密度流におけるコリオリ効果に関する研究 (2)-回転系の交換密度流実験-

Abstract

In order to clarify the effects of Coriolis' force on density currents in estuaries and lakes, experiments of rotating lock exchange flow were carried out under the condition of Reynoldsnumber Ro=140～1400, Rossby number Ro=O.14～11.8 and Ekman number Ev=2.4x10 -4～2.Ox10 -2.Discharge reduction in the underflow, transverse deviation of the underflow (salt water)fronts and increase of the front velocity were observed under rotating condition, and criterionof rotating regime is estimated from the discharge reduction as Ro-4.0. For the strongrotaing regime Ro<1, it was found that inviscid rotating hydraulics could be applied tothe flow in Ev<O(10-3). The effects of Ro and Ev on the exchange flow are evaluated fromthree kinds of time 1/f, b/V⊿ and H2/ν, where f; Coriolis' parameter, b; breadth of thebasin, V⊿=√g'H ; densimetric velocity, g'; reduced gravity accelaration, H ; the depth, ν;kinematic (eddy) viscosity.The characteristics of mixing layer of lock exchange flow and effects of abrupt channelexpansion on density currents are briefly discussed on the basis of experimental results bymeans of a new flow visualization technique.