Visualization of Multi-scale Turbulent Structure in Lobed Mixing Jet Using Wavelets

The two-dimensional orthogonal wavelet transform was applied to the LIF image of lobed mixing jet for identifying the multi-scale turbulent structures. The digital imaging slice photographs at z /D = 1.0 and 1.5 with Re = 3000 were respectively decomposed into seven image components with different broad scales. These image components provided the visualized information on the multi-scale structures in a lobed mixing turbulent jet. The cores and edges of the vortices and the coherent structures at different resolutions or scales can be easily extracted. It was found that the scale range of the coherent structure becomes narrow along the downstream direction. The size of the intermediateand small-scale structures does not vary significantly with downstream distance.