Modeling cooling water discharges from the Burrard Generating Station, BC Canada

A three-dimensional numerical model was applied to examine the impact of the Burrard Generating Station cooling water on the circulation patterns and thermal regime in the receiving water of Port Moody Arm. A key aspect of this study involved properly incorporating the submerged cooling water buoyant jet into the 3D model. To overcome the scale and interface barriers between the near-field and far-field zones of the buoyant jet, a sub-grid scheme was applied, and the coupled system of equations of motion, heat conservation and state are solved with a single modeling procedure over the complete field. Special care was taken with the diffusion and jet entrainment by using a second order turbulence closure model for vertical diffusion and the Smagorinsky formula for horizontal diffusion as well as jet entrainment. The model was calibrated and validated in terms of buoyant jet trajectory, centerline dilution, and temperature and velocity profiles. Extensive modeling experiments without and with the Burrard Generating Station in operation were then carried out to investigate the receiving water circulations and thermal processes under the influence of the cooling water discharge. The model results reveal that under the influence of the cooling water discharge, peak ebb currents are stronger than peak flood currents in the near-surface layer, and the reverse is true in the near-bottom layer. Meanwhile, the model revealed a well-developed eddy at the southeast side of the buoyant jet in the near-surface layer. It is also found that the warmer water released from the cooling water discharge is mainly confined to the upper layer of the Arm, which is largely flushed out of the Arm through tidal mixing processes, and a corresponding inflow of colder water into the Arm occurs within the lower layer.