Hydrofoil wing in fluent

wind_tunnel_contraction · September 28, 2016, 11:44

Hello all,

Currently I am working on a hydrofoil wing. I already calculated the lift en drag (coefficients) using XFoil. A software program for all kinds of airfoils. Now I wanted to know the lift and drag of the complete wing. This includes:

- two elliptical wing sections at the sides
- a middle wing section with same chord-length
- two nacelles to connect the wings to the struts and to house the bearings for pitch control of the wing sections.

As I already know the drag of the struts, I am only interested in the lift and drag of the complete wing including 2 nacelles.

Earlier, I used Ansys Fluent for the flow of a wind-tunnel contraction. Now I encounter a few problems:

- how to mesh this profile sufficiently (the enclosed box and the hydrofoil with nacelles)?

- which Turbulence model and turbulence values should I choose in water? Or is laminar flow sufficient for a low speed (12m/s max) foil?

Thank you in advance,

Martijn

Poompil · September 30, 2016, 10:30

Quote:

Originally Posted by wind_tunnel_contraction

- which Turbulence model and turbulence values should I choose in water? Or is laminar flow sufficient for a low speed (12m/s max) foil?

The second part of this depends on your Reynolds number.
http://airfoiltools.com/calculator/r...&yt0=Calculate

For a speed of 12 m/s, you'll essentially need to work in the turbulent regime, for any appreciable chord.

wind_tunnel_contraction · September 30, 2016, 10:45

Thank you for your answer,

which turbulent model should I use? I saw aerofoils with K-epsilon model. The problem with this model are the values for the parameters. How can I obtain these values?

Very low Turbulence Intensity value is assumed, but how low? The same for the viscosity ratio.

The chord length is approximately 0.08m and with a range of 5-12m/s the reynolds range is 5e5 to 1e6.

Poompil · September 30, 2016, 10:50

I don't know enough to answer all your questions, but yes, picking turbulence parameters is indeed a difficulty.

I would suggest the following approaches:
1) Look at literature on hydrofoils of similar scale and see if you can wean any information from there.
2) This page has some good guidelines on choosing turbulence parameters.

September 28, 2016, 11:44	Hydrofoil wing in fluent	#1
wind_tunnel_contraction New Member Martijn Join Date: Apr 2016 Posts: 10 Rep Power: 10	Hello all, Currently I am working on a hydrofoil wing. I already calculated the lift en drag (coefficients) using XFoil. A software program for all kinds of airfoils. Now I wanted to know the lift and drag of the complete wing. This includes: - two elliptical wing sections at the sides - a middle wing section with same chord-length - two nacelles to connect the wings to the struts and to house the bearings for pitch control of the wing sections. As I already know the drag of the struts, I am only interested in the lift and drag of the complete wing including 2 nacelles. Earlier, I used Ansys Fluent for the flow of a wind-tunnel contraction. Now I encounter a few problems: - how to mesh this profile sufficiently (the enclosed box and the hydrofoil with nacelles)? - which Turbulence model and turbulence values should I choose in water? Or is laminar flow sufficient for a low speed (12m/s max) foil? Thank you in advance, Martijn

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September 30, 2016, 10:45		#3
wind_tunnel_contraction New Member Martijn Join Date: Apr 2016 Posts: 10 Rep Power: 10	Thank you for your answer, which turbulent model should I use? I saw aerofoils with K-epsilon model. The problem with this model are the values for the parameters. How can I obtain these values? Very low Turbulence Intensity value is assumed, but how low? The same for the viscosity ratio. The chord length is approximately 0.08m and with a range of 5-12m/s the reynolds range is 5e5 to 1e6.

September 30, 2016, 10:50		#4
Poompil New Member Jobin Join Date: Sep 2016 Posts: 5 Rep Power: 10	I don't know enough to answer all your questions, but yes, picking turbulence parameters is indeed a difficulty. I would suggest the following approaches: 1) Look at literature on hydrofoils of similar scale and see if you can wean any information from there. 2) This page has some good guidelines on choosing turbulence parameters.