Newton method failed to converge for non-affine geometry when evaluating the function

General
1

I met this error when I try to evaluate the funcion V:

V = FunctionSpace(mesh, v_cg2)
u_ = Function(V)
u_.eval(inlet_cylinder_coord, inlet_cylinder_cell)

and inlet_cylinder_coord and inlet_cylinder_cell are defined by:

obstacle_cell = locate_dofs_topological(V, fdim, ft.find(self.obstacle_marker))
inlet_cell = locate_dofs_topological(V, fdim, ft.find(self.inlet_marker))
inlet_cylinder_cell = np.concatenate([inlet_cell, obstacle_cell], axis=0)
inlet_cylinder_coord = mesh.geometry.x[inlet_cylinder_cell]

Here are the full error info:

Traceback (most recent call last):
  File "/home/wulong/pycharm-community-2021.3.3/plugins/python-ce/helpers/pydev/_pydevd_bundle/pydevd_exec2.py", line 3, in Exec
    exec(exp, global_vars, local_vars)
  File "<input>", line 1, in <module>
  File "/home/wulong/anaconda3/envs/drl/lib/python3.10/site-packages/dolfinx/fem/function.py", line 328, in eval
    self._cpp_object.eval(_x, _cells, u)
RuntimeError: Newton method failed to converge for non-affine geometry

And here are the full code:

import gmsh
import numpy as np
import sys
from mpi4py import MPI
from fluid_mechanics.area import *
from petsc4py import PETSc
import dolfinx
from dolfinx import geometry
from dolfinx.fem import (Constant, Function, FunctionSpace,
                         assemble_scalar, dirichletbc, form, locate_dofs_topological, set_bc)
from dolfinx.fem.petsc import (apply_lifting, assemble_matrix, assemble_vector,
                               create_vector, create_matrix, set_bc)
from dolfinx.geometry import BoundingBoxTree, compute_collisions, compute_colliding_cells
from dolfinx.io import (XDMFFile, distribute_entity_data, gmshio)
from utils.encoder import normalization
from ufl import (FacetNormal, FiniteElement, Identity, Measure, TestFunction, TrialFunction, VectorElement,
                 as_vector, div, dot, ds, dx, inner, lhs, grad, nabla_grad, rhs, sym)


class simulation:
    def __init__(self, c_x, c_y, o_x, o_y, r, r2,
                 obstacle_type='cylinder',
                 save_mesh='false',
                 save='false',
                 visualize='false'):

        self.L = 2.2
        self.H = 0.41
        self.c_x = c_x
        self.c_y = c_y
        self.r = r
        self.gdim = 2
        self.model_rank = 0
        self.mesh_comm = MPI.COMM_WORLD
        self.save = save
        self.o_x = o_x
        self.o_y = o_y
        self.r2 = r2
        self.obstacle_type = obstacle_type
        self.save_mesh = save_mesh
        self.visualize = visualize

    def generate_mesh(self):
        # L*H:computational domain's size
        # (c_x,c_y):the coordinates of big cylinder
        # r:radius of the big cylinder
        # r2:radius of the small cylinder
        gmsh.initialize()
        gmsh.option.setNumber('General.Verbosity', 1)
        rectangle = gmsh.model.occ.addRectangle(0, 0, 0, self.L, self.H, tag=1)
        obstacle1 = gmsh.model.occ.addDisk(self.c_x, self.c_y, 0, self.r, self.r)
        pre_fluid = gmsh.model.occ.cut([(self.gdim, rectangle)], [(self.gdim, obstacle1)])
        if self.r2 == 0:
            fluid = pre_fluid
        else:
            if self.obstacle_type == 'cylinder':
                obstacle2 = gmsh.model.occ.addDisk(self.o_x, self.o_y, 0, self.r2, self.r2)
            elif self.obstacle_type == 'rectangular':
                obstacle2 = gmsh.model.occ.addRectangle(self.o_x, self.o_y, 0, self.r2, self.r2)
            fluid = gmsh.model.occ.cut([(self.gdim, rectangle)], [(self.gdim, obstacle2)])

        gmsh.model.occ.synchronize()
        fluid_marker = 1

        volumes = gmsh.model.getEntities(dim=self.gdim)
        assert (len(volumes) == 1)
        gmsh.model.addPhysicalGroup(volumes[0][0], [volumes[0][1]], fluid_marker)
        gmsh.model.setPhysicalName(volumes[0][0], fluid_marker, "Fluid")

        self.inlet_marker, self.outlet_marker, self.wall_marker, self.obstacle_marker = 2, 3, 4, 5
        inflow, outflow, walls, obstacle = [], [], [], []

