Citation:

Hunt, J., W. Snyder, Robert E. Lawson, AND Jr. FLOW STRUCTURE AND TURBULENT DIFFUSION AROUND A THREE-DIMENSIONAL HILL. FLUID MODELING STUDY ON EFFECTS OF STRATIFICATION. PART I. FLOW STRUCTURE. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/4-78/041.

Description:

This research program was initiated with the overall objective of gaining understanding of the flow and diffusion of pollutants in complex terrain under both neutral and stably stratified conditions. This report covers the first phase of the project; it describes the flow structure observed over a bell shaped hill (polynomial in cross section) through neutral wind tunnel studies and stably stratified towing tank studies. It verifies and establishes the limits of applicability of Drazin's theory for flow over three-dimensional hills under conditions of small Froude number. At larger Froude number a theory is developed, and largely verified, to classify the types of lee wave patterns and separated flow regions and to predict the conditions under which they will be formed. Flow visualization techniques are used extensively in obtaining both qualitative and quantitative information on the flow structure around the hill. Representative photographs of dye tracers, potassium permanganate, dye streaks, shadowgraphs, surface dye smears, and hydrogen bubble patterns are included. While emphasis centered on obtaining basic understanding of flow around complex terrain, the results are of immediate applicability by air pollution control agencies. In particular, the location of the surface impingement point from an upwind pollutant source can be identified under a wide range of atmospheric conditions. Part II, to be printed as a separate report, will describe the concentration field over the hill resulting from plumes released from upwind stacks and will further quantify the results obtained in Part I.

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