Add option to do collisions every # time steps (#1251)

* Update inputs_3d

* Update inputs_2d

* Add ndt

* Doc

* Doc

* Update inputs_3d

* Update inputs_2d

Co-authored-by: Axel Huebl <axel.huebl@plasma.ninja>

1 files changed, 7 insertions, 2 deletions

diff --git a/Source/Particles/MultiParticleContainer.cpp b/Source/Particles/MultiParticleContainer.cpp
index d1dde1837..f986e7dba 100644
--- a/Source/Particles/MultiParticleContainer.cpp
+++ b/Source/Particles/MultiParticleContainer.cpp
@@ -683,12 +683,16 @@ MultiParticleContainer::doFieldIonization (int lev,
 }
 
 void
-MultiParticleContainer::doCoulombCollisions ()
+MultiParticleContainer::doCoulombCollisions ( Real cur_time )
 {
     WARPX_PROFILE("MultiParticleContainer::doCoulombCollisions()");
 
     for( auto const& collision : allcollisions )
     {
+
+        const Real dt = WarpX::GetInstance().getdt(0);
+        if ( int(std::floor(cur_time/dt)) % collision->m_ndt != 0 ) continue;
+
         auto& species1 = allcontainers[ collision->m_species1_index ];
         auto& species2 = allcontainers[ collision->m_species2_index ];
 
@@ -709,7 +713,8 @@ MultiParticleContainer::doCoulombCollisions ()
                 CollisionType::doCoulombCollisionsWithinTile
                     ( lev, mfi, species1, species2,
                       collision->m_isSameSpecies,
-                      collision->m_CoulombLog );
+                      collision->m_CoulombLog,
+                      collision->m_ndt );
 
             }
         }