Skip to Content

Wanapum Dam

The Wanapum Dam on the Columbia River.

The Wanapum Dam is situated on the Columbia River near Vantage, Wash. (Photo Courtesy of Grant Co. PUD)

The performance of TDG-MP3 to predict the TDG distribution and water entrainment was evaluated using velocity data measured in a 1:52 reduced-scale model of Wanapum Dam and field data collected by the US Army Corps of Engineers on April 27 and May 2, 2000. Details of the numerical model are in Politano et al. (2009a) .

This figure illustrates the predicted free surface characteristics near the dam.

This figure illustrates the predicted free surface characteristics near the dam.

The isosurface of gas volume colored by tailwater elevation illustrates the predicted free surface characteristics near the dam. Slices through spillway show the water (red) and air (blue) regions. Velocity vectors and free surface (blue line) indicate the presence of a submerged surface jet with potential of high production of TDG.

Slices through spillway show the water (red) and air (blue) regions.

Slices through spillway show the water (red) and air (blue) regions.

Water entrainment was evident in Wanapum Dam in the simulated days. Entrainment is noticed close to the west bank in transect V1. In transect V2 high velocity is observed near the west bank as a result of the water entrainment. In transect V3 the effect of the entrainment has been diffused. On April 27, 2000, the model predicts a counterclockwise eddy near the east bank as a result of the strong water attraction from the powerhouse into the spillway region caused by high spillway flow rates. The differences in the tailrace flow pattern can be mainly attributed to the different spillway flow rates. The percentage of spill on April 27, 2000 and May 2, 2000, were approximately 52 percent and 37 percent, respectively.

The differences in the tailrace flow pattern can be mainly attributed to the different spillway flow rates.

The differences in the tailrace flow pattern can be mainly attributed to the different spillway flow rates.

Both experimental data and predictions in reduced-scale grossly under-predict the degree of entrainment observed in the field since turbulence, air entrainment, and bubble size could not be properly scaled in the laboratory model.

Turbulence, air entrainment, and bubble size could not be properly scaled in the laboratory model.

Turbulence, air entrainment, and bubble size could not be properly scaled in the laboratory model.

The predicted TDG agrees well with field data. Highest TDG values were observed on April 27, 2000, due to higher spillway flow and air entrainment. The model captures the reduction of TDG with the longitudinal distance and the lateral gradient observed in the field.

 

The predicted TDG agrees well with field data.

The predicted TDG agrees well with field data.

Streamlines colored by TDG concentration show that water from the powerhouse entrains into the spillway region increasing its TDG level as it travels within the aerated region. Water entrainment reduces the TDG by diluting the liquid close to the powerhouse but also increases the volume of water exposed to high gas volume fraction. If bubbles are available for dissolution, the net effect of the water entrainment might be an increase of the TDG downstream.

 

Last modified on September 26th, 2012
Posted on March 16th, 2012