In modal analysis, the requested frequencies have been calculated which can be seen in the solution data. but the solver continues on to another “Lanczos cycle” without converging further. How to stop this?
Tagged: frequency, modal-analysis
-
-
June 6, 2022 at 9:58 am
FAQ
ParticipantThis behavior is most usually due to a very ill-conditioned system. Try changing the solver from Block Lanczos (direct) to subspace. Subspace better handles indefinite matrices than the Block Lanczos (BL) method. This can be done in Analysis Settings -> Solver Type -> Subspace. Usually what is happening is that there is a disagreement between the number of modes to be found between what the BL found and what the Sturm sequence check finds. So a new BL cycle is done with a new shift, but then the same disagreement is found but in the opposite direction. the subspace does not perform a Sturm check by default, so it can bypass the issue altogether and ‘fix’ what is causing the ill conditioned model. But at the expensive of a possible less accurate model. There is also an option to turn off the Sturm checking for the BL method via the new LANBOPT command.
-

Introducing Ansys Electronics Desktop on Ansys Cloud
The Watch & Learn video article provides an overview of cloud computing from Electronics Desktop and details the product licenses and subscriptions to ANSYS Cloud Service that are...

How to Create a Reflector for a Center High-Mounted Stop Lamp (CHMSL)
This video article demonstrates how to create a reflector for a center high-mounted stop lamp. Optical Part design in Ansys SPEOS enables the design and validation of multiple...

Introducing the GEKO Turbulence Model in Ansys Fluent
The GEKO (GEneralized K-Omega) turbulence model offers a flexible, robust, general-purpose approach to RANS turbulence modeling. Introducing 2 videos: Part 1Â provides background information on the model and a...

Postprocessing on Ansys EnSight
This video demonstrates exporting data from Fluent in EnSight Case Gold format, and it reviews the basic postprocessing capabilities of EnSight.
- How can I change the normalization method of the vibration modes from modal analysis?
- Why does the prestress from Static analysis does not add up to the stress in Random Vibration analysis?
- In the results of a modal analysis, how can I define that a frequency is an output parameter ?
- A Shock absorber is represented as spring element with damping constant. Modal analysis is performed using Reduced Damped (QRDAMP) solver. How to perform a Modal super position harmonic or transient analysis further ?
- Why is damped frequency is lower than undamped frequency with viscous damping but larger with structural damping?
- What does the warning “Diagonal of the mass matrix is missing in file” indicate when using RSTMAC command?
- How do I get a frequency response of acceleration in the radial direction of a cylinder?
- In a Modal Analysis of Mechanical, why aren’t the Participation Factors Summary under Solution Information displayed?
- What is mass moment of inertia in Point Mass used for?
- How to solve for harmonic response at a specific frequency in Workbench?
© 2023 Copyright ANSYS, Inc. All rights reserved.