Wavy Walls, a Passive Way to Control the Transition to Turbulence. Detailed Simulation and Physical Explanation

Inducing spanwise motions in the vicinity of solid boundaries alters energy, mass and/or momentum transfer. Under some conditions, these are such that drag is reduced transition to turbulence delayed. There several possibilities induce those motions, be it through active imposition a predefined velocity distribution at walls or by careful design wall shape, which corresponds passive control.In this contribution, we investigate effect wavy might have on delaying turbulence. Direct Numerical Simulation both planar and wavy-walled channel flows laminar turbulent regimes conducted. A pseudo regime remains stable until Reynolds number 20% higher critical found for simulations. Dynamic Mode Decomposition applied simulation data reveals configurations, modes with wavelength frequency compatible surface undulation pattern appear. We explain visualize appearance modes. At numbers show remain present but not dominant anymore. This work an initial demonstration flow control strategies trigger underlying can keep conduct new configurations more than original one.