CFD and dimensionless parameter analysis of Froude number to determine the flow regime over ogee spillways

Authors

1 Assistant Professor of Islamic Azad University, South Tehran Branch, Faculty of Engineering and Technology.

2 M.S. Graduate of Civil Engineering, Majoring in Hydraulic Structures, Faculty of Engineering and Technology, Azad University, South Tehran Branch

Abstract

In this research, the numerical method of computational fluid dynamics and dimensionless parameter of Froude number have been applied to determine the flow regime over ogee spillways.
Froude number is a dimensionless dynamic parameter calculated using the square root of the ratio of inertia force and gravitational force. Considering that the study of the regimes of flow over hydraulic structures especially spillways is of great importance, and as the most applied spillway is ogee one, therefore it is required to study such structures. To study the sensitivity of the dimensionless parameters of Froude number and velocity using in the proper calculation of the profile of the flow over ogee spillway the software of fluent computational fluid dynamics software
has been used. Based on Gauss–Seidel convergence condition applied for the convergence and control of equations, the step time of 0.01 second, quad pave meshing and RNG k– turbulence model have been used. The results of this research shows that the decrease of reference design head by 10, 20, and 30 percent leads to the decrease of reference average Froude number and reference average velocity of the flow over ogee spillway by 7.646, 15.2 18.835, and 6.519, 12.787, and 26.113 percent respectively. Moreover, the increase of the average Froude number of flow by 6.519, 12.787, and 26.113 percent, and average reference velocity by 13.933, 4.211, and 1.839 causes the reference design head to increase by 10, 20, and 30 percent. Whereas p-value of the profile of the flow in SPSS software is around 0.006 and very lower than 5%, it can be claimed that the numeral study is of high precision. In conclusion, the results obtained from numerical simulation have been provided and compared with the existing numerical and laboratory studies. The accuracy of this research is describable.

Keywords