Periodic Boundary Conditions

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Periodic Boundary Conditions#

This example details the configuration and simulation of flow through a stator passage, employing rotational periodic boundary conditions via the Flow360 Python API. It outlines the procedure from importing a pre-existing mesh, defining the operating conditions using Mach and Reynolds numbers, specifying boundary conditions including rotational periodicity, configuring the Spalart-Allmaras turbulence model, and setting up various outputs like surface and slice data before initiating the simulation run.

  1import flow360 as fl
  2from flow360.examples import TutorialPeriodicBC
  3
  4TutorialPeriodicBC.get_files()
  5project = fl.Project.from_volume_mesh(
  6    TutorialPeriodicBC.mesh_filename,
  7    name="Tutorial Periodic Boundary Condition from Python",
  8)
  9volume_mesh = project.volume_mesh
 10
 11with fl.SI_unit_system:
 12    slice_inlet = fl.Slice(
 13        name="Inlet",
 14        normal=[1, 0, 0],
 15        origin=[-179, 0, 0] * fl.u.m,
 16    )
 17    slice_outlet = fl.Slice(
 18        name="Outlet",
 19        normal=[1, 0, 0],
 20        origin=[539, 0, 0] * fl.u.m,
 21    )
 22    slice_trailing_edge = fl.Slice(
 23        name="TrailingEdge",
 24        normal=[1, 0, 0],
 25        origin=[183, 0, 0] * fl.u.m,
 26    )
 27    slice_wake = fl.Slice(
 28        name="Wake",
 29        normal=[1, 0, 0],
 30        origin=[294.65, 0, 0] * fl.u.m,
 31    )
 32    operating_condition = fl.operating_condition_from_mach_reynolds(
 33        mach=0.13989,
 34        reynolds=3200,
 35        project_length_unit=1 * fl.u.m,
 36        temperature=298.25 * fl.u.K,
 37    )
 38    params = fl.SimulationParams(
 39        reference_geometry=fl.ReferenceGeometry(
 40            moment_center=[0, 0, 0], moment_length=[1, 1, 1], area=209701.3096271187
 41        ),
 42        operating_condition=operating_condition,
 43        time_stepping=fl.Steady(max_steps=5000, CFL=fl.AdaptiveCFL()),
 44        models=[
 45            fl.Fluid(
 46                navier_stokes_solver=fl.NavierStokesSolver(
 47                    absolute_tolerance=1e-11,
 48                    linear_solver=fl.LinearSolver(max_iterations=20),
 49                    order_of_accuracy=2,
 50                    kappa_MUSCL=0.33,
 51                    update_jacobian_frequency=1,
 52                    equation_evaluation_frequency=1,
 53                    numerical_dissipation_factor=1,
 54                ),
 55                turbulence_model_solver=fl.SpalartAllmaras(
 56                    absolute_tolerance=1e-10,
 57                    linear_solver=fl.LinearSolver(max_iterations=20),
 58                    update_jacobian_frequency=1,
 59                    equation_evaluation_frequency=1,
 60                    order_of_accuracy=2,
 61                ),
 62            ),
 63            fl.Wall(
 64                surfaces=[
 65                    volume_mesh["fluid/vane_*"],  # fluid/vane_ss and vane_ps
 66                    volume_mesh["fluid/bladeFillet_*"],  # fluid/bladeFillet_ss and bladeFillet_ps
 67                    volume_mesh["fluid/shroud"],
 68                    volume_mesh["fluid/hub"],
 69                ]
 70            ),
 71            fl.Freestream(
 72                surfaces=[
 73                    volume_mesh["fluid/inlet"],
 74                ]
 75            ),
 76            fl.Outflow(
 77                surfaces=[
 78                    volume_mesh["fluid/outlet"],
 79                ],
 80                spec=fl.Pressure(1.0032 * operating_condition.thermal_state.pressure),
 81            ),
 82            fl.SlipWall(
 83                surfaces=[
 84                    volume_mesh["fluid/bottomFront"],
 85                    volume_mesh["fluid/topFront"],
 86                ]
 87            ),
 88            fl.Periodic(
 89                surface_pairs=[(volume_mesh["fluid/periodic-1"], volume_mesh["fluid/periodic-2"])],
 90                spec=fl.Rotational(axis_of_rotation=(1, 0, 0)),
 91            ),
 92        ],
 93        outputs=[
 94            fl.VolumeOutput(
 95                output_format="tecplot",
 96                output_fields=[
 97                    "primitiveVars",
 98                    "vorticity",
 99                    "Cp",
100                    "Mach",
101                    "qcriterion",
102                    "mut",
103                    "nuHat",
104                    "mutRatio",
105                    "gradW",
106                    "T",
107                    "residualNavierStokes",
108                ],
109            ),
110            fl.SurfaceOutput(
111                surfaces=volume_mesh["*"],
112                output_format="both",
113                output_fields=[
114                    "primitiveVars",
115                    "Cp",
116                    "Cf",
117                    "CfVec",
118                    "yPlus",
119                    "nodeForcesPerUnitArea",
120                ],
121            ),
122            fl.SliceOutput(
123                slices=[slice_inlet, slice_outlet, slice_trailing_edge, slice_wake],
124                output_format="both",
125                output_fields=["Cp", "primitiveVars", "T", "Mach", "gradW"],
126            ),
127        ],
128    )
129
130
131project.run_case(params=params, name="Tutorial Periodic Boundary Condition from Python")

Notes#

  • Rotational periodicity between periodic-1 and periodic-2 surfaces is established using fl.Periodic combined with fl.Rotational.

  • fl.SlipWall boundary conditions are applied to the bottomFront and topFront surfaces, acting as buffer regions to improve convergence behavior near the inlet.

  • fl.SliceOutput is utilized to extract detailed flow field data at specified cross-sections (Inlet, Outlet, TrailingEdge, Wake) for post-processing.

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