des simulation around naca0012 airfoil using unstructured grid - welcome to...
TRANSCRIPT
![Page 1: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/1.jpg)
DES Simulation aroundNACA0012 Airfoil using
Unstructured Grid
Masafumi KurodaKazuhiro Nakahashi
Yu FukunishiDep’t. of Mechanical System and Design,
Tohoku University
![Page 2: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/2.jpg)
Background
・Unsteady, complex flowfield is created at wing-tip・Sound is generated by shear layer shedding from bottom edge and vortices in wake
![Page 3: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/3.jpg)
・ The computation around a single wing-tip flow using unstructured grid.
- To check the computational validity(preliminary test)
- For future extension (high lift devices)
The purpose of this research
![Page 4: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/4.jpg)
Numerical Method : Flow solver & Conditions
i. Mach # : 0.2ii. Reynolds # : 2.0 x 106
iii. Far boundary : Uniform Flowiv. Wall boundary : No slip conditionv. Time step : UΔt=c/5000vi. Newton subiterations : 3 times
i. Governing Eq. : Compressible Navier-Stokes Eq.ii. Spatial Discritization : Cell-Vertex, Finite Volume Methodiii. Numerical Flux Evaluation : HLLEW Riemann Solveriv. Time Integration : LU-SGS Implicit Method
TAS code, Tohoku univ. Aerodynamic Simulation code
Simulation conditions
![Page 5: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/5.jpg)
Computational Grid
・NACA0012 with blunt tip (span length = 2.5c)
![Page 6: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/6.jpg)
Grids in present study
・Grid 1 : isotropic grid・Grid 2 : stretched grid・Grid 3 : grid refinement
Grid 1 Grid 2 Grid 3
![Page 7: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/7.jpg)
Computation using isotropic grid (Grid1)
![Page 8: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/8.jpg)
・Grid is dense at wake, upper, side, and edge
Computational grid (Grid 1)
![Page 9: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/9.jpg)
Result (Grid 1)
instantaneous at t=80000Δt ω=10
Iso-surface of vorticity magnitude
ω=5
![Page 10: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/10.jpg)
instantaneous at t=120000Δt mean in 110000-120000Δt
Iso-surface of vorticity magnitude (ω=10)
・The unsteady fluctuations did not appear in Grid 1.
![Page 11: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/11.jpg)
middle: x=0.067c at center linelower: x=0.067c, y=2.4946c
Pressure record for last 10000 time step
![Page 12: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/12.jpg)
・Two vortices emerge from top and bottom edges.
y ×x
zvorticity magnitude x=0.2c
![Page 13: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/13.jpg)
・Departing vortices are captured.・Strong shear layers exist but are dissipated
y ×x
zx=0.5c
![Page 14: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/14.jpg)
・Shear layer is primary in sidewall region.・Two vortices merge over the upper surface
y ×x
zx=0.8c
![Page 15: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/15.jpg)
・Vortices and shear layer merge.・They dissipate by numerical viscosity.
y ×x
zx=1.0c
![Page 16: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/16.jpg)
Cp distributions at wing center line and 2.5% c inside
![Page 17: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/17.jpg)
Vortex footprintx ◎ z
y
Pressure contour at upper surface
![Page 18: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/18.jpg)
current resultexperiment
Comparison of U velocity at each section(0.5,0.7,0.95,1.1c)
![Page 19: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/19.jpg)
Computation using stretched grid (Grid2)
![Page 20: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/20.jpg)
Difficulties in using isotropic grid
・The flowfield is unique for rapid change in z-direction・Grid generation yields huge number of computational grids in vain, but it is too coarse in y-z plane
Streett et al
![Page 21: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/21.jpg)
Computational grid (stretched 5 times streamwise)
Surface mesh Volume mesh
x=2.0c
x=1.0c
![Page 22: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/22.jpg)
6,891,4376,778,675# of tetra10,498,18014,357,070# of edge
1,773,7472,758,260# of nodestretched gridisotropic grid
isotropic stretched
![Page 23: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/23.jpg)
Result (Grid 2)
instantaneous at t=27000Δt
Iso-surface of vorticity magnitude (ω=5)
mean for 5000Δt
![Page 24: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/24.jpg)
isotropic
stretched
Iso-surface of instantaneous vorticity magnitude at t=27000Δt(ω=10)
![Page 25: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/25.jpg)
・The strength of secondary vortex is different.
y ×x
zisotropic
stretched
vorticity magnitude x=0.5c
![Page 26: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/26.jpg)
・Merging of vortices is captured sharply.
y ×x
zisotropic
stretched
x=1.0c
![Page 27: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/27.jpg)
・Vortex in wake is captured well.
y ×x
z
stretched
x=1.5c
![Page 28: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/28.jpg)
isotropic stretched
Comparison of U velocity at each section (0.5,0.7,0.95,1.1c)
![Page 29: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/29.jpg)
Computation using grid refinement (Grid3)
![Page 30: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/30.jpg)
Difficulties in using equally sized grid
・Sharp shear layer is blurred completely
![Page 31: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/31.jpg)
Grid is dense at high vorticity, strong shear layer
Refined grid
Method:・Equi-dividing.・8-way cut based on shortest edge (tetra).・Vorticity-based refinement.
![Page 32: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/32.jpg)
before refinement after refinement
y ×x
z
0.0 40.0
・Sharp shear layer now emerges.・Strength of vortices is different.
vorticity magnitude x=0.5c
![Page 33: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/33.jpg)
before refinement after refinement
y ×x
z
0.0 40.0
・Merging of vortices and shear layer are captured sharply.
x=0.8c
![Page 34: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/34.jpg)
Comparison of Cp distributions (wing center line)
![Page 35: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/35.jpg)
Comparison of Cp distributions (2.5% c inside)
![Page 36: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/36.jpg)
before refinement after refinement
z ◎ x
y
0.975 1.0
Comparison of pressure contour(upper surface from x=0.2 to 0.4 c)
![Page 37: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/37.jpg)
before refinement after refinement
y ×x
z
0.0 40.0
・Vortex is captured well. This supports the existence of lower pressure region.
vorticity magnitude x=0.3c
![Page 38: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/38.jpg)
ascendingvortices vortices
at shear layer
Fluctuation of vorticity magnitude at t=32500Δt (ω=1)
![Page 39: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/39.jpg)
middle: x=0.067c at center linelower: x=0.067c, y=2.4946c
fluctuation is too weak to be seen
Pressure record for last 10000Δt span
![Page 40: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/40.jpg)
・Qualitative steady result is obtained.・Use of stretched computational grid yields favorable result.・Downstream grid resolution is important to capture shear layer correctly.・Shear layer instability could no be captured well possibly because of grid resolution.
Conclusion
![Page 41: DES Simulation around NACA0012 Airfoil using Unstructured Grid - Welcome to cfd…cfd.mace.manchester.ac.uk/desider/symposium/symp05/All... · 2005-12-05 · DES Simulation around](https://reader033.vdocuments.us/reader033/viewer/2022041911/5e678eff1973435d2a4b1282/html5/thumbnails/41.jpg)
0.96
Pressure distribution of bottom corner at x=0.5c surface
numericaldissipation