University of Tehran Journal of Computational Applied Mechanics 2423-6713 Articles in Press 2021 05 15 Numerical Investigations of Two-Phase Flow on a Stepped Spillway under Various Conditions 81334 10.22059/jcamech.2021.314069.573 EN Zafar Namazian Department of Mechanical Engineering, Yasooj Branch, Islamic Azad University, Yasooj, Iran 0000-0003-0951-4377 Ehsan Parhizgar Department of Civil Engineering, Yasooj Branch, Islamic Azad University, Yasooj, Iran Journal Article 2020 11 22 In this study, two-phase flow over a three-dimensional stepped spillway was numerically investigated using a finite volume code in ansys-Fluent commercial software. The numerical results were validated against experimental data. Then, the effects of several parameters were evaluated on the structure of the flow over the concerned spillway. Based on the natural roughness, several roughness heights of 0.0001, 0.0005, and 0.001 m were considered on the spillway surface to investigate the flow structure. In the next step, several surfaces with different contact angles, including 80, 120, and 160°, were used. Finally, a passive control method, including simultaneous blowing and suction with different configurations, was applied to the steps of the spillway. The results revealed that a change in the surface roughness or contact angle and applying the control method could change the flow regime from skipping to nappe. Also, variations in the speed of falling water and energy loss were attributed to changes in the surface roughness and contact angle and implementation of the proposed control method. https://jcamech.ut.ac.ir/article_81334_96651dd19d6d30ef453567dd77c0de2e.pdf