Hydrofoil Transition

Andrew Parker

Dear all,

My name is Andrew Parker, and I am a student on summer placement at Rolls-Royce Marine in-between 3rd and 4th year at University. I have been using a program called Xfoil to try and design a new fin stabiliser. I have then been using my results from this program in Fluent. I have been searching the web to try and learn more about how to try and model these stabilisers in 2D in Fluent. I am trying to get advise on the best way to simulate 2D flow over a fin stabiliser (hydrofoil). I have loads of questions, but by now you are probably going to delete the e-mail, so I will confine my questions to what I consider the most important; so here goes.

1. Is it best to model the flow over a hydrofoil in steady or unsteady state? 2. Is there an ideal turbulence model for this type of problem (I have been using k-epsilon, and Spalart-Allmaras)? 3. If you model it in unsteady situations can you still extract a lift coefficient, or does it become a lift coefficient for that moment in time? 4. I have been splitting my grid into two, the first half as laminar, and the second half split at the point of transition on the upper face (where I then apply the turbulence model), does this violate any rules (I get the transition point from Xfoil)? 5. Do you know of any other programs that predict the point of laminar to turbulent transition? 6. I get different answers for steady and unsteady lift, is this normal or am I doing something wrong? 7. Lastly, could you recommend any types of generic set up values that would help me to model the flow around the foil with more accuracy, i.e. types of Discretization, area of the domain-how far the wall of the domain should be from the foil to limit the effect on the program, and loads of other stuff.

Thanks again

Andy

Andrew Parker

Student Engineer Rolls-Royce Marine