cfd applications for marine foil configurations volker bertram, ould m. el moctar
TRANSCRIPT
![Page 1: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/1.jpg)
CFD Applications for Marine Foil Configurations
Volker Bertram, Ould M. El Moctar
![Page 2: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/2.jpg)
2
COMET employed to perform computations
RANSE solver:
Conservation of mass 1momentum 3volume concentration 1
In addition: k- RNG turbulence model 2In addition: cavitation model (optional) 1
HRIC scheme for free-surface flow
Finite Volume Method:• arbitrary polyhedral volumes, here hexahedral volumes• unstructured grids possible, here block-structured grids• non-matching boundaries possible, here matching boundaries
![Page 3: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/3.jpg)
3
Diverse Applications to Hydrofoils
Surface-piercing strut
Rudder at extreme angle
Cavitation foil
![Page 4: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/4.jpg)
4
Motivation: Struts for towed aircraft ill-designed
Wing profile bad choice in this case
![Page 5: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/5.jpg)
5
Similar flow conditions for submarine masts
![Page 6: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/6.jpg)
6
Similar flow conditions for hydrofoil boats
![Page 7: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/7.jpg)
7
Grid designed for problem
Flow highly unsteady: port+starboard modelled1.7 million cells, most clustered near CWL
10 L to each side
8 L
4 L
10 L 10 L
Starboard half of grid (schematic)
![Page 8: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/8.jpg)
8
Cells clustered near free surface
![Page 9: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/9.jpg)
9
Flow at strut highly unsteady
Circular section strut, Fn=2.03, Rn=3.35·106
![Page 10: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/10.jpg)
10
Wave height increases with thickness of profile
thickness almost
doubled
circular section strut, Fn=2.03, Re=3.35·106
Thickness “60” Thickness “100”
![Page 11: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/11.jpg)
11
Wave characteristic changed from strut to cylinder
parabolic strut cylinderFn=2.03, Re=3.35·106
![Page 12: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/12.jpg)
12
Transverse plate reduces waves
Transverseplate
attached
Parabolic strut, Fn=2.03, Re=3.35·106
![Page 13: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/13.jpg)
13
Transverse plate reduces waves
Transverseplate
attached
Parabolic strut, Fn=2.03, Rn=3.35·106
![Page 14: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/14.jpg)
14
Transverse plate less effective for cylinder
Transverseplate (ring)attached
cylinder, Fn=2.03, Re=3.35·106
![Page 15: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/15.jpg)
15
Problems in convergence solved
Large initial time steps
overshooting leading-edge wave for usual number of outer iterations
convergence destroyed
Use more outer iterations initially
leading-edge wave reduced
convergence good
![Page 16: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/16.jpg)
16
Remember:
• High Froude numbers require unsteady computations
• Comet capable of capturing free-surface details
• Realistic results for high Froude numbers
• Qualitative agreement with observed flows good
• Response time sufficient for commercial applications
• Some “tricks” needed in applying code
![Page 17: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/17.jpg)
17
Diverse Applications to Hydrofoils
Surface-piercing strut
Rudder at extreme angle
Cavitation foil
![Page 18: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/18.jpg)
18
Concave profiles offer alternatives
Rudder profiles employed in practice
![Page 19: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/19.jpg)
19
Concave profiles: higher lift gradients and max lift than NACA profiles of same maximum thickness
IfS-profiles: highest lift gradients and maximum lift due to the max thickness close to leading edge and thick trailing edge
NACA-profiles feature the lowest drag
![Page 20: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/20.jpg)
20
Validation Case (Whicker and Fehlner DTMB)
Stall Conditions
![Page 21: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/21.jpg)
21
Superfast XII Ferry used HSVA profiles
Superfast XII
Increase maximum rudder angle to 45º
![Page 22: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/22.jpg)
22
Fine RANSE grid used
RANSE grid with 1.8 million cells, details
• 10 c ahead• 10 c abaft• 10 c aside• 6 h below
![Page 23: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/23.jpg)
23
Grid generation allows easy rotation of rudder
![Page 24: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/24.jpg)
24
