Secondary vortices over spanwise heterogeneous roughness

Abstract eng:
A spanwise heterogeneity of roughness is known to lead to the formation of large-scale secondary motions. The secondary motions are investigated based on the data sets extracted from direct numerical simulations (DNS) of fully developed turbulent channel flow where streamwise stripes of modeled rough surface with varying spanwise extension and roughness layer thickness are introduced. In order to study the character of the secondary flow structures, the calculated flow fields are further post-processed by means of streamline-based topology analysis. The extracted topology maps indicate that stronger secondary motions occur for wider roughness stripes and thicker roughness layer, while the height of the roughness layer appears to not alter the secondary motion topology.

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