抄録
Separation phenomena in a 90-deg square section bend with long tangents were studied by the flow visualization technique.
A formula for the separation point on the inner wall is obtained by experiments at Reynolds numbers ranging from about 4000 to 20, 000.
The onset of separation is discussed on the basis of streamwise distribution of pressure in a bend. It is shown that the increment from the pressure at the inner wall in the 45-deg cross section to that at the separation point takes a constant value. This constant is independent of both the dimensionless curvature and the Reynolds number. By applying this value to the index for the separation, a calculation procedure for predicting the existence of separation is proposed.
There is good agreement between the calculation and the experiments for dimensionless curvatures from 0.125 to 0.5 at Reynolds numbers ranging from about 4000 to 20, 000. It can be predicted whether separation actually takes place or not in a 90-deg square section bend with long tangents.
