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Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
High fidelity gust simulations over a supercritical airfoil
B. Tartinville1, V. Barbieux2, L. Temmerman1
1Numeca International, 2 Numflo
AVIATION, 25–29 June 2018
Hyatt Regency Atlanta, Atlanta, Georgia
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
Outline of the presentation
1Objectives
and Methodology
2Gusts
simulations
3Analysis of the
flow solution
4Conclusions and
Perspectives
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
Outline of the presentation
1Objectives
and Methodology
2Gusts
simulations
3Analysis of the
flow solution
4Conclusions and
Perspectives
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
The major objectives of the AeroGust project are:
• To carry investigations using CFD so that the non-linearities in gust interactions are
understood.
• To create a gust load process that does not require wind tunnel data and hence reduces
the need for wind tunnel testing.
• To develop updated reduced order models for gust prediction that account for non-linearity
at an acceptable cost.
The objective of this work is to investigate aerodynamic non-linearities due to gust-aircraft
interactions by using high fidelity LES/DES methods for gust simulations.
Objectives and Methodology
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
High fidelity modelling of gust-airframe interaction
Only a few papers are dealing with high fidelity modelling to investigate gust-airframe
interaction. Those are mainly coming from DLR, Air Force Research Laboratory, and
University of Maryland.
Vorticity contours at different time demonstrating the effect of sharp-edge gust on a SD7703 airfoil at 4° angle of incidence from Golubev et al. [2010] ILES.
Gu
st f
ron
t
Gu
st r
ear
t=16.6 t=16.8 t=26.6 t=26.8 t=32.8
Objectives and Methodology
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
High fidelity modelling of gust-airframe interaction
One of the major challenge for such a high fidelity simulation is to be able to have a correct
gust shape close to the body. To do so, people are commonly using either local source terms,
or mesh refinement convected with the gust.
Objectives and Methodology
Example of mesh adaptation for a vortical structure from Tang and Baeder [2007] Example of chimera mesh from Radespiel et al. [2013]
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
Application of high fidelity gust modelling to FFAST Crank airfoil
• Final test case description has been defined: FFAST crank airfoil with flow condition “I”
• Altitude : 35,000 ft
• Free stream Mach number = 0.86 (U∞ = 255 m/s)
• Chord length : 8 m
• Three gust scenarios
• IDDES model has been retained with a physical time step of 2.10-4 s and an integration
time of several seconds.
• The span-wise extend has been set to half chord (based on best practices for LES/DES).
• A low dissipation scheme has been retained : 2nd order Jameson FV scheme with matrix
dissipation.
• A structured 3D mesh with 16 106 cells has been generated (65 points span-wise) and
mesh convergence has been verified: difference in drag between the two finest grids is
less than one count.
Objectives and Methodology
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
Application of high fidelity gust modelling to FFAST Crank airfoil
High fidelity Hybrid RANS/LES methods have been used by Numeca in the scope of several
EU projects such as ATAAC, DESider, UFAST, TFAST, VAILLANT, and MARS.
Time-mean pressure coefficient PSD for lift coefficient
Objectives and Methodology
ComputationExperiment
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
Gusts are imposed in the far field
• Three gust scenarios are selected H=30 ft, 150 ft, and 350 ft.
• Gusts are imposed via a time-space boundary condition imposing vertical velocity in the
far-field.
Example of time-space evolution of vertical velocity along the far-field boundaries @ x/C=-20
Objectives and Methodology
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
High density mesh for gust convection
• Computational domain extend 20 chords upstream and downstream with a O mesh
topology → domain size 320 m.
• Distribution of mesh points in the far field is sufficiently small to be able to capture the gust
length.
2H = 60 ft
2H = 300 ft
2H = 700 ft
Objectives and Methodology
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
Precursor simulation without gust has been performed
• 90 chord convective time steps (3 s) have been computed with a time step of 5.10-4 s and
a “pseudo periodic” state has been reached.
Animations over the last 0.5 s
Objectives and Methodology
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
Precursor simulation without gust has been performed
At a shock Mach number of about 1.4 a detached flow can be observed downstream.
Almost bi-dimensional fluctuations of the shocks are observed on both sides of the airfoil.
Mid-span Mach number distribution Velocity magnitude distribution [m/s] on iso-surface of l2=-5000
Objectives and Methodology
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
Outline of the presentation
1Objectives
and Methodology
2Gusts
simulations
3Analysis of the
flow solution
4Conclusions and
Perspectives
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
IDDES for FFAST crank airfoil with shortest gust (H=30 ft)
The passage of the gust has an impact on the shock position – mostly along the suction side.
