Small drag-reducing riblets and larger drag-increasing ridges are longitudinally invariant laterally periodic surface structures that differ only in the details of their lateral periodicity size viscous units. Due to different drag behaviour, typically have been analysed separately. By studying experimentally trapezoidal-grooved surfaces sizes, we address systematically transition from riblet-l...

Recent work in bio-fluid dynamics has studied the relation of fluid drag to flow speed for flexible organic structures, such as tree leaves, seaweed, and coral beds, and found a reduction in drag growth due to body reconfiguration with increasing flow speed. Our theoretical and experimental work isolates the role of elastic bending in this process. Using a flexible glass fiber wetted into a ver...

We present the results of an investigation of the drag force on a horizontal grid of bars moving vertically through a stratified fluid. A novel approach was used to calculate the drag, based on measurements of the terminal velocity of a freely rising grid. In the homogeneous case the drag coefficient of the grid is found to be approximately constant for a range of grid-based Reynolds numbers. I...

This paper investigates the influence of two crossovers on twin bare spheroids in close proximity. Firstly, to examine the impact of the crossovers to the flow behaviour and overall drag coefficient of spheroids. Secondly, to compare the drag coefficient for various speeds. The CFD RANS-SST with a commercial code ANSYS CFX simulation is performed for the fully submerged twin spheroids with tran...

A method is described for measuring the local drag coefficient on a long cylinder which exhibits vortex-induced vibration (VIV). Results are shown from a field experiment in which a long flexible pipe was instrumented with two-hundred and eighty fiber optic strain gauges. The measured local drag coefficients are compared to a commonly used drag coefficient prediction formula. The formula is sho...

Motor cycle accidents have been increased for the past two decades. Helmet can protect the vehicle riders from severe injuries during road accident to certain extent. To design a functional helmet, it is important to analyze the shape of the helmet and visor portion. Hence, an attempt has been made for design and analysis of new helmet by considering the drag pressure and anti-glare visor. The ...

This study presents experiments related to the role of solvent drag and solute drag in the transmembrane movement of nonelectrolytes in a perfused rat intestine preparation. Conditions were chosen to simulate the effects of luminal hyperosmolarity on the permeability of tracer solutes. Data are presented on net water flux, transepithelial potentials, and lumen-to-blood and blood-to-lumen tracer...

with speed increasing in high-speed trains, due to limitations of other types of brakes, aerodynamic brake has become an important braking method. in this task to make better use of brake’s panel different configurations are examined and the best panel shape which provides the reasonable drag coefficient is introduced. the results of simulations are carried out with the computational fluid dyna...

Tangential and normal velocity profiles of the boundary layer surrounding live swimming fish were determined by digital particle tracking velocimetry, DPTV. Two species were examined: the scup Stenotomus chrysops, a carangiform swimmer, and the smooth dogfish Mustelus canis, an anguilliform swimmer. Measurements were taken at several locations over the surfaces of the fish and throughout comple...

We study the drag force on discrete objects with circular cross section moving slowly through a spherical granular medium. Variations in the geometry of the dragged object change the drag force only by a small fraction relative to shape effects in fluid drag. The drag force depends quadratically on the object's diameter as expected. We do observe, however, a deviation above the expected linear ...