Unsteady hydrodynamics code

[Tom_McGuinness]

We've developed a new propulsion system that mimmicks the swimming motion of a class of marine animals known as thunniform swimmers...which includes sharks. The product performs very well, but since it's a new system, there's undoubtedly a lot of room for incremental improvement/optimization. The engineering prototype of our product can be viewed at (www.tailboats.com).

It would be "nice" to be able to perform CFD modelling of the propulsion system with regards to the propulsion fin's interaction with wake vortices. It would also be very useful of the code could include/model the effects of propulsion fin rotation about it's support shaft in response to fluid forces.

Having done a fair bit of CFD modelling with FLUENT some years ago, I suspect the answer to my question is...."sorry, not possible with a commercial code".

Just thought I'd ask. Perhaps some of the hydrodynamicists here can suggest an alternative analytical method.

Of course, having a working product to experiment with gives us a leg up, but having a code would be helpful in identifying promising areas for further investigation/optimization.

And for you hydrodynamic software developers out there, perhaps we've created a new market for you. (g)

Thank you for your comments and assistance. If you wish, please don't hesitate to email me directly at: info@tailboats.com

Best regards,

Tom McGuinness

[Dim]

It's very interesting work, Tom. What velocity you could develop on that hull, which is exhibited in gallery?

Best regards,
Dim.

[Tom_McGuinness]

Hi Dim,

Thanks for the kind words.

I can pedal the exisiting hull along up to about 4.5 kts. It will comfortably cruise circa 3 kts for hours. And that's "right out of the box", as it were, without having to make any design modifications. Undoubtedly, there's room for optimization of foil & hull design.

According to the computer performance model for the system, the boat is not propulsion system limited, but rather hull/power limited. The model is incapable of accounting for the beneficial effects of interaction with the "reverse Karman street" wake vortices, which are pronounced under certain circumstances. The propulsion system operates between 0.25<Strouhal<0.40, which is the range in which vortex interaction typically occurs.(Triantafyllou, et al) Pedal forces seem substantially less than predicted.

The existing hull is approx 14.5' LOA x 36" beam and weighs in at 85 lbm by itself. IMHO, the ideal hull would be more sailboat-like with retractable dagger-board, increased rocker, and no aft skeg....all of which would improve turning performance, crosswind tracking and reduce yaw resistance. As it is now, it can do 90+ degree turns.

I'd like to build a hull capable of 6-8 kt max speed, but would like to limit LOA to about 16' (or so). Would also like to get the hull weight down to about 50 lbm.

Best regards,

Tom