        boundaries = gmsh.model.getBoundary(volumes, oriented=False)
        for boundary in boundaries:
            center_of_mass = gmsh.model.occ.getCenterOfMass(boundary[0], boundary[1])
            if np.allclose(center_of_mass, [0, self.H / 2, 0]):
                inflow.append(boundary[1])
            elif np.allclose(center_of_mass, [self.L, self.H / 2, 0]):
                outflow.append(boundary[1])
            elif np.allclose(center_of_mass, [self.L / 2, self.H, 0]) or np.allclose(center_of_mass, [self.L / 2, 0, 0]):
                walls.append(boundary[1])
            else:
                obstacle.append(boundary[1])
        gmsh.model.addPhysicalGroup(1, walls, self.wall_marker)
        gmsh.model.setPhysicalName(1, self.wall_marker, "Walls")
        gmsh.model.addPhysicalGroup(1, inflow, self.inlet_marker)
        gmsh.model.setPhysicalName(1, self.inlet_marker, "Inlet")
        gmsh.model.addPhysicalGroup(1, outflow, self.outlet_marker)
        gmsh.model.setPhysicalName(1, self.outlet_marker, "Outlet")
        gmsh.model.addPhysicalGroup(1, obstacle, self.obstacle_marker)
        gmsh.model.setPhysicalName(1, self.obstacle_marker, "Obstacle")

        res_min = self.r / 3
        distance_field = gmsh.model.mesh.field.add("Distance")
        gmsh.model.mesh.field.setNumbers(distance_field, "EdgesList", obstacle)
        threshold_field = gmsh.model.mesh.field.add("Threshold")
        gmsh.model.mesh.field.setNumber(threshold_field, "IField", distance_field)
        gmsh.model.mesh.field.setNumber(threshold_field, "LcMin", res_min)
        gmsh.model.mesh.field.setNumber(threshold_field, "LcMax", 0.25 * self.H)
        gmsh.model.mesh.field.setNumber(threshold_field, "DistMin", self.r)
        gmsh.model.mesh.field.setNumber(threshold_field, "DistMax", 2 * self.H)
        min_field = gmsh.model.mesh.field.add("Min")
        gmsh.model.mesh.field.setNumbers(min_field, "FieldsList", [threshold_field])
        gmsh.model.mesh.field.setAsBackgroundMesh(min_field)

        gmsh.option.setNumber("Mesh.Algorithm", 8)
        gmsh.option.setNumber("Mesh.RecombinationAlgorithm", 2)
        gmsh.option.setNumber("Mesh.RecombineAll", 1)
        gmsh.option.setNumber("Mesh.SubdivisionAlgorithm", 1)
        gmsh.model.mesh.generate(self.gdim)
        gmsh.model.mesh.setOrder(2)
        gmsh.model.mesh.optimize("Netgen")
        mesh, _, ft = gmshio.model_to_mesh(gmsh.model, self.mesh_comm, self.model_rank, gdim=self.gdim)
        ft.name = "facet markers"

        if self.visualize == 'true':
            if '-nopopup' not in sys.argv:
                gmsh.fltk.run()
        if self.save_mesh == 'true':
            gmsh.write("cylinders.msh")

        return mesh, ft

    def compute(self, mesh, ft, probes, jet):
        jet_position = jet.get("position")
        jet_x = jet.get("jet_x")
        jet_y = jet.get("jet_y")
        inlet_cylinder = probes.get("inlet_cylinder")
        outlet = probes.get("outlet")
        probes = probes.get("probes")
        bb_tree = geometry.BoundingBoxTree(mesh, mesh.topology.dim)
        domain = mesh.geometry.x  # The coordinates of all mesh
        jet_cells = []
        jet_points = []
        probes_cells = []
        domain_cells = []
        probes_points_on_pro = []
        domain_points_on_pro = []
        domain_cell_candidates = geometry.compute_collisions(bb_tree, np.array(domain))
        probes_cell_candidates = geometry.compute_collisions(bb_tree, probes.T)
        jet_cell_candidates = geometry.compute_collisions(bb_tree, jet_position.T)
        domain_colliding_cells = geometry.compute_colliding_cells(mesh, domain_cell_candidates, np.array(domain))
        probes_colliding_cells = geometry.compute_colliding_cells(mesh, probes_cell_candidates, probes.T)
        jet_colliding_cells = geometry.compute_colliding_cells(mesh, jet_cell_candidates, jet_position.T)

        for i, point in enumerate(np.array(domain)):
            if len(domain_colliding_cells.links(i)) > 0:
                #print(len(domain_colliding_cells.links(i)))
                domain_points_on_pro.append(point)
                domain_cells.append(domain_colliding_cells.links(i)[0])

