Close #1688 : Transform the moving window velocity to its boosted-frame value.

Examples/Tests/moving_window_boost/inputs_3d

@@ -0,0 +1,47 @@
+#################################
+####### GENERAL PARAMETERS ######
+#################################
+max_step = 1000
+amr.n_cell = 16  16  128
+amr.max_grid_size = 32 
+amr.blocking_factor = 16 
+amr.max_level = 0
+geometry.coord_sys   = 0                  # 0: Cartesian
+geometry.is_periodic = 0 0 0     # Is periodic?
+geometry.prob_lo     = -1.e-5  -1.e-5  -1.e-6 
+geometry.prob_hi     =  1.e-5   1.e-5   0
+
+#################################
+############ NUMERICS ###########
+#################################
+algo.maxwell_solver = ckc
+warpx.verbose = 1
+warpx.do_dive_cleaning = 0
+warpx.use_filter = 1
+warpx.do_pml = 1
+warpx.cfl = 0.99
+warpx.do_moving_window = 1
+warpx.moving_window_dir = z
+warpx.moving_window_v = 0.95 # in units of the speed of light
+my_constants.lramp = 8.e-3
+my_constants.pi    = 3.141592653589793
+interpolation.nox = 3
+interpolation.noy = 3
+interpolation.noz = 3
+
+#################################
+######### BOOSTED FRAME #########
+#################################
+warpx.gamma_boost = 10.0
+warpx.boost_direction = z
+warpx.do_back_transformed_diagnostics = 0
+#warpx.num_snapshots_lab = 10
+#warpx.dt_snapshots_lab =  1.e-10
+
+# Diagnostics
+diagnostics.diags_names = diag 
+diag.intervals = 1000
+diag.diag_type = Full
+diag.fields_to_plot = Ex 
+
+

Examples/Tests/moving_window_boost/moving_window_v_boost.py

@@ -0,0 +1,22 @@
+import os
+import yt
+
+dlist0 = os.listdir('./diags')
+dlist = sorted(dlist0)
+
+kk = 0
+fn = './diags/'+dlist[kk]
+print(fn)
+ds=yt.load(fn)
+t1=ds.current_time.v[()]
+z1max=ds.domain_right_edge.v[2]
+
+kk = 1 
+fn = './diags/'+dlist[kk]
+print(fn)
+ds=yt.load(fn)
+t2=ds.current_time.v[()]
+z2max=ds.domain_right_edge.v[2]
+
+vv=(z2max-z1max)/(t2-t1)/299792458.
+print('moving_window_v in boosted frame =', vv)

Source/Utils/WarpXMovingWindow.cpp

@@ -44,7 +44,7 @@ WarpX::MoveWindow (bool move_j)
 
     // Update the continuous position of the moving window,
     // and of the plasma injection
-    moving_window_x += moving_window_v * dt[0];
+    moving_window_x += (moving_window_v - WarpX::beta_boost * PhysConst::c)/(1 - moving_window_v * WarpX::beta_boost / PhysConst::c) * dt[0];
     int dir = moving_window_dir;
 
     // Update warpx.current_injection_position