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

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.

scholarly journals Numerical Investigation on the Influence of the Streamlined Structures of the High-Speed Train’s Nose on Aerodynamic Performances

2021 ◽  
Vol 11 (2) ◽  
pp. 784
Author(s):  
Zhenxu Sun ◽  
Shuanbao Yao ◽  
Lianyi Wei ◽  
Yongfang Yao ◽  
Guowei Yang
Keyword(s):  
Drag Reduction ◽  
Pressure Distribution ◽  
Flow Separation ◽  
High Speed ◽  
Leeward Side ◽  
Detached Eddy Simulation ◽  
Side Force ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Asymmetrical Design

The structural design of the streamlined shape is the basis for high-speed train aerodynamic design. With use of the delayed detached-eddy simulation (DDES) method, the influence of four different structural types of the streamlined shape on aerodynamic performance and flow mechanism was investigated. These four designs were chosen elaborately, including a double-arch ellipsoid shape, a single-arch ellipsoid shape, a spindle shape with a front cowcatcher and a double-arch wide-flat shape. Two different running scenes, trains running in the open air or in crosswind conditions, were considered. Results reveal that when dealing with drag reduction of the whole train running in the open air, it needs to take into account how air resistance is distributed on both noses and then deal with them both rather than adjust only the head or the tail. An asymmetrical design is feasible with the head being a single-arch ellipsoid and the tail being a spindle with a front cowcatcher to achieve the minimum drag reduction. The single-arch ellipsoid design on both noses could aid in moderating the transverse amplitude of the side force on the tail resulting from the asymmetrical vortex structures in the flow field behind the tail. When crosswind is considered, the pressure distribution on the train surface becomes more disturbed, resulting in the increase of the side force and lift. The current study reveals that the double-arch wide-flat streamlined design helps to alleviate the side force and lift on both noses. The magnitude of side force on the head is 10 times as large as that on the tail while the lift on the head is slightly above that on the tail. Change of positions where flow separation takes place on the streamlined part is the main cause that leads to the opposite behaviors of pressure distribution on the head and on the tail. Under the influence of the ambient wind, flow separation occurs about distinct positions on the train surface and intricate vortices are generated at the leeward side, which add to the aerodynamic loads on the train in crosswind conditions. These results could help gain insight on choosing a most suitable streamlined shape under specific running conditions and acquiring a universal optimum nose shape as well.

Simulation of Dynamic Stall on an Elastic Rotor in High-Speed Turn Flight

2020 ◽  
Vol 65 (2) ◽  
pp. 1-12
Author(s):  
Johannes Letzgus ◽  
Manuel Keßler ◽  
Ewald Krämer
Keyword(s):  
High Speed ◽  
Separated Flow ◽  
Flight Test ◽  
Dynamic Stall ◽  
Minor Role ◽  
Detached Eddy Simulation ◽  
Rotor Aerodynamics ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
A Minor

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.

Detached Eddy Simulation of Transition in Turbomachinery: Linear Compressor Cascade

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.

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

2009 ◽  
Vol 131 (11) ◽  
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.

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

2007 ◽  
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.

Improvement of Delayed-Detached Eddy Simulation Applied to Separated Flow over Missile Fin

AIAA Journal ◽  
2009 ◽  
Vol 47 (2) ◽  
pp. 345-360 ◽  
Author(s):  
Jacques Riou ◽  
Eric Garnier ◽  
Sebastien Deck ◽  
Claude Basdevant
Keyword(s):  
Separated Flow ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation
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