

Article
Influence of corner geometry on the secondary flow in turbulent square ducts
Authors: 
Vidal, A V, Vinuesa, R., Schlatter, P., Nagib, H.M. 
Document Type: 
Article 
Pubstate: 
Published 
Journal: 
International Journal of Heat and Fluid Flow 
Volume: 
67
6978 
Year: 
2017 
AbstractDirect numerical simulations of fullydeveloped turbulent flow through a straight square duct with increasing corner rounding radius r were performed to study the influence of corner geometry on the secondary flow. Unexpectedly, the increased rounding of the corners from r = 0 to 0.75 does not lead to a monotonic trend towards the pipe case of r = 1. Instead, the secondary vortices relocate close to the region of wallcurvature change. This behavior is connected to the inhomogeneous interaction between nearwall bursting events, which are further characterized in this work with the definition of their local preferential direction. We compare our results with those obtained for the flow through a square duct (which corresponds to r = 0) and through a round pipe (r = 1), focusing on the influence of r on the wallshear stress distribution and the turbulence statistics along the centerplane and the corner bisector. The former shows that highspeed streaks are preferentially located near the transition between straight and curved surfaces. The Reynolds numbers based on the centerplane friction velocity and duct halfheight are Re_tau,c = 180 and 350 for the cases under study.

