Implement multi-ion collision sources

examples/tree_2d_dgsem/elixir_mhdmultiion_collisions.jl

@@ -0,0 +1,152 @@
+
+using OrdinaryDiffEq
+using Trixi
+
+###############################################################################
+# This elixir describes the frictional slowing of an ionized carbon fluid (C6+) with respect to another species 
+# of a background ionized carbon fluid with an initially nonzero relative velocity. It is the second slow-down
+# test (fluids with different densities) described in:
+# - Ghosh, D., Chapman, T. D., Berger, R. L., Dimits, A., & Banks, J. W. (2019). A 
+#   multispecies, multifluid model for laser–induced counterstreaming plasma simulations. 
+#   Computers & Fluids, 186, 38-57.
+#
+# This is effectively a zero-dimensional case because the spatial gradients are zero, and we use it to test the
+# collision source terms.
+#
+# To run this physically relevant test, we use the following characteristic quantities to non-dimensionalize
+# the equations:
+# Characteristic length: L_inf = 1.00E-03 m (domain size)
+# Characteristic density: rho_inf = 1.99E+00 kg/m^3 (corresponds to a number density of 1e20 cm^{-3})
+# Characteristic vacuum permeability: mu0_inf = 1.26E-06 N/A^2 (for equations with mu0 = 1)
+# Characteristic gas constant: R_inf = 6.92237E+02 J/kg/K (specific gas constant for a Carbon fluid)
+# Characteristic velocity: V_inf = 1.00E+06 m/s
+#
+# The results of the paper can be reproduced using `source_terms = source_terms_collision_ion_ion` (i.e., only
+# taking into account ion-ion collisions). However, we include ion-electron collisions assuming a constant 
+# electron temperature of 1 keV in this elixir to test the function `source_terms_collision_ion_electron`
+
+# Return the electron pressure for a constant electron temperature Te = 1 keV
+function electron_pressure_constantTe(u, equations::IdealGlmMhdMultiIonEquations2D)
+    @unpack charge_to_mass = equations
+    Te = 0.008029953773 # [nondimensional] = 1 [keV]
+    total_electron_charge = zero(eltype(u))
+    for k in eachcomponent(equations)
+        rho_k = u[3 + (k - 1) * 5 + 1]
+        total_electron_charge += rho_k * charge_to_mass[k]
+    end
+
+    # Boltzmann constant divided by elementary charge
+    kB_e = 7.86319034E-02 #[nondimensional]
+
+    return total_electron_charge * kB_e * Te
+end
+
+# Return the constant electron temperature Te = 1 keV
+function electron_temperature_constantTe(u, equations::IdealGlmMhdMultiIonEquations2D)
+    return 0.008029953773 # [nondimensional] = 1 [keV]
+end
+
+# semidiscretization of the ideal MHD equations
+equations = IdealGlmMhdMultiIonEquations2D(gammas = (5 / 3, 5 / 3),
+                                           charge_to_mass = (76.3049060157692000,
+                                                             76.3049060157692000), # [nondimensional]
+                                           gas_constants = (1.0, 1.0), # [nondimensional]
+                                           molar_masses = (1.0, 1.0), # [nondimensional]
+                                           ion_ion_collision_constants = [0.0 0.4079382480442680;
+                                                                          0.4079382480442680 0.0], # [nondimensional] (computed with eq (4.142) of Schunk&Nagy (2009))
+                                           ion_electron_collision_constants = (8.56368379833E-06,
+                                                                               8.56368379833E-06), # [nondimensional] (computed with eq (9) of Ghosh et al. (2019))
+                                           electron_pressure = electron_pressure_constantTe,
+                                           electron_temperature = electron_temperature_constantTe,
+                                           initial_c_h = 0.0) # Deactivate GLM divergence cleaning
+
+# Frictional slowing of an ionized carbon fluid with respect to another background carbon fluid in motion
