HTC elder problem error

Hi everyone,
I was testing the non-isothermal component transport feature. I tried to build a thermohaline Elder problem based on the OGS HTC test problem 2D_single_fracture_HTC and the saline Elder problem avaible online. In the 2D_single_fracture_HTC test problem variable density depending on temperature or solute concentration was not tested. When running it with version 6.5.3. it get the following error:

error: Failed during Eigen linear solve
info: [time] Linear solver took 0.0236348 s.
error: Picard: The linear solver failed in the solve() step.
info: [time] Solving process #1 (named as not given) took 0.100109 s in time step #1 coupling iteration #0.
warning: The nonlinear solver failed in time step #1 at t = 2629.8 s for process not given.
warning: The coupling iterations reaches its maximum number in time step #1 at t = 2629.8 s
info: [time] Time step #1 took 0.637689 s.
warning: Time step will be rejected due to nonlinear solver divergence.
critical: C:\Users\gitlab\gitlab_b\bg4d5s_d\1\ogs\ogs\ProcessLib\TimeLoop.cpp:398 ProcessLib::TimeLoop::computeTimeStepping()
error: The new step size of 2629.8000000000002 is the same as that of the previous rejected time step.

I tried to fix this using adaptive time stepping and loosening the convergence tolerances. It appears that the nonlinear concentration dependent density is the problem, even when the slope is set to 0.
I would be glad about any help. Thank you
Jonas
elderhtc.zip (190.0 KB)

Hi Jonas,

please check the merge request: https://gitlab.opengeosys.org/ogs/ogs/-/merge_requests/5128
to see if this updates work for your case. Please notice that it would be better to use the numerical stabilization: FluxCorrectedTransport

Best regards,
Chaofan