Comparison of two turbulence models in simulating an axisymmetric water jet evolving into a water tank

Experiments and computational fluid dynamics (CFD) simulations have been carried out to predict a turbulent water jet plunging into a tank filled with the same liquid. A zero distance of the free falling water jet to the free surface of the tank is considered in order to avoid air bubble entrainment which may be caused by surface instabilities.
For both impinging region and recirculation zone, measurements are made using Particle Image Velocimetry (PIV). Instantaneous and time-averaged velocity fields are obtained over the cross-section of the tank. Numerical data is obtained on the basis of both k-ε and SSG (Speziale, Sarkar and Gatski) of Reynolds Stresses Turbulent Model (RSM) in three dimensional frame and compared to experimental results via the axial velocity and turbulent kinetic energy.
It was found that, for axial distances lower than 5 cm from the jet impact point, the axial velocity matches well the measurements, using both models. A progressive difference is noticed near the jet for higher axial distances from the jet impact point. These discrepancies are more important in the case of RSM than in the case of k-ε model. Nevertheless, it was observed that the turbulent kinetic energy agrees very well with the measurements when applying the SSG-RSM model for the lower part of the tank, whereas it is underestimated in the upper region, especially in the region near the jet exit. Inversely, the k-ε model shows better results in the upper part of the water tank and underestimates results for the lower part of the water tank. From the overall results, it can be concluded that the k-ε model describes well the average axial velocity, whereas the turbulent kinetic energy is better represented by the SSG-RSM model. The flow pattern obtained using both turbulent models and the corresponding comments of the results are detailed in the paper.