Unsteady 2D Cylinder

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Unsteady 2D Cylinder#

This example demonstrates the configuration and execution of an unsteady simulation for laminar flow over a 2D cylinder using the Flow360 Python API. The script utilizes the operating_condition_from_mach_reynolds helper function to define the flow conditions based on specified Mach and Reynolds numbers. It sets up appropriate boundary conditions, including no-slip walls, freestream boundaries, and slip walls for periodic boundaries, and configures unsteady time stepping parameters.

 1import flow360 as fl
 2from flow360.examples import Cylinder2D
 3
 4Cylinder2D.get_files()
 5
 6
 7project = fl.Project.from_volume_mesh(
 8    Cylinder2D.mesh_filename, name="Unsteady 2D Cylinder from Python"
 9)
10
11vm = project.volume_mesh
12
13
14with fl.SI_unit_system:
15    params = fl.SimulationParams(
16        reference_geometry=fl.ReferenceGeometry(
17            area=20, moment_center=[0, 0, 0], moment_length=[1, 1, 1]
18        ),
19        operating_condition=fl.operating_condition_from_mach_reynolds(
20            reynolds=50, mach=0.1, project_length_unit=fl.u.m
21        ),
22        models=[
23            fl.Fluid(
24                navier_stokes_solver=fl.NavierStokesSolver(
25                    absolute_tolerance=1e-9, linear_solver=fl.LinearSolver(max_iterations=25)
26                ),
27                turbulence_model_solver=fl.NoneSolver(),
28            ),
29            fl.Wall(surfaces=[vm["fluid/wall"]]),
30            fl.Freestream(surfaces=[vm["fluid/farfield"]]),
31            fl.SlipWall(surfaces=[vm["fluid/periodic_0_l"], vm["fluid/periodic_0_r"]]),
32        ],
33        time_stepping=fl.Unsteady(
34            max_pseudo_steps=40,
35            step_size=2,
36            steps=20,
37        ),
38        outputs=[
39            fl.SurfaceOutput(output_fields=["Cp"], surfaces=[vm["*"]]),
40            fl.VolumeOutput(
41                output_fields=[
42                    "primitiveVars",
43                    "vorticity",
44                    "residualNavierStokes",
45                    "T",
46                    "Cp",
47                    "mut",
48                ],
49            ),
50        ],
51    )
52
53project.run_case(params, "Unsteady 2D Cylinder case from Python")

Notes#

  • The operating_condition_from_mach_reynolds function simplifies setting flow conditions based on Reynolds and Mach numbers, automatically calculating necessary parameters like velocity and density based on the chosen length unit.

  • Unsteady simulations are configured using the fl.Unsteady class within the time_stepping parameter, and specifying physical time step size (step_size), total number of physical steps (steps), and maximum inner iterations per physical step (max_pseudo_steps).

  • Note the use of fl.NoneSolver() for the turbulence_model_solver, indicating a laminar simulation appropriate for the low Reynolds number (Re=50) used here.

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