Abstract Friction drag is a nonnegligible matter when relative motion happens between solid and liquid phase, which brings many inconveniences in ship navigation, fluid transportation, microfluid devices, etc. Thereby various methods have been developed focusing on friction reduction. In this article, review of several widely studied reduction given, specially, their advantages limitations prac...

surface. I n today’s cost-conscious air transportation industry, fuel costs are a substantial economic concern. Drag reduction is an important way to increase fuel efficiency and reduce these costs. Even a 5% reduction in drag translates into estimated savings of millions of dollars in annual fuel costs. Organized structures that play an important role in turbulence transport may cause large sk...

This paper presents the application of a neural network controller to the problem of active drag reduction in a fully turbulent 3D fluid flow regime. The neural network learns a function nearly identical to an analytically derived control law. We then demonstrate the ability of a neural controller to maintain a drag-reduced flow in a fully turbulent fluid simulation. Finally we examine the amou...

Hydrodynamic performance of a marine vessel mainly depends on the frictional and pressure resistance. Pressure drag reduction could be achieved by improving the shape of the vessels with implementation of modern hull forms. Hull forms optimization techniques could also be used for this purpose. Other techniques are needed to deal with the viscous portion of the total resistance, which is mainly...

Active drag reduction of an Ahmed model with a slant angle of 25o is experimentally investigated based on a combination of steady blowing over the rear window and behind the vertical base. The Reynolds number Re examined is 0.9 × 10 2.7 × 10. Steady blowing S1 was applied along the upper edge of the rear window, which has been demonstrated to be effective in suppressing the recirculation bubble...

Lubricant-impregnated surfaces (LIS), where micro/nanotextured surfaces are impregnated with lubricating liquids, have received significant attention for their robust, superslippery properties. In this study, we systematically demonstrate the potential for LIS to reduce drag in laminar flows. We present a scaling model that incorporates the viscosity of the lubricant and elucidates the dependen...

In turbulent Taylor-Couette flow, the injection of bubbles reduces the overall drag. On the other hand, rough walls enhance the overall drag. In this work, we inject bubbles into turbulent Taylor-Couette flow with rough walls (with a Reynolds number up to 4 x 10(5), finding an enhancement of the dimensionless drag as compared to the case without bubbles. The dimensional drag is unchanged. As in...