        for i, point in enumerate(probes.T):
            if len(probes_colliding_cells.links(i)) > 0:
                probes_points_on_pro.append(point)
                probes_cells.append(probes_colliding_cells.links(i)[0])

        for i, jet_point in enumerate(jet_position.T):
            if len(jet_colliding_cells.links(i)) > 0:
                jet_points.append(jet_point)
                jet_cells.append(jet_colliding_cells.links(i)[0])
        t = 0
        T = 7  # Final time
        dt = 1 / 1600  # Time step size
        self.num_steps = 50
        k = Constant(mesh, PETSc.ScalarType(dt))
        mu = Constant(mesh, PETSc.ScalarType(0.001))  # Dynamic viscosity
        rho = Constant(mesh, PETSc.ScalarType(1))  # Density

        v_cg2 = VectorElement("CG", mesh.ufl_cell(), 2)
        s_cg1 = FiniteElement("CG", mesh.ufl_cell(), 1)
        V = FunctionSpace(mesh, v_cg2)
        Q = FunctionSpace(mesh, s_cg1)

        fdim = mesh.topology.dim - 1

        # Define boundary conditions
        class InletVelocity():
            def __init__(self, t):
                self.t = t

            def __call__(self, x):
                values = np.zeros((2, x.shape[1]), dtype=PETSc.ScalarType)
                values[0] = 4 * 1.5 * x[1] * (0.41 - x[1]) / (0.41 ** 2)
                return values

        class JetVelocity():
            def __init__(self, t, jet_x, jet_y):
                self.t_jet = t
                self.jet_x = jet_x
                self.jet_y = jet_y

            def __call__(self, x):
                values = np.zeros((2, x.shape[1]), dtype=PETSc.ScalarType)
                values[1] = self.jet_y
                index = np.where(x[1, :] < 0.2)
                values[1, index] = -self.jet_y
                values[0] = self.jet_x
                return values
        # Inlet
        u_inlet = Function(V)
        u_jet = Function(V)
        inlet_velocity = InletVelocity(t)
        jet_velocity = JetVelocity(t, jet_x, jet_y)
        u_inlet.interpolate(inlet_velocity)
        u_jet.interpolate(jet_velocity)
        bcu_inflow = dirichletbc(u_inlet, locate_dofs_topological(V, fdim, ft.find(self.inlet_marker)))
        # Jets
        bcu_jets = dirichletbc(u_jet, locate_dofs_topological(V, fdim + 1, jet_cells))
        # Walls
        u_nonslip = np.array((0,) * mesh.geometry.dim, dtype=PETSc.ScalarType)
        bcu_walls = dirichletbc(u_nonslip, locate_dofs_topological(V, fdim, ft.find(self.wall_marker)), V)
        # Obstacle
        bcu_obstacle = dirichletbc(u_nonslip, locate_dofs_topological(V, fdim, ft.find(self.obstacle_marker)), V)
        bcu = [bcu_inflow, bcu_obstacle, bcu_walls, bcu_jets]
        # Outlet
        bcp_outlet = dirichletbc(PETSc.ScalarType(0), locate_dofs_topological(Q, fdim, ft.find(self.outlet_marker)), Q)
        bcp = [bcp_outlet]
        obstacle_cell = locate_dofs_topological(V, fdim, ft.find(self.obstacle_marker))
        inlet_cell = locate_dofs_topological(V, fdim, ft.find(self.inlet_marker))
        inlet_cylinder_cell = np.concatenate([inlet_cell, obstacle_cell], axis=0)
        inlet_cylinder_coord = mesh.geometry.x[inlet_cylinder_cell]
        outlet_cells = locate_dofs_topological(V, fdim, ft.find(self.outlet_marker))
        outlet_coord = mesh.geometry.x[outlet_cells]


        u = TrialFunction(V)
        v = TestFunction(V)
        u_ = Function(V)
        u_.name = "u"
        u_s = Function(V)
        u_n = Function(V)
        u_n1 = Function(V)
        p = TrialFunction(Q)
        q = TestFunction(Q)
        p_ = Function(Q)
        p_.name = "p"
        phi = Function(Q)

        # the first step

        f = Constant(mesh, PETSc.ScalarType((0, 0)))
        F1 = rho / k * dot(u - u_n, v) * dx
        F1 += inner(dot(1.5 * u_n - 0.5 * u_n1, 0.5 * nabla_grad(u + u_n)), v) * dx
        F1 += 0.5 * mu * inner(grad(u + u_n), grad(v)) * dx - dot(p_, div(v)) * dx
        F1 += dot(f, v) * dx
        a1 = form(lhs(F1))
        L1 = form(rhs(F1))
        A1 = create_matrix(a1)
        b1 = create_vector(L1)

