TC2 Square/Cube 2

Abstract

A numerical simulation of flow around rectangular 2-D prisms of different cross-sectional aspect ratios, ranging from 0.3 to 7.0, is conducted at a Reynolds number of 105. The large eddy simulation (LES) scheme is utilized to solve the 3-D Navier-Stokes equations using a finite volume method on a non-uniform grid, with the Smagorinsky closure model representing the subgrid scale viscosity. This study identifies the influence of aspect ratio on flow features of the velocity/pressure field, i.e., instantaneous vorticity/pressure contours, mean flow streamlines, mean/RMS pressure distribution around the prism, base pressure, mean/RMS drag/lift coefficients, spectral description of drag/lift time history, the associated wavelet based scalograms, wavelet instantaneous frequency spectra and the Strouhal number. Results exhibit salient features in the flow field and associated pressure/aerodynamic forces due to changes in the after body length, demonstrating good agreement with observations from wind tunnel experiments. Findings include identification of the critical depth/breadth ratio and fluctuations in the drag/lift forces, containing features that vary with aspect ratio. A time-frequency analysis is introduced to identify the transient nature of these fluctuations. Wavelet based signal processing schemes combined with instantaneous vorticity/pressure contours are utilized to further highlight temporal variations in the frequency contents of these fluctuations and their influence on the force coefficients.