# Powerboat trim angle study **URL:** \ **Category:** Project Support\ **Created:** [May 26, 2016, 5:30pm UTC](https://www.simscale.com/forum/t/powerboat-trim-angle-study/24762 "2016-05-26T17:30:17Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![zgaryulo](https://www.simscale.com/forum/letter_avatar/zgaryulo/32/6_22734026db12803ebb3e059622ac3534.png) [@zgaryulo](https://www.simscale.com/forum/u/zgaryulo)\ **Post date:** [May 26, 2016, 5:30pm UTC](https://www.simscale.com/forum/t/powerboat-trim-angle-study/24762/1 "2016-05-26T17:30:17Z")
Hello to everybody, 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. Many thanks! ---
**Author:** ![ggiraldo](https://www.simscale.com/forum/user_avatar/www.simscale.com/ggiraldo/32/5226_2.png) [@ggiraldo](https://www.simscale.com/forum/u/ggiraldo)\ **Post date:** [May 27, 2016, 4:03pm UTC](https://www.simscale.com/forum/t/powerboat-trim-angle-study/24762/2 "2016-05-27T16:03:56Z")
Very nice idea, I’m in. 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. Greetings. ---
**Author:** ![dheiny](https://www.simscale.com/forum/user_avatar/www.simscale.com/dheiny/32/2_2.png) [@dheiny](https://www.simscale.com/forum/u/dheiny)\ **Post date:** [May 28, 2016, 7:32am UTC](https://www.simscale.com/forum/t/powerboat-trim-angle-study/24762/3 "2016-05-28T07:32:16Z")
Hi @zgaryulo, Hi @ggiraldo, 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 ? ![](https://www.simscale.com/forum/uploads/default/original/2X/7/75831690047251644652216b05c088c8eee32d7d.jpg) (Source: [Planing bow hull and getting over the bow wave hump | Boat Design Net](http://www.boatdesign.net/forums/boat-design/planing-bow-hull-getting-over-bow-wave-hump-16709.html)) If that’s correct, we’ll probably need to work with the 6DOF model. In the other topic over [here](https://www.simscale.com/forum/t/collaborative-simulation-project-multiphase-flow-around-a-boat-hull/71) the boat is fixed withing the domain, so \tau is prescribed and not computed. ![](https://www.simscale.com/forum/uploads/default/original/1X/68b9fac44203cd1c8937621d5c53886a65cfcd82.gif) 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: ![](https://www.simscale.com/forum/uploads/default/original/2X/e/e90e64ceb703af151bac02d852a0b2d2988fa558.png) 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? Looking forward to this! David ---
**Author:** ![zgaryulo](https://www.simscale.com/forum/letter_avatar/zgaryulo/32/6_22734026db12803ebb3e059622ac3534.png) [@zgaryulo](https://www.simscale.com/forum/u/zgaryulo)\ **Post date:** [May 28, 2016, 1:32pm UTC](https://www.simscale.com/forum/t/powerboat-trim-angle-study/24762/4 "2016-05-28T13:32:22Z")
Thanks @ggiraldo and @dheiny for your interest in the project, I am looking forward to work with both of you. First of all, I could send the original Savitsky’s paper to anyone interested in the matter, you only have to ask for it. I have examples done with equations with my own excel file, the results are something like this: ![](https://www.simscale.com/forum/uploads/default/original/2X/e/e9b459598b461281959e4c3bd223aed6e7fb8c96.PNG) ![](https://www.simscale.com/forum/uploads/default/original/2X/9/99ea99844dfdd9a0a6e1c45fcf05b1d428f28e0c.PNG) Unfortunately, I don’t have any CFD examples of this at the moment. * * * Here are some pictures of the boat that I would like to study, and the hull lines drawing. ![](https://www.simscale.com/forum/uploads/default/original/2X/f/f9d9ef71a93fa648c13408d13badfc00d7afb1cd.jpg) ![](https://www.simscale.com/forum/uploads/default/original/2X/0/06532e2d81713c930ca8df7646b6bb0881271707.PNG) ![](https://www.simscale.com/forum/uploads/default/original/2X/d/d393671e16b98aa89f97d89c1f11b0fbf2394ae7.PNG) ![](https://www.simscale.com/forum/uploads/default/original/2X/c/c30978e1f3f5fc74693ca5c596c3b5df2b370117.PNG) 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. ---
