Jaime Saelices 0 Report post Posted October 30, 2014 Hi, I want to optimize the wetted surface of a hull (heeled or not). My main concern is what curves of the hull must be transform into parameters. I've followed some of the tutorials that comes with CAESES but all of them modified the displacement or Cp (in my case both are constraints in the problem). I guess some people thought in this issues as well. Any advice would be great. Thanks a lot. Regards. Share this post Link to post Share on other sites
Matthias Maasch 21 Report post Posted November 18, 2014 Hi Jamie, I prepared a partially-parametric model to tackle your problem. I applied a combination of transformations and shifts to a simple yacht hull. First, I used a scale transformation in order to scale the hull in Y and X dimensions. Then, I used a Lackenby shift to change cb and cp if necessary (I know, you want to keep these values constant.) Finally, I used a Surface Delta shift in order to shift volume in the underwater hull. Pink area shows reduced volume Pink area shows added volumeThe Delta Surface is modeled in a way, that it reduces the volume below a certain boundary and adds the same amount of volume above this boundary. So the volume and the mainframe area are kept constant.In order to control the Surface Delta shift, you have control over the actual value of shift and the x-position where the maximum shift is applied. Position and elevation of Surface Delta ShiftBy using a Hydrostatics Computation, which comes with CAESES/ FRIENDSHIP Framework, the volume and the prismatic coefficient were compared to the initial value of the imported yacht hull. Sections of final hull and imported hull compared to each otherSo far, the Delta Surface shift is kind of limited, due to the feature definition I wrote to define the functions and boundary curves controlling the shift. If you want to have it more variable, you can simply define your own functions and boundary curves. Currently I use the keel curve, the draft line and a curve which is exactly in the middle between these curves (zero curve) with respect to the z-axis, to control the volume shift.What do you think? If you have questions, please do not hesitate to ask! Cheers P.S.: Most likely a fully parametric approach would be more variable and more effective. The advantage of the current approach is, that you can simply exchange the imported hull (as long as it is as simple as the one in the project). The only thing you have to do is to adapt the parameters, such as Lpp, draft, ... and so on. Matthiaspartially_parametric_yacht_hull.fdb Share this post Link to post Share on other sites
Jaime Saelices 0 Report post Posted November 19, 2014 Hi Matthias, Great job! Once parameterized the geometry which variables would you use as DV for optimization algorithm? Obviously main constraints would be displacement and Cp. Please allow me a couple of days in order to check your solution `cause am currently involved in another task. Thanks a lot! Share this post Link to post Share on other sites
Matthias Maasch 21 Report post Posted November 23, 2014 Hi Jamie, it is hard to answer this question as long as you don't know the parametric model in detail. 1. When you use the same approach for your parametric model as I used for the partially parametric approach, constraints for cb and cp would not be necessary, as the section definition would automatically hold these values. 2. I would probably define sectionwise angles for keel, waterline and deck. 3. Moreover I would introduce parameter, controling the values of the section area underwater and overwater. 4. Finally it is necessary to introduce parameters to follow the longitudinal curves such as keel line, water line and deck line. This is just a first guess. As a first step you could try to adapt one of our sample hulls, namely "yacht hull". Kind regards Matthias Share this post Link to post Share on other sites
Jaime Saelices 0 Report post Posted December 10, 2014 Hi Matthias, Back again with this issue. I`ve been analyzing your partial parametric approach. When you perform the surface deltashift you use a curve engine in order to obtain the deltasurface. This kind of approach may be useful but am unable to see the capabilities of using it. Because the parametric model is created for a later optimization algorithm implementation my main concern derive in the definitions of the constraints and design variables. As a first approach I will use the hull itself as delta surface. Several points (its coordinates obviously) of this surface will be the design variables of the problem. Using the displacement and center of buoyancy as main constraints (inequality constraints). Geometry constraints will not be needed as several points of the surface will be modified in the optimization. I realize that new internal volume optimization procedures are available in new versions of FFW but I hope that with this method It could be possible to get an enhanced hull form. As soon as I define the project will send you for your check. Thanks a lot for your help! Regards. Share this post Link to post Share on other sites
Jaime Saelices 0 Report post Posted December 11, 2014 Hi again, while working in the project I realize that the optimization should be done in the upright position and also when heeled. The problem is when using Hydrostatics connection it requires an angle for heel but it does not ask for a displacement so am wondering if the underwater volumes are actually isovolumes but i dont think so. However the most important heeled angle is 25 degrees due to sailing conditions. Another question is the possibility of inclusion of wetted surface calculation into the Hydrostatic connection. I assume the following values are: sections_V --> Volume displacementsections_IT --> Flotation inertiasections_B --> Coordinates of center of buoyancysections_F --> Coordinates of center of flotationsections_IT --> Traversal moment of inertia of waterplanesections_IL --> Longitudinal moment of inertia of waterplane Is this correct? Regards. Share this post Link to post Share on other sites
Mr. Claus Abt 14 Report post Posted December 12, 2014 Hi Jaime, Yes, correct. If you move the mouse over the items in the left column, you will get the information as shown in the picture below.CheersClaus Share this post Link to post Share on other sites
Jaime Saelices 0 Report post Posted December 15, 2014 Thanks Claus. I do not know it you are in sync with the case Matthias gave me a few weeks ago. He used several features that for me are some "tricky". I would like to know the logic under them and how to create the surface used for delta shift transformation. Particularly am interested in defining that surface and some points on it in order to apply a subsequent optimization algorithm. Thanks again. Regards. Share this post Link to post Share on other sites