The structure of turbulence associated with an internal thermal layer

Statistical properties of velocity and temperature fluctuations associated with an internal thermal layer are presented. An internal thermal layer is formed when a fully developed turbulent boundary layer is subjected to a step change in surface heat flux. Individual and joint probability density functions of longitudinal and normal velocity fluctuations and of the temperature fluctuation are derived both in the conventional sense and in the conditional mode, when only the heated or nonheated parts of the flow are considered. Several features of these density functions are discussed.