High speed water jets in air are extensively used in manufacturing industry for cutting and
cleaning operations. Water jets are used for removal of various coatings or deposits from the
substrates and also for the cutting of many materials. While water jet cutting involves the
penetration of a solid material by a continuous jet, water jet cleaning involves an erosion process
by which deposits are removed from the material surface. Hashish and duPlessis (1978,1979)
investigated the jet cutting process both analytically and experimentally. They performed a
control volume analysis to evaluate the hydrodynamic forces. Later, their work was extended to
find the optimal stand-off distance. Similar analysis was performed by Leu et al. (1998) for the
case of water jet cleaning. Cleaning water jets generally have the velocity range of ~80-200 m/s.
They exhibit a high velocity coherent core surrounded by an annular cloud of water droplets
moving in an entrained air stream. Leu et al. (1998) as well as Rajaratnam et al. (1994, 1998)
have discussed the anatomy of high speed water jets in air; see Figure