Supercritical flows past a square cylinder with rounded corners

• Published in: Physics of fluids (1994) 2017-08, Vol.29 (8)
• Main Authors: Cao, Yong, Tamura, Tetsuro
• Format: Article
• Language: English
• Subjects: Aerodynamics; Boundary layer; Circular cylinders; Computational fluid dynamics; Computer simulation; Corners; Fluid dynamics; Fluid flow; Laminar flow; Large eddy simulation; Mathematical models; Numerical methods; Physics; Pressure gradients; Reynolds number; Separation; Simulation; Subcritical flow; Turbulent boundary layer; Variation; Vortex shedding; Wall pressure
• ISSN: 1070-6631; 1089-7666
• DOI: 10.1063/1.4998739

Large-eddy simulations were used to investigate the supercritical aerodynamics of a square cylinder with rounded corners in comparison with those in the subcritical regime. First, the numerical methods, especially the dynamic mixed model, were validated on the basis of their prediction of supercritical flows past a circular cylinder. Then, the supercritical flows past a rounded-corner square cylinder were simulated and systematically clarified. Strong Reynolds number (Re) effects existed in the forces and local pressures as Re increased from o(104) to o(106). Changeover of flow patterns occurred as Re increased. At the supercritical Re, the free stream overall flowed along the cross sections of the cylinder, separated from the leeward corners and generated Karman vortices behind the cylinder. This pattern resulted in a much smaller recirculation region behind the cylinder compared with the subcritical flow. At the micro level, the flow experienced laminar separation and flow reattachment near the frontal corners, followed by the spatial development of turbulent boundary layers (TBLs) on the side faces and turbulent separation near the leeward corners. The feedback by large-scale primary vortex shedding and the small-scale turbulent motions in the high-frequency region with a slope of −5/3 were detected in the TBL. Their interaction affected the spanwise correlations of wall pressure fluctuations. The TBL on the side face differed from the zero-pressure-gradient flat-plate one; it was subjected to pressure gradients varying in space and time.