EXPERIMENTS ON RESPONSE OF IMPINGING-JET EDGE TONE TO EDGE MISALIGNMENT AND SPANWISE COHERENCE OF THE JET

The edge tone generated by two-dimensional jet impinging on a circular cylinder was modulated by; first, changing the normal distance between the axis of the jet and that of the cylinder Δy, second, inclining the axis of the cylinder with respect to the span of the jet by an angle θ iand third, reducing the spanwise coherence of the jet by the use of a thin circular rod (attached to the exit of the nozzle) whose axis was normal to the span of the jet. The normal distance Δy, the angle θ and the diameter and spanwise position of the rod were systematically changed. There existed a critical value of these parameters beyond which the regular edge tone of high amplitude was replaced by an irregular sound of a much lower level. The critical values were functions of the jet velocity. At the critical values of the parameters the regular edge tone and the irregular sound switched randomly with an average interval which was much greater than the period of the regular edge tone.