Experimental and Numerical Study of Orifice Discharge Coefficients in High-Speed Rotating Disks

Experimental and numerical results of the flow through orifices in rotating disks are presented, with emphasis on basic physical phenomena. It is shown that rotational effects strongly influence the massflow discharged, a phenomenon that cannot be modeled by a stationary setup. The study includes the determination of discharge coefficients under variation of the length-to-diameter ratio, pressure ratio, and rotational speed. The pressure ratio covers low as well as critical values, the maximum rotational speed is 10,000 rpm, which is equivalent to a tangential velocity of 110 m/s. In order to understand the flow structure, local flow velocities were measured by means of a two-dimensional Laser-Doppler Velocimeter. Phase-resolved measurements have been carried out in front of and behind the orifices. A three-dimensional Finite-Volume Code with body-fitted coordinates in a rotating frame of reference is employed for the numerical analysis and the verification of its possibilities and limitations. The results reveal a very complex flow field, which is dominated by high velocity gradients in close vicinity to the orifices. The comparison of the computational solutions with the experimental data shows good agreement. Based on the measurements in combination with the numerical solution, a detailed insight into the physical properties of the flow is achieved.