Merge pull request geodynamics#6672 from tiannh7/add_timescale_TS

Add time scaling factor in TS

Author: gassmoeller

doc/modules/changes/20250920_tiannh

@@ -0,0 +1,4 @@
+Changed: Added a scaling factor to allow time steps to be specified
+in years instead of seconds.
+<br>
+(Ninghui Tian, 2025/09/20)

source/time_stepping/function.cc

@@ -30,7 +30,8 @@ namespace aspect
     double
     Function<dim>::execute()
     {
-      double new_time_step = function.value(Point<1>(this->get_time()));
+      const double time_scale    = this->convert_output_to_years() ? constants::year_in_seconds : 1.0;
+      const double new_time_step = function.value(Point<1>(this->get_time()) / time_scale) * time_scale;
 
       AssertThrow (new_time_step > 0,
                    ExcMessage("The time step length for the each time step needs to be positive, "
@@ -52,7 +53,10 @@ namespace aspect
         Functions::ParsedFunction<1>::declare_parameters (prm, 1);
         prm.declare_entry("Function expression", "1.0",
                           Patterns::Anything(),
-                          "Expression for the time step size as a function of 'time'.");
+                          "Expression for the time step size as a function of 'time'."
+                          "Units: years if the "
+                          "'Use years instead of seconds' parameter is set; "
+                          "seconds otherwise.");
         prm.declare_entry("Variable names", "time",
                           Patterns::Anything(),
                           "Name for the variable representing the current time.");

tests/time_stepping_function_years.prm

@@ -0,0 +1,63 @@
+# test "Time stepping::Function" plugin, based on box_end_time_1e7_terminate.prm
+
+set Dimension = 2
+set CFL number                             = 1.0
+set End time                               = 1.5e4
+set Start time                             = 0
+set Adiabatic surface temperature          = 0
+set Surface pressure                       = 0
+set Use years instead of seconds           = true
+set Nonlinear solver scheme                = single Advection, single Stokes
+
+subsection Time stepping
+  set List of model names = function
+
+  subsection Function
+    set Function expression = if (time<5e3,2e2+1e2*cos(2*3.141*time/5e3),3e2+time/1e3)
+  end
+end
+
+subsection Gravity model
+  set Model name = vertical
+end
+
+subsection Geometry model
+  set Model name = box
+
+  subsection Box
+    set X extent = 1.2
+    set Y extent = 1
+    set Z extent = 1
+  end
+end
+
+subsection Initial temperature model
+  set Model name = perturbed box
+end
+
+subsection Material model
+  set Model name = simple
+
+  subsection Simple model
+    set Reference density             = 1
+    set Reference specific heat       = 1250
+    set Reference temperature         = 1
+    set Thermal conductivity          = 1e-6
+    set Thermal expansion coefficient = 2e-5
+    set Viscosity                     = 1
+  end
+end
+
+subsection Mesh refinement
+  set Initial adaptive refinement        = 0
+  set Initial global refinement          = 3
+end
+
+subsection Boundary velocity model
+  set Tangential velocity boundary indicators = 1
+  set Zero velocity boundary indicators       = 0, 2, 3
+end
+
+subsection Postprocess
+  set List of postprocessors =
+end