Investigation of Detached Eddy Simulations in Capturing the Effects of Coriolis Forces and Centrifugal Buoyancy in Ribbed Ducts

Abstract

The predictive capability of Detached Eddy Simulations (DES) is investigated in stationary as well as rotating ribbed ducts with relevance to the internal cooling of turbine blades. A number of calculations are presented at Re=20,000 and rotation numbers ranging from 0.18 to 0.67 with buoyancy parameters up to 0.29 in a ribbed duct with ribs normal to the main flow direction. The results show that DES by admitting a LES solution in critical regions transcends some of the limitations of the base RANS model on which it is based. This feature of DES is exemplified by its sensitivity to turbulence driven secondary flows at the rib side-wall junction, to the effect of Coriolis forces, and centrifugal buoyancy effects. It is shown that DES responds consistently to these non-canonical effects when RANS and URANS with the same model cannot, at a cost which is about a tenth of that of LES for the geometry and Reynolds number considered in this study.

A Review of Embedded Large Eddy Simulation for Internal Flows

“…Additionally several studies by Vishwanathan and Tafti [112,115,117], Liu et al [56] and Kubacki et al [47] successfully implemented hybrid based methods to predict the turbulent and mean flow features in stationary, rotating and roughened ribbed ducts -all documenting reasonable success.…”

High Reynold Number LES of a Rotating Two-Pass Ribbed Duct

“…In spite of DES taking a longer spatial extent to reach a fully-developed state, once it did so the predictions were in much better agreement with LES than URANS which failed to capture the secondary flows. In stationary fully-developed flow [94] and with rotation [95] at Re = 20,000, Ro = 0.18 to 0.67 and Bo up to 0.29, it was shown by Viswanathan and Tafti that DES was superior to RANS and URANS in capturing the effects of Coriolis and centrifugal buoyancy forces. Along the same lines of reducing the computational burden of LES, Patil and Tafti [96] used a zonal two layer-wall model for LES.…”

Simulation of the Flow in a Ribbed Rotating Duct with a Hybrid k-ω RANS/LES Model

“…Coletti et al [7] observed that the Coriolis force affects the dynamics of both large and small scales, leading to complicated flow patterns with recirculation zones and secondary vortex motions. As discussed above, the applicability of a hybrid RANS/LES technique of DES type to flow in a ribbed rotating duct was already investigated by Viswanathan and Tafti [12,13], but comparison was made with LES results. Since LES involves modelling, we argue that it has added value to compare with high-quality experimental data.…”

“…They found that the peak values of the turbulent kinetic energy differ by a factor of two in the boundary layers on the suction and pressure sides of the channel and that the amplitude of the small-scale fluctuations close to the pressure side changes significantly with the rotational speed. The LES data of Abdel-Wahab and Tafti [11] were used by Viswanathan and Tafti [12,13] as reference data for testing a hybrid RANS/LES turbulence model of DES-type (Detached Eddy Simulation), based on the k-ω SST model. They showed that the DES results are quite close to the LES results, although the grid for DES was a factor of 2 coarser in each direction.…”