This paper investigates the effects of local porous uniform blowing on skin-friction drag reduction in spatially developing compressible turbulent boundary layers through direct numerical simulations. Under influence blowing, decreases drastically within controlled regions, and effect extends downstream. The rate exceeds 10% for velocities considered herein. intrinsic mechanism decreased is fur...

Three different polysaccharides, aloe vera, Tamarind powder and pineapple fibers, are utilized as drag reducing agents in a turbulent flow. Using a Taylor–Couette setup, consisting of a rotating inner cylinder, for measuring the drag reduction, a range of Reynolds numbers from 4 × 104 to 3 × 105 has been explored in this study. The results are in good agreement with previous studies on polysacc...

Drag reduction (DR) agents are used in several ppm concentrations to accelerate significantly the flow through conduits in oil pipelines, oil well operations, flood water disposal, fire fighting, field irrigation, transport of suspensions and slurries, sewage systems, water heating and cooling systems, airplane tank filling, marine systems, and also in biomedical systems including blood flow. T...

Recent measurements revealed an anomalous Coulomb drag in graphene, hinting at new physics at charge neutrality. The anomalous drag is explained by a new mechanism based on energy transport, which involves interlayer energy transfer, coupled to charge flow via lateral heat currents and thermopower. The old and new drag mechanisms are governed by distinct physical effects, resulting in starkly d...

It is well known that a splash occurs when an object impacts at high velocity on a liquid’s surface. If the impact is fast enough, surface tension and air pressure gradients pull the crown-shape splash all the way towards the axis of symmetry, making it to collapse and seal the surface. In this paper we show that splash and surface sealing are also observed in impacts on soft, dry sand. We obse...

Reduction in surface shear stress in turbulent boundary layers implies suppression of turbulent momentum flux, a large-eddy phenomenon. The physics by which dilute concentrations of long-chain molecules alter large-eddy structure and momentum flux is not well understood. Experiment, however, indicates an essential mix of turbulent velocity fluctuations, polymer molecules, and mean shear. We stu...

This study experimentally and numerically investigated the hydrodynamic characteristics of a 180° curved open channel over rough bed under condition constant downstream water depth. Three different sizes particles (the small, middle big cases based upon grain size diameter D50) were selected for flume tests. Three-dimensional instantaneous velocities obtained by acoustic Doppler velocimeter (AD...

Experiments were carried out to determine the strain energy capacity and breaking strain of spider drag-line silk. These properties are discussed in terms of a mathematical model of a spider falling on a drag-line. It was found that the strain energy capacity of the drag-line was insufficient to absorb the potential energy lost by a falling spider and that in order to avoid failure of the drag-...

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...