Body forces model propeller action
Radial Force Distribution
RootTip
Source Terms
![Page 25: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/25.jpg)
25
Pressure distribution / Tip vortex
Rudder angle 25°
![Page 26: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/26.jpg)
26
Maximum before 35º
Superfast XII, rudder forces in forward speed
lift
shaft moment
drag
![Page 27: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/27.jpg)
27
Separation increases with angle
Velocity distribution at 2.6m above rudder base
25º 35º 45º
![Page 28: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/28.jpg)
28
Reverse flow also simulated
Velocity distribution at top for 35°
forward reverse no separation massive separation
![Page 29: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/29.jpg)
29
Stall appears earlier in reverse flow
![Page 30: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/30.jpg)
30
Remember:
• RANSE solver useful for rudder design
• higher angles than standard useful
![Page 31: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/31.jpg)
31
Diverse Applications to Hydrofoils
Surface-piercing strut
Rudder at extreme angle
Cavitation foil
![Page 32: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/32.jpg)
32
Cavitation model: Seed distribution
average seed radius R0average number of seeds n0
different seed types &spectral seed distribution
„micro-bubble“ &homogenous seed distribution
![Page 33: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/33.jpg)
33
Cavitation model: Vapor volume fraction
V
liquid Vl
„micro-bubble“ R0
vapor bubble R
Vapor volume fraction:
![Page 34: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/34.jpg)
34
Cavitation model: Effective fluid
The mixture of liquid and vapor is treated as an effective fluid:
Density:
Viscosity:
![Page 35: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/35.jpg)
35
Cavitation model: Convection of vapor bubbles
Task: model the rate of the bubble growth
convective transport bubble growth or collapse
Lagrangian observation of a cloud of bubbles
Equation describing the transport of the vapor fraction Cv:
&
![Page 36: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/36.jpg)
36
Cavitation model: Vapor bubble growth
Conventional bubble dynamic =
observation of a single bubble in infinite stagnant liquid
„Extended Rayleigh-Plasset equation“:
Inertia controlled growth model by Rayleigh:
![Page 37: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/37.jpg)
37
Application to typical hydrofoil
Stabilizing fin rudder
![Page 38: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/38.jpg)
38
First test: 2-D NACA 0015
Vapor volume fraction Cv for one period
![Page 39: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/39.jpg)
39
First test: 2-D NACA 0015
Comparison of vapor volume fraction Cv for two periods
![Page 40: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/40.jpg)
40
3-D NACA 0015
Periodic cavitation patternson 3-D foil
![Page 41: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/41.jpg)
41
2-D NACA 16-206
Vapor volume fraction Cvfor one period
![Page 42: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/42.jpg)
42
2-D NACA 16-206
Pressure coefficient Cp for one period
![Page 43: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/43.jpg)
43
2-D NACA 16-206
Comparison ofvapor volume fraction Cv
with
pressure coefficient Cp for one time step
![Page 44: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/44.jpg)
44
3-D NACA 16-206: Validation with Experiment
Experiment by Ukon (1986) Cv= 0.05
![Page 45: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/45.jpg)
45
3-D NACA 16-206
pressure distribution Cp and vapor volume fraction Cv
![Page 46: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/46.jpg)
46
3-D NACA 16-206
Cv= 0.005 Cv= 0.5
Correlation between visual type of cavitation
andvapor volume fraction Cv ?
![Page 47: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/47.jpg)
47
3-D NACA 16-206Pressure distribution
with and without calculation of cavitation
![Page 48: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/48.jpg)
48
3-D NACA 16-206
Minimal and maximalcavitation extent with
vapor volume fraction Cv= 0.05
Exp.
![Page 49: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/49.jpg)
49
3-D NACA 16-206: VRML model
![Page 50: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/50.jpg)
50
Remember
• cavitation model reproduces essential characteristics
of real cavitation
• reasonable good agreement with experiments
• threshold technology
![Page 51: CFD Applications for Marine Foil Configurations Volker Bertram, Ould M. El Moctar](https://reader035.vdocument.in/reader035/viewer/2022062322/56649f4f5503460f94c7127c/html5/thumbnails/51.jpg)
51