Wavelength measurement of a liquid jet based on spectral analysis of image intensity

Abstract

The instability analysis of the liquid jet issuing into ambient gas was conducted with the emphasis placed upon the evolution of surface wave on the jet surface. First, an experimental method was developed to visualize the microscopic surface wave on the liquid jet. Camera setting parameters significantly affecting the detection of desired jet features were discussed. Second, a spectral method was applied to process the obtained jet images. The accuracy of this method was validated in several ways. The results show that wavelengths increase monotonically along the streamwise direction and decrease with the increase in Reynolds number which corresponds to the boundary layer momentum thickness at nozzle exit. Various patterns of wave structures on jet surface are revealed. In this article, the pattern transforms from three-dimensional to two-dimensional at Reynolds number of 134.53.