Record Display for the EPA National Library Catalog


Main Title Fluid Modeling Simulation of Stack-Tip Downwash for Neutrally Buoyant Plumes.
Author Snyder, W. H. ; Lawson., R. E. ;
CORP Author Environmental Protection Agency, Research Triangle Park, NC. Atmospheric Research and Exposure Assessment Lab. ;National Oceanic and Atmospheric Administration, Research Triangle Park, NC. Atmospheric Sciences Modeling Div.
Publisher c1991
Year Published 1991
Report Number EPA/600/J-92/129;
Stock Number PB92-166644
Additional Subjects Fluid dynamics ; Air pollution ; Chimneys ; Plumes ; Reynolds number ; Simulation ; Wind tunnels ; Wind velocity ; Downwash ; Reprints ;
Library Call Number Additional Info Location Last
NTIS  PB92-166644 Some EPA libraries have a fiche copy filed under the call number shown. 07/26/2022
Collation 16p
Downwash of neutrally buoyant effluent on the immediate lee side of a circular stack was modeled using a wind-tunnel simulation. Both subcritical and supercritical turbulent flows were simulated, where the criticality refers to Reynolds numbers below and above the critical Reynolds number, Re(sub c) (approximately equal to 2x10(5)), where the boundary layer on the cylinder becomes turbulent and the drag coefficient drops sharply. Subcritical Reynolds numbers are typically attained by small-diameter stacks in relatively light winds; supercritical ones are attained by large-diameter stacks in strong winds. The downwash characteristics differ markedly in the two regimes. In the subcritical regime, downwash begins when the ratio of effluent speed to wind speed (W/U) is about 1.5; in the supercritical regime, downwash begins at W/U approximately equal to 1.1. The downwash in the immediate lee of the stack at W/U = 0.3 extends to 7 diameters down from the stack top in the subcritical regime and to 4 diameters down in the supercritical regime. Graphs and simple formulas are presented describing the plume trajectories and plume widths for 0.3 < or = W/U < or = 2.0 and for downwind distances from the source to 30 stack diameters. Practical recommendations are made for modeling the downwash of neutrally buoyant plumes.