The shock retrieves its original location after the passage of the gust.
Mid-span Vertical velocity distribution [m/s] Mid-span static pressure distribution [Pa]
Gust simulations
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
IDDES for FFAST crank airfoil with shortest gust (H=30 ft)
Shock displacement is almost bi-dimensional and impacts the downstream vortical structures
within the wake.
Mid-span Numerical Schlieren Velocity magnitude distribution [m/s] on iso-surface of l2=-5000
Gust simulations
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
IDDES for FFAST crank airfoil with intermediate gust (H=150 ft)
The passage of the gust has a significant impact on the shock position along both sides. On
the pressure side, the shock almost reaches the airfoil trailing edge.
Mid-span Vertical velocity distribution [m/s] Mid-span static pressure distribution [Pa]
Gust simulations
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
IDDES for FFAST crank airfoil with intermediate gust (H=150 ft)
For the most downstream shock position along the pressure side, the detached flow is
drastically reduced.
Mid-span Numerical Schlieren Velocity magnitude distribution [m/s] on iso-surface of l2=-5000
Gust simulations
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
IDDES for FFAST crank airfoil with long gust (H=350 ft)
The passage of the gust has a significant impact on the shock position along both sides. On
the pressure side, the shock almost reaches the airfoil trailing edge.
Mid-span Vertical velocity distribution [m/s] Mid-span static pressure distribution [Pa]
Gust simulations
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
IDDES for FFAST crank airfoil with long gust (H=350 ft)
For the most downstream shock position along the pressure side, the detached flow is
drastically reduced.
Mid-span Numerical Schlieren Velocity magnitude distribution [m/s] on iso-surface of l2=-5000
Gust simulations
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
Outline of the presentation
1Objectives
and Methodology
2Gusts
simulations
3Analysis of the
flow solution
4Conclusions and
Perspectives
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
Comparison of lift and momentum time evolutions
The two last gust scenarios have a significant impact on the evolution of lift and momentum,
but all the simulations exhibit similar high frequency fluctuations.
Analysis of the flow solution
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
Frequency content of the lift coefficient
A series of high frequency fluctuations of lift coefficient can be observed at about 35 Hz, 70
Hz, and 90 Hz.
Analysis of the flow solution
PSD of lift coefficient
St=0
.37
St=0
.29
St=0
.14
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
Frequency content of the lift coefficient
High frequency oscillations of lift coefficient are not linked to any high frequency shock
displacement : Kutta waves do not affect the shock location and therefore the lift.
Time evolution of shock location (no gust)Pressure distribution (no gust)
Analysis of the flow solution
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
Frequency content of the lift coefficient
High frequency oscillations of lift coefficient are linked to local variations in surface pressure
within the detached region.
PSD of wall pressure (gust #2)
Analysis of the flow solution
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
Analysis of shocks displacements.
Significant shock movements are observed during the passage of the gust.
They have a great impact on the downstream detached region.
Mid-span Numerical Schlieren gust #1 Mid-span Numerical Schlieren gust #2 Mid-span Numerical Schlieren gust #3
Analysis of the flow solution
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
Analysis of shocks displacements
Shocks movements exhibits a similar velocity.
Time evolution of shock location
~ 10 m/s
Analysis of the flow solution
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
Analysis of shock displacement
Several authors have proposed mechanisms in order to explain self sustained shock
movements.
Analysis of the flow solution
Model of self sustained shock oscillations from Lee [1990] Wave propagation and interaction with the shock wave from Alshabu and Oliver [2008]
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
Analysis of shock displacement
The passage of the gust leads to an excess of pressure along the pressure side and a deficit
along the suction side. With such a pressure disturbance of about 7%, Rankine-Hugoniot
equations can explain the observed shock motion.
Analysis of the flow solution
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
Outline of the presentation
1Objectives
and Methodology
2Gusts
simulations
3Analysis of the
flow solution
4Conclusions and
Perspectives
Funded by the European Union
AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS
A series of high fidelity IDDES gust simulations have been conducted over a
supercritical airfoil.
High frequency lift oscillations are caused by pressure fluctuations within the detached
regions along the surface of the airfoil.
Shock displacement is driven by Rankine-Hugoniot equations and shock velocity is
independent of the gust length.
In order to identify the non-linear impact of shock displacement, one can compare
characteristic times:
It is 0.09, 0.45, and 1.04 for the three gust scenarios.
Conclusions and Perspectives
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𝑈∞𝑐