Thermo-fluid-dynamics of submerged jets impinging at short nozzle-to-plate distance: A review

The complex flow structures of submerged jets impinging at relatively short nozzle-to-plate distance motivated a huge number of studies in order to allow for the understanding of their thermo-fluid-dynamic features. Herein, some of the experimental contributions evolved while studying the heat transfer behaviour of these jets (with a specific focusing on the secondary annular peak) are reviewed, along with the development of specific experimental techniques in thermal-fluid sciences over the last 50 years. A special attention is devoted to some particular, but very relevant, techniques in the field of modern experimental thermo-fluid-dynamics, namely infrared thermography and particle image velocimetry (PIV) along with the recently developed tomographic PIV. The outcomes of their visualization and flow inspection capabilities are compared with those of recent advanced computational methods. As computational simulations continue to grow in magnitude and complexity, it is essential to make certain their reliability, i.e. to validate their results. The experimental techniques of thermo-fluid-dynamics also have undergone a constant and enormous development, so they will provide further comprehensive benchmarks to computational methods. Future challenges for experimentalists in the thermal-fluid field, including convective heat transfer enhancement, are finally outlined.