        # the second step

        a2 = form(dot(grad(p), grad(q)) * dx)
        L2 = form(-rho / k * dot(div(u_s), q) * dx)
        A2 = assemble_matrix(a2, bcs=bcp)
        A2.assemble()
        b2 = create_vector(L2)

        # the last step

        a3 = form(rho * dot(u, v) * dx)
        L3 = form(rho * dot(u_s, v) * dx - k * dot(nabla_grad(phi), v) * dx)
        A3 = assemble_matrix(a3)
        A3.assemble()
        b3 = create_vector(L3)

        # Solver for step 1
        solver1 = PETSc.KSP().create(mesh.comm)
        solver1.setOperators(A1)
        solver1.setType(PETSc.KSP.Type.BCGS)
        pc1 = solver1.getPC()
        pc1.setType(PETSc.PC.Type.JACOBI)

        # Solver for step 2
        solver2 = PETSc.KSP().create(mesh.comm)
        solver2.setOperators(A2)
        solver2.setType(PETSc.KSP.Type.MINRES)
        pc2 = solver2.getPC()
        pc2.setType(PETSc.PC.Type.HYPRE)
        pc2.setHYPREType("boomeramg")

        # Solver for step 3
        solver3 = PETSc.KSP().create(mesh.comm)
        solver3.setOperators(A3)
        solver3.setType(PETSc.KSP.Type.CG)
        pc3 = solver3.getPC()
        pc3.setType(PETSc.PC.Type.SOR)
        # -

        u_probes = []
        p_probes = []
        inlet_cylinder_probes = []
        outlet_probes = []
        time_list = []
        eval_time = []
        init_domain_v_probes = []
        init_domain_p_probes = []
        xdmf = XDMFFile(mesh.comm, f"active_{jet_position}_{jet_x}_{jet_y}.xdmf", "w")
        xdmf.write_mesh(mesh)
        for i in range(self.num_steps):
            # Update current time step
            t += dt
            # Update inlet velocity
            inlet_velocity.t = t
            u_inlet.interpolate(inlet_velocity)

            # Step 1: Tentative velocity step
            A1.zeroEntries()
            assemble_matrix(A1, a1, bcs=bcu)
            A1.assemble()
            with b1.localForm() as loc:
                loc.set(0)
            assemble_vector(b1, L1)
            apply_lifting(b1, [a1], [bcu])
            b1.ghostUpdate(addv=PETSc.InsertMode.ADD_VALUES, mode=PETSc.ScatterMode.REVERSE)
            set_bc(b1, bcu)
            solver1.solve(b1, u_s.vector)
            u_s.x.scatter_forward()

            # Step 2: Pressure corrrection step
            with b2.localForm() as loc:
                loc.set(0)
            assemble_vector(b2, L2)
            apply_lifting(b2, [a2], [bcp])
            b2.ghostUpdate(addv=PETSc.InsertMode.ADD_VALUES, mode=PETSc.ScatterMode.REVERSE)
            set_bc(b2, bcp)
            solver2.solve(b2, phi.vector)
            phi.x.scatter_forward()

            p_.vector.axpy(1, phi.vector)
            p_.x.scatter_forward()

            # Step 3: Velocity correction step
            with b3.localForm() as loc:
                loc.set(0)
            assemble_vector(b3, L3)
            b3.ghostUpdate(addv=PETSc.InsertMode.ADD_VALUES, mode=PETSc.ScatterMode.REVERSE)
            solver3.solve(b3, u_.vector)
            u_.x.scatter_forward()

            # write the data of probes
            if i / 256 == 0:
                u_values = u_.eval(probes_points_on_pro, probes_cells)
                p_values = p_.eval(probes_points_on_pro, probes_cells)
                u_probes.append(u_values)
                p_probes.append(p_values)
                xdmf.write_function(u_, t)
                xdmf.write_function(p_, t)

            if i == 0:
                #print(V.tabulate_dof_coordinates())
                init_v_values = u_.eval(domain_points_on_pro, domain_cells)
                init_p_values = p_.eval(domain_points_on_pro, domain_cells)
                init_domain_v_probes.append(init_v_values)
                init_domain_p_probes.append(init_p_values)

            if i == self.num_steps - 1:
                inlet_cylinder_values = u_.eval(inlet_cylinder_coord, inlet_cylinder_cell)
                outlet_values = p_.eval(outlet_coord, outlet_cells)
                inlet_cylinder_probes.append(inlet_cylinder_values)
                outlet_probes.append(outlet_values)
            time_list.append(i)
            eval_time.append(i)

