Question #204014 on Yade changed: https://answers.launchpad.net/yade/+question/204014
Chareyre proposed the following answer: Hi Christian, As long as the facets are not dynamic, you don't need to consider facets in timestep definition. PWaveTimeStep can't be directly compared to GlobalStiffnessTimeStepper as you. You can consider PWaveTimeStep as an order of magnitude of the expected critical timestep (it at least scales correctly with sizes, modulus, density). Since it is only an order of magnitude, it's usually multiplied by a safety factor after trial and error for each type of simulation. GlobalStiffnessTimeStep computes the exact critical timestep for current configuration, but it gives nothing as long as there is no contact, so that it can't be used to define dt in the early steps of most simulations. So there is not to choose between them, most scripts use both: the first for early steps, the second to set dt to its maximum acceptable value in the rest of the simulation (hence save time). Both work equally well with facets. Last note: nothing can replace your own tests. It is not uncommon to read a "no it doesn't work" answer in this list when the thing actually works (Yade code is so huge that nobody knows the entire code now). So, when you wonder if something works, the best is to try it before asking. Bruno On 24/07/12 12:45, Christian Sommerfeld wrote: > New question #204014 on Yade: > https://answers.launchpad.net/yade/+question/204014 > > Hi, > > i'm not sure if i have to use the utils.PWaveTimeStep() in my case. I want to > simulate a facetbox which is rotating around the z-axes and enclosed by a > pack of spheres . Therefore i want to record the force which acts on the > facetbox. > The ducumentation says that the utils.PWaveTimeStep() makes some > simplifications, like > • all particles are spherical and have the same radius R; > • the sphere’s material has the same E and ρ > > All of my spheres have the same radius, but i use a facet as well. And i have > seen that the utils.PWaveTimeStep() in some examples with facets and spheres. > So i'm still wondering if i can use the utils.PWaveTimeStep() in my case? Or > should i use GlobalStiffnessTimeStepper because i use a facet? > > -- _______________ Bruno Chareyre Associate Professor ENSE³ - Grenoble INP Lab. 3SR BP 53 38041 Grenoble cedex 9 Tél : +33 4 56 52 86 21 Fax : +33 4 76 82 70 43 ________________ You received this question notification because you are a member of yade-users, which is an answer contact for Yade. _______________________________________________ Mailing list: https://launchpad.net/~yade-users Post to : [email protected] Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
