Hi, I am trying to define a time-dependent boundary condition in dolfinx. Previously, in dolfin, it was possible through the Expression object, for instance: f = Expression(“sin(2.0*t)”, t=0.0, degree = 1) What is the equivalent now in dolfinx? I couldn’t import from somewhere the Expression objec…

The Expression class has been removed, as it caused a headache for developers and it is not clear what it does. The new way of doing this is to interpolate an expression into a function: from dolfinx import UnitSquareMesh, Function, FunctionSpace, MPI, Constant from dolfinx.fem import assemble_vec…

Here is a minimal updated example for the latest version of DOLFINx: from dolfinx import mesh, fem from dolfinx.fem import FunctionSpace, Function,Constant from ufl import TestFunction, dx, inner import numpy as np from mpi4py import MPI class MyExpression: def __init__(self): self.t …

UFLValueError for vector valued expressions. I am trying to interpolate into the vector-valued Function object, different expressions for different components. Following the solution template for the scalar case, please find below a MWE. This throws UFLValueError. I appreciate any directions on ho…

[image] ampdes: def eval(self, x): return ufl.as_vector((-self.Ux*np.exp(-self.A*self.t)*x[0]*(1-x[0])*x[1]*(1-x[1]), -self.Uy*np.exp(-self.A*self.t)*x[0]*(1-x[0])*x[1]*(1-x[1])) ) Simply replace this with: class u_expres…

Hello, I am following this code trying to implement it in a Vectorfunctionspace (Example linear elasticity and have following error: Output exceeds the size limit. Open the full output data in a text editor --------------------------------------------------------------------------- TypeError …

[image] Thomas996: bc_r = fem.dirichletbc(u_D,right_dofs, V) By just looking over this quickly, you do not need to send in V to the dirichletbc constructor, as u_D is in the same space as your variational form will be, i.e. bc_r = fem.dirichletbc(u_D, right_dofs) should be sufficient

Thank you for your quick answer. Yes it is. The code works now.

Hi, dokken, when I implement such rotation as in code I posted before, i got following result: [Screenshot 2023-03-13 at 22.24.48] [Screenshot 2023-03-13 at 22.25.07] [Screenshot 2023-03-13 at 22.24.34] the rotation was as expected at the boundary; but it seems only the surface has rotated the …

Please post a code that can reproduce the result.

Here is the code that reproduce the result: import numpy as np import ufl from petsc4py import PETSc from mpi4py import MPI from dolfinx import fem, mesh, plot from dolfinx.fem import Function, FunctionSpace, Constant from ufl import TestFunction, dx, inner L = 10.0 domain = mesh.create_box(MPI.…

Equivalent for Expression in dolfinx

dolfinx

francesco-ballarin October 30, 2024, 3:47pm 32

@emna_frikha please open a new post, making sure you correctly format your code and read Read before posting: How do I get my question answered?

Topic		Replies	Views
Time dependent Dirichlet and Neumann BCs General	18	1202	September 27, 2023
Time-dependent dirichlet condition issue : AttributeError dolfinx	7	1072	April 27, 2022
Time dependent Dirichlet boundary conditions FEniCSx Errors	6	698	October 30, 2023
Expression in fenicsx General	3	1054	February 15, 2023
How to efficiently use `dolfinx.fem.Expression`? dolfinx performance	4	90	August 25, 2025

Equivalent for Expression in dolfinx

Related topics