Spectral analysis on dissimilarity between turbulent momentum and heat transfers in plane Couette turbulence

Nonlinear interactions between different scales in turbulence result in both interscale and spatial transport of turbulent energy, and their role in the turbulent heat transfer mechanism is also of practical importance from an engineering viewpoint. In this study, we investigate a turbulent plane Couette flow with passive-scalar heat transfer at the Prandtl number of 0.71 to discuss the similarity/difference between scale interactions in velocity and temperature fields. The constant-temperature-difference boundary condition is used so that the mean velocity and temperature profiles are similar, and then, the roles of interscale and spatial transports are compared for the spectral transport budgets of turbulent energies and temperature-related statistics. We show that turbulent heat transfer occurs at relatively small streamwise length scales compared to momentum transfer, although molecular diffusion is more significant in the temperature field as the Prandtl number is less than 1. Detailed analysis on the transport budgets of temperature-related spectra shows that scale interactions in the temperature field supply more energy to small scales than those in the velocity field. This significant temperature cascade causes more energetic temperature fluctuation at small scales, resulting in the spectral dissimilarity between turbulent heat and momentum transfers. Published under an exclusive license by AIP Publishing.

Automated summary

Nonlinear interactions between different scales in turbulence play an important role in the transport of turbulent energy and the heat transfer mechanism. This study investigates the interactions between scales in velocity and temperature fields in a turbulent plane Couette flow with passive-scalar heat transfer. The results show that turbulent heat transfer occurs at smaller length scales compared to momentum transfer, and the scale interactions in the temperature field supply more energy to small scales. The significant temperature cascade leads to more energetic temperature fluctuation at small scales, resulting in spectral dissimilarity between turbulent heat and momentum transfers. Published under an exclusive license by AIP Publishing.