Disk-patch now without drag force. Disk growth time-scale is now a parameter.

examples/Disk-Patch/GravityOnly/README

 Setup for a potential of a patch disk, see Creasey, Theuns &
 Bower, 2013, MNRAS, Volume 429, Issue 3, p.1922-1948
 
+The density is given by
 rho(z) = (Sigma/2b) / cosh^2(z/b)
-where Sigma is the surface density, and b the scale height
-the corresponding force is
-dphi/dz = 2 pi G Sigma tanh(z/b)
-
-which satifies d^2phi/dz^2 = 4 pi G rho
-
-
-
+where Sigma is the surface density, and b the scale height.
 
+The corresponding force is
+dphi/dz = 2 pi G Sigma tanh(z/b),
+which satifies d^2phi/dz^2 = 4 pi G rho.

examples/Disk-Patch/GravityOnly/disk-patch.yml

@@ -34,28 +34,10 @@ SPH:
 # Parameters related to the initial conditions
 InitialConditions:
   file_name:  Disk-Patch.hdf5       # The file to read
-  h_scaling:  1.                    # A scaling factor to apply to all smoothing lengths in the ICs.
-  shift_x:    0.                    # A shift to apply to all particles read from the ICs (in internal units).
-  shift_y:    0.
-  shift_z:    0.
 
 # External potential parameters
-PointMass:
-	position_x:      50.     # location of external point mass in internal units
-	position_y:      50.
-	position_z:      50.	
-	mass:            1e10     # mass of external point mass in internal units
-	timestep_mult:   0.03     # controls time step
-
-IsothermalPotential:
-	position_x:      100.     # location of centre of isothermal potential in internal units
-	position_y:      100.
-	position_z:      100.	
-	vrot:            200.     # rotation speed of isothermal potential in internal units
-	timestep_mult:   0.03     # controls time step
-
 Disk-PatchPotential:
-	surface_density: 10.
-	scale_height:    100.
-	z_disk:          300.
-	timestep_mult:   0.03
+  surface_density: 10.
+  scale_height:    100.
+  z_disk:          300.
+  timestep_mult:   0.03

examples/Disk-Patch/HydroStatic/README

 generate and evolve a disk-patch, where gas is in hydrostatic
-equilibrium with an imposed external gravutation force, using teh
+equilibrium with an imposed external gravutation force, using the
 equations from Creasey, Theuns & Bower, 2013, MNRAS, Volume 429,
 Issue 3, p.1922-1948
 
@@ -21,5 +21,4 @@ dynamica times
 Then, use the output as new initial conditions, run using
 #define EXTERNAL_POTENTIAL_DISK_PATCH
 only, and see whether it stays in hydrotatic equilibrium
-Use disk-patch.yml as parameter file
-
+Use disk-patch.yml as parameter file.

examples/Disk-Patch/HydroStatic/disk-patch-icc.yml

@@ -21,12 +21,12 @@ Statistics:
 Snapshots:
   basename:            Disk-Patch   # Common part of the name of output files
   time_first:          0.           # Time of the first output (in internal units)
-  delta_time:          12.           # Time difference between consecutive outputs (in internal units)
+  delta_time:          12.          # Time difference between consecutive outputs (in internal units)
 
 # Parameters for the hydrodynamics scheme
 SPH:
   resolution_eta:        1.2349   # Target smoothing length in units of the mean inter-particle separation (1.2349 == 48Ngbs with the cubic spline kernel).
-  delta_neighbours:      0.1       # The tolerance for the targetted number of neighbours.
+  delta_neighbours:      0.1      # The tolerance for the targetted number of neighbours.
   CFL_condition:         0.1      # Courant-Friedrich-Levy condition for time integration.
   max_ghost_iterations:  30       # Maximal number of iterations allowed to converge towards the smoothing length.
   max_smoothing_length:  70.      # Maximal smoothing length allowed (in internal units).
@@ -34,28 +34,11 @@ SPH:
 # Parameters related to the initial conditions
 InitialConditions:
   file_name:  Disk-Patch.hdf5       # The file to read
-  h_scaling:  1.                    # A scaling factor to apply to all smoothing lengths in the ICs.
-  shift_x:    0.                    # A shift to apply to all particles read from the ICs (in internal units).
-  shift_y:    0.
-  shift_z:    0.
 
