Numerical study of turbulent flow in USBR VI stilling basin

Abstract

The USBR VI stilling basin is one of the oldest basins designed to dissipate the energy at the outlet of pipes. In this study, the effect of two parameters including the Froude number (Fr) of inlet flow to the basin and the ratio of basin width to equivalent depth of the inlet flow (W/D) on the characteristics of mean and turbulent flow inside the USBR VI stilling basin were investigated, numerically. Reynolds Averaged Navier–Stokes (RANS) equations were solved with Re-Normalization Group (RNG) k-ε turbulence model. Results showed that by increasing W⁄D, from 3.50 to 9.23, decreasing rate of the average velocity at the end of the basin to the average velocity of the inflow increases from 80 to 97% and decreasing rate of the maximum velocity at the end of the basin to the average velocity of the inflow increases from 40 to 87%. Also, by increasing W⁄D, from 3.50 to 9.23, the average turbulent dissipation rate in the whole basin increases to 4.5 times, moderately. Moreover, by increasing W⁄D, from 3.50 to 9.23, the dissipation of turbulent flow energy in the basin becomes four times. Therefore, to design a USBR VI stilling basin based on the existing conditions, W⁄D recommended to increase as much as possible until nearly 10.