        gmsh.clear()
        xdmf.close()
        # Update variable with solution form this time step
        with u_.vector.localForm() as loc_, u_n.vector.localForm() as loc_n, u_n1.vector.localForm() as loc_n1:
            loc_n.copy(loc_n1)
            loc_.copy(loc_n)
        time = np.repeat(np.array(time_list), 4)
        eval_time = np.repeat(np.array(eval_time), len(V.tabulate_dof_coordinates()))
        domain_eval = np.tile(np.array(domain), (50, 1))
        u0 = np.array(u_probes)[:, :, 0]
        u1 = np.array(u_probes)[:, :, 1]
        inlet_u0 = np.array(inlet_cylinder_probes)[:, :, 0]
        inlet_u1 = np.array(inlet_cylinder_probes)[:, :, 1]
        init_u0 = np.array(init_domain_v_probes)[:, :, 0]
        init_u1 = np.array(init_domain_v_probes)[:, :, 1]
        probes_points_on_pro = np.tile(np.transpose(probes_points_on_pro), 50)
        obstacle_cell = locate_dofs_topological(V, fdim, ft.find(self.obstacle_marker))
        inlet_cell = locate_dofs_topological(V, fdim, ft.find(self.inlet_marker))
        inlet_cylinder_cell = np.concatenate([inlet_cell, obstacle_cell], axis=0)
        inlet_cylinder_coord = mesh.geometry.x[inlet_cylinder_cell]


        probes = {
            "p": np.array(p_probes).reshape(-1, 1).flatten(),
            "u0": u0.reshape(-1, 1).flatten(),
            "u1": u1.reshape(-1, 1).flatten(),
            "t": time,
            "x": probes_points_on_pro[0],
            "y": probes_points_on_pro[1]
        }

        jet_config = {
            "jet_x": jet.get("jet_x"),
            "jet_y": jet.get("jet_y")
        }

        domain_train = {
            "x": domain[:, 0],
            "y": domain[:, 1],
            "z": domain[:, 2]
        }

        cylinder_inlet = {
            "x": inlet_cylinder_coord[:, 0],
            "y": inlet_cylinder_coord[:, 1],
            "u0": inlet_u0.reshape(-1, 1).flatten(),
            "u1": inlet_u1.reshape(-1, 1).flatten()
        }
        outlet = {
            "x": outlet_coord[:, 0],
            "y": outlet_coord[:, 1],
            "p": np.array(outlet_probes).reshape(-1, 1).flatten()
        }

        IC_0_1 = {
            "x": domain[:, 0],
            "y": domain[:, 1],
            "z": domain[:, 2],
            "p": np.zeros((len(domain))),
            "u0": init_u0.reshape(-1, 1).flatten(),
            "u1": init_u1.reshape(-1, 1).flatten(),
        }
        eval = {
            "x": domain_eval[:, 0],
            "y": domain_eval[:, 1],
            "t": eval_time
        }
        return cylinder_inlet, outlet, domain_train, IC_0_1, probes, jet_config, eval

if __name__ == "__main__":
    from fluid_mechanics.area import *
    from math import sin, cos, pi
    import os
    import pandas as pd

    dataset_dir = "datasets"
    ic_dir = "datasets/initial"
    probes_dir = "datasets/probe"

    if not os.path.exists(dataset_dir):
        os.makedirs(dataset_dir)

    if not os.path.exists(probes_dir):
        os.makedirs(probes_dir)

    if not os.path.exists(ic_dir):
        os.makedirs(ic_dir)

    r = 0.05
    x1 = r * cos(pi / 2) + 0.3
    y1 = r * sin(pi / 2) + 0.2
    x2 = r * cos(3 / 2 * pi) + 0.3
    y2 = r * sin(3 * pi / 2) + 0.2
    jet_positions = [(x1, y1, 0), (x2, y2, 0)]
    jet_coordinates = positions(jet_positions)
    jet = {
        "jet_x": 0,
        "jet_y": 0,
        "position": jet_coordinates
    }
    input_points = pinn_inlet()
    outlet_points = pinn_outlet()
    cylinder_points = pinn_cylinder()
    inlet_cylinder_points = add_points(input_points, cylinder_points)
    probes_points = circle_probes(0.05, 4)
    points = {
        "inlet_cylinder": inlet_cylinder_points,
        "outlet": outlet_points,
        "probes": probes_points
    }

    jet_x = jet.get("jet_x")
    jet_y = jet.get("jet_y")
    simu = simulation(c_x=0.3, c_y=0.2, o_x=0.3, o_y=0.2, r=0.05, r2=0.02)
    mesh, ft = simu.generate_mesh()
    cylinder_inlet, outlet, domain_train, IC_0_1, probes, jet_config, eval = simu.compute(mesh=mesh, ft=ft,
                                                                                                 probes=points,
                                                                                                 jet=jet)
2

