In the present study, the effect of elliptical-shaped contraction has been investigated to reduce flow energy using FLOW-3D software. The values of contraction are 10 and 15 cm. The results showed that the statistical indexes in the RNG turbulence model such as percentage Relative Error, Absolute Error, Root Mean Square Error and Kling Gupta Efficiency yield acceptable accuracy results compared to the k-ε, k-ω, and LES turbulence models. In this study, the amplitude of the Froude number after the gate as the most effective dimensionless parameter in energy dissipation varied from 2.8 to 7.5. The results showed that in 10 cm elliptical-shaped contractions, the ratio of energy dissipation to the upstream and downstream specific energy was 24.62% and 29.84%, more than the classical hydraulic free jump, respectively. For the contractions of 15 cm, these values were 46.14% and 48.42%, respectively. In addition, by examining the obtained results, it was observed that the elliptical-shaped contractions have a better performance in terms of energy dissipation compared to the sudden contraction, obtained from the previous studies. By increasing the upstream Froude number, the relative energy dissipation increased so that the application of contraction reduces the downstream Froude number of the contracted cross-section in the range of 1.6 to 2.3. In this study, based on dimensional analysis, non-linear polynomial regression equations were presented to predict the relative energy dissipation.
