Research on Wave Phenomena in Hydraulic Lines : 9th Report, Experimental Investigation of Oscillatory Orifice Flows

Abstract

Reciprocating oil flows through orifices are measured with the intention to verify the 'viscous end correction' theory developed in the previous paper. The impedance tube technique in acoustics can help detect varying-with-time flow rates. The transitional relation between the pressure drop across and flow rate through an orifice over one period is observed as a colsed hysteresis curve. These curves show such peculiar features as sharp tips, inflected distortions and eventual self-crossings according as the nonlinearity grows. Although obtained data are more or less subject to the nonlinear effects, the orifice resistance in the linear region is successfully evaluated from them by extrapolation. The results endorse the validity of the present theory, dismissing Sivian's attempt to apply Rayleigh's end correction tube to harmonic viscous flows. Another finding is that the nonlinear pressure loss in an oscillatory orifice flow falls below its steady-state conterpart.