Home Engineering



Table of Contents:
Continuity EquationThe continuity equation for the solidphase i can be written as
e_{i}p_{i} = n_{i}m_{i} is the mass of phase i per unit volume of mixture, e_{i} is its solid volume fraction, and p_{i} is density of phase i. Here у =< c_{;} > is the mean velocity of the particle i. The instantaneous velocity c_{;} is defined as the sum of the average velocity, v_{;}, and peculiar velocity, С;, c = v_{;} + С; with < C >= 0 Momentum EquationThe momentum equation for phase i may be expressed as
Fluctuating Energy EquationThe fluctuating energy equation for solidphase i can be expressed as where
0_{i} is the granular temperature or the fluctuating granular energy of the solidphase I,
In the above governing equations, the relevant variables describing the flow field are the average velocities, the solid volume fractions, and the granular temperatures evaluated at location r of the center of the particle at time t. Kinetic EquationThe kinetic equations that characterize the flow of a multiphase system are where g_{ip}(r) is the spatialpair radial distribution function when the particles i and p are in contact. A solution of Eq. (2.87) near the equilibrium was obtained using the ChapmanEnskog method (Ferziger and Kaper 1972; Chapman and Cowling 1970),
where f^{0} is the Maxwellian velocity distribution
and ф is a perturbation to the Maxwellian velocity distribution. It is a linear function of the first derivative of n_{i}, d_{i}, and v_{i}. Note that ф is function of the phase mean velocity, v_{i}, and not the total flow velocity, because, as mentioned in the introduction, each kind of particle is treated as a separate phase and the interaction is at the interface. The radial distribution function g_{ip}(e_{i}, e_{p}) describes a multisized mixture of hard spheres at contact. Iddir and Arastoopour (2005) modified the Lebowitz (1964) radial distribution function. This approach is in agreement with the results of molecular dynamics (MD) simulation obtained by Alder and Wainwright (1967) at both lower and higher solid volume fractions. This equation can be written as
The expression of g_{pp}(e_{i}, e_{p}) is obtained by simply interchanging the indices i andp. For a more detailed explanation for constitutive relation expressions for all solid phases, see Iddir and Arastoopour (2005). 
<<  CONTENTS  >> 

Related topics 