Experimental and Numerical investigation of flow structures behind Bluff Bodies in Tandem Arrangement

Abstract

Flow structures attracted scientist since many decades. When a fluid flows around a bluff body or an object moves within a fluid at different Reynolds numbers different flow regimes can be observed. The flow properties plays great importance in analysis of different applications. These properties either calculated with numerical or experimental techniques. Experimental studies are time consuming and more expensive. Developments in computers enabled scientist to analyse and simulate almost all flow conditions easily. But always these results must be compared with experimental results to have more healty conclusions. In this study flow properties such as instantaneous velocity, normalized velocity and incoherent flow structures analyzed numerically behind two normal flat plates in tandem arrangement at six different gap ratios. Reynolds Stress Model versus Two-Equation Shear Stress Transport model compared effectively for different gap ratios. Also results of double tandem plates and square cylinder were examined. Computational Fluid Dynamics (CFD) codes ANSYS/FLUENT 13.0® was used to simulate the flow around the normal flat plates. The equations of shear stress transport model and Reynolds Stress Model (RSM) were considered as solution techniques. But since, the validity of any theoretical prediction can only be assessed in practice, the comparison was done between numerical data and achieved data from the experiments, for both cases based on literature. The experiments were done on an open type sub-sonic wind tunnel at Reynolds number of 33000 with turbulence intensity around 0.5-0.8%. The effects of gap ratio on the flow characteristics were tested for tandem arrangements. Experimental errors, high cost equipment and spending too much time on testing, result in fulfilling the problem by CFD processes. These numerical methods compared with experimental results to justify the effects of different turbulence model.