Terminal speed

Wallis, G.B., The terminal speed of liquid drops and bubbles in an infinite medium, International Journal ofMultiphase Flow, l,pp. 491-511 (1974). 

In the event of quick disconnect a torque imbalance occurs and the PCU shaft begins to over speed. If no control action is taken the terminal speed is a function of PCU loop friction losses and the turbo-machine performance curves. To prevent damage from the over speed condition, a bypass valve is opened to redirect flow from the high pressure compressor to the outlet of the turbine. 

The significance of si is then clear it is a constant that is the reciprocal of the relaxation time for stopping a particle in a stagnant fluid. Similarly, on can show that /sl represents the time for a particle falling in a gravitational field to achieve its terminal speed. Note that the terminal speed qs = gsi l. As t/sAoo, the distance over which the particle penetrates, or the stopping distance L, is qosA l. 

Wallis GB (1974) The terminal speed of single drops or bubbles in an infinite medium. Int J Multiphase Flow 1 491-511... 

For a liquid drop held spherical by surface tension, the terminal speed from Eq. (5.1.4) is given by... 

Where V = the terminal speed of falling rocks h = the free-standing height of the overhang roof Among these three control measures, forced roof caving is the most economical and practical one and has been adopted widely to tackle this issue... 

Stokes law A law that predicts the frictional force f on a spherical ball moving through a viscous medium. According to this law F = Biurti v, where r is the radius of the ball, 1/ is its velocity, and ti is the viscosity of the medium. The sphere accelerates until it reaches a steady terminal speed. For a falling ball, f is equal to the gravitational force on the sphere, less any upthrust. The law was discovered by Sir George Stokes. 

Further experimental tests indicated that the terminal speed of the shuttle was in excess of 100 n h. 

Electrophoresis describes the migration of a charged molecule in a separation medium under the influence of an electric field. An accelerating force (F) acting on the molecule with charge by an electric field E can be expressed by Newton s law (F = qE). A terminal speed ( e) of the molecule under the electric field can be achieved when the acceleration force equals to the frictional force (/ e) generated by the separation medium [3]... 

TABLE 3-2 Equations for Terminal Speed of Large Spheres... 

The previous paragraphs focused on the settling velocity of a single particle or widely separated particles. The presence of a vessel or cylindrical walls tends to multiply the interaction between particles and cause some collisions. Extensive tests have been conducted on flows in vertical tubes. Brown and associates (1950) recommended multiplying the terminal speed of a single particle by a wall correction factor For laminar flows they proposed to use the Francis equation ... 

The actual process of sedimentation in a tube is based on the settling (or terminal) speed that was discussed at great length in Chapter 3. It is also depicted in Figure 7-43. Initially, the slurry is uniformly mixed. Gradually, the solids sink, forming three layers of liquid free of solids, a dilute mixture, and a relatively dense layer. Eventually, all the solids in the dilute layer sediment out, leaving only two layers, one of water and one of a dense mixture with solids at minimmn void ratio. The use of certain chemicals can accelerate the sedimentation of solids. 

The kinetic energy required to accelerate a solid slug of length Lss and unit cross-sectional area to its terminal speed Up at the start of a slugging... 

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