Experimental Study on the Stably Stratified Flow over Three-dimensional Ridges

An experimental study has been made of the stably stratified flow over three-dimensional ridges with isosceles triangle sections. The experiments were performed by towing models through saline-water solutions with linear density gradients. The ratios of the spanwise width of the model to its height have been changed between 2 and 6. Flow structures around models were visualized by means of the electrolytic precipitation method and tracer particles method. The velocity fields at several vertical cross sections were determined by PIV method. The Froude number Fr (=U0/Nh) was changed from 0.05 to 1.65 (and ∞), where U0 is the towing speed, N the Brunt-Vaisala frequency and h the height of models. The structure of the flow over the ridge is characterized by the value of Fr. The value of the dividing-streamline height on the upstream side of the ridge has become a little small with increase of the aspect ratios for each value of Fr.