DNS OF TURBULENT FLOW IN A ROD-ROUGHENED CHANNEL

By Alireza Ashrafian, Helge I. Andersson, Michael T. Manhart. Proceeding of Third Symposium on Turbulence and Shear Flow Phenomena, 2004

159 citations recorded by the source corpus.

Abstract A numerical investigation has been performed to study pressure-driven turbulent flow in a rod-roughened channel at Reynolds number Re τ =400 based on the mean pressure-gradient. Both channel walls were roughened by square rods with a height k of only 1.7% of the channel height or k + =13.6 in wall units. The pitch-to-height ratio was 8, which corresponds to the so-called “ k -type” roughness and the resulting flow field was classified as “transitionally rough”. The Reynolds-averaged streamline pattern exhibited two co-rotating vortices which filled the cavity between two consecutive rods. The averaged flow field which separated from one rod did not reattach and a return flow was observed all along the bottom of the cavity. Outside the roughness sublayer, i.e. beyond 5 k , no discernible streamwise variation of the mean velocity and second-order statistics could be observed, whereas the correlation between the streamwise and wall-normal mean velocity components persisted somewhat further away from the surface. Inside the roughness sublayer, however, significant differences in the turbulence field between smooth- and rough-wall layers were observed, for instance the high-energy region formed by the shear layer emanating from the crest of the roughness elements. Visualizations of instantaneous flow fields revealed the presence of elongated streaky structures similar to those routinely observed in flows along a smooth surface.

Subfields: Computational Mechanics, Mechanical Engineering

View Paper: https://www.semanticscholar.org/paper/97a8b0498647bb9314bb15df57cc584f9c5521dc

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Citations in the corpus

Direct numerical simulation of the turbulent boundary layer over a rod-roughened wall (2007, methodology): “For example, a DNS study by Ashrafian et al. (2004) of turbulent channel flow with the same two-dimensional rod-roughened wall used the roughness height of h/k = 29.4 and 5ks = 0.82h, where h is the channel half-width.”
An experimental and numerical study of channel flow with rough walls (2005, background): “The DNS shows that above y/h > 0.17 the mean velocity profiles are virtually independent of streamwise position (Ashrafian et al. 2004).”
DNS of turbulent channel flows with two- and three-dimensional roughness (2006, background): “Other groups, Miyake et al. [13] and Ashrafian and Anderson [14], performed simulations of turbulent flow past square bars.”
Effect of Roughness on Wall-Bounded Turbulence (2004, methodology): “Ashrafian and Andersson [10] obtained U+ of 7.”
Effect of wall-boundary disturbances on turbulent channel flows (2006, result): “Both figures are consistent with previous results obtained over rough walls in experiments (Bakken et al. 2005; Poggi et al. 2003) and in numerical simulations (Ashrafian et al. 2004; Leonardi et al. 2003; Orlandi et al. 2003).”
Direct numerical simulation of the turbulent boundary layer over a cube-roughened wall (2010, result): “(2005) compared the experimental results of Bakken & Krogstad (2005) for turbulent flow in a symmetric channel with the results obtained by Ashrafian et al. (2004) in a DNS of the same height of a rod roughness. They observed good agreement between the experimental and simulation results, with both ”
Direct simulations of a rough-wall channel flow (2007, background): “On the other hand, the observation by Ashrafian & Andersson (2003) on the momentum fluxes near a rib-roughened wall shows that the dispersive term could be significant over several roughness heights, while the roughness height in their simulation is relatively low, 13.6 wall units.”