You are correct in both of your questions. This discussion relates only to stationary, time-invariant, problems. (Although frequency-domain problems can also be treated as stationary in that they assume a sinusoidal time-variation.) We will work on a series of articles on transient problems in the future. ]]>

Very impressive review of how to solve the COMSOL Multiphysics problems more effectively. Here are two things I am concerned and would like to follow up based on your posts:

(1). The linear or nonlinear problems you mentioned are all “static”, based on my understanding, in steady state right? Would you have future plans to focus on if the problem is “unsteady state”, in which the parameters are time dependent?

(2). In the discussion of linear or nonlinear problems the force applied on a spring is always taken as an example along with fundamental equations. Does that mean any equations used in COMSOL physics can be re-organized to the form of fundamental equations mentioned in the spring case? If that is true can that be used as a criterion to judge whether the problem is linear or nonlinear?

Thanks again for your effort and time to post such helpful materials and I really appreciate.

Terry

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