Jerome B. Fanucci

On the formation of bubbles in gas-particulate fluidized beds

The method of characteristics is applied to the nonlinear equations describing two phase flow. The method shows how a small disturbance changes with time and distance and can, eventually, produce a flow discontinuity similar to a shock wave in gases. The parameters entering the analysis are the amplitude of the initial disturbance, the wave length of the original disturbance, the particulate pressure function, the particulate size, the uniform fluidization voidage, the uniform fluidization velocity, the fluid viscosity, the particulate density, and the fluid density. A study of the parameters indicates a qualitative agreement with experimental data for gas-particulate fluidized beds. It is shown theoretically, and these results have been confirmed experimentally, that the following factors increase bed stability: a decrease in the particulate size, an increase in the bed density, an increase in the fluid viscosity, and a decrease in the particulate density. This theory is the first to show rigorously that a small disturbance can lead to a particulate shock wave which may indicate the creation of a bubble. 18 figs, 2 tables. (RWR)

Structure of shock waves in gas‐particulate fluidized beds

The structure of a two‐phase shock wave in a gas‐particulate fluidized bed is investigated. The present study gives (i) the jump relation across the two‐phase shock, (ii) the critical condition beyond which the stable two‐phase shock breaks up, and (iii) the distribution of the dependent variables through the two‐phase shock and the two‐phase shock thickness.

Nonuniform Expansion of a Piston Into an Ionized Medium with a Weak Magnetic Field

The nonuniform expansion of a rigid, perfectly conducting piston into an infinitely conducting fluid wherein there exists a weak uniform magnetic field is considered. A solution for the state of the plasma and the magnetic field between the piston and the magnetohydrodynamic shock is obtained by a small perturbation method; the dependent variables are expressed in double expansions about a zero order (hydrodynamic) solution. The solution is valid for pistons (either cylindrical or spherical) whose expansion velocity is expressible by a small perturbation on a constant velocity. The development includes second order terms; however, numerical results are restricted to first order. Within the first order perturbation, it is shown that the fluid dynamic analysis is uncoupled from the magnetic field, and the shock shape retains its cylindrical or spherical symmetry. Calculations are carried out for a spherical piston, for several values of γ (specific heat ratio), and a∞/v0 where a∞ is the ambient speed of sou...