Improved Delayed Detached Eddy Simulation of Separated Flow

A highly loaded, high-speed turn flight of Airbus Helicopters' Bluecopter demonstrator helicopter is simulated to investigate dynamic stall using a loose computational fluid dynamics/structural dynamics (CFD/CSD) coupling of the flow solver FLOWer and the rotorcraft comprehensive code CAMRAD II. The rotor aerodynamics is computed using a high-fidelity delayed detached-eddy simulation (DDES). A three-degree-of-freedom trim of an isolated rotor is performed, yielding main-rotor control angles that agree well with the flight-test measurements. The flow field in this flight condition is found to be highly unsteady and complex, featuring massively separated flow, blade–vortex interaction, multiple dynamic-stall events, and shock-induced separation. The computed pitch-link loads are compared to flight-test measurements. This shows that all CFD/CSD cases underpredict the amplitudes of the flight test and yield phase shifts. However, overall trends agree reasonably. Also, varying the computational setup reveals that the shear stress transport–DDES turbulence model performs better than Spalart–Allmaras–DDES, that the consideration of the rotor hub and fuselage improves the agreement with flight-test data, and that the elastic twist plays only a minor role in the dynamic-stall events.

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Detached Eddy Simulation of Transition in Turbomachinery: Linear Compressor Cascade

Journal of Turbomachinery ◽

10.1115/1.4052309 ◽

2021 ◽

pp. 1-10

Author(s):

Zifei Yin ◽

Paul Durbin

Keyword(s):

Boundary Layer ◽

Large Scale ◽

Separated Flow ◽

Adaptive Model ◽

Detached Eddy Simulation ◽

Compressor Cascade ◽

Linear Compressor ◽

Eddy Simulation ◽

Delayed Detached Eddy Simulation ◽

Linear Compressor Cascade

Abstract The adaptive, l2-omega delayed detached eddy simulation model was selected to simulate the flow in the V103 linear compressor cascade. The Reynolds number based on axial chord length is 138,500. Varies inflow turbulent intensities from 0% to 10% were tested to evaluate the performance of the adaptive model. The adaptive model is capable of capturing the laminar boundary layer and the large scale perturbations inside it. The instability of large scale disturbances signals the switch to a hybrid simulation of turbulent boundary layer -- the transition front is thus predicted. In the case of separation-induced transition, the adaptive model, which uses eddy simulation in separated flow, can predict the separation bubble size accurately. Generally, the adaptive, delayed detached eddy simulation model can simulate the transitional separated flow in a linear compressor cascade, with a correct response to varying turbulent intensities.

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Computational study of active flow control drag reduction device for utility vehicle

E3S Web of Conferences ◽

10.1051/e3sconf/201912809003 ◽

2019 ◽

Vol 128 ◽

pp. 09003

Author(s):

Jęedrzej Mosiężny ◽

Bartosz Ziegler

Keyword(s):

Drag Reduction ◽

Computational Study ◽

Active Flow Control ◽

Separated Flow ◽

Flow Region ◽

Detached Eddy Simulation ◽

Eddy Simulation ◽

Delayed Detached Eddy Simulation ◽

Active Flow ◽

Base Drag

The study presents a computational study of a drag reduction device based on an active boundary layer control for a generic truck-trailer utility road vehicle. The conceptual device is in accordance with upcoming EU regulations regarding attachable aerodynamic devices for heavy utility vehicles. Design and principles of operation of the conceptual device are presented. The device is intended to increase decrease the trailer’s base drag coefficient by manipulation of the separated flow region behind the vehicle base. Results of a steady state Reynolds averaged analysis and Delayed Detached Eddy Simulation are presented to show the discrepancies of fluid flow patterns between baseline and augmented configuration as well as between mentioned CFD approaches. Results for drag reduction for baseline truck-trailer configuration and aerodynamically augmented configuration are presented.

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Assessment of DES Models for Separated Flow From a Hump in a Turbulent Boundary Layer

Journal of Fluids Engineering ◽

10.1115/1.4000376 ◽

2009 ◽

Vol 131 (11) ◽

Cited By ~ 15

Author(s):

Daniel C. Lyons ◽

Leonard J. Peltier ◽

Frank J. Zajaczkowski ◽

Eric G. Paterson

Keyword(s):

Boundary Layer ◽

Turbulent Boundary Layer ◽

Mean Field ◽

Separated Flow ◽

Separation Point ◽

Navier Stokes ◽

Detached Eddy Simulation ◽

Flow Solver ◽

Eddy Simulation ◽

Delayed Detached Eddy Simulation

Separated flow past a hump in a turbulent boundary layer is studied numerically using detached-eddy simulation (DES), zonal detached-eddy simulation (ZDES), delayed detached-eddy simulation (DDES), and Reynolds-averaged Navier–Stokes (RANS) modeling. The geometry is smooth so the separation point is a function of the flow solution. Comparisons to experimental data show that RANS with the Spalart–Allmaras turbulence model predicts the mean-field statistics well. The ZDES and DDES methods perform better than the DES formulation and are comparable to RANS in most statistics. Analyses motivate that modeled-stress depletion near the separation point contributes to differences observed in the DES variants. The order of accuracy of the flow solver ACUSOLVE is also documented.

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Assessment of DES Models for Separated Flow From a Hump in a Turbulent Boundary Layer

Volume 1: Symposia, Parts A and B ◽

10.1115/fedsm2007-37298 ◽

2007 ◽

Cited By ~ 4

Author(s):

Daniel C. Lyons ◽

Leonard J. Peltier ◽

Frank J. Zajaczkowski ◽

Eric G. Paterson

Keyword(s):

Boundary Layer ◽

Turbulent Boundary Layer ◽

Mean Field ◽

Turbulence Models ◽

Separated Flow ◽

Navier Stokes ◽

Detached Eddy Simulation ◽

Eddy Simulation ◽

Delayed Detached Eddy Simulation ◽

Rans Modeling

Turbulent flow past the Glauert-Goldschmied body, a flow-control hump in a turbulent boundary layer, is studied numerically using detached-eddy simulation (DES), zonal detached-eddy simulation (ZDES), delayed detached-eddy simulation (DDES), and Reynolds-Averaged Navier-Stokes (RANS) modeling. The geometry is smooth so the downstream separation point is not set by facets of the geometry but is a function of the pressure gradient, a challenging condition for turbulence models. Comparisons to experimental data show that RANS with the Spalart-Allmaras turbulence model predicts the mean-field statistics well. The ZDES and DDES methods perform better than the DES formulation and are comparable to RANS in most statistics. An analysis of model behavior indicates that modeled stress depletion in the detached shear layer shortly after separation leads to loss of accuracy in the DES variants.

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