Static Pressure Fluctuations in Round Jet Region of Jet Mixing

Abstract

Static pressure fluctuations were measured in a turbulent jet region of jet mixing by a probe which consisted of electrodes for measuring velocity and a small pressure transducer. Experimental results about the root-mean-square value of static pressure fluctuations p′ were newly obtained, and the relation between p′ and velocity fluctuations u′ was quantitatively investigated by using the turbulent Euler number Eu, which was defined as the ratio of p′ to the representative turbulent kinetic energy ρu′².
The value of Eu was constant in the jet region of fully-developed turbulent conditions near the nozzle exit at large Reynolds numbers. On the other hand, with decreasing Reynolds number Re or with greater distance of the measured point from the nozzle exit, the value of Eu showed a tendency to increase. The distribution of Eu along the jet axis was correlated with Re·d/ (z+a) ((z+a) /d: dimensionless distance from the virtual source of the jet) and a critical value of Re·d/ (z+a) for the turbulent condition in the jet region was found.