Nozzles for jet stabilization of rocks

Abstract

The shape of the exit nozzles has great importance when developing the working part of a hydraulic jet monitor. All possible types of nozzles have already been investigated in certain experimental works of A. D. Al'tshul', I. E. Idel'chik, B. N. Siov, S. S. Shavlovskii, et al. [1, 2, 4]. In the present article the authors make an attempt to generalize collected data and to substantiate the type of nozzle which can be used in jet technology of rock stabilization. During discharge of a fluid through a round orifice without an extension (Fig. la), i.e., a sharp-edge orifice, the fluid particles smoothly round it. The extreme streams impart to the jet a conoidal shape and cause its contraction at the exit from the orifice. Contraction of the jet occurs also during discharge of a fluid through a cylindrical orifice having an extension (Fig. lb). But after that the discharge can flow differently. In the ftrst case, behind the smallest section of the jet its gradual expansion occurs. It reaches the inside walls of the orifice and flows out without contraction. An isolated annular cavity forms. This is that region which is filled with air and is located between the orifice walls and contracted section of the jet. The pressure in this region is Pc. In the second case the discharge differs in no way from discharge from a orifice without an extension, but the velocity in the contracted section can be described by the equation