Date of Award

Summer 1975

Document Type

Dissertation

Degree Name

Doctor of Engineering Science in Mechanical Engineering

Department

Mechanical Engineering

First Advisor

Rong-Yaw Chen

Second Advisor

R. A. Comparin

Third Advisor

John Vincent Droughton

Fourth Advisor

Roman I. Andrushkiw

Fifth Advisor

Robert P. Kirchner

Abstract

In this investigation, the deposition of suspensions in laminar flow in the entrance region of a channel and a diffuser was considered.

The particulate phase was considered to he under the action of the electric field force clue to electrostatic charges. In addition, a lift force acting on each particle at the wall arising from the fluid shear near the wall and an adhesive force between each particle and the wall due to the difference of the material properties for both particle and walls were considered as surface forces.

The suspension flow was assumed to be incompressible, laminar, dilute, and with negligible gravity effect.

The complete solution of the problem involved solving the Navier-Stokes equations for two-phase flow. Since the resulting governing equations are non-linear partial differential equations, finite difference and numerical techniques were used to obtain solutions. All the numerical work was carried out on an IBM 360 computer.

The complete flow characteristics of the particulate phase and the rate of deposition of the solid particles were studied under different flow conditions. Deposition due to surface adhesion only, electrostatic charge only and both surface adhesion and electrostatic charge including the lift-force action at the wall was considered. Moreover, the case when the channel is connected to a diffuser which is considered as an approximate model for the splitter region of a fluidic device was discussed.

From this study, it was found that an appreciable amount of particle deposition can result because of the electrostatic charge on the solid particles. Also it was found that surface adhesion has a smaller effect on the rate of deposition than that due to electrostatic charge. The lift-force action at the wall has a negligible effect on the rate of deposition. In addition, it was concluded that the diffusive Peciet number has a considerable effect on the particle velocities, concentration and rate of deposition. The axial distribution of rate of deposition has a maximum only at low diffusive Peclet number.

Moreover, it was observed that the angle of divergence has a great effect on the rate of deposition in a diffuser flow. The pressure gradient and the rate of deposition increase with increasing diffuser angle. However, at larger diffuser angles, separation takes place and the rate of deposition increases rapidly in the presence of electric charge. In the absence of electric charge, the rate of deposition decreases rapidly with increasing diffuser angle.

Share

COinS