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Numerical Simulation of an Industrial Cumulus and Comparison with Observations

Francis W. MurrayThe Rand Corporation, Santa Monica, Calif. 90406

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L. Randall KoenigThe Rand Corporation, Santa Monica, Calif. 90406

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Paul M. TagNaval Environmental Prediction Research Facility, Monterey, Calif. 93940

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Abstract

A two-dimensional field-of-flow numerical model of cloud development is used to study a cloud that formed over a refinery as a result of heat dissipated to the atmosphere. The observed vertical structure of the atmosphere provided initial conditions. The wind necessarily was simplified to a unidirectional flow. The cloud-initiating perturbation consisted of sensible and latent heat equal to the waste heat rejected to the atmosphere by the refinery.

When conditions were matched to those reported, the simulated cloud agreed in most particulars with the observations. Sensitivity tests showed that the simulated cloud depends too strongly on ambient wind speed and shear. This perhaps is a generic defect of two-dimensional formulations. The response of the simulated cloud to expected changes in heat flux density appears more realistic than its response to small changes in ambient wind.

The cloud evolution consists of bubbles forming and breaking away from the main cloud mass, then moving downwind and dissipating. This behavior characterizes real clouds associated with a stationary heat source. The simulations also predict that under appropriate conditions secondary clouds form far downwind.

Abstract

A two-dimensional field-of-flow numerical model of cloud development is used to study a cloud that formed over a refinery as a result of heat dissipated to the atmosphere. The observed vertical structure of the atmosphere provided initial conditions. The wind necessarily was simplified to a unidirectional flow. The cloud-initiating perturbation consisted of sensible and latent heat equal to the waste heat rejected to the atmosphere by the refinery.

When conditions were matched to those reported, the simulated cloud agreed in most particulars with the observations. Sensitivity tests showed that the simulated cloud depends too strongly on ambient wind speed and shear. This perhaps is a generic defect of two-dimensional formulations. The response of the simulated cloud to expected changes in heat flux density appears more realistic than its response to small changes in ambient wind.

The cloud evolution consists of bubbles forming and breaking away from the main cloud mass, then moving downwind and dissipating. This behavior characterizes real clouds associated with a stationary heat source. The simulations also predict that under appropriate conditions secondary clouds form far downwind.

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