Abstract
This 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
/π
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.
Reference33 articles.
1. Baines P. G. 1977 Upstream influence and Long's model in stratified flows. J. 82. 147-159.
2. Observations of stratified flow over two-dimensional obstacles;Baines P. G.;Tellus,1977
3. Stratified flow over finite obstacles with weak stratification
4. Stratified flow over two-dimensional topography in fluid of infinite depth: a laboratory simulation. J. atmos;Baines P. G.;Sci.,1985
5. The nature of upstream blocking in uniformly stratified flow over long obstacles
Cited by
38 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献