 # External potential parameters
-PointMass:
-	position_x:      50.     # location of external point mass in internal units
-	position_y:      50.
-	position_z:      50.	
-	mass:            1e10     # mass of external point mass in internal units
-	timestep_mult:   0.03     # controls time step
-
-IsothermalPotential:
-	position_x:      100.     # location of centre of isothermal potential in internal units
-	position_y:      100.
-	position_z:      100.	
-	vrot:            200.     # rotation speed of isothermal potential in internal units
-	timestep_mult:   0.03     # controls time step
-
 Disk-PatchPotential:
-	surface_density: 10.
-	scale_height:    100.
-	z_disk:          200.
-	timestep_mult:   0.03
+  surface_density: 10.
+  scale_height:    100.
+  z_disk:          200.
+  timestep_mult:   0.03
+  growth_time:     5.

examples/Disk-Patch/HydroStatic/disk-patch.yml

@@ -19,14 +19,14 @@ Statistics:
   
 # Parameters governing the snapshots
 Snapshots:
-  basename:            Disk-Patch-dynamic # Common part of the name of output files
-  time_first:          968.       # Time of the first output (in internal units)
-  delta_time:         24.         # Time difference between consecutive outputs (in internal units)
+  basename:           Disk-Patch-dynamic # Common part of the name of output files
+  time_first:         968.               # Time of the first output (in internal units)
+  delta_time:         24.                 # Time difference between consecutive outputs (in internal units)
 
 # Parameters for the hydrodynamics scheme
 SPH:
   resolution_eta:        1.2349   # Target smoothing length in units of the mean inter-particle separation (1.2349 == 48Ngbs with the cubic spline kernel).
-  delta_neighbours:      0.1       # The tolerance for the targetted number of neighbours.
+  delta_neighbours:      0.1      # The tolerance for the targetted number of neighbours.
   CFL_condition:         0.1      # Courant-Friedrich-Levy condition for time integration.
   max_ghost_iterations:  30       # Maximal number of iterations allowed to converge towards the smoothing length.
   max_smoothing_length:  70.      # Maximal smoothing length allowed (in internal units).
@@ -34,28 +34,10 @@ SPH:
 # Parameters related to the initial conditions
 InitialConditions:
   file_name:  Disk-Patch-dynamic.hdf5       # The file to read
-  h_scaling:  1.                    # A scaling factor to apply to all smoothing lengths in the ICs.
-  shift_x:    0.                    # A shift to apply to all particles read from the ICs (in internal units).
-  shift_y:    0.
-  shift_z:    0.
 
 # External potential parameters
-PointMass:
-	position_x:      50.     # location of external point mass in internal units
-	position_y:      50.
-	position_z:      50.	
-	mass:            1e10     # mass of external point mass in internal units
-	timestep_mult:   0.03     # controls time step
-
-IsothermalPotential:
-	position_x:      100.     # location of centre of isothermal potential in internal units
-	position_y:      100.
-	position_z:      100.	
-	vrot:            200.     # rotation speed of isothermal potential in internal units
-	timestep_mult:   0.03     # controls time step
-
 Disk-PatchPotential:
-	surface_density: 10.
-	scale_height:    100.
-	z_disk:          200.
-	timestep_mult:   0.03
+  surface_density: 10.
+  scale_height:    100.
+  z_disk:          200.
+  timestep_mult:   0.03

examples/parameter_example.yml

@@ -66,15 +66,22 @@ DomainDecomposition:
   
 # Point mass external potentials
 PointMass:
-  position_x:      50.     # location of external point mass in internal units
+  position_x:      50.      # location of external point mass (internal units)
   position_y:      50.
   position_z:      50.
-  mass:            1e10     # mass of external point mass in internal units
-  timestep_mult:   0.03     # Pre-factor for the time-step condition
+  mass:            1e10     # mass of external point mass (internal units)
+  timestep_mult:   0.03     # Dimensionless pre-factor for the time-step condition
 
 IsothermalPotential:
-  position_x:      100.     # Location of centre of isothermal potential in internal units
+  position_x:      100.     # Location of centre of isothermal potential (internal units)
   position_y:      100.
   position_z:      100.
-  vrot:            200.     # Rotation speed of isothermal potential in internal units
-  timestep_mult:   0.03     # Pre-factor for the time-step condition
+  vrot:            200.     # Rotation speed of isothermal potential (internal units)
+  timestep_mult:   0.03     # Dimensionless pre-factor for the time-step condition
+
+Disk-PatchPotential:
+  surface_density: 10.      # Surface density of the disk (internal units)
+  scale_height:    100.     # Scale height of the disk (internal units)
+  z_disk:          200.     # Disk height (internal units)
+  timestep_mult:   0.03     # Dimensionless pre-factor for the time-step condition
+  growth_time:     5.       # (Optional) Time for the disk to grow to its final size (multiple of the dynamical time)

src/const.h

@@ -76,9 +76,6 @@
 #define EXTERNAL_POTENTIAL_POINTMASS
 //#define EXTERNAL_POTENTIAL_ISOTHERMALPOTENTIAL
 //#define EXTERNAL_POTENTIAL_DISK_PATCH
-/* Add viscuous force to gas particles to speed-up glass making for disk-patch
- * ICs */
-//#define EXTERNAL_POTENTIAL_DISK_PATCH_ICS
 
