High fidelity gust simulations around a transonic airfoil

Size: px

Start display at page:

Download "High fidelity gust simulations around a transonic airfoil"

Dora Johns
5 years ago
Views:

1 High fidelity gust simulations around a transonic airfoil AEROGUST Workshop 27 th - 28 th April 2017, University of Liverpool Presented by B. Tartinville (Numeca)

2 Outline of the presentation 1Objectives and Methodology 2Gusts simulations 3Analysis of the flow solution 4Perspectives for AeroGust project

3 Outline of the presentation 1Objectives and Methodology 2Gusts simulations 3Analysis of the flow solution 4Perspectives for AeroGust project

4 Objectives and Methodology 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. This work belongs to the activity of Work Package 2. Its aim is to investigate aerodynamic non-linearities due to gust-aircraft interactions by using high fidelity LES/DES methods for gust simulations.

Gust front Gust rear Objectives and Methodology High

papers are dealing with high fidelity modelling to

Those are mainly coming from DLR, Air Force Research

5 Gust front Gust rear Objectives and Methodology 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. t=16.6 t=16.8 t=26.6 t=26.8 t=32.8 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.

To do so, people are commonly using either local source terms, or mesh refinement convected with the gust.

6 Objectives and Methodology 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. Example of mesh adaptation for a vortical structure from Tang and Baeder [2007] Example of chimera mesh from Radespiel et al. [2013]

7 Application of high fidelity gust modelling to FFAST Crank airfoil Objectives and Methodology 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 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 : 2 nd order Jameson FV scheme with Matrix dissipation. A structured 3D mesh with 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.

scope of several EU projects such as ATAAC, DESider, UFAST, TFAST, VAILLANT, and

8 Application of high fidelity gust modelling to FFAST Crank airfoil Objectives and Methodology 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. Computation Experiment Time-mean pressure coefficient PSD for lift coefficient

9 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. Objectives and Methodology Example of time-space evolution of vertical velocity along the far-field x/c=-20

10 High density mesh for gust convection Computational domain extend 20 chords upstream and downstream with a O mesh topology domain size 320 m. Objectives and Methodology 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

11 Precursor simulation without gust has been performed 90 chord convective time steps (3 s) have been computed with a time step of s and a pseudo periodic state has been reached. Objectives and Methodology Animations over the last 0.5 s

12 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 side of the airfoil. Objectives and Methodology Mid-span Mach number distribution Velocity magnitude distribution [m/s] on iso-surface of l 2 =-5000

13 Outline of the presentation 1Objectives and Methodology 2Gusts simulations 3Analysis of the flow solution 4Perspectives for AeroGust project

14 IDDES for FFAST crank airfoil with shortest gust (H=30 ft) Lift and momentum coefficients are only slightly impacted by the passage of the gust. Time variations are similar to the ones computed by linear models for other configuration, see for instance Dong et al. [2013]. Gust simulations Mid-span Vertical velocity distribution [m/s] Time evolution of lift and momentum coefficients

15 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. Gust simulations Mid-span Vertical velocity distribution [m/s] Mid-span static pressure distribution [Pa]

16 IDDES for FFAST crank airfoil with shortest gust (H=30 ft) Shock displacement is almost bi-dimensional and impacts the downstream vortical structure within the wake. Gust simulations Mid-span Numerical Schlieren Velocity magnitude distribution [m/s] on iso-surface of l 2 =-5000

17 Gust simulations IDDES for FFAST crank airfoil with intermediate gust (H=150 ft) Lift and momentum coefficients are greatly impacted by the passage of the gust. Lift becomes negative and momentum coefficient is higher than 0.1 Mid-span Vertical velocity distribution [m/s] Time evolution of lift and momentum coefficients

18 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. Gust simulations Mid-span Vertical velocity distribution [m/s] Mid-span static pressure distribution [Pa]

19 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. Gust simulations Mid-span Numerical Schlieren Velocity magnitude distribution [m/s] on iso-surface of l 2 =-5000

20 Gust simulations IDDES for FFAST crank airfoil with long gust (H=350 ft) Lift and momentum coefficients are greatly impacted by the passage of the gust. Lift becomes negative and momentum coefficient reaches up to Mid-span Vertical velocity distribution [m/s] Time evolution of lift and momentum coefficients

21 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. Gust simulations Mid-span Vertical velocity distribution [m/s] Mid-span static pressure distribution [Pa]

22 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. Gust simulations Mid-span Numerical Schlieren Velocity magnitude distribution [m/s] on iso-surface of l 2 =-5000

23 Outline of the presentation 1Objectives and Methodology 2Gusts simulations 3Analysis of the flow solution 4Perspectives for AeroGust project

24 Comparison of lift and momentum time evolutions Analysis of the flow solution 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.

