SELF-EXCITED VIBRATION OF A FLAT PLATE WITH A HOLE FOR WATER FLOW

In fluid machines such as turbo-pumps and hydro-turbines, self-exited vibrations are among the most serious problems that can cause accidents. However, there have been few reports on the self-excited vibrations, which are treated as a coupled problem between the stiffness of the plate and flow disturbance. Basic studies have been performed to clarify the mechanism of the cover-plate vibration induced in the turbo machinery. In the present study, we employ a water tunnel using a test section comprising a flat plate with a hole and pressure chamber that simulates the passage of impeller of the hydraulic machines, and we discuss the characteristics of the self-excited vibration of a flat plate using a hole for water flow. The results show that the vibration occurs when the natural frequency of the plate corresponds approximately with the specific frequency when the Strouhal number St approximate to 0.5, and the frequency of flat-plate vibration depends on the flow velocity. In addition, we show that the amplitude of the vibration is related to the thickness of the plate, geometry of the hole (circle, square), and flow angle for the square hole.