Speed and velocity

This brings us to the subject of velocity, a word that is frequently misused. Let s imagine rolling a patient towards the operating room on a gurney. How fast are you moving This is where the distinct concepts of velocity and speed become confused. Average velocity is formally defined as the displacement divided by the time it takes to make that trip. 

We see that the velocity and speed distribution functions are thus functions of position as well as velocity [that is, P(v,z), P(c, )]. 

Speed, velocity, and acceleration also can be distinguished. The terms velocity and speed are often used interchangeably however, the two quantities are frequently not identical. Velocity means the rate of motion in a particular direction. Acceleration results from a change in velocity over time. General velocity and acceleration measurements are beyond the intent of this chapter. Reaction speed and response speed are other related variables also not considered. 

A flux F is defined as the amount that flows through a unit area per unit of time F = Ag/qAr (q area). Flux in this definition is a vector. However, in general flux in earth system research relates to the movement of a substance between compartments. This looser usage (Chapter 2) is equivalent to a rate (change of mass per time) sometimes, the term specific rate is used in the more exact sense of time-and area-related flux. Generally, the terms rate and flux as well as velocity and speed are often not separated in the literature in such an exact physical sense, but used synonymously. 

One can also find a functional form for the trajectory of the large droplets that are formed at the CBL. The path of these droplets represents the maximum spray penetration. Since they are not connected to the jet and are in direct contact with a strong gas flow, they do not necessarily follow a path of the form of (29.9) anymore. A schematic view of the trajectory of these drops is shown in Fig. 29. Ic with a local coordinate system attached to the CBL for convenience. In general most applications of LJICF are concerned with high momentum ratios for which the jet deflection is not pronounced. For those cases, it is fair to assume that the droplets formed at the CBL have a zero initial velocity in the x-direction as they separate fi om the jet and have an initial upward velocity of mj. As these droplets leave the jet, they lose their vertical velocity and speed up in the gas-streamwise direction and finally reach their terminal x-direction velocity. Of course, all these are true for one droplet without considering its interaction with other droplets and also with neglecting the effects of evaporation. With these assumptions, the equations governing the motion of the drop take the form... 

The ratio between the actual gas velocity and speed of sound is <0.3. 

At this point, we would like to proceed to apply the KMTG to experimentally measurable quantities, but we need a firmer foundation for the velocities and speeds of atoms/molecules in the gas phase. The velocity based on the phenomenological ideal gas law is suspect because we know it may not apply to high pressure and/or low temperature, so we need a more rigorous method. The concept/principle of weighted averaging occurs in kinetics, statistical thermodynamics, and in quantum mechanics, so we think this is more than just a math interlude it is a unifying principle. 

A. Lipatnikov, J. Chomiak, Turbulent burning velocity and speed of developing, curved, and strained flames. Proc. Combust. Inst. 29, 2113-2121 (2002)... 

The previous investigations of hard particle transport processes during laser beam dispersing have shown, that the high speed microfocus radioscopy system is a usable arrangement to observe and analyse the movements, velocities and accelerations of particles inside the molten bath. That possibility was, until now, not given by conventional techniques of process... 

As might be expected, this simple picture does not hold perfectly. The coefficient of friction tends to increase with increasing velocity and also is smaller if the pavement is wet [14]. On a wet road, /x may be as small as 0.2, and, in fact, one of the principal reasons for patterning the tread and sides of the tire is to prevent the confinement of a water layer between the tire and the road surface. Similarly, the texture of the road surface is important to the wet friction behavior. Properly applied, however, measurements of skid length provide a conservative estimate of the speed of the vehicle when the brakes are first applied, and it has become a routine matter for data of this kind to be obtained at the scene of a serious accident. 

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. ... 

When the gas speed is sufficiently high, the separation factor corresponding to a given value of the cut is essentially independent of the gas velocity and, hence, at high speeds, is given (104) to a good approximation as... 

Vapor Cloud Explosion (VCE) Explosive oxidation of a vapor cloud in a non-confined space (not in vessels, buildings, etc.). The flame speed may accelerate to high velocities and produce significant blast overpressure. Vapor cloud explosions in plant areas with dense equipment layouts may show acceleration in flame speed and intensification of blast. 

If we accept the assumption that the elastic wave can be treated to good aproximation as a mathematical discontinuity, then the stress decay at the elastic wave front is given by (A. 15) and (A. 16) in terms of the material-dependent and amplitude-dependent wave speeds c, (the isentropic longitudinal elastic sound speed), U (the finite-amplitude elastic shock velocity), and Cfi [(A.9)]. In general, all three wave velocities are different. We know, for example, that... 

As a general rule, the veloeity (speed) of the impeller and the diameter of the impeller, will determine the head or pressure that the pump can generate. As a general rule, the velocity and the height of the impeller blades, will determine the flow (gpm) that the pump can generate (Figure 6-13). 

Extremely High Velocity Shaft Speed Some pump companies use very high velocity, 30,000 rpm, to improve efficiency and generate high head with small equipment. U.se a stationary seal, with the springs in the stationary element. 

The choice of a turboexpander load may be influenced by the desire to optimize refrigeration. In other words, a dynamometer load may be chosen over a generator load due to speed considerations. Additionally, there are other constraints imposed on optimal design. Factors such as impeller peripheral velocity (tip speed), bearing design, axial load balance, material selection, and manufacturing methods (which have greatly improved in the recent decades) all have an influence. 

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