Wind Tunnel, Field and Numerical Investigations of Plume Downwash and Dispersion at AN Arctic Industrial Site

This study was designed to investigate the influence of the arctic atmospheric boundary layer and the complex flow pattern generated by building clusters on dispersion from a buoyant source. This was accomplished by analyzing data from wind tunnel, field, and numerical dispersion experiments for flow around a specific Prudhoe Bay, Alaska oil-gathering center. The results were used to describe plume downwash and the arctic boundary layer and to evaluate current Gaussian plume downwash techniques. Field observations indicate that the winter-time tundra surface has a very small (0.3 mm) surface roughness. A persistent temperature inversion was observed near the cold tundra surface and was attributed to the limited solar insolation and a relatively warm maritime-influenced air mass. Observations of turbulence and surface layer structure at heights above 15 m are similar to measurements made at lower latitudes. Field tracer measurements indicate that plume downwash and dispersion dominates the distribution of ground-level concentrations near the buoyant, short stack sources typical of arctic industrial facilities. An order of magnitude increase in maximum concentration occurs as wind speed increases from 5 to 8 m s^ {-1} and another order of magnitude increase occurs as wind speed increases to 16 m s ^{-1}. Maximum ground-level concentration occurs near the buildings and varies by a factor of 6 with changes in wind direction. Concentrations estimated by Gaussian plume models ranged from a factor of 6 lower than field observations to a factor of 8 higher. A three-dimensional, two-equation (k - epsilon) turbulence closure numerical model was capable of simulating the mean streamline bending, turbulence enhancement, and velocity defects observed in the recirculation cavity and building wake downwind of buildings. This technique provides a potential alternative to the wind tunnel and field studies which are currently the only means of estimating accurately ground-level concentrations near arctic industrial facilities.