How to deal with the errors of a poorly defined structural model
This error can be caused by several factors, the most common of which is the use of a non-physical structural definition for the blade or tower. In order to address this error:
1. Check any warnings, as they can often indicate the problem.
2. Look for any physical impossibilities in the model, such as very low mass members, or very low stiffnesses. Remember to check torsional inertia and stiffness properties as well as mass and bending stiffness.
3. Ensure that there are no very small blade elements, as created by two blade stations very close together. A similar problem could be caused by a very small blade element being adjacent to a very large element.
4. For a support structure, check that any rigid members are defined in Project Info, if desired. Very stiff members should be made rigid through Project Info rather than simply choosing a very high stiffness value. Please refer to this article about how to define it in the "project info".
5. If the above doesn't yield a solution, it may help to narrow the problem down by switching off flexibility in one or more components and re-run to see which component is triggering the error.
Category: Structural dynamics
Problem
Here is a list of errors indicate that part of the structure (blades, foundations, tower, or drivetrain/mounting flexibility if present) has a mass or stiffness matrix with some invalid entries. How can these errors be resolved?
1. Error message:
2. Error message:
"Factorisation failed - Invalid non-positive definite matrix"
Solution
Versions of Bladed affected: 4.0 onwards.
Last updated: 25.04.2023
This error can be caused by several factors, the most common of which is the use of a non-physical structural definition for the blade or tower. In order to address this error:
1. Check any warnings, as they can often indicate the problem.
2. Look for any physical impossibilities in the model, such as very low mass members, or very low stiffnesses. Remember to check torsional inertia and stiffness properties as well as mass and bending stiffness.
3. Ensure that there are no very small blade elements, as created by two blade stations very close together. A similar problem could be caused by a very small blade element being adjacent to a very large element.
4. For a support structure, check that any rigid members are defined in Project Info, if desired. Very stiff members should be made rigid through Project Info rather than simply choosing a very high stiffness value. Please refer to this article about how to define it in the "project info".
5. If the above doesn't yield a solution, it may help to narrow the problem down by switching off flexibility in one or more components and re-run to see which component is triggering the error.
Keywords Factorisation, non-positive definite matrix, mass, stiffness, structural