Characteristics of the turbulent/non-turbulent interface of a non-isothermal jet.
The turbulent/non-turbulent interface of a jet is characterized by sharp jumps ('discontinuities') in the conditional flow statistics relative to the interface. Experiments were carried out to measure the conditional flow statistics for a non-isothermal jet, i.e. a cooled jet. These experiments are complementary to previous experiments on an isothermal Re=2000 jet, where, in the present experiments on a non-isothermal jet, the thermal diffusivity is intermediate to the diffusivity of momentum and the diffusivity of mass. The experimental method is a combined laser-induced fluorescence/particle image velocimetry method, where a temperature-sensitive fluorescent dye (rhodamine 6G) is used to measure the instantaneous temperature fluctuations. The results show that the cooled jet can be considered to behave like a self-similar jet without any significant buoyancy effects. The detection of the interface is based on the instantaneous temperature, and provides a reliable means to detect the interface. Conditional flow statistics reveal the superlayer jump in the conditional vorticity and in the temperature.
J. M. Burgers Centre for Fluid Dynamics, Laboratory for Aero and Hydrodynamics, Delft University of Technology, Mekelweg 2, 2628 CD Delft, The Netherlands. j.westerweel@tudelft.nl
Jerry
J
Westerweel
Alberto
A
Petracci
René
R
Delfos
Julian C R
JC
Hunt