Research on Reynolds number effect of bluff bodies based on aerodynamic parameter identification techniques

In order to reveal the mechanisms causing and influencing the Reynolds number effect with limited experimental data, the key is to identify some aerodynamic parameters for representing the Reynolds number effect efficiently. Based on the series of Reynolds number tests of a circular cylinder model, the key parameters associating with boundary-layer separation, transition and vortex shedding were proposed and corresponding identification methods were discussed. For a circular cylinder, some physical information regarding boundary-layer separation and flow transition can be derived from the pressure coefficient time histories and pressure gradient distributions. It is found that in the particular critical regime, the pressure coefficient time histories show strong instability near the separation point with the occurrence of pressure jumps, resulting in large magnitude of pressure gradient, which can be used for recognizing the flow transition indirectly. Finally, to investigate the advection features of dominant vortex structures at various Re numbers, the spectral proper transformation (SPT) technique was utilized to identify the vortex structures and evaluate their energy contribution to the pressure field, which has been introduced and demonstrated some potentials to study the Reynolds number effect of bluff bodies with similar geometries. © 2016, Science Press. All right reserved.