Uncertainty Quantification in Heat and Fluid Flows Around Staggered Pin-Fin Arrays Based on Hybrid RANS/LES Model

Abstract

In the present work, the three dimensional heat and fluid flows around staggered pin-fin arrays are predicted using two Hybrid RANS/LES, Improved Delayed Detached Eddy Simulation(IDDES) and Stress Blended Eddy Simulation (SBES) and one transitional Unsteady Reynolds Averaged Navier-Stokes (URANS) model, k- SSTLM. The periodic segment geometry with total 8 pins is considered with the channel height of 2D and the distance of 2.5D between each pin. The corresponding Reynolds number based on the pin diameter and the maximum velocity between pins is 10,000. Two Hybrid RANS/LES results show superior prediction in mean velocity profiles around pins, pressure distributions on the pin wall and Nusselt number distributions. However, transitional model, k- SSTLM show large discrepancy except in the front part where the flow is not fully developed. The two Hybrid RANS/LES models resolve the vortical structures well Specially, SBES model is able to capture the three dimensional vortical structures after the pin. The effect of the blending function switching between RANS and LES mode of two Hybrid RANS/LES model is investigated.

The Uncertainty Quantification Forward problem is conducted with non-intrusive polynomial chaos expansion. The input variable is set as inlet velocity. it is assumed as a uniform distribution or normal distribution. Its mean μ is 3.45m/s and standard deviation σ is ±0.1 μ. The quantity of interest is the average Nusselt number and the local Nusselt number. The results show that probability density function of output is strongly affected by probability distribution of input.