Effects of adjacent wall on turbulent jets. 2nd Report. Turbulence energy balance.

Abstract

Three components of velocity fluctuation have been measured in a wall jet and offset jets which are discharged from a circular nozzle placed away from a flat plate. Measurments are made by the technique of rotating a probe with an inclined hot wire. Distributions of the turbulence intensity, the Reynolds stress, and the turbulence energy are shown in the cross section of the jets. Also, the balance of turbulence energy is estimated in the central symmetric plane of the developing region by using the measured data. The results of the offset jets are compared with those of the wall jet, and wall interaction effects on the turbulence structure are discussed. Main conclusions have been derived as follows ; (1) The turbulence energy in the offset jet grows and declines more rapidly than that in the wall jet. (2) The turbulence energy transfer toward the lateral direction due to the triple correlation in the offset jet is opposite to that in the wall jet near the wall. (3) In the offset jet, the new wall shear layer is brought up on the wall rather than the free shear layer of the upstream is attached to the wall. (4) The production and the dissipation of the turbulence energy keep in equilibrium on the whole even in the developing region of the offset jet, and so on.