25 St=0.14 St=0.29 St=0.37 Frequency content of the lift coefficient Analysis of the flow solution A series of high frequency fluctuations of lift coefficient can be observed at about 35 Hz, 70 Hz, and 90 Hz. PSD of lift coefficient

Frequency content of the lift coefficient Analysis of the flow solution High frequency oscillations of lift coefficient are not linked to any high

26 Frequency content of the lift coefficient Analysis of the flow solution High frequency oscillations of lift coefficient are not linked to any high frequency shock displacement : Kutta waves do not affect the shock location. Time evolution of shock location (no gust) Pressure distribution (no gust)

27 Frequency content of the lift coefficient Analysis of the flow solution High frequency oscillations of lift coefficient are linked to local variations in surface pressure within the detached region. PSD of wall pressure (gust #2)

28 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. Analysis of the flow solution Mid-span Numerical Schlieren gust #1 Mid-span Numerical Schlieren gust #2 Mid-span Numerical Schlieren gust #3

29 Analysis of the flow solution Analysis of shocks displacements Shocks movements exhibits a similar velocity. ~ 10 m/s Time evolution of shock location

Analysis of shock displacement Several authors have proposed mechanisms in order to explain shock movements (see for instance the PhD Thesis from Grossi [2014]).

30 Analysis of shock displacement Several authors have proposed mechanisms in order to explain shock movements (see for instance the PhD Thesis from Grossi [2014]). 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]

31 Analysis of shock displacement Analysis of the flow solution The wake distorsion generates an upstream running pressure wave that travels around the shock. Time evolution of shock location Mid-span distribution of difference between the Mach and the isentropic Mach

32 Analysis of the flow solution Conclusions A series of long term simulations of gust passage along an airfoil using IDDES approach has been conducted. Those simulations reveal that for large gust lengths, the gust passage impacts on the shock location and on the downstream recirculation region caused by shock boundarylayer interaction. Several mechanisms for shock displacement have been investigated, and it appears that this displacement is likely to be caused by perturbation of the downstream wake that induces upstream running pressure waves. Such waves travel around the shock through the subsonic flow above.

33 Outline of the presentation 1Objectives and Methodology 2Gusts simulations 3Analysis of the flow solution 4Perspectives for AeroGust project

34 Comparison of high fidelity results with ROM A comparison of perturbations in lift and momentum coefficients is performed. Perspectives for AeroGust project Gust along profile ~ 0.1 s Gust along profile ~ 0.1 s

35 Perspectives for AeroGust project Inter-comparison of results

36 NASA LRN 1015 test case is under investigation for flow condition P Perspectives for AeroGust project Numeca s ROM model has been adapted to unstructured grids in order to be able to handle more complex configurations.

Harmonic method (NLH) which is a frequency domain method.

37 NASA LRN 1015 test case is under investigation for flow condition P Perspectives for AeroGust project The ROM model is based on Non-Linear Harmonic method (NLH) which is a frequency domain method. Mid-span Vertical velocity distribution [m/s] Pressure distribution along the airfoil and mirror plane [Pa]

38 NASA LRN 1015 test case Perspectives for AeroGust project This test case is used in order to develop and implement a method to determine the effect of aerodynamics and structural uncertainties. Structural uncertainties * Aerodynamic uncertainties * Coupled system OOFELIE & FINE Structural ROM : Modal Aerodynamic ROM : NLH Non-determinsitic Aeroelastic response * The uncertainties are propagated into the coupled system through non-intrusive probabilistic collocation method.

NASA CRM test case has already been investigated for DPW5 Perspectives for AeroGust project A mesh convergence study has been performed and results

39 NASA CRM test case has already been investigated for DPW5 Perspectives for AeroGust project A mesh convergence study has been performed and results compared to measured data and results from other institutions. Application of ROM to gust simulations on NASA CRM test case will be performed for flow condition F.

40 Thank you for your attention!

41 The research leading to this work has received funding from the s Horizon 2020 research and innovation programme under grant agreement number

ANALYSIS OF AERODYNAMIC CHARACTERISTICS OF A SUPERCRITICAL AIRFOIL FOR LOW SPEED AIRCRAFT

ANALYSIS OF AERODYNAMIC CHARACTERISTICS OF A SUPERCRITICAL AIRFOIL FOR LOW SPEED AIRCRAFT P.Sethunathan 1, M.Niventhran 2, V.Siva 2, R.Sadhan Kumar 2 1 Asst.Professor, Department of Aeronautical Engineering,