Measurement and prediction of the mean and fluctuating temperature field downstream of a multi-bore jet block in which one jet is heated

Measurements were performed in water of mean and fluctuating velocity and temperature fields downstream of a multi-bore jet block which was designed to simulate flow obtained in nuclear reactor subassemblies. Power laws similar to those in grid turbulence were found to describe the decay of the fluctuating field and the growth of the length scales but significantly different exponents were obtained due to the nonisotropy produced in the jet block. A gradient diffusion model with a streamwise varying eddy diffusion coefficient was found to give excellent predictions of mean temperature profiles. Distributions of temperature fluctuation intensities were predicted with the transport equation for this scalar. Agreement between measurement and prediction was obtained by use of identical eddy diffusivities for the production and diffusion of the temperature fluctuations. (author)