Wall attached strucures of velocity and tempreture fluctuations in high-speed turbulent channel flows

The study employs a clustering method to extract the coherent structures associated with intense streamwise velocity fluctuations and temperature fluctuations in high-speed turbulent channel flow. Based on their spatial locations, these structures are categorized into wall-attached and wall-detached types. A subset of the wall-attached structures exhibits self-similarity in scale, consistent with Townsend's attached eddy hypothesis, and are further classified into squat, self-similar, and tall structures. Conditional averaging results indicate that the streamwise Reynolds normal stress and the intensity of temperature fluctuations follow a logarithmic law in the logarithmic layer, a phenomenon that aligns with the attached eddy hypothesis; meanwhile, the strong Reynolds analogy relationship between velocity and temperature fluctuations remains valid within these attached structures. Analysis based on the RD identity decomposition reveals that tall structures associated with low streamwise momentum predominantly govern the generation of wall friction and heat flux, whereas tall structures linked to high-temperature events play a primary role in the transport of wall-normal heat flux.