Experimental study of stability of strongly underexpanded laminar free and impact jets

The growth rates of density fluctuations in the mixing layer of strongly underexpanded low-density jets are measured by the electron-beam technique within the range of Reynolds numbers $\mathrm{Re}_{\mathrm{L}} = 50-230$. Regimes of self-induced oscillations are determined for these flow conditions in the case of a jet incident normally onto a finite-size target. Results on the frequency of pressure oscillations on the target are obtained and compared with the spectra of the growth rates of density fluctuations in the mixing layer of free jets. It is shown that self-induced oscillations cannot be sustained because of the development of instability in the mixing layer of the jet.