scholarly journals Simulation of transonic buffet with an automated zonal DES approach

2020 ◽  
Vol 11 (4) ◽  
pp. 1025-1036
Author(s):  
Maximilian Ehrle ◽  
Andreas Waldmann ◽  
Thorsten Lutz ◽  
Ewald Krämer
Keyword(s):  
Three Dimensional ◽  
Reynolds Numbers ◽  
Research Model ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Shock Motion ◽  
Convection Speed ◽  
Transonic Buffet ◽  
Simulation Time

Abstract A study of transonic buffet on the NASA Common Research Model at flight Reynolds numbers is presented. The ability of two different hybrid RANS/LES models as well as the URANS approach for resolving three-dimensional buffet motion was evaluated by means of spectral analysis. Automated Zonal DES and URANS simulations show similar results in terms of buffet frequency and spanwise propagation of buffet cells, whereas the Delayed Detached Eddy Simulation results indicate a strong interaction between flow separation and shock motion. The extracted characteristic frequencies which are associated with transonic buffet are located in a range of Sr = 0.2–0.65 for URANS and AZDES and are therefore in accordance with findings from related recent research. Furthermore, the simulation time series were investigated and a structure of spanwise moving buffet cells with varying convection speed and wavelength could be observed.

scholarly journals Prediction and measurement of the aerodynamic performance of a wind turbine

2018 ◽  
Vol 240 ◽  
pp. 04001
Author(s):  
Ali Cemal Benim ◽  
Michael Diederich ◽  
Fethi Gül
Keyword(s):  
Wind Turbine ◽  
Transport Model ◽  
Three Dimensional ◽  
Detached Eddy Simulation ◽  
Simulation Framework ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Shear Stress Transport Model ◽  
Flow Turbulence ◽  
Good Agreement

Aerodynamic behavior of a small wind turbine is analyzed, both experimentally and numerically. Mainly, an unsteady three-dimensional formulation is adopted, where the flow turbulence is modelled by an Improved Delayed Detached Eddy Simulation framework, using the four-equation transitional Shear Stress Transport model, as the turbulence model. A quite good agreement between the measurements and calculations is observed.

scholarly journals Numerical Investigation of Powered Jet Effects by RANS/LES Hybrid Methods

2019 ◽  
Vol 37 (3) ◽  
pp. 565-571
Author(s):  
Zhibin Gong ◽  
Jie Li ◽  
Jixiang Shan ◽  
Heng Zhang
Keyword(s):  
Numerical Investigation ◽  
Hybrid Methods ◽  
Three Dimensional ◽  
Jet Flow ◽  
Weno Scheme ◽  
Detached Eddy Simulation ◽  
Turbulent Structures ◽  
Ambient Flow ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation

For the high-precision simulation of engine jet effects, an improved delayed detached eddy simulation (IDDES) method based on the two-equation shear stress transport (SST) model is developed, and the fifth-order finite-volume weighted essentially non-oscillatory (WENO) scheme is employed to enhance accuracy of spatial discretization, and then numerical investigation of powered jet effects by RANS/LES hybrid methods is carried out. The effects of the grid distributions and the accuracy of the spatial schemes are discussed during the RANS/LES validation analysis on the fully expanded jet flow and Acoustic Reference Nozzle (ARN) jet flow. The results show that, by enlarging the grid density and improving the accuracy of the spatial schemes, the velocity distributions in the jet flow can be better predicted, the non-physical steady flow after the jet nozzle can be shortened, the instantaneous flow structures are clearer and the turbulent intensities are more accurate. Then IDDES simulation of turbofan engine jet flow is carried out. The mixing characteristics of the external fan jet flow and internal core jet flow as well as the ambient flow are obtained, and the three-dimensional turbulent structures are also given.

Optimizing Jets for Active Control of Wake Refinement for Ground Vehicles

2015 ◽  
Vol 137 (12) ◽  
Author(s):  
Domenic L. Barsotti ◽  
Eduardo A. Divo ◽  
Sandra K. S. Boetcher
Keyword(s):  
Rear Surface ◽  
Reynolds Numbers ◽  
Special Focus ◽  
Detached Eddy Simulation ◽  
Ground Vehicles ◽  
Slant Angle ◽  
Eddy Simulation ◽  
Turbulent Coherent Structures ◽  
Delayed Detached Eddy Simulation ◽  
Ahmed Body

The present study investigates active drag reduction of an Ahmed body with a rear slant angle of 25 deg. The drag is reduced by implementing slot jets on the rear slant and rear surface of the Ahmed body. Transient numerical experiments were conducted using the improved delayed detached eddy simulation (IDDES) turbulence model. Jet velocity, position, size, and angle were parametrically varied, and time-averaged drag coefficients for various jet configurations were calculated. Reynolds numbers based on the length of the Ahmed body were varied, but special focus was given to the high-drag case when Re = 1.4 × 106. It was found that by using slot jets at the rear and rear slant, the drag coefficient was reduced by 22%. In order to investigate the physical mechanisms for the reduction in drag, proper orthogonal decomposition (POD) was used to visualize the turbulent coherent structures in the near wake of the Ahmed body.

Hydraulic modelling of brown trout habitat in a hydropower-impacted Alpine braided stream

2020 ◽  
Author(s):  
Yufang Ni ◽  
Stuart N. Lane
Keyword(s):  
Environmental Flows ◽  
Lateral Displacement ◽  
Three Dimensional ◽  
Suitable Habitat ◽  
Detached Eddy Simulation ◽  
Three Dimensional Model ◽  
Ice Melt ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Alpine Streams

<p>Braided rivers have complex and dynamic bed morphologies. In Alpine streams, they may be impacted upon by natural flow variability (e.g. snow and ice melt) that can lead to the lateral displacement of suitable habitat. To date, this process has been investigated in two-dimensional models due to the difficulty of applying fully three-dimensional computational fluid dynamics at the scale of river reaches. This is problematic because lateral and vertical variations in kinetic energy and vorticity and their change through time are crucial determinants of where good habitat is found and where it migrates to as river discharge changes. Here we attempt a reach-scale three-dimensional model of stream habitat using the open-source toolbox OpenFoam, with turbulence resolved by Delayed Detached Eddy Simulation (DDES), to model the flow structures in a braided reach of the Turtmanna, a tributary of the Rhône river, Switzerland. The results show that locations deemed suitable in a 2D solution are not when looked at in 3D, and vice versa. This result has important implications for the use of hydraulic habitat modelling for the design of environmental flows in human impacted Alpine streams.</p>

scholarly journals Prediction of Transonic Buffet by Delayed Detached-Eddy Simulation

AIAA Journal ◽  
2014 ◽  
Vol 52 (10) ◽  
pp. 2300-2312 ◽  
Author(s):  
Fernando Grossi ◽  
Marianna Braza ◽  
Yannick Hoarau
Keyword(s):  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Transonic Buffet
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