Microshape Control, Riblets, and Drag Minimization

Towards Large Eddy Simulations of Turbulent Drag Reduction Using Sinusoidal Riblets

A new modification to the drag reduction method using riblets is proposed, which consists of adding a sinusoidal variation to the riblet shape in spanwise direction. It is anticipated that more significant drag reduction will be achieved with sinusoidal riblets due to an oscillatory spanwise component added to the mean flow. First, Large Eddy Simulations of conventional riblet geometry consisti...

Energy Amplification of Streamwise Constant Channel Flow Over Riblets

Riblets have been used as a passive method of reducing the drag of a fluid flowing over an airfoil. Riblets are structures that run parallel to one another that are positioned longitudinally to the flow. It has been shown experimentally that the drag coefficients over the surface can be reduced by up to 10% when the shape, spacing and height of the riblets are optimized. However, the mechanism ...

Drag reduction: enticing turbulence, and then an industry.

We examine drag-reduction proposals, as presented in this volume and in general, first with concrete examples of how to bridge the distance from pure science through engineering to what makes inventions go into service; namely, the value to the public. We point out that the true drag reduction can be markedly different from an estimate based simply on the difference between turbulent and lamina...

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

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(...