The development and structure of turbulent plane jets

Abstract

The structure and development of turbulent plane jets in still air and moving streams are described. The nature of the small-scale turbulence cannot be accurately ascertained because of the difficulties inherent in the measurement of dissipation in highly turbulent flows. Although correlation measurements in a jet in still air indicate a large-scale structure which can best be described as ‘local flapping’, measurements in a jet in a moving stream do not reveal a similar structure. The development of the turbulence structure in a jet in a moving parallel stream is described and the properties of turbulent jets and wakes are shown to be reasonably well predicted by the use of a variable-eddy-viscosity formula together with the formal self-preserving properties of the equations of motion.

Comparison of flow and dispersion properties of free and wall turbulent jets for source dynamics characterisation

“…For the plane jet, they used Rodi's (1975) spreading value of 0.11 for a comparison with their simulation results. This value was also reported by Everitt and Robins (1978) in their experimental studies of jets in still and moving streams. Other researchers reported spreading rates varying from 0.087 to 0.128 (Haworth and Pope, 1987).…”

“…The earliest experimental investigation was conducted by Forthmann (1934) on a plane turbulent jet (Rajaratnam, 1976). Since then, free jets have been studied with different experimental equipments such as pitot tubes (Forthmann, 1934), Hot Wire Anemometry (Everitt and Robins, 1978), Laser Doppler Anemometry (Ramaprian and Chandrasekhara, 1985) and Particle Image Velocimetry .…”

“…Everitt and Robins (1978) also highlighted this problem and reported that this was the major cause of experimental errors encountered using HWA, because of the "high ratio of the velocity fluctuations" present in the outer region of the flow. Ramaprian and Chandrasekhara (1985) also emphasised this point and concluded that this has a consequence in generating errors "due to nonlinearity and large changes in instantaneous flow orientation".…”

“…Tangemann and Gretler (2000) explained this behaviour by highlighting the wall's influence as the main reason for the reduction in the spreading growth in comparison to the free jet. Everitt and Robins (1978) showed that there are problems associated with HWA measurements of a jet issuing into still air. In addition, Ramaprian and Chandrasekhara (1985) and Namer and Otugen (1988) reported some other problems when temperature differences are introduced between the jet and the ambient fluid.…”

“…These include "calibration drifts, sensitivity of the velocity sensors to temperature and vice-versa, and probe interference" (Ramaprian and Chandrasekhara, 1985). Everitt and Robins (1978) discussed one possible way of solving some of the problems by including an external parallel moving stream to the jet. They observed, like Rodi (1975), that this setup reduces the problem of high turbulent intensities in the outer regions of the flow and thus measurements errors.…”