+function initial_condition_slow_down(x, t, equations::IdealGlmMhdMultiIonEquations2D)
+    v11 = 0.65508770000000
+    v21 = 0
+    v2 = v3 = 0.0
+    B1 = B2 = B3 = 0.0
+    rho1 = 0.1
+    rho2 = 1.0
+
+    p1 = 0.00040170535986
+    p2 = 0.00401705359856
+
+    return prim2cons(SVector(B1, B2, B3, rho1, v11, v2, v3, p1, rho2, v21, v2, v3, p2, 0),
+                     equations)
+end
+
+# Temperature of ion 1
+function temperature1(cons, equations::IdealGlmMhdMultiIonEquations2D)
+    prim = cons2prim(cons, equations)
+    rho, _, _, _, p = Trixi.get_component(1, prim, equations)
+
+    return p / rho / equations.gas_constants[1]
+end
+
+# Temperature of ion 2
+function temperature2(cons, equations::IdealGlmMhdMultiIonEquations2D)
+    prim = cons2prim(cons, equations)
+    rho, _, _, _, p = Trixi.get_component(2, prim, equations)
+
+    return p / rho / equations.gas_constants[2]
+end
+
+initial_condition = initial_condition_slow_down
+tspan = (0.0, 0.1) # 100 [ps]
+
+# Entropy conservative volume numerical fluxes with standard LLF dissipation at interfaces
+volume_flux = (flux_ruedaramirez_etal, flux_nonconservative_ruedaramirez_etal)
+surface_flux = (flux_lax_friedrichs, flux_nonconservative_central)
+
+solver = DGSEM(polydeg = 3, surface_flux = surface_flux,
+               volume_integral = VolumeIntegralFluxDifferencing(volume_flux))
+
+coordinates_min = (0.0, 0.0)
+coordinates_max = (1.0, 1.0)
+mesh = TreeMesh(coordinates_min, coordinates_max,
+                initial_refinement_level = 1,
+                n_cells_max = 1_000_000)
+
+# Ion-ion and ion-electron collision source terms
+# In this particular case, we can omit source_terms_lorentz because the magnetic field is zero!
+function source_terms(u, x, t, equations::IdealGlmMhdMultiIonEquations2D)
+    source_terms_collision_ion_ion(u, x, t, equations) +
+    source_terms_collision_ion_electron(u, x, t, equations)
+end
+
+semi = SemidiscretizationHyperbolic(mesh, equations, initial_condition, solver,
+                                    source_terms = source_terms)
+
+###############################################################################
+# ODE solvers, callbacks etc.
+
+ode = semidiscretize(semi, tspan)
+
+summary_callback = SummaryCallback()
+
+analysis_interval = 1
+analysis_callback = AnalysisCallback(semi,
+                                     save_analysis = true,
+                                     interval = analysis_interval,
+                                     extra_analysis_integrals = (temperature1,
+                                                                 temperature2))
+alive_callback = AliveCallback(analysis_interval = analysis_interval)
+
+stepsize_callback = StepsizeCallback(cfl = 0.01) # Very small CFL due to the stiff source terms 
+
+save_restart = SaveRestartCallback(interval = 100,
+                                   save_final_restart = true)
+
+callbacks = CallbackSet(summary_callback,
+                        analysis_callback, alive_callback,
+                        save_restart,
+                        stepsize_callback)
+
+###############################################################################
+
+sol = Trixi.solve(ode, Trixi.SimpleSSPRK33();
+                  dt = 1.0, # solve needs some value here but it will be overwritten by the stepsize_callback
+                  save_everystep = false, callback = callbacks);
+
+summary_callback() # print the timer summary

src/Trixi.jl

@@ -218,7 +218,8 @@ export boundary_condition_do_nothing,
        BoundaryConditionCoupled
 
 export initial_condition_convergence_test, source_terms_convergence_test,
-       source_terms_lorentz
+       source_terms_lorentz, source_terms_collision_ion_electron,
+       source_terms_collision_ion_electron_ohm, source_terms_collision_ion_ion
 export source_terms_harmonic
 export initial_condition_poisson_nonperiodic, source_terms_poisson_nonperiodic,
        boundary_condition_poisson_nonperiodic