No abstract

No abstract

No abstract

Experimental measurements of the wall shear stress combined with those of the velocity profiles via the electrochemical technique and ultrasonic pulsed Doppler velocimetry are used to analyze the flow behavior in transient flows caused by a downstream short pipe valve closure. The Reynolds number of the steady flow based on the pipe diameter is Re=148,600. The results show that the quasisteady approach of representing unsteady friction is valid during the initial phase for relatively large decelerations. For higher decelerations, the unsteady wall shear stress is consistently higher than the quasisteady values obtained from the velocity profiles. Attention has been focused on the friction acceleration model. The results obtained from this study show the ability of the electrochemical method in determining the local unsteady wall shear stress even in severe decelerating transient flows.

In this work, the porous ceramic multilayer ultrafiltration membrane is developed. Macroporous support was formed by extrusion of ceramic paste derived from natural Moroccan Sahara Clay. The microporous interlayer was then performed by slip casting from zirconia commercial powders and finally the active ultrafiltration toplayer was obtained by solgel route using TiO2 sol. The performance of TiO2 ultrafiltration membrane was evaluated by pores diameter, thickness of the top layer, water flux, and molecular weight cut off (MWCO). The water permeability measured for this composite membrane is 9.051 l/(m2·h·bar), the thickness is around 900nm, the pore diameter is centered near 7nm and the MWCO was about 5000Da.