Aircraft viscous drag reduction using riblets

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,...

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

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...

Viscous Drag Reduction with Surface-Embedded Grooves

Turbulent drag reduction in wall-bounded flows is investigated experimentally by considering the dynamic effects provoked by large variation of anisotropy in the velocity fluctuations. It is shown that high drag reduction is obtained when the velocity fluctuations near the wall reach the statistically axisymmetric state with invariance under rotation about the axis aligned with the mean flow. D...