This example is from a Research Study Project for AWWARF (American Water Works Association Research Foundation, Project #260; "Water Quality Modelling of Distribution System Storage Facilities").

This is a simulation of half of a cylindrical tank inspired by the Blackhawk tank near Oakland, CA. This tank has a maximum depth of 50 feet, instead of the 38 feet depth of Blackhawk. Otherwise the geometry is identical.

The tank is modeled in filling mode with the inlet near the outside wall. The criteria of interest is how well the inlet fluid mixes with the rest of the water in the tank, and how quickly the mixing occurs.

Three cases are shown for comparison purposes.

Isothermal Inlet (750x410 GIF 31K).

This first image shows the tank under isothermal conditions. The temperature of the water coming in the inlet is the same as the temperature of the fluid in the tank. The walls are insulating. The inlet fluid is colored red, the tank was initially full of blue fluid. The image shows the extent of mixing of the inlet fluid throughout the tank after ~2.5 hours.

Warm Inlet (750x410 GIF 26K).

This tank has fluid 3.35 Deg. C warmer flowing in the inlet.

Again, the inlet fluid is color coded red, and the display shows the mixing of the inlet flow after 2.5 hours. Note how the warmer (red) fluid prefers to remain near the upper surface. In this case the tank is better mixed than the isothermal case after the same period of time.

Cold Inlet (750x410 GIF 26K).

This tank has fluid 1.00 Deg. C cooler flowing in the inlet. As in the two previous cases, the inlet fluid (now the cooler fluid) is colored red, and the display shows the mixing after 2.5 hours. The inlet fluid sinks to the bottom of the tank and spreads out along the floor. In this case the mixing within the tank is less efficient than the other two cases.

The tank initially mixes with different efficiencies for the three different temperature conditions at the inlet. Differences in the mixing efficiency becomes much smaller at later times. The sensitivity of the mixing to inlet temperatures is greater when the inlet is located closer to the tank's center (note for example two other inlet locations to see the effect: Modified Blackhawk Tank , Center Fill Blackhawk Tank ).