Linear stability of 2D rough channels
Flow past rough walls have been deeply studied in the past, initially in laboratory experiments and recently by numerical simulations. In practical applications as for instance for flow over urban settlements or past wings, the flows are turbulent and the drag largely depends on the shape of the surfaces. In general the roughness produces a drag increase. However in particular conditions, for instance riblets, the drag may decrease. The comprehension of the flow physics near the roughness and their dependence on the shape of the surfaces can be understood by the numerical simulations also for the experimental evidence that the friction coefficient do not strongly depend on the Reynolds number.
In laboratory experiments difficulties are encountered to perform measurements near the rough elements (Burattini et al. 2008), that are absent in numerical simulations. The simulations, starting from that by Leonardi et al. 2003, in the last years increased the knowledge of the flow physics of fully turbulent flows. On the other hand, simulations of stability and transition regimes are lacking. The present work is devoted to analyse the variations of the critical Reynolds in channels with different kind of rough surfaces on a wall.
KeywordsDirect Numerical Simulation Linear Stability Critical Reynolds Number Smooth Wall Turbulent Regime
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