**Author:** ![ggiraldo](https://www.simscale.com/forum/user_avatar/www.simscale.com/ggiraldo/32/5226_2.png) [@ggiraldo](https://www.simscale.com/forum/u/ggiraldo)\ **Post date:** [May 28, 2016, 4:29pm UTC](https://www.simscale.com/forum/t/powerboat-trim-angle-study/24762/5 "2016-05-28T16:29:25Z")
Please send the paper to me at [guillegiraldo@gmail.com](mailto:guillegiraldo@gmail.com) ---
**Author:** ![dheiny](https://www.simscale.com/forum/user_avatar/www.simscale.com/dheiny/32/2_2.png) [@dheiny](https://www.simscale.com/forum/u/dheiny)\ **Post date:** [May 29, 2016, 6:46am UTC](https://www.simscale.com/forum/t/powerboat-trim-angle-study/24762/6 "2016-05-29T06:46:44Z")
Hi @zgaryulo, 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? Best, David ---
**Author:** ![zgaryulo](https://www.simscale.com/forum/letter_avatar/zgaryulo/32/6_22734026db12803ebb3e059622ac3534.png) [@zgaryulo](https://www.simscale.com/forum/u/zgaryulo)\ **Post date:** [May 29, 2016, 7:00pm UTC](https://www.simscale.com/forum/t/powerboat-trim-angle-study/24762/7 "2016-05-29T19:00:02Z")
Hi David, 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). ---
**Author:** ![bkocijan](https://www.simscale.com/forum/letter_avatar/bkocijan/32/6_22734026db12803ebb3e059622ac3534.png) [@bkocijan](https://www.simscale.com/forum/u/bkocijan)\ **Post date:** [May 30, 2016, 9:36am UTC](https://www.simscale.com/forum/t/powerboat-trim-angle-study/24762/9 "2016-05-30T09:36:57Z")
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… ---
**Author:** ![zgaryulo](https://www.simscale.com/forum/letter_avatar/zgaryulo/32/6_22734026db12803ebb3e059622ac3534.png) [@zgaryulo](https://www.simscale.com/forum/u/zgaryulo)\ **Post date:** [May 30, 2016, 11:45am UTC](https://www.simscale.com/forum/t/powerboat-trim-angle-study/24762/10 "2016-05-30T11:45:48Z")
Welcome aboard! 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. ---
**Author:** ![dheiny](https://www.simscale.com/forum/user_avatar/www.simscale.com/dheiny/32/2_2.png) [@dheiny](https://www.simscale.com/forum/u/dheiny)\ **Post date:** [May 30, 2016, 7:47pm UTC](https://www.simscale.com/forum/t/powerboat-trim-angle-study/24762/11 "2016-05-30T19:47:36Z")
@bkocijan - excellent! @zgaryulo, 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! @anon62721193 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 😉 Best, David ---
**Author:** ![zgaryulo](https://www.simscale.com/forum/letter_avatar/zgaryulo/32/6_22734026db12803ebb3e059622ac3534.png) [@zgaryulo](https://www.simscale.com/forum/u/zgaryulo)\ **Post date:** [June 5, 2016, 2:00pm UTC](https://www.simscale.com/forum/t/powerboat-trim-angle-study/24762/12 "2016-06-05T14:00:08Z")
Hi! Here is the link to the project: > **[Powerboat trim angle study by zgaryulo | SimScale](https://www.simscale.com/projects/zgaryulo/powerboat_trim_angle_study_1/)** > > Predict the resistance and trim angle of a planing hull. | Simulation project by zgaryulo The geometry is very simple, very prismatic: ![](https://www.simscale.com/forum/uploads/default/original/2X/2/275ef912897de145887391495bf83c22ae978b08.PNG) ![](https://www.simscale.com/forum/uploads/default/original/2X/3/34ec4ba4b32ef8cc4d667184bf014c63d4ebad69.PNG) The loading coefficient is around 6 (Ap/V^(2/3)), the CG is around 35.5% of the Lp (chine length). The weight of the craft is 6855 kg. These are the results expected from my Savitsky analysis: ![](https://www.simscale.com/forum/uploads/default/original/2X/9/962ea3d014a5acaa938d5335ecad00155e20004d.png) Any doubts, please send me a message. ---
**Author:** ![dheiny](https://www.simscale.com/forum/user_avatar/www.simscale.com/dheiny/32/2_2.png) [@dheiny](https://www.simscale.com/forum/u/dheiny)\ **Post date:** [June 8, 2016, 10:50am UTC](https://www.simscale.com/forum/t/powerboat-trim-angle-study/24762/13 "2016-06-08T10:50:59Z")
Hi @zgaryulo, awesome - excited to get started. I’ll get back to you soon. Best, David ---
