Experimental and theoretical studies on confined vortex flow structures

The structure of confined air vortex flow including turbulence effects has been studied experimentally and theoretically.;A measurement technique using Laser Doppler Velocimetry (LDV) was developed to investigate the characteristics of confined air vortex flows: the turbulence intensity, the turbulence kinetic energy, the Reynolds stresses, the mean and fluctuating velocities, etc. Special types of testing devices were designed and built to extend the one-component LDV to three-dimensional measurements. The air vortex flow was produced in a cylindrical chamber using various contraction ratios and inlet Reynolds numbers.;A physical model for the turbulence intensity in the tangential direction for a confined air vortex flow is proposed based on experimental observations. The model divides the turbulence intensity distribution along the radius of the vortex chamber into three regions based on individual characteristic features. A mathematical approach is utilized to obtain expressions for turbulence intensity and to predict the turbulence intensity within the vortex chamber under different conditions.;Equations concerning the kinetic energies due to the mean motion, the fluctuating motion and the two combined have been derived. Experimental results reveal the behaviour of turbulence kinetic energy in the confined vortex flow. The contribution of each parameter to the kinetic energy as well as the overall performances of the kinetic energy is analyzed.;Furthermore, the distribution profiles for both the Reynolds shear stresses and the Reynolds normal stresses in confined air vortex flows are presented. The former is obtained by solving the energy differential equations analytically, and the latter is obtained from the air vortex chamber flow experiments.;Meanwhile, the mean velocities and fluctuating velocities are investigated experimentally. A new profile for the tangential velocity distribution is proposed. An integration is formulated to determine the vortex core size. A computer program is developed for calculation of numerical values of the vortex core size corresponding to different configurations.