Computational simulation of the turbulent flow around a surface mounted rectangular prism

Engineering structures considered as bluff bodies are often associated with complex unsteady turbulent flow structures that are not yet fully understood and difficult to reproduce numerically. One of the main challenges is to find a numerical model that accurately account for turbulence in the flow without using too much computational resources. In this paper the Spalart-Allmaras improved delayed detached eddy simulation (IDDES) turbulence model with an all-y+ wall treatment is used to numerically reproduce the flow features around a rectangular cross-sectioned beam in a wind tunnel at a Reynolds number of 7.6×104. The beam is orientated with the long edge of the cross-section parallel to the flow and can be characterised by the ratios of L/D=2.63 and H/L=5. The simulation results are compared to time-averaged experimental data which includes particle image velocimetry (PIV) and pressure. The comparison of the simulation results against experimental data shows that the Spalart-Allmaras IDDES model accurately reproduces the flow field around the beam with only minor discrepancies. Furthermore, the complex time-varying three-dimensional flow field is discussed in detail. Alternating vortex shedding occurs but this seems to be periodically interrupted. The Strouhal number over the height of the beam was found to vary between 0.053 and 0.059 which corresponds well with studies of similar L/D ratios in the literature. The maximum cyclic loading was found to occur at a height of y=0.5H and along the side wall at 0.8L from the upstream edge of the beam.