Comparative analysis of the modification of turbulence and its effects on a trapezoidal section stilling basin.

Juan césar Luna, Cristian Alfonso Salas Vázquez, jesús Gracia Sánchez, Victor Manuel Ortiz Martinez

Tuesday 30 june 2015

12:39 - 12:42h at Africa (level 0)

Themes: (T) Water engineering, (ST) Experimental facilities and instrumentation, Poster pitches

Parallel session: Poster pitches: 5F. Engineering - Instrument

This present work aims to characterize a turbulent flow that occurs in a trapezoidal section stilling basin, which belongs to the "Tunel Emisor Central" (TEO) project, concerning to the deep drainage system from the Mexico City, with a design caudal of 240 m³ / s. The physical model was constructed with a 1:30 scale, where it was found that its functionality during the design condition set up would be committed due to overflow. Through modification of the geometrical characteristics of the chute, at the entrance section of the tank, we sought to obtain a higher dissipation of turbulent kinetic energy (TKE) and decrease the levels variations of water depth. To evaluate these new geometries and their effects, three different physical assays were performed on the model, these being: the test on the smooth chute (smooth chute), the second one was carried out by increasing its roughness using steps in the chute (stepped chute) and the third and last one exchanging the steps with two rows of baffles with the form of teeth (toothed chute). The physical model was instrumented with acoustic Doppler speedometer (ADV) and a digital water level gage. With which the instantaneous speed and level fluctuations was measured, also with this a grid was drawn to calculate the velocity, turbulent kinetic energy (TKE) and its dissipation. In addition, a CFD modeling was performed using the computational software FLOW 3D with same dimensions as the physical model to compare the modification of turbulence. From the comparison of the physical and numerical models some similarity in the calculated indexes is observed, however it is noted that the numerical model overestimates values, so it is necessary some modification in its parameters in order to obtain better results, closer to reality.