The effect of spanwise length on the near-field dynamics of flow past a cylinder using Large-Eddy Simulation

Abstract

Understanding of the turbulent flow generated by the flow past a bluff body, such as cylinder, is very pertinent to many modern engineering applications. This paper aims to investigate the effect of spanwise length of flow past a circular cylinder on the near-field aerodynamic characteristics at Re=10,000, using Large Eddy Simulation with the WALE subgrid-scale model. Four different spanwise lengths are considered for the computational domain, namely Lz=0.5πD, πD, 2πD and 4πD. For all cases, the pressure coefficient 𝑪 𝒑 , drag coefficient 𝑪 𝒅 , tone frequencies of PSD are predicted with a reasonable accuracy compared to experiments. The results have shown that changing the spanwise length of the LES case has very limited impact on the pressure coefficient 𝑪 𝒑 , the velocity PSD and the pressure PSD at different spanwise locations. The 𝑪 𝒑 𝒓𝒎𝒔 is overvalued by the LES, and the growth of the spanwise length Lz improves the agreement of the simulated 𝑪 𝒑 𝒓𝒎𝒔 with the experimental data. The spanwise pressure coherence is also analyzed. The spanwise pressure coherence value is observed to decrease with larger spanwise distances between probes. The LES cases with 2πD and 4πD spanwise lengths show relatively smaller coherence value and higher coherence decay rates, indicating they capture more three-dimensional flow features which is important for accurate prediction of the radiated noise of the flow.