CFD Analysis

[ENG Student]

Hi Guys

Ive done some basic single state CFD analysis of a simple hull design for a catamaran. The length and width of the hull is a constant however the shape of is what im changing to give me minimum drag.
Basically one of my designs has quite baffled me to say the least,
Heres the printscreen

Any help would be much appreciated
Cheers

[ENG Student]

you can see the wake separates creating two wakes, i dont have a clue why this has happened but its given me lower drag than the initial design.

[jehardiman]

Common enough. Though it appears there is no energy loss accounted for in the boundary layer; the hydraulic jump points to that. So is it 2D inviscid? You only said "simple", and that may well skew your resistance calculations. What are the body length and beam given the ~7 knot speed.

[ENG Student]

The overall length of the hull is 9m, the beam is 3m

The CFD program i am using is simple, it is called PHEONICS,
Because of the limitations of the program i am only looking at single state flow (only the part of the hull which is submerged). I understand that this isnt ideal as it doesnt take into account wave making resistance.

[jehardiman]

Ok, fixed surface with no sinkage and trim will definitely skew your results.

Beam of one hull is 3m? or total beam is 3m? FWIW, the transom looks too wide in the figure for the speed length ratio if 7 knots is design speed (which is why you get wakes off the transom corners) but it doesn't look like a a L/B of 3.