Rayleigh scattering temperature measurements in a plane turbulent air jet at moderate Reynolds numbers

Rayleigh scattering temperature measurements were made in a slightly heated plane jet at various Reynolds numbers and the effect of this parameter on the temperature field was determined. The axial and lateral distributions of the mean and rms temperature as well as the temperature spectra along the jet axis were determined. Results indicated that increasing Reynolds numbers led to lower levels of rms temperature and jet dilution in the moderate Reynolds number regime (between 700 and 2500). It was also found that slower spread rates of the thermal jet occured with larger Reynolds numbers in this regime.List of symbols b_T temperature half-width of the jet - C calibration constant for Rayleigh scattering optics - C_T, C_T,0 constants defining the temperature decay rate - D nozzle width - E_T power spectrum of temperature fluctuations - f frequency - I_L laser light intensity - I_R Rayleigh signal intensity - K_T, K_T,0 constants defining the jet spread rate - k wavenumber (2f/ U) - N total molecular number density - Re Reynolds number (U₀D/) - T mean excess temperature - T_m mean excess temperature on the jet axis - T₀ mean excess temperature at jet exit - T fluctuating temperature - U local mean velocity - U₀ mean velocity at the jet exit - x axial distance from the nozzle exit - y lateral distance from the jet axis - z spanwise distance from the jet axis - Rayleigh scattering cross section - density - kinematic viscosityA version of this paper was presented as paper no 86-WA/ HT-98 at the 1986 ASME Winter Annual Meeting.