Frequency evaluation of temperature fluctuations related to thermal striping phenomena using a direct numerical simulation code DINUS-3

A three-dimensional temperature fluctuation analysis was carried out using a general-purpose multi-dimensional thermohydraulics direct numerical simulation code DINUS-3 for a parallel impinging jet experiment in water simulating thermal striping phenomena. The code was incorporated with a third-order upwind scheme and an adaptive control system based on the Fuzzy theory to control time step sizes. Calculational results showed good agreement with the measured peak-to-peak value and its dominant frequency component of the temperature fluctuations. From the analysis, it was concluded that: (1) the third-order upwind scheme is recommended in specific engineering applications such as thermal striping analysis where thermohydraulic interactions between turbulent flow and temperature fields are of great importance, (2) the scheme has a sufficiently high potential in providing good interpretation of experimental results related to the temperature fluctuation phenomena such as thermal striping, and (3) the adaptive control system using the Fuzzy theory can be used as one of the efficient measures to save computing efforts when one wishes to perform extremely large scale turbulence flow computations in transient thermohydraulics