Correction: Efficient Optimization of Riblets for Drag Reduction over the Complete Mission Profile

Drag reduction by riblets.

The interaction of the overlying turbulent flow with riblets, and its impact on their drag reduction properties are analysed. In the so-called viscous regime of vanishing riblet spacing, the drag reduction is proportional to the riblet size, but for larger riblets the proportionality breaks down, and the drag reduction eventually becomes an increase. It is found that the groove cross section A(...

Superposition of drag reduction due to riblets on drag reduction due to polymers

Optimal microstructures. Drag reducing mechanism of riblets

We consider an optimal shape design problem of periodically distributed three-dimensional microstructures on surfaces of swimming bodies in order to reduce their drag. Our model is restricted to the flow in the viscous sublayer of the boundary layer of a turbulent flow. There the flow is described by the incompressible steady-state Navier-Stokes equation with a Couette Flow profile. Because of ...

Microshape Control, Riblets, and Drag Minimization

Relying on the rugosity effect, we analyse the drag minimization problem in relation with the micro-structure of the surface of a given obstacle. We construct a mathematical framework for the optimization problem, prove the existence of an optimal solution by Γ-convergence arguments and analyse the stability of the drag with respect to the micro-structure. For Stokes flows we justify why rugosi...

viscous drag reduction on axisymmetric bodies using helical riblets

a series of subsonic wind tunnel tests was conducted on an ogive-cylinder-flare configuration at zero angle of attack to study the effects of small helical protuberances on viscous drag reduction behavior. the experiments have been carried out on a smooth model and two wire-wrapped models with different spacing between the helical riblet rings, known as pitch length. in the present experiments,...