On the flow and thermal characteristics of high Reynolds numbers (2800-17000) dye cell: simulation and experiment

This paper presents computational and experimental studies on wavelength/frequency fluctuation characteristics of high pulse repetition rate (PRR: 18 kHz) dye laser pumped by frequency doubled Nd:YAG laser (532 nm). The temperature gradient in the dye solution is found to be responsible for wavelength fluctuations of the dye laser at low flow rates (2800<Red<5600). The turbulence Reynolds number (ReT) and the range of eddy sizes present in the turbulent flow are found to be responsible for the fluctuations at high flow rates (8400<Red<17000). A new dimensionless parameter, dimensionless eddy size (l_plus), has been defined to correlate the range of eddy sizes with the experimentally observed wavelength fluctuations. It was found that fluctuations can be controlled by keeping ReT~10 and l_plus max~1. The simulated result explains the experimental observation and provides a basis for designing the dye cells for high PRR pumping.