Numerical investigation of the surface roughness effects on the subsonic flow around a circular cone-cylinder

Abstract

The flow around a circular-cone is 3D, unsteady and turbulent. As reported in many research works on this type of flow, boundary layer separations, vortex structures and the effect of surface roughness are strongly related. The effect of roughness is still not completely understood and proves challenging both for numerical and experimental approaches. The present work aims to gain more insights in understanding and numerically predicting this type of flows. Particularly, it attempts to improve the accuracy of numerical predictions of the effects of roughness on the asymmetric vortex flow around a circular-cone at subsonic flow conditions. This is performed using numerical simulations, which predict the flow field details across different transversal stations along the cone. Therefore, we have analyzed the effect of many turbulence models, notably, the transition SST, using ANSYS Fluent code. Flows characteristics are highlighted and validated against the well-known theory and some experimental measurements. The findings depict that a surface roughness height about 0.32 mm has efficaciously triggered the boundary layer to change from a laminar to a fully turbulent state in both sides of the body, in addition to a significant reduction in the global lateral force. Moreover, it seems that the roughness reduces the asymmetry of the vortex in the leeward side of the cone. Testing many roughness heights has allowed us to determine the way in which it is possible to reduce the side force effectively at high angles of attack without affecting the lift of the cone cylinder.