Papers by Keyword: Wall Shear Stress

Abstract: In order to study the role of growing cavitation bubbles in the context of ultrasonic cleaning, we perform two-dimensional, axisymmetric Navier-Stokes simulation for compressible, multicomponent flow and examine the so-called Rayleigh growth of an air bubble (with initial radius 33 µm and pressure 10 MPa) near a rigid wall. The simulation suggests that strong shear stress, which is important in physical cleaning such as particle removal, appears as a result of the bubble-growth-induced shock passage. The parametric study with varying a standoff distance of the bubble to the wall shows that the wall shear stress linearly decreases against the standoff distance.

Abstract: The one-dimensional mixture model efficiently predicts gas-liquid flows dominated by gravity force. The advantages of the mixture model are the absence of interfacial terms and the reduced number of transport equations, but its weakness lies on the constitutive laws to predict the wall shear force of a gas-liquid mixture. The objective of this work is to realize a sensitivity analysis of the wall shear model (based on the intermittent behavior of the gas and liquid structures) to the correlations for frequency and slug holdup in the one-dimensional, steady state mixture model applied to an isothermal gas-liquid mixture flowing in the slug regime. The numerical results for the pressure gradient obtained here are compared against experimental data from previous work.

Abstract: According to the problem of bionic shark gill jet can reduce friction on shark surface, a model of bionic jet surface was established based on shark surface was analyzed by measurements, and its numerical simulation was processed by using RNG k-ε turbulence model. The results show that: the gill jet can reduce frictional resistance on shark surface, and the best drag reduction can be got when the speed of main field is 5m/s, furthermore the maximum drag reduction rate can be up to 17.15%. The pressure of jet hole upstream is reduced which due to the barrier to the facing fluid by the jet, so that the pressure resistance of jet surface is reduced as well. Besides, jet fluid is blocked in the boundary layer by mainstream fluid, which caused the fluid velocity of jet hole downstream is reduced, the thickness of boundary layer is increased, and the normal velocity gradient of wall is reduced, so as to achieve the effect of drag reduction.

Abstract: The rate of mean blood flow through arteries depend on the resistance to flow presented by the blood vessels. Mean blood pressure decreases as the circulating blood moves away from the heart through arteries and capillaries due to viscous losses of energy. Atherosclerosis is a common phenomenon that is observed causing blockage in coronary arteries leading to cardiac arrest. This blockage is due to the deposition of cholesterol or plaque on the inner walls of the coronary artery. This paper provides an analytical study on the variation of static pressure with multiple blockages in the artery implementing the conventional simulation software. A general three dimensional section of the coronary artery was taken for the analysis and the variation of static pressure with increase in the number of blockages due to cholesterol deposition was studied. Meshing of the geometry and specification of the boundary types have been accomplished using GAMBIT 2.3.16 and the analysis has been carried out using ANSYS FLUENT 6.3.26.