  Velocity profiles and wall shear stress values in the wall jet region of
planar underexpanded impinging jets are parameterized based on nozzle
parameters (stand-off height, jet hydraulic diameter, and nozzle pressure
ratio). Computational fluid dynamics is used to calculate the velocity fields
of impinging jets with height-to-diameter ratios in the range of 15 to 30 and
nozzle pressure ratio in the range of 1.2 to 3.0. The wall jet has an
incomplete self-similar profile with a typical triple-layer structure as in
traditional wall jets. The effects of compressibility are found to be
insignificant for wall jets with Ma<0.8. Wall jet analysis yielded power-law
relationships with source dependent coefficients describing maximum velocity,
friction velocity, and wall distances for maximum and half-maximum velocities.
Source dependency is determined using the conjugate gradient method. These
power-law relationships can be used for the mapping of wall shear stress as a
function of nozzle parameters.
