BECASv3.1 is released!

Friday 24 Jul 15
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A new version of BECAS is available – BECAS v3.1. This release includes a few improvements and some important bug fixes. A detailed description of each of the changes is presented.

 

Among other, BECAS now provides input to the new beam formulation included in the latest version of HAWC2. This represents an important milestone for the interface between the two codes as it is now possible to take full advantage of the BECAS results to, e.g., configure the composite laminates to control the aeroelastic response of wind turbine blades.

 

Recent work with BECAS has focused on the development of a new structural topology optimization module. We publish here a few initial results. The topology optimization module will be included in the next release of the code.

 

Finally, as you may know by now, the BECAS source code has been moved to a GIT repository. Details of the new setup are described here.

 

We wish you all a nice summer,

 

The BECAS team


LIST OF IMPROVEMENTS

  1. Fixed bug in the Maximum Strain and Maximum Stress failure index calculation. The failure index was output in the wrong order, i.e., not the same order as the strain and stress components given as input. This bug affected only the results from the functions BECAS_MaxStrain and BECAS_MaxStress which compute the strength index according to the maximum strain and maximum stress failure criteria, respectively.The bug did NOT affect the BECAS_TsaiWu results, i.e., the strength index values determine according to the Tsai-Wu failure criterion. The function BECAS_CheckFailure, BECAS_MaxStrain, BECAS_MaxStress, and BECAS_TsaiWu have been updated so that the standard BECAS ordering is used all throughout. Finally, the function BECAS_CheckFailure can now retrieve results at Gauss points. 
  2. Improved the function BECAS_ParseFailMat to ensure that compressive strength values are always negative. Henceforth, input values of maximum allowed compressive stress or strain may be either positive or negative as BECAS will always make them negative. This is to ensure that the expression for the Tsai-Wu strength index returns the correct results as it assumes negative compression values. Thank you to Frederik Zahle and Peter Berring at the Technical University of Denmark for pointing out the inconsistency. 
  3. Fixed issue with the bend-twist coupling term of the shear center position. The expression for the shear center position xs has been corrected both in the code and user’s manual. Nonetheless, this fix does NOT affect the positon of the shear center calculated by BECAS. As stated in the the user’s manual, the position xs is obtained as the sum of two terms, i.e., xs = -Fs,62/Fs,66 + Fs,64(L-z)/Fs,66. The correction affects only the second term – the sign is positive instead of negative. However, in the code L-z=0 and thus the second term vanishes. As such the position of the shear center is unaffected by this fix. Thank you to Roque Garcia at Polytechnic University of Valencia for pointing out the inconsistency. 
  4. Fixed bug in the calculation of the area moments of inertia csprops.Axx and csprops.Ayy. The functions BECAS_Q4_ElementMassProps, BECAS_Q8_ElementMassProps, and BECAS_T6_ElementMassProps have been updated. Note that these are NOT the mass moment of inertia used for the cross section mass matrix calculation. The cross section mass matrix is therefore correct and unaffected by this fix. Thank you to Michael Filipe at University of Toronto for finding the bug and suggesting the fix.
  5. Fixed bug in element label and numbering mapping. Thank you to Nikolay Dimitrov at Technical University of Denmark for reporting the bug. 
  6. Fixed several typos and inconsistencies in the Background section of the User’s Manual. Thank you to Roque Garcia at Polytechnic University of Valencia for reporting the bugs and fixing them.
  7. Updated the BECAS2HAWC2 function. The most recent version of HAWC2- verson 12.1 - can now handle anisotropic beams and therefore allows for the input of all terms of the cross section stiffness matrix. The output file BECAS_Becas2Hawc2 has been updated to reflect this improvement. A new options field has been created allowing the user to control which type of HAWC2 input is desired. The output from BECAS is by default the one used by older versions of HAWC2. Please see the user’s manual for more information on how to set this flag. Thank you to Christian Pavese at the Technical University of Denmark for providing the update. 

NEW REPOSITORY

BECAS has been distributed through the subversion server https://svn-04.risoe.dk/svn/DTU-WIND-BECAS/  since 2012. Due to a reorganization of our IT systems this server will be closed down in the near future. We have used this opportunity to not only move BECAS to a new server, but also to the more modern revision control system Git (https://git-scm.com/).

If you have a BECAS license and would like to continue having access to the BECAS source code please do the following:

  1. Go to http://gitlab.windenergy.dtu.dk/ and create an new account using your full name and university/company e-mail address. If you already have a DTU user account, please simply log in with your standard password.
  2. Send an e-mail with your username to BECAS-DTUwind@dtu.dk. We will then give the newly created user access to BECAS and related software.

Note that the organization of the source code has slightly changed on the new server.

The README file in the “templates project” describes the best way to install BECAS using the new server: https://gitlab.windenergy.dtu.dk/BECAS_stable/templates.

THINGS TO COME

Recent work in BECAS have focused on the development of the structural topology optimization module. The work is being carried out by Miguel Perez as part of his MSc thesis. The new code is being used to redesign the internal structural lay-out of the DTU10MW reference wind turbine. Initial work has focused on the implementation and validation of the code and testing different problem formulations to take advantage of the beam model. You can see some preliminary results in Figure 1. Once completed this module will be useful to, e.g., optimize the position of the caps and shear webs, or the distribution of materials in existing blades.

 topopt

Figure 1 – Minimum mass optimization with stiffness constraint of the internal structure of three sections along the length of the DTU10MW reference wind turbine blade for the design load cases obtained from nonlinear aeroelastic analysis in HAWC2.

JOIN THE COMMUNITY

We are always looking for an extra pair of hands to help us develop BECAS further. If you are a student looking for a purposeful project, a company with an innovative idea, or you would simply like to participate, do not hesitate to contact us.