Added co-moving Sod shock test.

Added a new version of the Sod shock test that runs in a co-moving frame. For gamma = 5/3, the result should still match the analytic expectation, albeit for a re-scaled time value.

The test runs from z=999 to z=960.5, which is a regime of relatively strong expansion.

examples/ComovingSodShock_1D/makeIC.py

+###############################################################################
+ # This file is part of SWIFT.
+ # Copyright (c) 2016 Matthieu Schaller (matthieu.schaller@durham.ac.uk)
+ #               2018 Bert Vandenbroucke (bert.vandenbroucke@gmail.com)
+ # 
+ # This program is free software: you can redistribute it and/or modify
+ # it under the terms of the GNU Lesser General Public License as published
+ # by the Free Software Foundation, either version 3 of the License, or
+ # (at your option) any later version.
+ # 
+ # This program is distributed in the hope that it will be useful,
+ # but WITHOUT ANY WARRANTY; without even the implied warranty of
+ # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ # GNU General Public License for more details.
+ # 
+ # You should have received a copy of the GNU Lesser General Public License
+ # along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ # 
+ ##############################################################################
+
+import h5py
+from numpy import *
+
+# Generates a swift IC file for the 1D Sod Shock in a periodic box
+
+unit_l_in_cgs = 3.086e18
+unit_m_in_cgs = 2.94e55
+unit_t_in_cgs = 3.086e18
+
+# Parameters
+gamma = 5./3.          # Gas adiabatic index
+numPart_L = 800        # Number of particles in the left state
+x_min = -1.
+x_max = 1.
+rho_L = 1.             # Density left state
+rho_R = 0.125          # Density right state
+v_L = 0.               # Velocity left state
+v_R = 0.               # Velocity right state
+P_L = 1.               # Pressure left state
+P_R = 0.1              # Pressure right state
+a_beg = 0.001
+fileName = "sodShock.hdf5" 
+
+
+#---------------------------------------------------
+
+# Find how many particles we actually have
+boxSize = x_max - x_min
+numPart_R = int(numPart_L * (rho_R / rho_L))
+numPart = numPart_L + numPart_R
+
+# Now get the distances
+delta_L = (boxSize/2)  / numPart_L
+delta_R = (boxSize/2)  / numPart_R
+offset_L = delta_L / 2
+offset_R = delta_R / 2
+
+# Build the arrays
+coords = zeros((numPart, 3))
+v = zeros((numPart, 3))
+ids = linspace(1, numPart, numPart)
+m = zeros(numPart)
+h = zeros(numPart)
+u = zeros(numPart)
+
+# Set the particles on the left
+for i in range(numPart_L):
+    coords[i,0] = x_min + offset_L + i * delta_L
+    u[i] = P_L / (rho_L * (gamma - 1.))
+    h[i] = 1.2348 * delta_L
+    m[i] = boxSize * rho_L / (2. * numPart_L)
+    v[i,0] = v_L
+    
+# Set the particles on the right
+for j in range(numPart_R):
+    i = numPart_L + j
+    coords[i,0] = offset_R + j * delta_R
+    u[i] = P_R / (rho_R * (gamma - 1.))
+    h[i] = 1.2348 * delta_R
+    m[i] = boxSize * rho_R / (2. * numPart_R)
+    v[i,0] = v_R
+
+# Shift particles
+coords[:,0] -= x_min
+
+u /= (a_beg**(3. * (gamma - 1.)))
+    
+#File
+file = h5py.File(fileName, 'w')
+
+# Header
+grp = file.create_group("/Header")
+grp.attrs["BoxSize"] = boxSize
+grp.attrs["NumPart_Total"] =  [numPart, 0, 0, 0, 0, 0]
+grp.attrs["NumPart_Total_HighWord"] = [0, 0, 0, 0, 0, 0]
+grp.attrs["NumPart_ThisFile"] = [numPart, 0, 0, 0, 0, 0]
+grp.attrs["Time"] = 0.0
+grp.attrs["NumFilesPerSnapshot"] = 1
+grp.attrs["MassTable"] = [0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
+grp.attrs["Flag_Entropy_ICs"] = 0
+grp.attrs["Dimension"] = 1
+
+#Units
+grp = file.create_group("/Units")
+grp.attrs["Unit length in cgs (U_L)"] = unit_l_in_cgs
+grp.attrs["Unit mass in cgs (U_M)"] = unit_m_in_cgs
+grp.attrs["Unit time in cgs (U_t)"] = unit_t_in_cgs
+grp.attrs["Unit current in cgs (U_I)"] = 1.
+grp.attrs["Unit temperature in cgs (U_T)"] = 1.
+
+#Particle group
+grp = file.create_group("/PartType0")
+grp.create_dataset('Coordinates', data=coords, dtype='d')
+grp.create_dataset('Velocities', data=v, dtype='f')
+grp.create_dataset('Masses', data=m, dtype='f')
+grp.create_dataset('SmoothingLength', data=h, dtype='f')
+grp.create_dataset('InternalEnergy', data=u, dtype='f')
+grp.create_dataset('ParticleIDs', data=ids, dtype='L')
+
+
+file.close()
+
+