Air drag on yarn and package surfaces affects yarn tension, which in turn affects energy consumption and ends-down in ring spinning. This paper investigates the effects of yarn hairiness on air drag in ring spinning. Theoretical models of skin friction coefficient on the surface of rotating yarn packages were developed. The predicted results were verified with experimental data obtained from co...

The quest for reductions in fuel consumption and CO2 emissions transport has been a powerful driving force scientific research into methods that might underpin drag-reducing technologies variety of vehicular on roads, by rail, the air, or water. In civil aviation, skin-friction drag accounts around 50% total cruise conditions, thus being preferential target research. With laminar conditions exc...

Skin friction drag contributes a major portion of the total drag for small and large water vehicles at high Reynolds number (Re). One emerging approach to reducing drag is to use superhydrophobic surfaces to promote slip boundary conditions. However, the air layer or "plastron" trapped on submerged superhydrophobic surfaces often diminishes quickly under hydrostatic pressure and/or turbulent pr...

A model for minimizing the effects of skin drag and pressure drag is constructed. We show that a simple scaling technique can be used to transform a dual, constrained minimization problem into a volume constrained surface area minimization. We discuss some successes and failures with implementing numerical methods for the problem.

The computation of boundary layer properties and laminar-to-turbulent transition location is a very complex problem, generally not undertaken in the context of aircraft design. Yet if an aircraft is to exploit the advantages of laminar flow and proper trade-offs between inviscid drag, structural weight, and skin friction are to be made, this is just what must be done. This paper summarizes a de...

Although the success of compliant walls in mimicking dolphin skin is well known, the drag-reducing properties of a dolphin's skin are still unclear. Moreover, little is known about the relation between the 3D structure of the skin and the local flow conditions. To study the role of a dolphin's skin in reducing the drag the skin morphology parameters were compared with the parameters of an aniso...

Hypersonic rareŽ ed-gas  ows near two side-by-side plates have been studied numerically with the direct simulationMonte Carlo technique under transitional rareŽ ed-gas- ow conditions (Knudsen numbers from 0.024 to 1.8). Strong in uences of the geometrical factor (ratio of distance between plates to plate length) and the Knudsen number on the  ow structure (the shape of shock waves, the conŽ...

Drag analysis is vital to measure the performance of the autonomous underwater vehicle (AUV) as well as the AUV thruster. Most of the previous drag studies is regarding to the shape and swimming method that contribute to the AUV performance. However, few attention was given on drag which influence the development of thruster. Hence, this research was conducted to analyze the drag of the micro A...

Wall-roughness induces extra drag in wall-bounded turbulent flows. Mapping any given roughness geometry to its fluid dynamic behaviour has been hampered by the lack of accurate and direct measurements skin-friction drag. Here Taylor-Couette (TC) system provides an opportunity as it is a closed allows directly reliably measure skin-friction. However, wall-curvature potentially complicates connec...