New model of an optical technique for measuring local turbulent temperature fluctuations inside a hot free-plane jet of air

Genetic Algorithm Approach and Experimental Confirmation of a Laser-Based Diagnostic Technique for the Local Thermal Turbulence in a Hot Wind Tunnel Jet

“…Since the incident radiation wavelength is λ 0 = 6328Å, and the measurements [25] of the inner and outer scales of turbulence in the jet under study are l 0 = 1 mm and L 0 = 10 mm, it is proved in our previous works [26][27][28][29] done with the same jet, that those conditions which allow the applicability of the geometrical optics approximation are satisfied.…”

“…(1e) Although the results derived in [26][27][28][29] are satisfactory in terms of the order of magnitude of the values obtained, these measurements contain shortcomings that highlight a central issue. The problem resides in the fact that no local information about the turbulence of the jet studied can directly be deducted from these results.…”

“…The solution of the inverse problem explained in this work belongs to these laser beam diagnostic techniques, and the turbulent medium studied is a hot turbulent jet of air derived from the nozzle aperture of a wind tunnel. This paper represents a continuation of our previous works [26][27][28][29][30]. About experiments, we consider the experimental set-up shown in Figure 1 and already used in our previous papers [26,29].…”

“…The jet width L which is the distance between those borders must be carefully determined before solving Equation (10), in order to obtain accurate results. In our previous works [26][27][28][29], we have assumed, for simplicity, that L is equal to the width of the nozzle aperture = 200 mm. Since the inverse problem stated in this paper needs a rigorous determination of the jet width, we have to measure the mean speed U and the mean temperature T along the whole laser beam path.…”

“…measurement of the statistical properties of the laser beam propagation in the medium [24][25][26][27][28]. The solution of the inverse problem explained in this work belongs to these laser beam diagnostic techniques, and the turbulent medium studied is a hot turbulent jet of air derived from the nozzle aperture of a wind tunnel.…”