This is not correct, as locate_dofs_topological returns a degree of freedom not a cell.
If you want the cells connected to ft.find(self.inlet_marker) you should use

        inlet_cells = dolfinx.mesh.compute_incident_entities(domain, ft.find(self.inlet_marker), domain.topology.dim-1, domain.topology.dim)

which would give you a list of all cells connected to inlet.

As your example is way to long (and not executable), I cant give you any further guidance.

maybe you could explain why you want to use a point evaluation at some point at the inlet?

3

Hi dokken，I want to log the value of cells which are marked with facets during computation by u_.eval().
And now I met some problem: The output of
inlet_index = dolfinx.mesh.compute_incident_entities(domain, ft.find(self.inlet_marker),domain.topology.dim-1, domain.topology.dim), print(domain[inlet_index]) is unexpected，which is far from my inlet boundary.

4

domain[inlet_index] is not the correct usage, as inlet_index is a list of cells, not mesh vertices.

Again, for me to give further comments, you would have to drastically simplify your example.

5

Here are the easy example:


import gmsh
import numpy as np
import dolfinx
from mpi4py import MPI
from petsc4py import PETSc
from dolfinx.cpp.mesh import to_type, cell_entity_type
from dolfinx import geometry
from dolfinx.fem import (Constant, Function, FunctionSpace,
                         assemble_scalar, dirichletbc, form, locate_dofs_topological, set_bc)
from dolfinx.fem.petsc import (apply_lifting, assemble_matrix, assemble_vector,
                               create_vector, create_matrix, set_bc)
from dolfinx.graph import create_adjacencylist
from dolfinx.geometry import BoundingBoxTree, compute_collisions, compute_colliding_cells
from dolfinx.io import (XDMFFile, distribute_entity_data, gmshio)
from dolfinx.mesh import create_mesh, meshtags_from_entities

from ufl import (FacetNormal, FiniteElement, Identity, Measure, TestFunction, TrialFunction, VectorElement,
                 as_vector, div, dot, ds, dx, inner, lhs, grad, nabla_grad, rhs, sym)

gmsh.initialize()

L = 2.2
H = 0.41
c1_x = c1_y = 0.2
r1 = 0.05
gdim = 2
mesh_comm = MPI.COMM_WORLD
model_rank = 0
fluid_marker = 1
if mesh_comm.rank == model_rank:
    rectangle = gmsh.model.occ.addRectangle(0, 0, 0, L, H, tag=1)
    obstacle = gmsh.model.occ.addDisk(c1_x, c1_y, 0, r1, r1)
    fluid = gmsh.model.occ.cut([(gdim, rectangle)], [(gdim, obstacle)])
    gmsh.model.occ.synchronize()
    volumes = gmsh.model.getEntities(dim=gdim)
    assert (len(volumes) == 1)
    gmsh.model.addPhysicalGroup(volumes[0][0], [volumes[0][1]], fluid_marker)
    gmsh.model.setPhysicalName(volumes[0][0], fluid_marker, "Fluid")
inlet_marker, outlet_marker, wall_marker, obstacle_marker = 2, 3, 4, 5
inflow, outflow, walls, obstacle = [], [], [], []
if mesh_comm.rank == model_rank:
    boundaries = gmsh.model.getBoundary(volumes, oriented=False)
    for boundary in boundaries:
        center_of_mass = gmsh.model.occ.getCenterOfMass(boundary[0], boundary[1])
        if np.allclose(center_of_mass, [0, H / 2, 0]):
            inflow.append(boundary[1])
        elif np.allclose(center_of_mass, [L, H / 2, 0]):
            outflow.append(boundary[1])
        elif np.allclose(center_of_mass, [L / 2, H, 0]) or np.allclose(center_of_mass, [L / 2, 0, 0]):
            walls.append(boundary[1])
        else:
            obstacle.append(boundary[1])
    gmsh.model.addPhysicalGroup(1, walls, wall_marker)
    gmsh.model.setPhysicalName(1, wall_marker, "Walls")
    gmsh.model.addPhysicalGroup(1, inflow, inlet_marker)
    gmsh.model.setPhysicalName(1, inlet_marker, "Inlet")
    gmsh.model.addPhysicalGroup(1, outflow, outlet_marker)
    gmsh.model.setPhysicalName(1, outlet_marker, "Outlet")
    gmsh.model.addPhysicalGroup(1, obstacle, obstacle_marker)
    gmsh.model.setPhysicalName(1, obstacle_marker, "Obstacle")

