Mr. Heinrich von Zadow

Dear Atiyah, you are very welcome. About the file you might want to get in touch with my colleague Daehwan Park -- his mail is shown in the screenshot you sent. Best regards, Heinrich

Dear Nuttarat, I am sorry that I didn't find some time to look into this earlier. From what you have sent, it can be seen, that the discontinuity in the rail of your surface causes the irregularities: If you replace this rail with a continuous version that looks somewhat like this, the surface quality already gets much better: In a BRep, you can now simply extend this surface and trim it at the symmetry plane: It is far from perfect, but hopefully a good starting point for you... Cheers, Heinrich Waterjet_intake_Diffuser_HvZ.fdbc

Hi Atiyah, the working mechanism ist the same for both (actually, the Lackenby is also a Delta Shift). A function is defined along the ship which defines by how much the geometry is shifted at the respective longitudinal position. As you can imagine, this easily allows to shift the longitudinal center of buoyancy and adjust the displacement. Since this is such a common task in hull design, we offer the Lackenby which allows you to manipulate prismatic coefficient (CP) and longitudinal center of buoyancy (LCB) simultaneously. So basically, there is no difference except that you can use the Lackenby if this is what you need, or alternatively set up the geometry variation all by yourself through a standard Delta Shift... E.g. you could also use a delta shift to move the design waterline up and down without changing the height of the hull... A typical scenario of the Lackenby being used in an optimization would be to fix LCB and CP all the while the geometry is modified. This way, you can better compare the different geometry variants on a "fair" level (Otherwise you would often just find that the geometry variant with lowest displacement has lowest resistance, which is usually not what you where looking for...). Also, often times these two measures are fixed constraints, anyways... Like said, there is a Tutorial that covers the complete setup. Cheers, Heinrich

Dear Anand, I took a look at the hull surface you started with. The control polygon looks a bit distorted. I suggest, you sort that out first -- especially the bow region seems to have some folding issues, as you can tell from the attached screenshots. After adjusting the control polygon in this region a little and sorting out a few other things (which probably won't occur if you start with a better surface right away) I managed to get everything to work as intended, although you might want to spend some more time on the fairing! Most importantly you should focus on getting the control points shown in the following picture into a straight line (the middle one is the corner of the surface and there is one point currently very close to it, which needs to be exactly the same!) To adjust the control points, you can use the edit mode: I also moved the project to our latest release of CAESES5 which is why the file type is now a *.cdbc. Cheers, Heinrich NPL hull.cdbc

Hi Atiyah, I would recommend that you take a look at the Lackenby (there is also a tutorial "Lackenby Hull Variation"). It is a partially parametric modelling technique that allows you to set both, longitudinal center of buoyancy and prismatic coefficient (and thereby displacement) at the same time. Best regards, Heinrich

Hi Christina, what you need is a design variable that gives you control over the volume, without changing the length. i.e. the beam of the bulbous bow should work fine. You then need to set up a nested optimization (for example a Brent) that adjusts the beam to match the target volume. You should find plenty of material about these so called "nested optimizations" if you search the forum. Cheers, Heinrich

This might not be the perfect forum for this kind of question since CAESES is not a CFD tool, but rather a parametric CAD and optimization platform that allows you to connect any CFD (or other external) software. However, as far as I know, there is -- and has been for a long time -- extensive research carried out in the field of alternative surfaces both on micro and macro scale. Whether you would actually model these things (e.g. fish-like scales or certain roughness and patterns) or just treat them specifically in your CFD code via boundary conditions depends. Both ways are feasible and have their pro's and con's. Cheers, Heinrich

Dear RWM, please provide some more information so that I can understand what you are having trouble with. Best regards, Heinrich

Hi Christina, you are looking at curves, not surfaces (both have a category "curve based"). On your screen it seems that surfaces are collapsed: If you are on a small screen this is probably fine. Otherwise, you can change the font size by pressing ctrl and scrolling the mouse wheel. Best regards, Heinrich

Hi Christina, if you are working with the latest (currently 5.0.6) version of CAESES, you should find lofted surfaces in the category of curve-based surfaces: I am not aware that this is excluded from non-commercial packages. apart from lofting you might want to take a look at sweep surfaces or, if non of the "standards" works for your application dig into the topic of meta surfaces. Cheers, Heinrich

Dear Christina, as mentioned in the other post, you can refer to the "freeformdeformationbulb" tutorial to get a very basic idea of how to apply a ffd to modify an existing bulbous bow. This is one (out of a much larger set) of the available morphing techniques that come with CAESES5. For a bulbous bow I can also definitely recommend to look into delta shifts and BRepMorphing. With these 3 you should have absolutely everything you need to modify an existing bulb geometry. For an optimization of a bulbous bow I would definitely recommend to include some variation of the forward shoulder (so you can achieve a favorable cancellation of waves) as well. Once you do that, you will probably also need to keep an eye on hydrostatics (check if the Lackenby suits your needs) to avoid shifting the LCB to much, or changing the displacement beyond what's feasible for your application. We have recently hosted a Webinar about morphing capabilities in CAESES5 which might be interesting for you ("How to Efficiently Optimize your Geometry with Morphing in CAESES 5") here: https://www.caeses.com/support/videos/ About the optimization, there are plenty of other tutorials and useful guidelines included in the documentation that should give you a good starting point. Hope this helps to get you started. Best regards, Heinrich

Dear Christina, the file Rull has posted further up seems to be very similar (if not identical) to the sample we ship with CAESES5. Just search for it in the help workspace (bottom left corner of the GUI) and you should find this: Best regards, Heinrich

Dear Atiyah, I recommend to start with the general documentation and then work your way forward through tutorials and samples. There is plenty of maritime-specific material on fully, as well as partially parametric hull-design available to get you started. Best regards, Heinrich

Dear Mr. Saeed, although I have no experience with such a design I am positive that something like this could be modelled with CAESES. Instead of the standard blade modeling functionality I would go for a meta surface to create the special shape. You could model the central u-turn-curve (dashed line in your last picture) first and then create the blade along this path while providing functions like chord, pitch, thickness etc. along this path. I guess, if you check the propeller and meta-surface tutorials and samples you should have a good idea how to proceed. Fell free to get back to me in case you get stuck. Cheers, Heinrich