Simultaneous measurement of velocity and pressure near the turbulent/non-turbulent interface of a planar turbulent jet

• Velocity and pressure near the turbulent/non-turbulent interface was measured.
• There was a thin interfacial layer between the turbulent/non-turbulent region.
• Layer thickness was 0.08 times the half-width of cross-streamwise profile of velocity.
• Rapidly changing of velocity, Reynolds stress, and pressure were found at the layer.
• Pressure diffusion has a role to transport turbulent energy to non-turbulent region.

Simultaneous measurement of velocity and pressure near the interface of turbulent/non-turbulent region of a planar turbulent jet is performed. Simultaneous measurement is achieved by means of a combined probe comprising an X-type hot-wire and a static pressure probe. The measurement data are analyzed by the conditional sampling technique and the ensemble-averaging technique on the basis of the intermittency function for the turbulent/non-turbulent decision. Obtained results show that there is a thin interfacial layer between the turbulent/non-turbulent region accompanied with the rapidly changing of velocity, Reynolds stress, and pressure. The thickness of the interfacial layer is 0.08 times the half-width of the cross-streamwise profile of the mean streamwise velocity and almost the same as Taylor transverse micro scale at the measurement position. Further, the velocity and pressure field near the interfacial layer indicates the existence of vortices whose core is at the middle of the interfacial layer and its diameter is the same as the thickness of the interfacial layer. The turbulent energy production and diffusion near the interface are also investigated by estimating the production term and the diffusion term in the transport equation for the turbulent energy. Estimated results show that the turbulent energy is transported from the turbulent region to the outer non-turbulent region by the pressure diffusion. Therefore, the existence of the vortices near the interface has an important role to transport the turbulent energy to the outer non-turbulent region.