res_min = r1 / 3
if mesh_comm.rank == model_rank:
    distance_field = gmsh.model.mesh.field.add("Distance")
    gmsh.model.mesh.field.setNumbers(distance_field, "EdgesList", obstacle)
    threshold_field = gmsh.model.mesh.field.add("Threshold")
    gmsh.model.mesh.field.setNumber(threshold_field, "IField", distance_field)
    gmsh.model.mesh.field.setNumber(threshold_field, "LcMin", res_min)
    gmsh.model.mesh.field.setNumber(threshold_field, "LcMax", 0.25 * H)
    gmsh.model.mesh.field.setNumber(threshold_field, "DistMin", r1)
    gmsh.model.mesh.field.setNumber(threshold_field, "DistMax", 2 * H)
    min_field = gmsh.model.mesh.field.add("Min")
    gmsh.model.mesh.field.setNumbers(min_field, "FieldsList", [threshold_field])
    gmsh.model.mesh.field.setAsBackgroundMesh(min_field)

if mesh_comm.rank == model_rank:
    gmsh.option.setNumber("Mesh.Algorithm", 8)
    gmsh.option.setNumber("Mesh.RecombinationAlgorithm", 2)
    gmsh.option.setNumber("Mesh.RecombineAll", 1)
    gmsh.option.setNumber("Mesh.SubdivisionAlgorithm", 1)
    gmsh.model.mesh.generate(gdim)
    gmsh.model.mesh.setOrder(2)
    gmsh.model.mesh.optimize("Netgen")

mesh, _, ft = gmshio.model_to_mesh(gmsh.model, mesh_comm, model_rank, gdim=gdim)

bb_tree = geometry.BoundingBoxTree(mesh, mesh.topology.dim)
ft.name = "Facet markers"

domain = mesh.geometry.x
inlet_index = dolfinx.mesh.compute_incident_entities(mesh, ft.find(inlet_marker), mesh.topology.dim-1, mesh.topology.dim)
inlet_coord = domain[inlet_index]

t = 0
T = 8  # Final time
dt = 1 / 1600  # Time step size
num_steps = int(T / dt)
k = Constant(mesh, PETSc.ScalarType(dt))
mu = Constant(mesh, PETSc.ScalarType(0.001))  # Dynamic viscosity
rho = Constant(mesh, PETSc.ScalarType(1))  # Density

v_cg2 = VectorElement("CG", mesh.ufl_cell(), 2)
s_cg1 = FiniteElement("CG", mesh.ufl_cell(), 1)
V = FunctionSpace(mesh, v_cg2)
Q = FunctionSpace(mesh, s_cg1)

fdim = mesh.topology.dim - 1


# Define boundary conditions
class InletVelocity():
    def __init__(self, t):
        self.t = t

    def __call__(self, x):
        values = np.zeros((gdim, x.shape[1]), dtype=PETSc.ScalarType)
        values[0] = 4 * 1.5 * np.sin(self.t * np.pi / 8) * x[1] * (0.41 - x[1]) / (0.41 ** 2)
        return values


# Inlet
u_inlet = Function(V)
inlet_velocity = InletVelocity(t)
u_inlet.interpolate(inlet_velocity)
bcu_inflow = dirichletbc(u_inlet, locate_dofs_topological(V, fdim, ft.find(inlet_marker)))
# Walls
u_nonslip = np.array((0,) * mesh.geometry.dim, dtype=PETSc.ScalarType)
bcu_walls = dirichletbc(u_nonslip, locate_dofs_topological(V, fdim, ft.find(wall_marker)), V)
# Obstacle
bcu_obstacle = dirichletbc(u_nonslip, locate_dofs_topological(V, fdim, ft.find(obstacle_marker)), V)
bcu = [bcu_inflow, bcu_obstacle, bcu_walls]
# Outlet
bcp_outlet = dirichletbc(PETSc.ScalarType(0), locate_dofs_topological(Q, fdim, ft.find(outlet_marker)), Q)
bcp = [bcp_outlet]


u = TrialFunction(V)
v = TestFunction(V)
u_ = Function(V)
u_.name = "u"
u_s = Function(V)
u_n = Function(V)
u_n1 = Function(V)
p = TrialFunction(Q)
q = TestFunction(Q)
p_ = Function(Q)
p_.name = "p"
phi = Function(Q)


f = Constant(mesh, PETSc.ScalarType((0, 0)))
F1 = rho / k * dot(u - u_n, v) * dx
F1 += inner(dot(1.5 * u_n - 0.5 * u_n1, 0.5 * nabla_grad(u + u_n)), v) * dx
F1 += 0.5 * mu * inner(grad(u + u_n), grad(v)) * dx - dot(p_, div(v)) * dx
F1 += dot(f, v) * dx
a1 = form(lhs(F1))
L1 = form(rhs(F1))
A1 = create_matrix(a1)
b1 = create_vector(L1)

