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doc:user:integration:general:time_step

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doc:user:integration:general:time_step [2014/12/08 10:25] – jorisdoc:user:integration:general:time_step [2020/12/28 10:55] (current) – [Use of Metafac] tanaka
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-====== Archiving and time step manager ======+====== Managing Time Steps ======
 ===== Archiving manager ===== ===== Archiving manager =====
 ==== General Points ==== ==== General Points ====
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 __Automatic creation of the movie:__ __Automatic creation of the movie:__
  
-    * Run a programm to create movies from the files (for example [[http://www.helesic.cz/en/avimaker.php|AVImaker]]).+    * Run a program to create movies from the files (for example [[http://www.helesic.cz/en/avimaker.php|AVImaker]]).
  
  
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     tsm = metafor.getTimeStepManager()     tsm = metafor.getTimeStepManager()
     tsm.setTimeStepComputationMethod(meth)     tsm.setTimeStepComputationMethod(meth)
 +    tsm.setTolOnFac(tolOnFac)
     tsm.setIntegrationErrorTolerance(prec)     tsm.setIntegrationErrorTolerance(prec)
     tsm.setExplicitTimeStepSecurity(secu)     tsm.setExplicitTimeStepSecurity(secu)
     tsm.setNbOfStepsForCriticalTimeStepUpdate(nrit)     tsm.setNbOfStepsForCriticalTimeStepUpdate(nrit)
     tsm.setMaxNbOfItInAdaptOfTimeStep(nbIter) (option: used in implicit or quasi-static)     tsm.setMaxNbOfItInAdaptOfTimeStep(nbIter) (option: used in implicit or quasi-static)
 +    tsm.setMinimumTimeStep(minTimeStep) 
 +    
 ^ Parameter ^ Default value ^ Description ^ ^ Parameter ^ Default value ^ Description ^
 | ''meth'' |   | = ''TSM_NBOFITERATIONSMETHOD'' : in implicit, the current time step depends on the number of iterations in the previous time step, when in explicit it only depends on the critical one and the parameter ''secu''| | ''meth'' |   | = ''TSM_NBOFITERATIONSMETHOD'' : in implicit, the current time step depends on the number of iterations in the previous time step, when in explicit it only depends on the critical one and the parameter ''secu''|
-|   |    |= ''TSM_INTEGRATIONERRORMETHOD'' : the current time step is calculated based on an integration error (and based on the critical one and the parameter ''secu'' in explicit) |+|   |    |= ''TSM_INTEGRATIONERRORMETHOD'' : the current time step is computed based on an integration error (and based on the critical one and the parameter ''secu'' in explicit) |
 | ''prec'' |  1.E-4  |accuracy on the integration error | | ''prec'' |  1.E-4  |accuracy on the integration error |
 | ''secu'' |  2.0/3.0  | safety coefficient which multiplies the critical time step in explicit | | ''secu'' |  2.0/3.0  | safety coefficient which multiplies the critical time step in explicit |
 | ''nrit'' |  1  | number of time steps before updating the critical time step | | ''nrit'' |  1  | number of time steps before updating the critical time step |
 | ''nbIter'' |  5  | Minimal number of iterations in the algorithm in charge of reducing the time step. If the required number is greater than ''nbIter'', the subsequent time step will be lower than the current one. Otherwise, it will be equal or greater. | | ''nbIter'' |  5  | Minimal number of iterations in the algorithm in charge of reducing the time step. If the required number is greater than ''nbIter'', the subsequent time step will be lower than the current one. Otherwise, it will be equal or greater. |
 +| ''minTimeStep'' |  1.0E-10  | minimum time step below which metafor stops running. | 
 +| ''tolOnFac'' | 0.1 | tolerance on time step for the discrete times corresponding to archiving (FAC). |
 ==== Quasi-static and dynamic implicit schemes ===== ==== Quasi-static and dynamic implicit schemes =====
  
-Two possibilities are used to calculate the time step:+Two possibilities are used to compute the time step:
   * A method based on the number of iterations before convergence. If lower than 3, the time step is increased. If greater than 4, it is decreased. This method does not provide any guaranty on accuracy.    * A method based on the number of iterations before convergence. If lower than 3, the time step is increased. If greater than 4, it is decreased. This method does not provide any guaranty on accuracy. 
-  * A method based on an integration error. It calculates an integration error based on the difference of the norm of the acceleration (dynamic case) or speed (quasi-static case) to adjust the time step, depending on the accuracy required.+  * A method based on an integration error. It computes an integration error based on the difference of the norm of the acceleration (dynamic case) or speed (quasi-static case) to adjust the time step, depending on the accuracy required.
  
  
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 $ \Delta t = \gamma_s \Delta t_{crit} $ $ \Delta t = \gamma_s \Delta t_{crit} $
  
-Where $\Delta t_{crit}$ depends on the maximal eigenfrequency of the system (obtained using the method called "power iteration", and updated regularly) and $\gamma_s$, a safety coefficient which can be calculated two ways:+Where $\Delta t_{crit}$ depends on the maximal eigenfrequency of the system (obtained using the method called "power iteration", and updated regularly) and $\gamma_s$, a safety coefficient which can be computed two ways:
   * Constant safety, coefficient, no guaranty on the accuracy.   * Constant safety, coefficient, no guaranty on the accuracy.
-  * Safety coefficient based on an integration error. It calculates an integration error based on the difference of the norm of the acceleration. A maximal value is set by the user. Practically, the safety coefficient will only be lower than this user parameter for highly dynamic situations, such as impact.+  * Safety coefficient based on an integration error. It computes an integration error based on the difference of the norm of the acceleration. A maximal value is set by the user. Practically, the safety coefficient will only be lower than this user parameter for highly dynamic situations, such as impact. 
 + 
 +==== New Interface For Time Step Computation Method ==== 
 + 
 +<note important> 
 +The commands from the new interface are discussed in the following page 
 +Cf. [[commit:2015:11_18]]  
 +</note> 
 + 
doc/user/integration/general/time_step.1418030747.txt.gz · Last modified: 2016/03/30 15:22 (external edit)
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