Journal Article

Numerical predictions of detailed flow structural characteristics in a channel with angled rib turbulators

Ligrani, P. M., Park, Jongmyung, Park, Samgyu

2015

Overview

Turbulent air flows within a channel with angled rib turbulators (45 degrees) on one wall are numerically predicted using the numerical code ANSYS CFX with a Shear-stress transport (SST) κ-ω turbulence model, and a hexahedral grid with 7115346 cells and no wall function. Three-dimensional turbulent transport, and detailed flow structural characteristics are considered to provide new insight into the mechanisms which result in surface heat transfer augmentations. Time-averaged turbulent flow characteristics and surface Nusselt number distributions are presented for an inlet turbulence intensity level of 1.0 percent, and for Reynolds numbers based upon channel height of 18300 and 48000. Overall, the numerically-predicted results show that large-scale, secondary flow induces a collection of small-scale vortical flows in the channel, as a result of local interactions with individual rib turbulators. These are often associated with different sized and highly skewed vortex pairs, which also induce secondary advection and increased turbulent mixing near ribbed channel surfaces. Within the flow separation regions, just downstream of each rib, surface Nusselt number ratios which are locally lower than for other surface locations, and local secondary flows are generally and partially characterized as upwash flows, with large positive magnitudes of spanwise vorticity, large static pressure deficits, and large static pressure augmentation regions. As the shear layers (initially located above the recirculation zones) impinge onto the test surface, increased mixing develops, as well as local thinning of the reattaching boundary layers, which lead to local Nusselt numbers which are generally higher than for other locations along the test surface.

• Publisher: Korean Society of Mechanical Engineers,Springer Nature B.V,대한기계학회
• Subject: Air flow / Boundary layer / Boundary layers / Channels / Computational fluid dynamics / Control / Dynamical Systems / Engineering / Flow characteristics / Flow separation / Fluid flow / Heat transfer / Industrial and Production Engineering / Mathematical models / Mechanical Engineering / Numerical prediction / Nusselt number / Reynolds number / Secondary flow / Shear layers / Static pressure / Turbulence / Turbulence intensity / Turbulence models / Turbulent flow / Turbulent mixing / Upwash / Vibration / Viscosity / Vorticity / Walls / 기계공학