbers. Importantly, the zero drag condition is well-described by theory, and states that at this condition, the sphere velocity is proportional to the applied pressure gradient. This result was verified for a range of spacing and diameter ratios. Theoretical approximations agree with computational results for Reynolds numbers up toO(100).The geometry dependence of the zero axial force condition is examined, and for a particular choice of the applied dimensionless pressure gradient, it is found that this condition occurs at increasing Reynolds numbers with increasing diameter ratio, and decreasing Reynolds number with increasing sphere spacing.Three-dimensional simulations and predictions of a Floquet linear stability analysis independently elucidate the bifurcation scenario with increasing Reynolds number for a specific diameter ratio and sphere spacing. The steady axisymmetric flow first experiences a small region of time-dependent non-axisymmetric instability, before undergoing a regular bifurcation to a steady non-axisymmetric state with azimuthal symmetrym= 1. Landau modelling verifies that both the regular non-axisymmetric mode and the axisymmetric Hopf transition occur through a supercritical (non-hysteretic) bifurcation.

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