The Unsteady Jet from the Metering Orifice of a Spool Valve : The Case Where the Upstream-side Wall is Oscillating

Abstract

This paper deals with the unsteady free jet issuing from a spoolvalve opening which varies sinusoidally. The flow pattern of the free jet is analyzed using conformal mapping, where the flow is assumed nonviscous. Experiments were conducted to visualize the flow inside the spool-valve. The theoretical results agree fairly well with the experimental ones. The following conclusions are drawn ; (a) The unsteady velocity component ν_x1 in the axial direction at infinity takes a maximum at ΩΞ2αf/ν_∞=0.3∼0.4 where a is the width of the jet at infinity, f the frequency of the valve opening and ν_∞ the steady flow velocity at infinity. (b) The increase of the clearance between the valve body and the spool land decreases ν_x1 for Ω>0.18 and increases it for Ω<0.18. (c) The phase lag of ν_x1 to the velocity U of the boundary wall increases with Ω or h/l for Ω>0.3. (d) The amplitude of the jet angle increases with the amplitude of U.