**Author:** ![ggiraldo](https://www.simscale.com/forum/user_avatar/www.simscale.com/ggiraldo/32/5226_2.png) [@ggiraldo](https://www.simscale.com/forum/u/ggiraldo)\ **Post date:** [June 10, 2016, 2:18pm UTC](https://www.simscale.com/forum/t/powerboat-trim-angle-study/24762/14 "2016-06-10T14:18:28Z")
Hi @zgaryulo @dheiny I took the hull geometry and modeled the domain in OnShape, imported to Simscale and meshed for a laminar simulation. Links are: [OnShape project](https://cad.onshape.com/documents/071091506e2e916f79df72b0/w/ed6824e9e02277def00d5a82/e/2d8bbe2d6282895f1a0fe4a1) [Simscale project](https://www.simscale.com/projects/ggiraldo/powerboat_trim_angle_study/) 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? ---
**Author:** ![dheiny](https://www.simscale.com/forum/user_avatar/www.simscale.com/dheiny/32/2_2.png) [@dheiny](https://www.simscale.com/forum/u/dheiny)\ **Post date:** [June 11, 2016, 6:20am UTC](https://www.simscale.com/forum/t/powerboat-trim-angle-study/24762/15 "2016-06-11T06:20:10Z")
Hi @ggiraldo, mhm - you mean this here, right: ![](https://www.simscale.com/forum/uploads/default/original/2X/7/7858869d6229497b4ea76f229ad2156a93520ae0.png) I’ll take a closer look and will get back! Best, David ---
**Author:** ![dheiny](https://www.simscale.com/forum/user_avatar/www.simscale.com/dheiny/32/2_2.png) [@dheiny](https://www.simscale.com/forum/u/dheiny)\ **Post date:** [June 11, 2016, 6:20am UTC](https://www.simscale.com/forum/t/powerboat-trim-angle-study/24762/16 "2016-06-11T06:20:50Z")
Forgot to mention - nice mesh setup!! ---
**Author:** ![bkocijan](https://www.simscale.com/forum/letter_avatar/bkocijan/32/6_22734026db12803ebb3e059622ac3534.png) [@bkocijan](https://www.simscale.com/forum/u/bkocijan)\ **Post date:** [June 11, 2016, 1:23pm UTC](https://www.simscale.com/forum/t/powerboat-trim-angle-study/24762/17 "2016-06-11T13:23:35Z")
Wow guys you don’t waste time! 🙂 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? @zgaryulo : Which model did you choose? ---
**Author:** ![ggiraldo](https://www.simscale.com/forum/user_avatar/www.simscale.com/ggiraldo/32/5226_2.png) [@ggiraldo](https://www.simscale.com/forum/u/ggiraldo)\ **Post date:** [June 11, 2016, 3:46pm UTC](https://www.simscale.com/forum/t/powerboat-trim-angle-study/24762/18 "2016-06-11T15:46:59Z")
@dheiny Exactly, that’s it. And thanks (I got inspiration from the Free Float Boat simualtion project)! Hope we can fix it and start simulating. @bkocijan I agree, we should make turbulent simulations. Will add boundary layers to the mesh. ---
**Author:** ![ggiraldo](https://www.simscale.com/forum/user_avatar/www.simscale.com/ggiraldo/32/5226_2.png) [@ggiraldo](https://www.simscale.com/forum/u/ggiraldo)\ **Post date:** [June 22, 2016, 7:10pm UTC](https://www.simscale.com/forum/t/powerboat-trim-angle-study/24762/19 "2016-06-22T19:10:00Z")
@dheiny Could you find something in the mesh? Has anyone made any advancement? ---
**Author:** ![dheiny](https://www.simscale.com/forum/user_avatar/www.simscale.com/dheiny/32/2_2.png) [@dheiny](https://www.simscale.com/forum/u/dheiny)\ **Post date:** [June 23, 2016, 7:43am UTC](https://www.simscale.com/forum/t/powerboat-trim-angle-study/24762/20 "2016-06-23T07:43:49Z")
@ggiraldo, thanks a lot for following up. Unfortunately no progress on my end yet - I’m planning on working on it again this weekend. I also saw that @Zoran is doing interesting stuff over here: [SimScale](https://www.simscale.com/projects/Zoran/v1hull_fs/) - very interesting model + mesh! How did you generate the mesh? Best, David ---
**Author:** ![radenpm9](https://www.simscale.com/forum/user_avatar/www.simscale.com/radenpm9/32/5989_2.png) [@radenpm9](https://www.simscale.com/forum/u/radenpm9)\ **Post date:** [June 23, 2016, 4:49pm UTC](https://www.simscale.com/forum/t/powerboat-trim-angle-study/24762/21 "2016-06-23T16:49:59Z")
Dear all, 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. @zgaryulo, do you mind to send me the papers, the old and recent, to [rpmuayyad@gmail.com](mailto:rpmuayyad@gmail.com)? Best regards, Raden [Next page](https://www.simscale.com/forum/t/powerboat-trim-angle-study/24762.md?page=2)