Mean Velocity and Static Pressure in a Sharp-edge Circular Nozzle Jet

An axisymmetric jet issued from a sharp edged circular convergent nozzle has been studied experimentally in the near field at Reynolds number ۵.۳x۱۰۴  to search the saddle shape behavior of mean velocity and the role of mean static pressure in the jet flow. Due to the vena contracta effect the centerline mean velocity of the jet increases about ۴.۲% of its exit value and corresponding decrease of mean static pressure is found in the potential core of the jet. Streamwise mean velocity shows saddle shape profile adjacent to the mixing layer near the exit (due to secondary current). Velocity peaks are associated with corresponding drop of mean static pressure. This saddle shape behavior is found to die down at the end of the potential core. The geometric virtual origin is at downstream of the nozzle tip and the entrainment rate is increased nonlinearly with the axial distance. A partial self-preservation of mean velocity is attained earlier than that of mean static pressure.

Keywords:

Axisymmetric Jet , Circular Convergent Nozzle , Saddle Shape Behavior , Jet Flow. Vena Contracta Effect