Hi Chao Peng, thanks for the quick response!
The problem is that using different sections for A and B the system doesnt solve at all. I could narrow it down to the section rotation angle, if the rotation varies over sectionA and sectionB the system doesnt solve. See the image below for such an exemplary distribution that doesnt solve. [image: distribution.png] What I dont understand is that if I use the same distribution for the section rotation and average only the section rotation manually (and then assigning it to both A and B sections) , while all other sectional parameters are averaged by GetAverageSectionParameters(), everything works, so the problem seems to occur only when there is a different rotation for sectionA and sectionB. Best regards, David [email protected] schrieb am Samstag, 30. September 2023 um 03:19:35 UTC+2: > Hi David, > > Thank you for your test and feedback. > > It seems the evaluation for the average *EImyy and * *EImzz *is a bug > since they are definitely positive in the sense of the physics, you can try > to fix it as: > double EImyy1 = abs(EIyy1 * cosphi1 + EIzz1 * sinphi1); > double EImzz1 = abs(-EIyy1 * sinphi1 + EIzz1 * cosphi1); > double GAmyy1 = abs(GAyy1 * cosphi1 + GAzz1 * sinphi1); > double GAmzz1 = abs(-GAyy1 * sinphi1 + GAzz1 * cosphi1); > > But the stiffness parameters (EImyy1,EImzz1,GAmyy1,GAmzz1) described at > the mass center and mass axis are not used in the evaluation of the > stiffness matrix (Km) of the element, your problem encountered in your test > might come from other aspects. > > *ChBeamSectionTaperedTimoshenkoAdvancedGeneric *should be able to support > two different *ChBeamSectionTimoshenkoAdvancedGeneric *for sectionA and > sectionB since I have used in this way for several years. I would > suggest you check whether the section parameters along blade spanwise > change in a continuous function first, especially for the blade root > sections. If they look like a zigzag shape along spanwise, the accuracy of > the tapered Timoshenko beam element will decrease. > > Let me know if you have further questions. > > Best regards, > Chao Peng. > > 在2023年9月30日星期六 UTC+8 02:36:34<David Marten> 写道： > >> Dear all, >> >> I have been using Timoshenko beams recently to model wind turbine blades >> in the QBlade code. >> >> Overall the beams are performing great (both "standard" and FPM) and the >> prediction of internal blade shear forces is improved greatly. The >> anisotropic damping feature is also of great use and I could validate its >> correct functionality based on a very large blade design (22MW). >> >> I have a question regarding the functionality of >> *ChBeamSectionTaperedTimoshenkoAdvancedGeneric*, which does not seem to >> work as intended in my tests. The only way I can get the simulation to run >> is by using the same *ChBeamSectionTimoshenkoAdvancedGeneric *for both >> sections (sectionA and sectionB) of the tapered section. >> >> I tried to look into the issue that I am having, and it seems like during >> the evaluation of *ChBeamSectionTaperedTimoshenkoAdvancedGeneric*:: >> ComputeAverageSectionParameters() material values can turn out to be >> negative. I found at least the value *EImyy *to appear as a negative >> values my tests. I think that this happens during the "rotation" of *EIyy >> *onto the mass axis, as nothing "prevents" the values from turning >> negative (for certain angles of *mass_phi*), see below: >> >> double cosphi1 = cos(mass_phi1); >> double sinphi1 = sin(mass_phi1); >> double EImyy1 = EIyy1 * cosphi1 + EIzz1 * sinphi1; >> double EImzz1 = -EIyy1 * sinphi1 + EIzz1 * cosphi1; >> double GAmyy1 = GAyy1 * cosphi1 + GAzz1 * sinphi1; >> double GAmzz1 = -GAyy1 * sinphi1 + GAzz1 * cosphi1; >> >> I am not sure if this really is the problem, but wanted to ask if someone >> has experience using the tapered section and has some suggestions or tips >> on how to get it to work correctly. >> >> Thanks and best regards, >> >> David >> > -- You received this message because you are subscribed to the Google Groups "ProjectChrono" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/projectchrono/1fa50b46-daf8-4d40-920e-523a8ebadc15n%40googlegroups.com.
