Velocity transients

A.F. Huxley s 1957 Theory Further Structural Approaches Hugh Huxley s 1969 Theory Transient Mechanical Properties Velocity Transients Tension Transients... 

Cook (1958), 91 3 (Steady-state detonation head for solid unconfined and confined charges) 93-7 (Experimental detonation head in gases) 97-9 (Experimental detonation head in condensed explosives) 120-22 (Detonation head model proposed in 1943) and 128 (Detonation head in ideal detonation with maximum velocity transient)... 

Detonation Transients and Unstable Detonation Processes. Allen et al (Ref 1) made detonation velocity vs chge length. measurements on RDX (—65+100 mesh), fine grained TNT (—35 —150) coarse, low-density TNT (—8+10) 50/50 fine-coarse TNT, cast TNT, low-density. mixts of 80/20 TNT/AN, and mixts of 90/10 AN/RDX. Deton velocities were measured by a rotating mirror streak camera and by the pin oscillograph technique, in most cases simultaneously Their exptl data showed six different types of velocity transients ... 

Smoothly accelerating velocity-transient stabilizing at L /d = 3(+l). LD =end of vel transient and beginning of stable vel, d = diameter in cm. This type of transient, predicted by the deton head model and characteristic of non-ideal deton in point initiated chges, was observed in low density 80/20 AN/TNT, 90/l0 AN/RDX mixts, and in 50/50 cast Amatol... 

Smoothly accelerating velocity transient stabilizing in less than 3 charge diameters. 

Smoothly accelerated velocity transient which finally stabilizes at L/d = 3 1.0 (where L is length and d is diam of chge). 

M.A. Cook et al, JACS 79, 32(1957) (Velocity-diameter curves, velocity transients and reaction rates in PETN, RDX, EDNA Tetryl)... 

Schwartz BD, Maron BA, Evans WJ, Winstead DK. 1999. High velocity transient visual processing deficits diminish ability of patients with schizophrenia to recognize objects. Neuropsychiatry Neuropsychol Behav Neurol 12 170-177. 

In the 1950s, Hansell observed the production of drops by electro-mechanically induced pressure waves [8]. In this type of system, a voltage pulse applied to a piezoelectric material that is directly or indirectly coupled to the fluid, at ambient pressure, induces a volumetric change in the fluid. This volumetric change creates pressure/velocity transients within the fluid that are directed so as to produce a drop from an orifice [9-11]. Since the voltage is applied only when the drop is needed, these types of systems are called drop-on-demand or demand mode. ... 

In addition, since the SAW Is sensitive to minute perturbations occurring in thin films which are In Intimate contact with the surface, SAW devices can be used to monitor physical and chemical processes occurring In these overlayers. Based on this effect, SAW devices have recently found applications In the characterization of the properties of thin films (8-10). In this paper, we report on the utility of SAW devices to characterize (1) the surface area and pore size distribution of porous thin films based on Nj adsorption Isotherms and (2) diffusion coefficients (D) for thin polymer films based on absorption transients (l.e., mass absorbed as a function of time) as indicated by SAW velocity transients (l.e., SAW velocity... 

Squeeze flow between parallel plates was analyzed in Section 6.3 as an elementary model of compression molding. In that treatment we were able to obtain an analytical solution to the creeping flow equations for isothermal Newtonian fluids by making the kinematical assumption that the axial velocity is independent of radial position (or, equivalently, that material surfaces that are initially parallel to the plates remain parallel). In this section we show a finite element solution for non-isothermal squeeze flow of a Newtonian hquid. The geometry is shown schematically in Figure 8.16. We retain the inertial terms in the Navier-Stokes equations, thus including the velocity transient, and we solve the full transient equation for the temperature, including the viscous dissipation terms. The computational details. 

The transmission coefficient Cl (Qj,t), considering transient (broadband) sources, is time-dependent and therefore accounts for the possible pulse deformation in the refraction process. It also takes account of the quantity actually computed in the solid (displacement, velocity potential,...) and the possible mode-conversion into shear waves and is given by... 

Flow which fluctuates with time, such as pulsating flow in arteries, is more difficult to experimentally quantify than steady-state motion because phase encoding of spatial coordinate(s) and/or velocity requires the acquisition of a series of transients. Then a different velocity is detected in each transient. Hence the phase-twist caused by the motion in the presence of magnetic field gradients varies from transient to transient. However if the motion is periodic, e.g., v(r,t)=VQsin (n t +( )q] with a spatially varying amplitude Vq=Vq(/-), a pulsation frequency co =co (r) and an arbitrary phase ( )q, the phase modulation of the acquired data set is described as follows ... 

The operation of system valves (also starting and shutdown of pumps) has a significant effect on the transient fluid pressures in the piping system because of the acceleration and deceleration of the fluid as it changes its velocity. As a simple example, the maximum head rise caused by the instantaneous closing of a valve is given by... 

S has been approximated for flames stabili2ed by a steady uniform flow of unbumed gas from porous metal diaphragms or other flow straighteners. However, in practice, S is usually determined less directly from the speed and area of transient flames in tubes, closed vessels, soap bubbles blown with the mixture, and, most commonly, from the shape of steady Bunsen burner flames. The observed speed of a transient flame usually differs markedly from S. For example, it can be calculated that a flame spreads from a central ignition point in an unconfined explosive mixture such as a soap bubble at a speed of (p /in which the density ratio across the flame is typically 5—10. Usually, the expansion of the burning gas imparts a considerable velocity to the unbumed mixture, and the observed speed will be the sum of this velocity and S. ... 

Cavitation Loosely regarded as related to water hammer and hydrauhc transients because it may cause similar vibration and equipment damage, cavitation is the phenomenon of collapse of vapor bubbles in flowing liquid. These bubbles may be formed anywhere the local liquid pressure drops below the vapor pressure, or they may be injected into the hquid, as when steam is sparged into water. Local low-pressure zones may be produced by local velocity increases (in accordance with the Bernouhi equation see the preceding Conservation Equations subsection) as in eddies or vortices, or near bound-aiy contours by rapid vibration of a boundaiy by separation of liquid during water hammer or by an overaU reduction in static pressure, as due to pressure drop in the suction line of a pump. 

Distance-Velocity Lag (Dead-Time Element) The dead-time element, commonly called a distance-velocity lag, is often encountered in process systems. For example, if a temperature-measuring element is located downstream from a heat exchanger, a time delay occurs before the heated fluid leaving the exchanger arrives at the temperature measurement point. If some element of a system produces a dead-time of 0 time units, then an input to that unit,/(t), will be reproduced at the output a.s f t — 0). The transfer function for a pure dead-time element is shown in Fig. 8-17, and the transient response of the element is shown in Fig. 8-18. 

Impact of a thin plate on a sample of interest which is, in turn, backed by a lower impedance window material leads to an interaction of waves which will carry an interior planar region into tension. Spall will ensue if tension exceeds the transient strength of the test sample. A velocity or stress history monitored at the interface indicated in Fig. 8.4 may look as indicated in Fig. 8.5. The velocity (stress) pull-back or undershoot carries information concerning the ability of the test material to support transient tensile stress and, with appropriate interpretation, can provide a reasonable measure of the spall strength of the material. 

Flashback usually happens during unexpected engine transients, e.g., compressor surge. The resultant change of air velocity would almost certainly result in flashback. Unfortunately, as soon as the flame-front approaches... 

The draft risk due to cold air pillows under the roof glazing dropping into the occupied zone was determined by transient CFD calculations. As can be seen from Fig. 11.57, velocities do not exceed 0.2 m/s. Therefore, the draft risk was assumed to be marginal. 

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