抄録
The discharge coefficient of a circular orifice set concentrically to the bottom of a circular cylinder vessel was studied experimentally in the flow into the air under the head lowering with the time. The discharge coefficient of orifices Cd was determined by the conventional formula and the effect of several factors (Reynolds number Re, Weber number Wr, diameter ratio D/d, thickness-diameter ratio h/d and dimensionless head H/d) to Cd was discussed. It was found that Cd decreased with an increase of Re under a constant value of Wr, Cd was almost independent of D/d and Cd increased with an increase of h/d. Besides, we tried to formulate the effect of some factors (Re, Wr and h/d) to Cd and proposed an experimental formula in the range of Re=1100-14500, Wr=100-700 and h/d=0.1-0.4.
