THERMODYNAMICS OF AN ISOTHERMAL FLOW - THE 2-DIMENSIONAL TURBULENT JET

This study illustrates the thermodynamic information that is being routinely overlooked by a pure fluid mechanics analysis. The integral analysis of the two-dimensional turbulent jet is used as an example. It is shown that even when the temperature difference between the nozzle fluid and the reservoir fluid is zero, the jet region is nonisothermal. At every position along the jet, the temperature rise becomes maximum when the entrainment coefficient assumes a value that is comparable with the value determined experimentally. Furthermore, it appears that the natural shape of the velocity and temperature profiles of the jet is the one that minimizes the total entropy generation rate. This study suggests that an important relationship exists between the empirical components of the pure-fluid-mechanics integral treatment, and the temperature and entropy generation extrema unveiled by the thermodynamic analysis.