Dynamic pressure stresses

Dynamic Pressure Stresses. Below, methods for the determination and evaluation of pressure and temperature stresses are explained by means of examples. Temperature and pressure stresses have been chosen because these types of stresses are by far the most frequent and are thus of special interest. 

It is traditional to nondimensionalize the shear stress in terms of the dynamic pressure associated with the mean velocity. The nondimensional friction factor is defined as... 

The drag stress in a fluid is proportional to the dynamic pressure PiVpH, where Pi is the mass density of water. Thus, the force on a single blade, = CoApPiVpl. Cj) is the coefficient of drag and Ap is the projected area of the blade in the direction of its motion. Power is force times velocity, so the power dissipation per blade is therefore... 

The implication of (10-282) is that the hydrostatic variation in pressure at the bubble surface is negligible for Rc >> I relative to the dynamic pressure variation in (10-278). Finally, collecting the results (10-273)-(10-282), we canrewrite the normal-stress condition (10-270) in the form... 

APPLICATIONS OF THE EQUATIONS OF CHANGE IN FLUID DYNAMICS In vector-tensor notation, pressure stress is written as a second-rank tensor as... 

Answer Based on the final result in part (e) for dFsoM on fluid, the normal stress is due to Xrr and fluid pressure. In the absence of centrifugal forces, one calculates fluid pressure from the hydrostatic situation where dynamic pressure is constant throughout the fluid. Hence,... 

Flow stresses occur when a mass of flowing fluid induces a dynamic pressure on a conduit wall. The force of the fluid striking the wall acts as the load. This type of stress may be applied in an unsteady fashion when flow rates fluctuate. Water hammer is an example of a transient flow stress. 

With re-entry vehicles and spaceplanes, the material resistance to extremes of temperature becomes a matter of major concern. When spacecraft dive into the Earth s atmosphere, aerodynamic surfaces are exposed to high thermal and mechanical loads maximum heat fluxes of the order of MW/nr, dynamic pressure, shear stress, acoustic vibrations and material degradation put the vehicles structures to a hard test. Payload and passenger survival is committed to the efficiency of the thermal protection system (TPS) which has to maintain the internal temperature within appropriate limits through various energy dissipating mechanisms. 

ABSTRACT The reasonable width of narrow coal pillar along gob not only improves the recovery rate of coal resources, but also can reduces the roadway maintenance difficulty and improves the roadway maintenance state. This paper studies the reasonable narrow coal pillar width using the theoretical analysis and numerical simulation of the dynamic pressure, by analyzing the plastic zone of surrounding rock in the different width of coal pillar and the distribution of the vertical stress to determine the reasonable coal pillar width. The application effect demonstrates that the narrow coal pillar width is reasonable, which provides the basis for the narrow coal pillar width setting of the gob side entry driving. 

Through analyzing the simulation on the surrounding rock stress field and displacement field of different width of coal pillar along goaf dynamic pressure roadway, some conclusions can be made as follows ... 

The repeated triaxial test applies a repeated axial cyclic stress of fixed magnitude, load duration and cycle duration to a cylindrical specimen. While the specimen is subjected to the dynamic cyclic stress, it is also subjected to a static confining stress provided by a pressure chamber. The cyclic load application, though, is to better simulate the actual traffic loading. 

The proportionality coefficients in Eqs. (5.10) and (5.11) are approximately 2 and 0.4, respectively (Liepe 2003). That usually means that the stress on large agglomerates that experience dynamic pressure fluctuations in the inertial subrange is much larger than the laminar shear stress on small agglomerates that fall into the viscous subrange. 

Hinze (1955) proposed that bubble breakup is caused by the dynamic pressure and the shear stresses on the bubble surface induced by different liquid flow patterns, e.g., shear flow and turbulence. When the maximum hydrodynamic force in the liquid is larger than the surfaee tension foree, the bubble disintegrates into smaller bubbles. This mechanism can be quantified by the liquid Weber number. When the Weber number is larger than a eritical value, the bubble is not stable and disintegrates. This theory was adopted to prediet the breakup of bubbles in gas liquid systems (Walter and Blaneh, 1986). Calculations by Lin et al. (1998) showed that the theory underprediets the maximum bubble size and cannot predict the effeet of pressure on the maximum bubble size. 

Micro- and Nanoscale Anemometry Implication for Biomedical AppiicaUens, Rgure 8 (a) An array of MEMS sensors embedded in a 3D bifurcation model, (b) Computational fluid dynamics (CFD) solutions for skin friction coefficient (Cf) at a R nolds number of 6.7. Cj represents local wall shear stress values normalized by the upstream dynamic pressure. Cj values are shown along the interior surface of bifurcation, (c) Comparison of the CFD On blue), experimental On green), and theoretical On red) skin friction for the 180° edge. x/D/cos(12.5) is the x distance normalized to the diameter of the inlet pipe and parallel to the centerline of the outlet pipes... 

The Fanning friction factor is a nondimensional number defined as the ratio of the wall shear stress to the dynamic pressure of the flow ... 

Khan and Richardson (1996) pointed out that the concept of an equivalent sand roughness is very speculative as the transition between one layer and the other. By subsequent iterations, the friction factor and velocity for each of the two layers are obtained from the shear stress as the product of the friction factor and the dynamic pressure ... 

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