COBEM99

SR13 Mecânica dos Fluidos

Title:

NUMERICAL STUDY OF 3D ATMOSPHERIC POLLUTANT DISPERSION OVER REAL TERRAIN

Summary :

A NON ISOTROPIC TURBULENCE MODEL IS EXTENDED AND APPLIED TO THREE DIMENSIONAL STABLY STRATIFIED FLOWS AND DISPERSION CALCULATIONS. THE MODEL IS DERIVED FROM THE ALGEBRAIC STRESS MODEL (INCLUDING WALL PROXIMITY EFFECTS), BUT IT RETAINS THE SIMPLICITY OF THE "EDDY VISCOSITY" CONCEPT OF FIRST ORDER MODELS. THE "MODIFIED K-E" IS IMPLEMENTED IN A THREE DIMENSIONAL NUMERICAL CODE. ONCE THE FLOW IS RESOLVED, THE PREDICTED VELOCITY AND TURBULENCE FIELDS ARE INTERPOLATED INTO A SECOND GRID AND USED TO SOLVE THE CONCENTRATION EQUATION. IN THIS WORK THE MODEL IS EVALUATED AGAINST A FULL SCALE DISPERSION EXPERIMENT. FLOW AND TRACER DISPERSION OVER CINDER CONE BUTTE (USA) IS COMPUTATIONALY SIMULATED. THE LATERAL DIVERGENCE AT LOW LEVELS, A MARKED CHARACTERISTIC OF STABLE FLOWS, IS WELL REPRODUCED BY THE MODEL. THE PLUME PATH AND ITS SENSITIVITY TO THE APPROACHING WIND DIRECTION ARE WELL CAPTURED. GROUND LEVEL CONCENTRATIONS ARE OVERESTIMATED BY THE NUMERICAL MODEL, PROBABLY BECAUSE OF LARGE DEVIATIONS OF THE WIND DIRECTION NEAR THE GROUND DURING THE FIELD EXPERIMENT, WHICH SPREADED THE PLUME AND RESULTED IN LOW GROUND LEVEL CONCENTRATIONS.

Author :

Bocon, Fernando Tadeu
Maliska, Clovis Raimundo

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