Record Display for the EPA National Library Catalog


Main Title Obstacle Drag in Stratified Flow.
Author Castro, I. P. ; Snyder, W. H. ; Baines., P. G. ;
CORP Author Environmental Protection Agency, Research Triangle Park, NC. Atmospheric Research and Exposure Assessment Lab. ;Surrey Univ., Guildford (England). Dept. of Mechanical Engineering. ;Commonwealth Scientific and Industrial Research Organization, Aspendale (Australia). Div. of Atmospheric Research.
Publisher c1990
Year Published 1990
Report Number EPA/600/J-90/185;
Stock Number PB91-116814
Additional Subjects Atmospheric motion ; Fluid flow ; Drag ; Stratification ; Inviscid flow ; Turbulent flow ; Wakes ; Reynolds number ; Three dimensional flow ; Lee waves ; Air currents
Library Call Number Additional Info Location Last
NTIS  PB91-116814 Some EPA libraries have a fiche copy filed under the call number shown. 07/26/2022
Collation 25p
The paper describes an experimental study of the drag of two- and three-dimensional bluff obstacles of various cross-stream shapes when towed through a fluid having a stable, linear density gradient with Brunt-Vaisala frequency, N. Drag measurements were made directly using a force balance, and effects of obstacle blockage (h/D, where h and D are the obstacle height and the fluid depth, respectively) and Reynolds number were effectively eliminated. It is shown that even in cases where the downstream lee waves and propagating columnar waves are of large amplitude, the variation of drag with the parameter K (=ND/U) is qualitatively close to that implied by linear theories, with drag minima existing at integral values of K. Under certain conditions large, steady, periodic variations in drag occur. Simultaneous drag measurements and video recordings of the wakes show that this unsteadiness is linked directly with time-variations in the lee and columnar wave amplitudes. It is argued that there are, therefore, situations where the inviscid flow is always unsteady even for large times; the consequent implications for atmospheric motions are discussed.