Averaging effects in models of threedimensional twophase flows
Abstract
In order to avoid the treatment of individual particle motion in twophase flow description, one can use volume averaged descriptors. However, if the averaging volume is too small then individual particles can cause large undulations of the averages. In this report the amplitude of such undulations is estimated by a bound. It is shown that in general, one must average over 30150 particles in order to obtain reasonably smooth averages. A consequence for interior ballistics calculations is that volume averages may be used to model the core flow but in general they cannot be used to resolve radial structures in two phases. Also presented are examples of the representation of a gasparticle aggregate boundary in terms of the gas volume fraction, and an approximate expression is derived for the transition curve.
 Publication:

NASA STI/Recon Technical Report N
 Pub Date:
 October 1984
 Bibcode:
 1984STIN...8519371C
 Keywords:

 Boundary Layer Flow;
 Flow Distribution;
 Gas Flow;
 Interior Ballistics;
 Particle Trajectories;
 Three Dimensional Flow;
 Two Phase Flow;
 Computation;
 Lattice Vibrations;
 Models;
 Numerical Analysis;
 Particles;
 Volume;
 Fluid Mechanics and Heat Transfer