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How to apply artificial numerical damping in linear elastic model in COMSOL

Posted Mar 17, 2022, 5:24 a.m. EDT Electromagnetics, Acoustics & Vibrations, Structural Mechanics Version 6.0 4 Replies

Abhijit Paul
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Hi all.

In COMSOL I found the option for applying the physical damping methods in any linear elastic model in terms of, (a)Rayleigh damping, (b) Viscous damping, (c) Isotropic loss factor, and (d) anisotropic loss factor.

Can we apply the artificial numerical damping method (like hourglass) in any linear elastic model in COMSOL. Does the options like (i) spring foundation and (ii) added mass, serves the role of artificial numerical damping method in COMSOL.

In other softwares like LS DYNA this artificial numerical damping is available in the name of hourglass numerical damping.

Thank for your attention.

4 Replies Last Post Mar 24, 2022, 5:30 a.m. EDT
Henrik Sönnerlind COMSOL Employee

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Posted: 2 years ago Mar 17, 2022, 8:32 a.m. EDT

Hourglass stabilization is only needed when using reduced integration. If you select the Reduced integration check box in a material model, then you will see the settings for Hourglass stabilization. As a default, it is included when necessary.

However, the hourglass stabilization is not a damping, it is an artificial stiffness, active also in stationary analysis.

Why do you need this artificial damping?

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Henrik Sönnerlind
COMSOL
Hourglass stabilization is only needed when using reduced integration. If you select the *Reduced integration* check box in a material model, then you will see the settings for *Hourglass stabilization*. As a default, it is included when necessary. However, the hourglass stabilization is not a damping, it is an artificial stiffness, active also in stationary analysis. Why do you need this artificial damping?
Abhijit Paul
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Posted: 2 years ago Mar 18, 2022, 6:02 a.m. EDT
Updated: 2 years ago Mar 18, 2022, 10:03 a.m. EDT

Thank you Henrik for your time and effort.

I am solving a linear wave propagation model applying an external impulsive force in soft tissue medium. So in order to reduce the high frequency oscillations, it might be advantageous to use numerical damping besides physical damping. Do I need to choose the "water" and "non solid" option in the material settings of COMSOL for this?

Actually I am trying to validate my model with literature where they used hourglassing to improve the computational efficay apart from Rayleigh damping using another software. With the same physical and boundary conditions, large deviations in displacement values are coming between my and literature model. Although qualitatively results are matching but not quantitatively.

I am using the physical Rayleigh damping method in my model. Additionally if I use the spring foundation and added mass, will it be benificial, do they serve the numerical damper role in COMSOL. Do I really need hourglass stabilization to validate my model using COMSOL.

I searched in COMSOL 5.6, I found the "stabilization" check box in material model, can you help me more in finding the "reduced integration" check box.

Your attention will be very helpful.

Abhijit IIT Gandhinagar

Thank you Henrik for your time and effort. I am solving a linear wave propagation model applying an external impulsive force in soft tissue medium. So in order to reduce the high frequency oscillations, it might be advantageous to use numerical damping besides physical damping. Do I need to choose the "water" and "non solid" option in the material settings of COMSOL for this? Actually I am trying to validate my model with literature where they used hourglassing to improve the computational efficay apart from Rayleigh damping using another software. With the same physical and boundary conditions, large deviations in displacement values are coming between my and literature model. Although qualitatively results are matching but not quantitatively. I am using the physical Rayleigh damping method in my model. Additionally if I use the spring foundation and added mass, will it be benificial, do they serve the numerical damper role in COMSOL. Do I really need hourglass stabilization to validate my model using COMSOL. I searched in COMSOL 5.6, I found the "stabilization" check box in material model, can you help me more in finding the "reduced integration" check box. Your attention will be very helpful. Abhijit IIT Gandhinagar
Henrik Sönnerlind COMSOL Employee

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Posted: 2 years ago Mar 21, 2022, 5:19 a.m. EDT

Assuming that you are using Generalized alpha as time-dependent solver, then you can use the setting Amplification for high frequency to tune the numerical damping in the solver itself. Lowering the value will give more efficient suppression of high frequencies.

-------------------
Henrik Sönnerlind
COMSOL
Assuming that you are using *Generalized alpha* as time-dependent solver, then you can use the setting *Amplification for high frequency* to tune the numerical damping in the solver itself. Lowering the value will give more efficient suppression of high frequencies.
Abhijit Paul
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Posted: 2 years ago Mar 24, 2022, 5:30 a.m. EDT

Thank you Henrik.

Your comments are very helpful to solve my issue. I also got to know new things about the COMSOL sover which will definately help me in my future work.

Abhijit Paul IIT Gandhinagar

Thank you Henrik. Your comments are very helpful to solve my issue. I also got to know new things about the COMSOL sover which will definately help me in my future work. Abhijit Paul IIT Gandhinagar

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