# Next we define the second step

a2 = form(dot(grad(p), grad(q)) * dx)
L2 = form(-rho / k * dot(div(u_s), q) * dx)
A2 = assemble_matrix(a2, bcs=bcp)
A2.assemble()
b2 = create_vector(L2)

# We finally create the last step

a3 = form(rho * dot(u, v) * dx)
L3 = form(rho * dot(u_s, v) * dx - k * dot(nabla_grad(phi), v) * dx)
A3 = assemble_matrix(a3)
A3.assemble()
b3 = create_vector(L3)

# +
# Solver for step 1
solver1 = PETSc.KSP().create(mesh.comm)
solver1.setOperators(A1)
solver1.setType(PETSc.KSP.Type.BCGS)
pc1 = solver1.getPC()
pc1.setType(PETSc.PC.Type.JACOBI)

# Solver for step 2
solver2 = PETSc.KSP().create(mesh.comm)
solver2.setOperators(A2)
solver2.setType(PETSc.KSP.Type.MINRES)
pc2 = solver2.getPC()
pc2.setType(PETSc.PC.Type.HYPRE)
pc2.setHYPREType("boomeramg")

# Solver for step 3
solver3 = PETSc.KSP().create(mesh.comm)
solver3.setOperators(A3)
solver3.setType(PETSc.KSP.Type.CG)
pc3 = solver3.getPC()
pc3.setType(PETSc.PC.Type.SOR)


for i in range(50):
    # Update current time step
    t += dt
    # Update inlet velocity
    inlet_velocity.t = t
    u_inlet.interpolate(inlet_velocity)

    # Step 1: Tentative velocity step
    A1.zeroEntries()
    assemble_matrix(A1, a1, bcs=bcu)
    A1.assemble()
    with b1.localForm() as loc:
        loc.set(0)
    assemble_vector(b1, L1)
    apply_lifting(b1, [a1], [bcu])
    b1.ghostUpdate(addv=PETSc.InsertMode.ADD_VALUES, mode=PETSc.ScatterMode.REVERSE)
    set_bc(b1, bcu)
    solver1.solve(b1, u_s.vector)
    u_s.x.scatter_forward()

    # Step 2: Pressure corrrection step
    with b2.localForm() as loc:
        loc.set(0)
    assemble_vector(b2, L2)
    apply_lifting(b2, [a2], [bcp])
    b2.ghostUpdate(addv=PETSc.InsertMode.ADD_VALUES, mode=PETSc.ScatterMode.REVERSE)
    set_bc(b2, bcp)
    solver2.solve(b2, phi.vector)
    phi.x.scatter_forward()

    p_.vector.axpy(1, phi.vector)
    p_.x.scatter_forward()

    # Step 3: Velocity correction step
    with b3.localForm() as loc:
        loc.set(0)
    assemble_vector(b3, L3)
    b3.ghostUpdate(addv=PETSc.InsertMode.ADD_VALUES, mode=PETSc.ScatterMode.REVERSE)
    solver3.solve(b3, u_.vector)
    u_.x.scatter_forward()

    inlet_values = u_.eval(inlet_coord, inlet_index)
6

I met the same non-affine geometry problem when I interpolate a function from a mesh onto another one in 2nd order 3D meshes. However, it cannot be reproduced in a pair of simpilified meshes. How can we find the problematic cells to cause the problem in the meshes? Or any other recommend methods to locate the problem?

7

@Chris_Richardson made some changes to the gjk algorithm to support coplanar cells (affine second order cells) in: Use boost multiprecision for GJK by chrisrichardson · Pull Request #3770 · FEniCS/dolfinx · GitHub

The other option, which hasn’t been fixed, would be to expose the nokaffine pullback tolerance in eval:

8

I have been using v0.9.0 for a while. Indeed, switching to v0.10.0 without changing of API resolves my non-affine geometry in my test case. But the speed of nonmatching meshes interpolation in v0.10.0 seems to be slower. Is my feeling correct?

9

The collision routines uses higher precision floats to be more accurate, so it might be a bit slower.
I’ve also made a PR for exposing the pull-back parameters in: