Swith to fixed timestep (#2621)

Author: DanielDoehring

examples/dgmulti_1d/elixir_euler_shu_osher_gauss_shock_capturing.jl

@@ -84,16 +84,15 @@ analysis_callback = AnalysisCallback(semi, interval = 100, uEltype = real(dg))
 save_solution = SaveSolutionCallback(interval = 100,
                                      solution_variables = cons2prim)
 
-# handles the re-calculation of the maximum Δt after each time step
-stepsize_callback = StepsizeCallback(cfl = 0.13)
-
 # collect all callbacks such that they can be passed to the ODE solver
-callbacks = CallbackSet(summary_callback, analysis_callback, save_solution,
-                        stepsize_callback)
+callbacks = CallbackSet(summary_callback, analysis_callback, save_solution)
 
 # ###############################################################################
 # # run the simulation
 
+# We use a fixed time step here, as the wave speed estimate 
+# (which aims to bound the largest eigenvalues from above)
+# in the stepsize callback produced sometimes unphysical values
 sol = solve(ode, SSPRK43(), adaptive = false;
-            dt = 1.0, # solve needs some value here but it will be overwritten by the stepsize_callback
+            dt = 2e-3,
             callback = callbacks, ode_default_options()...)

test/test_dgmulti_1d.jl

@@ -57,16 +57,8 @@ end
 @trixi_testset "elixir_euler_shu_osher_gauss_shock_capturing.jl " begin
     @test_trixi_include(joinpath(EXAMPLES_DIR,
                                  "elixir_euler_shu_osher_gauss_shock_capturing.jl"),
-                        l2=[
-                            1.696712726264938,
-                            6.018435800027037,
-                            21.774221602026298
-                        ],
-                        linf=[
-                            3.2229930998898952,
-                            10.702431261492814,
-                            38.37420027341893
-                        ])
+                        l2=[1.6967163299095107, 6.018450129099115, 21.774272062049693],
+                        linf=[3.2229821729393437, 10.702811890261692, 38.37413018581744])
     # Ensure that we do not have excessive memory allocations
     # (e.g., from type instabilities)
     @test_allocations(Trixi.rhs!, semi, sol, 1000)