要約

A proper orthogonal decomposition (POD) analysis of fully developed turbulent channel flow with density variation under some conditions of unstable stratification at Re_τ = 150 and Pr = 0.71 is considered. The minimum size of POD integration domain necessary to cover at least one whole coherent structure in the cross-stream direction is determined to be equivalent to that of minimal flow unit. To apply POD to the fully developed turbulent channel flow with density variation, the flow field ( u, υ, ω, ρ and θ) is scaled by the corresponding root mean square values (rms) so that the flow field becomes dimensionless. A five-vector POD problem is solved numerically. The reconstructed velocity, temperature, and density from POD eigenfunctions are compared with the original data. The method is tested by applying POD to an isothermal channel flow data at the same Re_τ with and without scaling the flow field. The POD eigenfunctions from both cases are identical. The reconstructed coherent structures from the channel with density variation are less than those reconstructed from the isothermal channel for the same domain size.