F.S. Godeferd- Shock/boundary layer interactions: Turbulent compressible channel flows

8/3/2019 F.S. Godeferd- Shock/boundary layer interactions: Turbulent compressible channel flows

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Shock/boundary layer interactions

Turbulent compressible channel ows

F.S. Godeferd

Laboratoire de M ecanique des Fluides et d’AcoustiqueEcole Centrale de Lyon, France

Journ ee Calcul Intensif en Rh one Alpes

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Contents

• Presentation of the UFAST project

•

Numerical method• Shock in a curved channel

• Shock reection

• Perspectives

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An example of normal shock/boundary layer interaction

[Experiment at the University of Cambridge - Bruce & Babinsky ]

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The UFAST project — 2006-2009

Unsteady eFfects of shock

wAve induced SeparaTion European STREP project18 academic and industrialpartners

• Experiments

• RANS, URANS

• LES

• Control

http://www.ufast.gda.pl

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Motivation of the study

unsteady shock wave boundary layer interaction

• Aeronautical industry shock waves on wings/proles, nozzle ows and inlet ows

• Interaction unsteadiness initiated and/or generated by SWBLI; often destabilized bythe outer ow eld; response of shock wave and separation to periodic excitations

• Control methods : synthetic jets, electro-hydrodynamic actuators, stream-wise vortex

generators and transpiration ow

Can we reproduce the unsteady interaction with URANS ? Need of costly LES ?

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LMFA: URANS using platform elsA (ONERA)

Unsteady Reynolds-Averaged Navier-Stokes Simulations Physical model

• mean ow → Reynolds-averaged Navier-Stokes equations

• turbulence → two-equation model k -L (turbulent kinetic energy, mixing length); orone-equation model Spalart-Allmaras for turbulent viscosity ν t .

• Sutherland viscosity law ν (T ) = ν 0T 0 + C T + C

T T 0

3 / 2

• Adiabatic walls

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Numerical method

• Conservative nite volume method

• Roe uxes with limiters

• Implicit Euler timestepping

• Multi-blocks structured mesh

•

Parallel resolution

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Initialization - Example: Channel ow with bump [expe. in Queens U. Belfast]

Uniform initialization → Euler → laminar Navier-Stokes → turbulent Navier-Stokes

• Subsonic freestream: Ma = 0 .783• Peak: Ma = 1 .365•

Normal shock

Animation

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http://qub.mpeg/

http://qub.mpeg/



Performance

Location Architecture # proc. # cores cpu/pt/ite Mem/pt Static max

seconds bytes speedup

LMFA Opteron 280 2Ghz 2 4 2 . 3 10 − 6 347 3.9

P2CHPD Opteron 252 2.6Ghz x3550 16 6 . 5 10 − 7 510 10 a

IDRIS Nec SX8 1 1 6 . 7 10 − 7 394 1´ECL

α

-Server EV7 1.15Ghz 1 19 . 9 10 − 6

495 1

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http://-/?-



URANS of curved channel ow at Ma = 1 .45Polish Institute of Mechanics experiment

Inlet conditions: P=101kPa; T=290K. Turbulence: Tu=1%; L=1% channel height.Outlet conditions: pressure ratio specied in URANS to match experimental shocklocation

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Splitted geometry with N = 8 procs; 4.5 × 106 grid points

• Bottom wall boundary layer resolution: y+ 2• Side walls: y+ 20

Need to test the dependence of the solution on various elements of the simulation

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Details of ow in shock zone

The simulation allows a detailed investigation of the owMach contours, showing Ma = 1 .45 upstream the shock

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Oil ow visualization URANS streaklines

Detachment/re-attachment length

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URANS streamlines → access to 3D ow structure

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Adjustment of shock position: dependence on geometry

1 degree opening of channel at the outlet

Mach number contours in a transverse wall for choked and unchoked geometries. The

curve shows the Mach number at mid-section in this plane.

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Dependence on expression of uxes and outlet pressure

Effect of counterpressure. Effect of uxes scheme: Roe or Jameson.

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Shock reection case: expe. TU Delft

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URANS

Turbulence model: k − L

Mach number at two times and uctuations at point in shock region

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Unphysical solution! Huge detachment and unsteadiness due to poorly performingturbulence model.

Reason: turbulence is strongly damped in incoming boundary layer.

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URANS

Turbulence model: Spalart-Allmaras

More reasonable shock detachment but steady ow

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Perspective: introduce explicit uctuations at inlet

BL uctuations are sufcient to trigger SWBLI unsteadiness

Synthetic uctuations injection

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Perspectives of UFAST project

• Control of experimental ows

• Simulations with control

• Large eddy simulations and hybrid RANS/LES methods

• Comparison experiment/simulation results and synthesis, with industry partners

• Database available on web: 2009

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F.S. Godeferd- Shock/boundary layer interactions: Turbulent compressible channel flows

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