RANS feasibility study of using roughness to mimic transition strip effect on the crossflowseparation over a 6:1 prolate-spheroid

• DOI: 10.1007/s42241-019-0005-5
• Publication Date: 2019-01-09T13:27:24Z
• Authors: Mojtaba M. Amiri; Marcelo A. Vitola; Sergio H. Sphaier; Paulo T. Esperança
• Keywords: Separation (statistics); Reynolds stress

An axisymmetric body at incidence experiences the three-dimensional crossflow separation. This separation is attributed to the adverse circumferential pressure gradient. However, the separation pattern is also dependent upon the structure of the boundary layer. In this regard, utilization of transition strip devices in experiments on axisymmetric bodies may modify this structure, and consequently the crossflow separation pattern. The main objective of the present research is to mimic numerically the transition strip effect on the crossflow separation over a 6:1 prolate-spheroid up to α = 30° incidence and ReL = 4.2×106. However, to avoid direct modeling of the strip, which would increase the computational cost, an attempt was made to add roughness over the body surface. To estimate the roughness that simulates closely the transition strip effect, three different roughness values were considered. The numerical model is based on RANS and a Reynolds stress turbulence model implemented in STARCCM+. The simulations have been evaluated based on the local and global variables and validated against the available experimental data. The results demonstrate the effectiveness of using a proper roughness value to mimic the transition strip effect. They also show the importance of modeling the transition strip effect, which is normally not considered, to capture the crossflow separation pattern.