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Drag force spherical

The drag force is exerted in a direction parallel to the fluid velocity. Equation (6-227) defines the drag coefficient. For some sohd bodies, such as aerofoils, a hft force component perpendicular to the liquid velocity is also exerted. For free-falling particles, hft forces are generally not important. However, even spherical particles experience lift forces in shear flows near solid surfaces. [Pg.676]

The term mist generally refers to liquid droplets from submicron size to about 10 /xm. If the diameter exceeds 10 /xm, the aerosol is usually referred to as a spray or simply as droplets. Mists tend to be spherical because of their surface tension and are usually formed by nucleation and the condensation of vapors (6). Larger droplets are formed by bursting of bubbles, by entrainment from surfaces, by spray nozzles, or by splash-type liquid distributors. The large droplets tend to be elongated relative to their direchon of mohon because of the action of drag forces on the drops. [Pg.474]

Consider a spherical particle of diameter dp and density pp falling from rest in a stationary fluid of density p and dynamic viscosity p.. The particle will accelerate until it reaches its terminal velocity a,. At any time t, let a be the particle s velocity. Recalling that the drag force acting on a sphere in the Stokes regime is of magnitude iirdppu, application of Newton s second law of motion can be written as... [Pg.311]

Assuming the bubbles to be spherical, the frontal area Af of the bubble becomes nd2/4. Further, by making use of the expression v = Qjnd2, the drag force can be written in terms of Froude number, the drag coefficient, and the volume of the bubble. Thus... [Pg.305]

Rowe and Henwood(26) made similar studies by supporting a spherical particle 12.7 mm diameter, in water, at the end of a 100 mm length of fine nichrome wire. The force exerted by the water when flowing in a 150 mm square duct was calculated from the measured deflection of the wire. The experiments were carried out at low Reynolds numbers with respect to the duct (< 1200), corresponding to between 32 and 96 relative to the particle. The experimental values of the drag force were about 10 per cent higher than those calculated from the Schiller and Naumann equation. The work was then extended to cover the measurement of the force on a particle surrounded by an assemblage of particles, as described in Chapter 5. [Pg.164]

Because most shear-thinning fluids, particularly polymer solutions and flocculated suspensions, have high apparent viscosities, even relatively coarse particles may have velocities in the creeping-flow of Stokes law regime. Chhabra(35,36) has proposed that both theoretical and experimental results for the drag force F on an isolated spherical particle of diameter d moving at a velocity u may be expressed as a modified form of Stokes law ... [Pg.169]

R o Drag force per unit projected area of isolated spherical particle N/m2 ML- T-2... [Pg.289]

For a spherical particle with radius a moving at low Reynolds number, the drag force is Stokesian,... [Pg.7]

In this chapter, we extend the discussion of the previous chapter to nonspherical shapes. Only solid particles are considered and the discussion is limited to low Reynolds number flows. The flow pattern and heat and mass transfer for a nonspherical particle depend on its orientation. This introduces complications not present for spherical particles. For example, the net drag force is parallel to the direction of motion only if the particle has special shape properties or is aligned in specific orientations. [Pg.69]

Classical, macroscopic devices to measure friction forces under well-defined loads are called tribometers. To determine the dynamic friction coefficient, the most direct experiment is to slide one surface over the other using a defined load and measure the required drag force. Static friction coefficients can be measured by inclined plane tribometers, where the inclination angle of a plane is increased until a block on top of it starts to slide. There are numerous types of tribometers. One of the most common configurations is the pin-on-disk tribometer (Fig. 11.6). In the pin-on-disk tribometer, friction is measured between a pin and a rotating disk. The end of the pin can be flat or spherical. The load on the pin is controlled. The pin is mounted on a stiff lever and the friction force is determined by measuring the deflection of the lever. Wear coefficients can be calculated from the volume of material lost from the pin during the experiment. [Pg.230]

Consider the collision of particles due to wake attraction, as shown in Fig. E3.1. It is assumed that (a) the motion of the leading particle is not affected by the approach of the trailing particle (b) particles are equal-sized, rigid, and spherical and (c) initially, the particles move nearly at their terminal velocities with a very small velocity difference and are separated by a characteristic distance Zo- An empirical relation can be used to describe the effects of the interparticle distance Z and particle Reynolds number Rep on the drag force of the trailing particle as... [Pg.128]

To simplify the following analysis, we assume that (1) the particles are spherical and of identical size (2) for the momentum interaction between the gas and solid phases, only the drag force in a locally uniform flow field is considered, i.e., all other forces such as Magnus force, Saffman force, Basset force, and electrostatic force are negligible and (3) the solids concentration is low so that particle-particle interactions are excluded. [Pg.206]

For kinetic energy loss at high flow rates, the theory of Burke and Plummer [Ergun and Oming, 1949] assumes that the total resistance of the packed bed can be treated as the sum of the resistances of the individual particles. For the fully developed turbulent flow, the drag force acting on an isolated spherical particle is... [Pg.228]

When a spherical particle exists in a stagnant, suspending gas, its velocity can be predicted from viscous fluid theory for the transfer of momentum to the particle. Perhaps no other result has had such wide application to aerosol mechanics as Stokes (1851) theory for the motion of a solid particle in a stagnant medium. The model estimates that the drag force 2) acting on the sphere is... [Pg.60]

Problem. Calculate the drag force exerted on a spherical particle, diameter 25 mm, as it moves through water at 2 m s-1. [Pg.182]

The property of viscosity is a very useful measure of the size and shape of a particle long thin molecules give rise to increased solution viscosity as opposed to small spherical molecules. This is because the drag force exerted by one macromolecule on another or on a neighboring water molecule is proportional to the surface area. The surface area of rods is greater than the surface area of an equivalent sphere and therefore rodlike molecules have a higher surface-to-mass ratio than do spherical ones. This also implies... [Pg.121]

Suppose a spherical particle is moving under the action of a constant force toward a solid surface having a radius of curvature much larger than the particle. Friction between the fluid and the particle creates a drag force which opposes motion. As the particle approaches the plane solid surface, its velocity decreases as a result of an increase in the drag caused by additional friction between the fluid and the wall. This decrease in particle velocity under a... [Pg.97]

Pore control, Vg = MpFg Maximum drag force on spherical pore. ... [Pg.829]


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See also in sourсe #XX -- [ Pg.753 ]




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