My name is Zeus, I am a naval architect from Uruguay, working in the UK at the moment.
I am really interested in predicting the trim angle of planning hulls, because in my office we do this with old Savitsky’s equations (forgive me dear Sav!), but I would like to try which are the results with CFD.
So, I would like to invite all the people interested in the project to work together and try to solve the problem.
I don’t know anything about CFD, but I can help with the hull, naval architecture and later to compare the results with the old Savitsky equations.
Maybe, first it would be better to simulate one of Savitsky experiments, and then try with a different hull.
Let me know your questions, of course the project will be public, so everybody can learnt from it.
I propose that as a first step you show us an example case done with equations, in order to analyse the phenomena and the kind of simulation we can make. If you have seen this done in CFD before, an example of that would be very useful also.
Second, you can select the Savistky experiment we will use as a benchmark and show it to us, alongside the reference results, so can we build the simulation and plan the posprocessing to extract the relevant data.
excellent - interested in this topic as well. @zgaryulo do I get you correct, that the quantity that you want the simulation to predict is the angle the boat has with respect to the horizontal axis? So the boat can not be fixed in the domain, but free at least in rotation across the lateral axis? So looking at the graphic below, you’re looking for \tau ?
If that’s correct, we’ll probably need to work with the 6DOF model. In the other topic over here the boat is fixed withing the domain, so \tau is prescribed and not computed.
In any case, what we’ll need to do is upload a model of the flow domain, as SimScale is not yet capable to build an external flow mesh with a split face inlet to allow for both water and air entering the domain on the side. I did this briefly over in Onshape:
Let me know if you’re fine with me making the Onshape model public - then you could work on it as well.
As a side note: Middle of next week, there will be some improvements to SimScale with respect to multiphase flow analysis (@jprobst currently busy with this). So I’ll wait until then and run the first analysis and make my project public, okay?
The thing is, original Savitsky’s paper was done for prismatic hulls (same deadrise angle, single chine hulls), nowadays, hulls are double chined with warp (variation of deadrise angle with lenght), people continue to use the method with some minor modifications, but it would be interesting to study the problem with CFD to see the differences.
Before trying to solve this complex problem, we could try with one of Savitsky’s prismatic hulls first, at the moment I am looking for results and geometry descriptions of the hull used in the test, so I can model this in Rhino (and the domain also) and then run the simulation.
yes, the paper would be great. Could you post a link to it here? I think first reproducing the known application with a prismatic hull is a great approach. That way, we can validate the sim setup and then apply it to the new hull you’re designing.
Interesting to see you using Rhino. Is there a specific reason for it?
I don’t know how to upload the file here in the forum (shame on me), but if you give me your email I’ll send it to you, and also another paper with a recent tank testing from Southampton University, because I can’t find original Savtsky’s results…
In naval architecture and yacht design Rhino is a must, because it’s easier and faster than other softwares, SolidEdge, Solidworks or Catia, are used only in big projects (generally speaking).
Hello everyone!
Zeus, it’s a GREAT Idea.
I am also a Naval Architect with similar interest in CFD so I am IN!
I think we need the solid model we can mesh and COG with the correct displacement of the boat.
Because as you know, the position of COG in relation to the center point in which dinamic lift acts, is crucial for the trim.
And also for resistance…
But I think the real validation of this CFD analysis is possible if we have some basin model testing results…
I have some results from a tank testing that I would like to discuss with you, please give me your email so I can send you the paper.
I couldn’t find Savitsky’s results, but we may use Series 62 of Blount, if I remember well, the geometry of the hulls was described very well in that paper.
once you’ve got the geometry that you suggest for the initial validation step, it would be great if you simply put it into a public SimScale projet and post the link here. I’m happy to set up the first baseline simulation, from which we can start tweaking! @gholami will be the go to guy once we model the boat free floating. In a first step, I’d probably start with having it fixed. I think I’ve mentioned that often in this forum - I’m the “crawl, walk, run” type of guy when it comes to simulation
If you look at it, I am having an issue with the mesh. The region refinement for the fluids interface is producing this triangular refinement outside of the region box. I don’t know why this happens, and I have tried many variations on the region box and this always happens. Maybe David can help me with this?
But I think we should do a turbulent simulation.
We should use the Re mentioned in the paper Zeus suggested.
I suggest we use omega-SST turbulence model, what do you guys think?
I am now pursuing a career as naval architect while developing new skills in FEA and CFD. I really happy to meet the experts here to learn from. Also, I am excited to collaborate with you if I may.