 /* Are we debugging ? */
 //#define SWIFT_DEBUG_CHECKS

src/potentials.c

@@ -76,6 +76,8 @@ void potential_init(const struct swift_params* parameter_file,
       parser_get_param_double(parameter_file, "Disk-PatchPotential:z_disk");
   potential->disk_patch_potential.timestep_mult = parser_get_param_double(
       parameter_file, "Disk-PatchPotential:timestep_mult");
+  potential->disk_patch_potential.growth_time = parser_get_opt_param_double(
+      parameter_file, "Disk-PatchPotential:growth_time", 0.);
   potential->disk_patch_potential.dynamical_time =
       sqrt(potential->disk_patch_potential.scale_height /
            (phys_const->const_newton_G *
@@ -94,7 +96,7 @@ void potential_print(const struct external_potential* potential) {
 
   message(
       "Point mass properties are (x,y,z) = (%e, %e, %e), M = %e timestep "
-      "multiplier = %e",
+      "multiplier = %e.",
       potential->point_mass.x, potential->point_mass.y, potential->point_mass.z,
       potential->point_mass.mass, potential->point_mass.timestep_mult);
 
@@ -104,24 +106,25 @@ void potential_print(const struct external_potential* potential) {
 
   message(
       "Isothermal potential properties are (x,y,z) = (%e, %e, %e), vrot = %e "
-      "timestep multiplier= %e",
+      "timestep multiplier = %e.",
       potential->isothermal_potential.x, potential->isothermal_potential.y,
       potential->isothermal_potential.z, potential->isothermal_potential.vrot,
       potential->isothermal_potential.timestep_mult);
 
 #endif /* EXTERNAL_POTENTIAL_ISOTHERMALPOTENTIAL */
+
 #ifdef EXTERNAL_POTENTIAL_DISK_PATCH
+
   message(
       "Disk-patch potential properties are surface_density = %e disk height= "
-      "%e scale height= %e timestep multiplier= %e",
+      "%e scale height = %e timestep multiplier = %e.",
       potential->disk_patch_potential.surface_density,
       potential->disk_patch_potential.z_disk,
       potential->disk_patch_potential.scale_height,
       potential->disk_patch_potential.timestep_mult);
-#ifdef EXTERNAL_POTENTIAL_DISK_PATCH_ICS
-  message(
-      "Disk-patch potential: imposing growth of gravity over time, and adding "
-      "viscous force to gravity");
-#endif
+
+  if (potential->disk_patch_potential.growth_time > 0.)
+    message("Disk will grow for %f dynamiccal times.",
+            potential->disk_patch_potential.growth_time);
 #endif /* EXTERNAL_POTENTIAL_DISK_PATCH */
 }

src/potentials.h

@@ -61,6 +61,7 @@ struct external_potential {
     double scale_height;
     double z_disk;
     double dynamical_time;
+    double growth_time;
     double timestep_mult;
   } disk_patch_potential;
 #endif
@@ -148,30 +149,19 @@ external_gravity_disk_patch_potential(
   g->a_grav[0] += 0;
   g->a_grav[1] += 0;
 
-#ifdef EXTERNAL_POTENTIAL_DISK_PATCH_ICS
   float reduction_factor = 1.;
-  if (time < 5 * t_dyn) reduction_factor = time / (5 * t_dyn);
-#else
-  const float reduction_factor = 1.;
-#endif
+  if (time < potential->disk_patch_potential.growth_time * t_dyn)
+    reduction_factor =
+        time / (potential->disk_patch_potential.growth_time * t_dyn);
 
   const float z_accel =
       reduction_factor * 2 * G_newton * M_PI *
       potential->disk_patch_potential.surface_density *
       tanh(fabs(dz) / potential->disk_patch_potential.scale_height);
 
-  if (dz > 0)
-    g->a_grav[2] -=
-        z_accel /
-        G_newton; /* returned acceleraton is multiplied by G later on */
+  /* Accelerations. Note that they are multiplied by G later on */
+  if (dz > 0) g->a_grav[2] -= z_accel / G_newton;
   if (dz < 0) g->a_grav[2] += z_accel / G_newton;
-
-#ifdef EXTERNAL_POTENTIAL_DISK_PATCH_ICS
-  /* TT: add viscous drag */
-  g->a_grav[0] -= g->v_full[0] / (2 * t_dyn) / G_newton;
-  g->a_grav[1] -= g->v_full[1] / (2 * t_dyn) / G_newton;
-  g->a_grav[2] -= g->v_full[2] / (2 * t_dyn) / G_newton;
-#endif
 }
 #endif /* EXTERNAL_POTENTIAL_DISK_PATCH */