# Gridap use for finite element modelling for electrochemical electrode modelling

**URL:** <https://discourse.julialang.org/t/gridap-use-for-finite-element-modelling-for-electrochemical-electrode-modelling/135377>\
**Category:** Modelling & Simulations\
**Tags:** finite-element, gridap\
**Created:** [January 31, 2026, 6:34pm UTC](https://discourse.julialang.org/t/gridap-use-for-finite-element-modelling-for-electrochemical-electrode-modelling/135377 "2026-01-31T18:34:15Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![algoking](https://avatars.discourse-cdn.com/v4/letter/a/3ec8ea/32.png) [@algoking](https://discourse.julialang.org/u/algoking)\
**Post date:** [January 31, 2026, 6:34pm UTC](https://discourse.julialang.org/t/gridap-use-for-finite-element-modelling-for-electrochemical-electrode-modelling/135377/1 "2026-01-31T18:34:16Z")

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Hi everyone,  
I am currently transitioning our lab’s electrochemical modeling workflow from **COMSOL** to **Gridap.jl**. My goal is to move away from proprietary licenses and leverage the flexibility of the Julia ecosystem.

The system I am modeling is a **1D stationary** system with 6 coupled nonlinear PDEs (poisson equations). The unknowns are potentials and species concentrations. In the future, I would need to dive into transient terms as well. For now, stationnary problem would do.

The coupling is highly nonlinear due to **Butler-Volmer reaction rates** acting as source terms in the porous electrodes.

**The Problem:** When calling the solver, the REPL hangs indefinitely (10+ minutes) with no output of any sorts. Even with `autodiff=false` and a very low `maxiter`, I am seeing a “black screen” during the solving phase.

**Current Implementation:** I am using a `MultiFieldFESpace`. To troubleshoot, I have attempted to bypass Automatic Differentiation to rule out compilation hangs:

```julia-auto
op = FEOperator(res, U, V)
ls = LUSolver() 
nls = NLSolver(ls; show_trace=true, method=:newton, linesearch=BackTracking(), atol=1e-8, rtol=1e-10, maxiter=1, autodiff=false) 
solver = FESolver(nls)

println("\nsolving phase")
u_solution = solve(solver, op)

```

where `res` is the residual function that I defined, `U` and `V` are of following types.

```julia-auto
typeof(U) MultiFieldFESpace{Gridap.MultiField.ConsecutiveMultiFieldStyle, Gridap.FESpaces.UnConstrained, Vector{Float64}}
typeof(V) MultiFieldFESpace{Gridap.MultiField.ConsecutiveMultiFieldStyle, Gridap.FESpaces.UnConstrained, Vector{Float64}}

```

I verfied that the `res` function is properly implemented as well, using the following code, which didn’t cause any errors and returns `DomainContribution()`

```julia-auto
u_test = interpolate_everywhere([1.0, 1.0, 1.0, 1.0, 1.0, 1.0], U)
v_test = get_fe_basis(V)
println("running residual for testing: ", res(u_test, v_test))

```

And I am using this particular `solve()`, where I am giving only the nonlinear solver (FESolver) and the FEoperator. I would need a method to be able to define the initial values manually that are currently defaulted to zero in this method. I have tried `solve!(u_test, solver, op)`. But the aforementioned problem persists.

Any pointers to what I am missing out, to any documentation are welcome.

I am currently using Julia 1.10.10 and Gridap 0.19.17. I had to use julia 1.10 because I ran into some compatibility issues installing Gridap and ForwardDiff in the latest julia. I had to downgrade to 1.10. Kindly, let me know if you require any further information.

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<div class="post-metadata">

**Author:** ![marteaua](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/marteaua/32/214927_2.png) [@marteaua](https://discourse.julialang.org/u/marteaua)\
**Post date:** [June 17, 2026, 12:35pm UTC](https://discourse.julialang.org/t/gridap-use-for-finite-element-modelling-for-electrochemical-electrode-modelling/135377/2 "2026-06-17T12:35:11Z")

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Hi @algoking, can you provide a full MWE ?