This set of simulations were done using inflow and outflow rates measured in the field from 9pm, July 21 to 9pm July 23, 1997. During this period, the typical flow rate was 24 MGD (18,000 gpm), though rates from 12 to 48 MGD were measured over periods of ~1 hour.

One clear difference between this case and the simulation of constant inflow and outflow rates is the speed of mixing for the tracer. Time changing inflow and outflow improves the mixing characteristics in the tank.

Below the Baseline Geometry with Field data Boundary Conditions is shown.

Geometry and Mesh for Tank (1100x850 GIF 40K).

This image shows the tank geometry and mesh. Inlet and outlet area are shown with additional detail. This mesh has ~64,000 cells.

Tank Geometry near Inlet and Outlet pipe (1100x850 GIF 18K).

This image shows the details of the tank geometry near the inlet and outlet pipe. Both inlet and outlet pipes are below the elevation of the floor of the tank.

Typical Velocity Field during Fill Mode (1100x850 GIF 31K).

This image shows the velocity field at 1:40am, ~4.5 hour after the start of the fill cycle. The display plane is 2 feet below the water's surface. This field requires ~ 3 hours to develope, and varies somewhat during the fill cylcle as the inflow rate changes. Other example flow fields are the ones seen during the constant fill rate (e.g. 36 minutes , 4.7 hours (both 1100x850 GIF 52K) ).

Fluoride Concentration during Fill Mode (1100x850 GIF 30K).

This image shows the distribution of a tracer fed to the tank during the filling cycle. This is the distibution after ~4.5 hours 2 feet below the water's surface. The interaction of the inlet jet with the nearest pillar creates a pair of jets. More distant pillars appear to have little additional effect.

Typical Velocity Field during Draw Mode (1100x850 GIF 31K).

This image shows the velocity field at 9:50am, ~4.5 hour after the start of the draw cycle. The display plane is 2 feet below the water's surface. This field looks similar to the fill cycle on the outlet side of the Baffle wall. The velocity field on the inlet side is very quiet.

Fluoride Concentration during Draw Mode (1100x850 GIF 30K).

This image shows the distribution of a tracer during the draw cycle. Mixing is complete on the inlet side of the baffle wall, but not on the outlet side.

Fluoride Concentration History (1100x850 GIF 20K).

This image shows the fluoride tracer history at 7 taps in the tank. Field data was also collected at these locations. Comparison with the field data is quite close for all but the Southeast Corner where the field data shows a later arrival for the fluoride than seen in the simulation.

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