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The flow characteristics of suband supersonic under-expanded jets issued from circular nozzles have been studied well. For example, Donaldson & Snedeker (1971) classified the flow pattern of suband supersonic under-expanded jets issued from a smoothly converged contour nozzle in three depending on the pressure ratio of the supplied pressure p0 to the ambient pressure pa. In the ranges of 1.0 < P0/Pa < 1.89, 1.89 < p0/pa < 3.85 and 3.85 < p0/pa , the jets are subsonic, moderately under-expanded, and highly under-expanded jets, respectively, as shown in the following figure. Kojima, et el. (1986), and Zapryagaev & Pivovarov (2015) showed the mechanism of shock waves and the pressure and velocity distribution of supersonic jet, Shadow, et al. (1990) showed the compressible spreading rates of supersonic coaxial jets, Katanoda, et al. (1995) showed the effects of divergence angle of nozzle and Mach number on shock cell length, Murakami & Papamoschou (2000) showed the flow characteristics of coaxial supersonic jet, Ikui & Matsuo (2001) showed the theoretical and experimental flow characteristics of supersonic jet, and Otobe (2007) studied the effect of non-equilibrium condensation on supersonic jet. However, the suband supersonic jets from an orifice nozzle have not been studied well (Shakouchi et al.,2016). In this study, the flow characteristics of suband supersonic under-expanded jets issued from an orifice or notched orifice nozzle are investigated experimentally using the results of visualized flow pattern by the Schlieren method and the measurements of velocity distribution using a thin supersonic Pitot tube (Shakouchi et al., 2016). The effects of the nozzle shape (Shakouchi et al., 2016; Zaman, 1999; Chanpagne & Wygnanski, 1971; Shakouchi, 2005; Carletti et al., 1996; Behrouzi et al., 2008; Shakouchi et al., 2001) on the flow characteristics such as the decay of the jet centerline velocity, velocity distribution at the cross section and increments in the jetwidth and flow rate to the downstream are examined. An orifice nozzle with small or large notches was used in addition to circular and orifice nozzles with various contraction area ratios. The notch was used to disturb the flow around the outer edge of the jet and to enhance the entrainment flow rate. Received: 22 April 2019; Revised: 23 July 2019; Accepted: 6 September 2019

Flow characteristics of sub- and supersonic jets issued from orifice and notched orifice nozzles, and application to ejector