Theoretical, Numerical, and Experimental Studies of Bi-directional Hydrofoils
IVAYLO NEDYALKOV (Ivo)
ADVISER: MARTIN WOSNIK
HYDROFOIL DESIGN GOALS
[email protected]
[email protected]
The foils should have:
EXPERIMENTS
Foils are tested experimentally in the 6-inch X 6-inch X 36-inch test section
UNIVERSITY OF NEW HAMPSHIRE
•High lift/drag ratios (over a wide range of angles-of-attack)
of the UNH HiCaT. The speed in the test section can exceed 13 m/s and the
CENTER FOR OCEAN RENEWABLE ENERGY
•Low cavitation inception numbers (for operational angles-of-attack)
pressure can be varied independently. A custom-designed force balance
•Low susceptibility and sensitivity to biofouling
can simultaneously measure lift and drag forces. The test section has
A few foil classes were created and studied. Some sample foils are:
optical access from all four sides allowing the use of optical measurement
SAMPLE APPLICATION
Tidal current turbines encounter flows with reversing direction.
Some ways to account for the reversing flow direction are:
techniques, and visual observation of cavitation.
B0−2010
B0−2015
B0−3015
B3−151540
B3−301540
B3−301520
B5−70−30
B5−140−30
B5−140−50
NACA 1315B
NACA 0015B
NACA 63−424B
HYDROFOIL
•Changing the yaw of the rotor
•Changing the pitch of the blades
•Using bi-directional blades
DRAG MEMBER (ONLY 1 SHOWN)
LIFT MEMBERS
CLAMP
NUMERICAL TEST-BED
A numerical “test-bed” was developed to study (bidirectional) hydrofoils. It
is a code written in Matlab which generates all files required for OpenFOAM
simulations. The algorithm finds any sharp edges, and points where the
tangent line is at 450 with respect to the x-axis, to create the mesh files
for each foil geometry and angle-of-attack. The code also generates files
FLOW
ANGLE-OF-ATTACK SETTING
ANGLE-OF-ATTACK LOCK
for: the simulation parameters, boundary and initial conditions, automatic
VACUUM PUMP AND TANK
execution of all simulations in a case, reading and plotting data of interest,
PRESSURE VALVES
and a summary of the reference and modified parameters for each case.
RISER TANK
TEST SECTION
FLOW
Using bi-directional foils may be cost-effective, as no yaw or pitch
control mechanisms are required, reducing the complexity, hence
decreasing initial and more importantly maintenance costs.
THEORY
of rotation when the flow reverses direction. However, the first option
3.5
0.8
0.4
0.6
The lift, drag, and cavitation numbers obtained with the CFD code were
University of New Hampshire High-Speed Cavitation Tunnel (HiCaT).
C L /C D for a NACA63−424B foil
20
requires undesirable 0 pitch angle and high rotational speed.
Cavitation Inception Number for a NACA63−424B foil
0.4
0.3
0.2
CD [ ]
compared to experimental data obtained for 3 reference foils at the
3
0.35
Cavitation number σ [ ]
direction; and rotational symmetry if the blades change their direction
Cavitation Inception Number for a B3−351045 foil
4
CFD
Experiments
0.45
L
have symmetry about the chord if the blades remain rotating in the same
C D for B3−351045 foil at Re=375 000
0.5
1
C []
In order for the flow to “see” the same foil shape, bi-directional foils must
C L for B3−351045 foil at Re=375 000
0
0.25
0.2
−0.2
0.15
−0.4
2.5
2
1.5
1
0.1
−0.6
CFD
Experiments
−0.8
−10
−5
0
5
10
Angle of attack [deg]
15
20
0.5
0.05
0
−10
−5
0
5
10
Angle of attack [deg]
15
20
0
CFD
Experiments
−10
−5
0
Angle of attack [deg]
5
2.5
18
16
2
Cavitation number [ ]
14
L
C /C
D
12
10
8
6
CFD Re 225000
CFD Re 300000
CFD Re 375000
EXP Re 225000
EXP Re 300000
EXP Re 375000
4
2
0
0
5
10
Angle of attack [deg]
1.5
1
CFD Re 225000
CFD Re 300000
CFD Re 375000
EXP Re 600000 inception
EXP Re 600000 desinence
0.5
15
FUNDING FOR THE PROJECT WAS PROVIDED BY
20
0
−5
0
5
Angle of attack [degrees]
10
ACKNOWLEDGEMENTS
•Department of Energy grant to the UNH Center for Ocean Renewable Energy (PIs: Ken Baldwin, Martin Wosnik)
Martin Wosnik, Ryan Therrien, Ben Comtois, Spencer Roux, Ian Gagnon, Nicholas Landry, Peter Bachant, •UNH College of Engineering and Physical Sciences (start-up funding for Martin Wosnik)
Vincent Lyon, John J Turner V, Tracey Harvey, Sheri Millette, Jesse Shull, John Brindley
•UNH Graduate School (Dissertation-Year Fellowship)
10