Self-Induced Oscillations of a Jet Flowing Over the Wedge. The Mechanism of Appearance of the Feedback

Resumo

As a result of the direct numerical analysis of the nonstationary system of Navier–Stokes equations, we solve the problem of submerged jet formed by a narrow channel (nozzle) and flowing over a sharp rigid wedge. The time dependences of the vortex and pressure fields in the course of the transient processes and the process of stationary self-induced oscillations of the jet are established. It is shown that the role of hydrodynamic feedback channels in the transient process is played by the vortex formations generated at the time when the jet meets the wedge and moving against the jet flow. In the process of steady self-induced oscillations, the hydrodynamic feedback channel is formed due to the pressure drop on the wedge faces and periodic changes in its sign. This leads to the formation of a periodic flow in the medium from one face of the wedge to the other face and, hence, to the periodic transverse deflections of the jet. The comparison of the theoretically estimated frequency of self-induced oscillations of the jet with the experimentally obtained value reveals their coincidence with graphical accuracy.