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Velocity vertical pulsating

Figure 3.39 Typical vertical distributions over the smooth surface flow (A) mean velocity and pulsation intensity (B) energy spectra of velocity pulsations in logarithmic coordinates on various elevations (1 - z= 2 mm, 2-20, 3-40, 4-60, 5-70, 6-80, 7-90, 8-100, 9-110, 10-130, 110-150 and 12-200 mm). Figure 3.39 Typical vertical distributions over the smooth surface flow (A) mean velocity and pulsation intensity (B) energy spectra of velocity pulsations in logarithmic coordinates on various elevations (1 - z= 2 mm, 2-20, 3-40, 4-60, 5-70, 6-80, 7-90, 8-100, 9-110, 10-130, 110-150 and 12-200 mm).
Adhesion of Particles to Bottom of Air Duct. Dust particles will not fall to the bottom of a duct (and hence there will be no dust adhesion) if the vertical pulsating velocity Vy of the air flow is greater than the terminal (free-fall) velocity of the particles in air, i.e., if Vy > Uff. If we know Vy and its relation to the flow velocity, we can calculate the minimum air-flow velocity to prevent the settling of dust. Ryzhenko [242] found that for particles with diameters smaller than 10 ixm in moving air, the allowable velocities in air ducts with circular, rectangular, or trapezoidal sections, i.e., Vq, v, and are expressed by the formula... [Pg.281]

Dust carried by a stream may adhere to the inside surfaces of air ducts or to obstacles placed in the stream. In order to prevent the deposition and adhesion of particles on the bottom of an air duct, the vertical pulsating velocity of the stream must exceed the settling rate of the dust particles. If the flow velocity is limited to about 30 m/sec, this is possible only for small particles with diameters less than 10 /xm larger particles may adhere to the bottom of the air duct. [Pg.348]

Adhesion of Particles to Walls (Sides) of Air Duct. Adhesion to vertical walls takes place as a result of the action of the normal velocity component of the dust-containing air stream. This component arises from turbulent pulsations of the flow in a direction perpendicular to the wall surface of the air duct. The correctness of this view is confirmed by the studies of Ryzhenko and Shcherbina [246], who showed that the amount of dust sticking to 80 X 80 mm duralumin plates mounted around the perimeter of a vent drift in the Kochegarka mine was approximately the same on the sidewalls and the roof. [Pg.283]

Thus we see that the conditions for particle detachment can be expressed in terms of a critical velocity, in terms of the forces acting on the particles from the water stream, and in terms of certain dimensionless quantities characterizing the start of movement for the bed-load particles. It should be noted that there are a number of different points of view as to the causes of particle detachment from the bottom. Particle detachment may take place under the influence of a lifting force generated by the action of the vertical component of pulsating velocities in a turbulent stream, or detachment may be a consequence of unsym-metrical flow around the particles at the bottom. [Pg.427]

On vertical and battered walls, upward projected velocities (v ) have been related to inshore wave celerity (see Chap. 16). Relative velocities, Vzici, have been found to be roughly constant at Vzjci 2.5 for pulsating and slightly impulsive conditions, but increase significantly for impulsive conditions, reaching v /cj 3-7. [Pg.376]


See other pages where Velocity vertical pulsating is mentioned: [Pg.225]    [Pg.161]    [Pg.45]    [Pg.324]    [Pg.37]    [Pg.351]    [Pg.709]   
See also in sourсe #XX -- [ Pg.225 , Pg.247 ]




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