Flow Characteristics of Axisymmetric Expansions

Characteristics of flow for four abrupt expansions with half angles of 15○, 30○, 45○, and 90○ have been determined by a combination of analytical and experimental means. The data, duly corrected for the errors inherent in the measuring technique, are checked, and the development of the force field is determined through the application of the momentum equation. The transformation of mean energy, the rate of production of turbulence, and the rate of dissipation of turbulence energy are determined. The evaluated head-loss results from the air-duct studies are checked by independent measurements in a water-pipe assembly. Because of the complex nature of the phenomena, it is not possible to express the results and the details of the flow characteristics in simple mathematical terms. Therefore, the kinetic energy of the mean motion, kinetic energy of turbulence, pressure distribution, turbulence production, and turbulence shear are presented in the form of their spatial distribution for all expansion angles. Although not affecting the maximum intensity that the turbulence attains, the boundary proximity to the separation surface had a striking effect on the production and diffusion of turbulence to approximately a 32○ separation angle; the smaller the angle of expansion, the earlier is the onset of diffusion. Beyond that angle, the effect is insignificant.