Predictions of the spatial representation instantaneous wall-bounded flows, via coherent structure-based models, are highly sensitive to geometry representative structures employed by them. In this study, we propose a methodology extract three-dimensional (3-D) statistically significant eddies from multi-point wall-turbulence datasets, for direct implementation into these models improve their p...

The paper presents Large Eddy Simulations of plane channel flow at a friction Reynolds number of 180 and 395 with a block-structured Finite Volume method. Local grid refinement near the solid wall is employed in order to reduce the computational cost of such simulations or other simulations of wall-bounded flows. Different subgrid-scale models are employed and different expressions for the leng...

An experimental study was carried out to investigate the effect of local ultrasonic forcing on a turbulent boundary layer. The ultrasonic forcing system was constructed by adhering six ultrasonic transducers to a flat plate over which water was flowed. In this system, the ultrasonic waves projected into the water by the transducers caused cavitation, giving rise to an enormous number of tiny ai...

Flow and thermal convection in heat exchangers can be affected by variations in viscosity. In circular pipes the significance of this effect was expressed by Sieder and Tate’s empirical formula. Similar correction can be derived for other heat transfer problems. Exact solutions for heat transfer during the non-isoviscous laminar flow of Newtonian and non-Newtonian liquids in circular and flat d...

In the present study, non-Newtonian flow in annular pipe is considered. The analytical solution for velocity and temperature fields is presented while entropy generation due to fluid friction and heat transfer is formulated. The third grade fluid with constant properties is accommodated in the analysis. It is found that reducing non-Newtonian parameter increases maximum velocity magnitude and m...

Direct numerical simulation of turbulent channel flow over a compliant surface has been performed to evaluate the friction drag reduction effect. It is found that a slight drag reduction is observed over a compliant surface. This observation indicates that drag reduction is possible using a compliant surface that is deformed passively by wall pressure fluctuation. A small wall displacement and ...

A new adaptive controller based on a neural network was constructed and applied to turbulent channel ow for drag reduction. A simple control network, which employs blowing and suction at the wall based only on quantities measured at the wall, was shown to reduce the skin friction by as much as 20% in direct numerical simulations of low-Reynolds number turbulent channel ow. Also, a pattern was o...

In the present study, heat transfer and entropy analysis for flow through a pipe system is considered. The Reynolds number and the pipe wall temperature effects on entropy distribution and total entropy generation in the pipe are investigated. Numerical scheme employing a control volume approach is introduced when solving the governing equations. Steel is selected as pipe material, while water ...

Many microfluidic devices use macroscopic pressure differentials to overcome viscous friction and generate flows in microchannels. In this work, we investigate how the chemical and geometric properties of the channel walls can drive a net flow by exploiting the autophoretic slip flows induced along active walls by local concentration gradients of a solute species. We show that chemical patterni...

Background Wall shear stress (WSS) is the friction force that blood flow exerts on the vessel wall. It is thought to affect the function of endothelial cells and the development of atherosclerosis and aneurysms. A promising technique to measure blood flow is three-dimensional phase contrast MRI (3D PC-MRI). Due to limited spatial resolution and SNR, estimating WSS from time-resolved 3D PC-MRI i...