Bubble-injection methods are considered to be a prospective approach to reduce skin-frictional drag for ships. To apply this technique for unsteady flows, we attempt to introduce a feedback loop of air injection in future applications. Hence, we wish to establish reduced order models of unsteady bubbly flows from the information at the bottom of the ship, but this must be achieved with a limite...

A simple, scalable, non-lithographic, technique for fabricating durable superhydrophobic (SH) surfaces, based on the fingering instabilities associated with non-Newtonian flow and shear tearing, has been developed. The high viscosity of the nanotube/elastomer paste has been exploited for the fabrication. The fabricated SH surfaces had the appearance of bristled shark skin and were robust with r...

Hypersonic flows of nitrogen, oxygen, argon, and carbon dioxide near a toroidal ballute have been investigated numerically using the Direct Simulation Monte-Carlo technique under transition rarefied-gas flow conditions (Knudsen numbers from 0.005 to 10). Strong influences of the geometrical factor (a ratio of the distance between the axis of symmetry and the torus disk center, and the torus rad...

Heat transfer in a porous medium over a stretching surface with internal heat generation and suction or injection has been analyzed numerically in the presence of radiation. In this analysis, the governing equations are transformed into a system of ordinary differential equations and solved them numerically using Nachtsheim-Swigert shooting iteration technique. The local similarity solutions fo...

Light scattering was used to measure the time-dependent loss of air entrapped within a submerged microporous hydrophobic surface subjected to different environmental conditions. The loss of trapped air resulted in a measurable decrease in surface reflectivity and the kinetics of the process was determined in real time and compared to surface properties, such as porosity and morphology. The ligh...

A comprehensive study of thermal radiation on a steady two-dimensional laminar flow of a viscous incompressible electrically conducting micropolar fluid past a stretching surface embedded in a non-Darcian porous medium is analyzed numerically. The governing equations of momentum, angular momentum, and energy equations are solved numerically using RungeKutta fourth order method with shooting tec...

As air is injected into a flowing liquid, the resultant bubble characteristics depend on the properties of the injector, near-wall flow, and flowing liquid. Previous research has shown that near-wall bubbles can significantly reduce skin-friction drag. Air was injected into the turbulent boundary layer on a test section wall of a water tunnel containing various concentrations of salt and surfac...

Related Articles Probing high-Reynolds-number effects in numerical boundary layers Phys. Fluids 25, 021704 (2013) Experimental study of skin friction drag reduction on superhydrophobic flat plates in high Reynolds number boundary layer flow Phys. Fluids 25, 025103 (2013) Study of instabilities and quasi-two-dimensional turbulence in volumetrically heated magnetohydrodynamic flows in a vertical ...

Aerodynamic drag force breakdown of a typical transport aircraft shows that lift-induced drag can amount to as much as 40% of total drag at cruise conditions and 80-90% of the total drag in take-off configuration. One way of reducing lift-induced drag is by using wing-tip devices. By applying several types of winglets, which are already used on commercial airplanes, we study their influence on ...

In Coulomb drag, a current flowing in one conductor can induce a voltage across an adjacent conductor via the Coulomb interaction. The mechanisms yielding drag effects are not always understood, even though drag effects are sufficiently general to be seen in many low-dimensional systems. In this Letter, we observe Coulomb drag in a Coulomb-coupled double quantum dot and, through both experiment...