Date of Award

Spring 1979

Document Type

Thesis

Degree Name

Master of Science in Mechanical Engineering - (M.S.)

Department

Mechanical Engineering

First Advisor

P. Hrycak

Second Advisor

Martin J. Levy

Third Advisor

John Vincent Droughton

Abstract

Experimental investigation was conducted on an axisymmetric, submerged air jet impinging normally on a smooth convex hemisphere. Three nozzle diameters of 0.5" (12.7mm), 0.375" (9.525mm) and 0.25" (6.35mm) were used and tests were run at Reynolds number range of 14,700 to 84,000.

The results obtained in the free jet and deflection zones were found to confirm the works of previous investigators. As for the fully developed wall jet region, the following points are noted:

  1. The maximum wall-velocity decay was found to possess a slightly higher rate than that of either the flat plate or the concave hemisphere.

  2. The mean velocity profile at a given wall distance from the stagnation point follows the same profile as those of the flat plate and the concave hemisphere; but deviates from them at the outer envelope (Z/Z 1/2 > 1.2) where it decays at the highest rate, followed by the curves of the flat plate and of the concave surface, in that order.

  3. Both the inner boundary layer and the outer boundary were established. In comparison with the flat plate case, the inner boundary layer grows at a slightly higher rate (with respect to the wall distance), while the outer boundary layer grows at a slightly lower rate,

  4. Negative static pressure distributions were found laterally across the wall jet. The maximum value occurs at Z/Z 1/2 equal 0.9 and is a function of nozzle diameter, distance of the nozzle exit from the impingement surface, and the distance from the stagnation point along the wall surface. The measurements of such negative static pressure serve as a verification of the Coanda Effect.

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