Line data    Source code

       1             : //* This file is part of the MOOSE framework
       2             : //* https://mooseframework.inl.gov
       3             : //*
       4             : //* All rights reserved, see COPYRIGHT for full restrictions
       5             : //* https://github.com/idaholab/moose/blob/master/COPYRIGHT
       6             : //*
       7             : //* Licensed under LGPL 2.1, please see LICENSE for details
       8             : //* https://www.gnu.org/licenses/lgpl-2.1.html
       9             : 
      10             : #pragma once
      11             : 
      12             : #include "TimeIntegrator.h"
      13             : 
      14             : /**
      15             :  * Explicit TVD (total-variation-diminishing)
      16             :  * second-order Runge-Kutta time integration methods:
      17             :  *
      18             :  *
      19             :  *   Stage 1. R_{NL} = M*(U^{(1)}-U^n)/dt - F(t^n,U^n)
      20             :  *
      21             :  *            t^{(1)} = t^{n} + dt = t^{n+1}
      22             :  *
      23             :  *   Stage 2. R_{NL} = M*(2*U^{(2)}-U^{(1)}-U^n)/(2*dt) - (1/2)*F(t^{(1)},U^{(1)})
      24             :  *
      25             :  *            U^{n+1} = U^{(2)}
      26             :  *
      27             :  *   Reference:
      28             :  *   Gottlieb, S., & Shu, C. W. (1998).
      29             :  *   Total variation diminishing Runge-Kutta schemes.
      30             :  *   Mathematics of computation of the American Mathematical Society,
      31             :  *   67(221), 73-85.
      32             :  *
      33             :  * The method requires two mass matrix (linear) system solves
      34             :  * per timestep. Although strictly speaking these are "two stage"
      35             :  * methods, we treat the "update" step as a third stage, since in
      36             :  * finite element analysis the update step requires a mass matrix
      37             :  * solve.
      38             :  *
      39             :  * IMPORTANT: To use the explicit TimeIntegrators derived from this
      40             :  * method, you must generally add "implicit=false" to the Kernels,
      41             :  * Materials, etc. used in your simulation, so that MOOSE evaluates
      42             :  * them correctly!  An important exception are TimeDerivative kernels,
      43             :  * which should never be marked "implicit=false".
      44             :  */
      45             : class ExplicitTVDRK2 : public TimeIntegrator
      46             : {
      47             : public:
      48             :   static InputParameters validParams();
      49             : 
      50             :   ExplicitTVDRK2(const InputParameters & parameters);
      51             : 
      52             :   virtual void preSolve() override;
      53           0 :   virtual int order() override { return 2; }
      54             : 
      55             :   virtual void computeTimeDerivatives() override;
      56             :   void computeADTimeDerivatives(ADReal & ad_u_dot,
      57             :                                 const dof_id_type & dof,
      58             :                                 ADReal & ad_u_dotdot) const override;
      59             :   virtual void solve() override;
      60             :   virtual void postResidual(NumericVector<Number> & residual) override;
      61         872 :   virtual bool overridesSolve() const override { return true; }
      62             : 
      63             : protected:
      64             :   /**
      65             :    * Helper function that actually does the math for computing the time derivative
      66             :    */
      67             :   template <typename T, typename T2, typename T3>
      68             :   void computeTimeDerivativeHelper(T & u_dot, const T2 & u_old, const T3 & u_older) const;
      69             : 
      70             :   unsigned int _stage;
      71             : 
      72             :   /// Buffer to store non-time residual from the first stage.
      73             :   NumericVector<Number> * _residual_old;
      74             : 
      75             :   /// The older solution
      76             :   const NumericVector<Number> & _solution_older;
      77             : };
      78             : 
      79             : template <typename T, typename T2, typename T3>
      80             : void
      81        1462 : ExplicitTVDRK2::computeTimeDerivativeHelper(T & u_dot, const T2 & u_old, const T3 & u_older) const
      82             : {
      83        1462 :   if (_stage < 3)
      84             :   {
      85         564 :     u_dot -= u_old;
      86         564 :     u_dot *= 1. / _dt;
      87             :   }
      88             :   else
      89             :   {
      90         898 :     u_dot *= 2.;
      91         898 :     u_dot -= u_old;
      92         898 :     u_dot -= u_older;
      93         898 :     u_dot *= 0.5 / _dt;
      94             :   }
      95        1462 : }