Merge pull request #278 from akhoubani/howto-timestep

Adding adaptive_time_step.md  file

docs/how-to/adaptive_time_step.md

@@ -0,0 +1,38 @@
+# How to set adaptive time step in Nek5000
+
+In the Nek5000 documentation, `variableDT` in `GENERAL` keys in [`.par` file](https://nek5000.github.io/NekDoc/problem_setup/case_files.html#parameter-file-par) is used to control whether the step size will be adjusted to match the `targetCFL`.
+
+In Snek5000, you can enable this feature by setting `params.nek.general.variable_dt` to `True`.
+
+For example, in the script below, we set `variable_dt` as `True`, which subsequently leads to an adaptive time step based on the `target_cfl`:
+
+```python
+---
+emphasize-lines: 20-21
+---
+from snek5000_tgv.solver import Simul
+
+params = Simul.create_default_params()
+params.output.sub_directory = "examples_snek/tuto"
+
+params.oper.nx = params.oper.ny = params.oper.nz = 8
+params.oper.elem.order = params.oper.elem.order_out = 8
+params.oper.nproc_min = 2
+
+params.nek.velocity.residual_tol = 1e-07
+params.nek.pressure.residual_tol = 1e-05
+
+params.nek.general.write_control = "runTime"
+params.nek.general.write_interval = 2.0
+
+params.output.spatial_means.write_interval = 0.5
+
+params.nek.general.end_time = 10
+params.nek.general.dt = 1
+params.nek.general.target_cfl = 1.4
+params.nek.general.variable_dt = True
+params.nek.general.extrapolation = "OIFS"
+
+sim = Simul(params)
+sim.make.exec("run_fg", nproc=2)
+```

docs/how-to/history_points.md

@@ -10,7 +10,7 @@ params.output.history_points.coords: list[tuple[float, float, float] | tuple[flo
 ```
 
 For example, see the
-[parameters used in the tutorial for snek5000-cbox](../tuto_cbox.myst.md#a-more-advanced-script-adated-for-a-particular-instability).
+[parameters used in the tutorial for snek5000-cbox](../tuto_cbox.myst.md#a-more-advanced-script-adapted-for-a-particular-instability).
 
 This should be coupled along with a `hpts()` call in `userchk()` subroutine in the
 Nek5000 user file. For more information, see *documentation for

docs/how-to/index.md

@@ -16,6 +16,7 @@ rebuild-nek.md
 export-sans-snek5000.myst.md
 archive-simulation-data.md
 templates.md
+adaptive_time_step.md
 ```
 
 ## For developer of Snek5000 solvers

docs/tuto_cbox.myst.md

@@ -14,7 +14,7 @@ kernelspec:
 
 # Demo sidewall convection (`snek5000-cbox` solver)
 
-## A more advanced script adated for a particular instability
+## A more advanced script adapted for a particular instability
 
 This example is based on
 [the study *From onset of unsteadiness to chaos in a differentially heated square cavity* by Le Quéré & Behnia (1998)](https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/abs/from-onset-of-unsteadiness-to-chaos-in-a-differentially-heated-square-cavity/617F4CB2C23DD74C3D0CB872AE7C0045).