Fluid Drag Reduction by Magnetic Confinement

Abstract

The frictional forces of a viscous liquid flow are a major energy loss issue and severely limit microfluidics practical use. Reducing this drag by more than a few tens of percent remain elusive. Here, we show how cylindrical liquid−in−liquid flow leads to drag reduction of 60−99% for sub-mm and mm-sized channels, regardless of whether the viscosity of the transported liquid is larger or smaller than that of the confining one. In contrast to lubrication or sheath flow, we do not require a continuous flow of the confining lubricant, here made of a ferrofluid held in place by magnetic forces. In a laminar flow model with appropriate boundary conditions, we introduce a modified Reynolds number with a scaling that depends on geometrical factors and viscosity ratio of the two liquids. It explains our whole range of data and reveals the key design parameters for optimizing the drag reduction values. Our approach promises a new route for microfluidics designs with pressure gradient reduced by orders of magnitude.

Drag Reduction Related to Boundary Layer Control in Transportation of Heavy Crude Oil by Pipeline: A Review

“…156 The idea of magnetic fluid DR is as follows: under the action of the external magnetic field, the magnetic fluid is attached to the inner wall of the pipe, and the flexible boundary interface is used to replace the rigid boundary interface, which makes the boundary surface fluctuate synchronously with the flow of the fluid, resulting in the change of velocity distribution in the laminar boundary layer. 154 When the velocity on the surface of the boundary layer is greater than zero, the velocity gradient on the boundary surface decreases, thus reducing the shear force on the boundary surface and the energy consumed by the shear force, to achieve the purpose of DR. Sun et al 157 built a set of experimental facilities based on drag reduction of magnetic fluid consisting of a liquid container, magnets, a plexiglass pipe with a length of 800 mm and an inner diameter of 40 mm. Nd−Fe−B magnet is used to generate an external magnetic field outside the pipeline, and the experimental fluid is silicon oil.…”

“…152 Dunne et al 153 pointed out that the use of magnetic fluid can create an almost frictionless liquid−liquid channel in which water flows in the center of the pipe and avoids direct contact with the solid wall (see Figure 18). Dev et al 154 reported that the drag of ferromagnetic fluid in a microchannel (submillimeter or millimeter) liquid flow is reduced by 60% to 99%, and the process is not affected by the viscosity of the transported liquid, which means that this technology is suitable for both light and heavy oil. At present, magnetic fluid has been successfully prepared under laboratory conditions, which has been widely utilized in the fields of machinery, aerospace DR, and has potential application value in the fields of medicine, chemical industry, fluid transport and other fields.…”

Effects of the Yaw Angle on Air Drag Reduction for Various Riblet Surfaces

“…Reduction of fluid resistance is of significance to increasingly emerging energy and environmental issues. − Turbulence is the major source of fluid resistance in many cases and has attracted extensive attention. − Hence, research into drag reduction has focused on methods to depress turbulence near walls. − Biomimetic riblet surfaces, such as blade, wavy, sinusoidal, and herringbone riblet (Blade, Wavy, Sinusoidal, and Herringbone, respectively) surfaces, inspired by sharks and birds have achieved significant reductions in turbulent drag reduction. Blade surfaces have been proven to provide obvious drag reduction, and they have shown promise for many potential applications in the pipeline, aircraft, energy, and transportation industries. ,− …”