A spiral long-periodic structure of the turbulent flow core in a heated rectangular duct with inclined ribs at a wall

Paper presents the results of the numerical modeling of the turbulent airflow in a rectangular duct 50 caliber length, on one wall of which straight ribs inclined to the axis of the channel at an angle of 45 degrees are periodically located. The simulation covered the range of the Reynolds number from 10$^4$ to 2 $\cdot$ 10$^5$. It has been established that with all Re number values the long areas of statistically stationary spiral flow are formed. Specific phases of the spiral flow structures formation have been identified as they developed from the channel entrance. It is shown that the parameters (friction and heat transfer) of the flow with developed spiral structures are close to the parameters of the spatially periodic flow with the same Re number. The presence of specific phases of the spiral flow formation obtained in a numerical modeling are confirmed with the presented in the literature results of physical experiments.