Phase measurements with reduced sensitivity of a supersonic shock flow by two-wavelength dual hologram shearing interference technique

A novel two-wavelength technique has been applied to holographic shearing interferometry of shock wave flows around sharp and blunt nose cone models in a supersonic wind tunnel. The technique with reduced sensitivity and practically full compensation for optical aberrations, makes it possible to eliminate the difficulties of interference analysis of areas where step discontinuities in the density gradients occur. Such a case takes place in the region near the bow shock. Reconstructed lateral shearing interferograms with reduced sensitivity having a maximal fringe shift less than unity, could be used to conduct simplified numerical analysis of the density gradient distribution in the vicinity of the nose of models, without any complementary assumptions.