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Vanadis 3D v2026.3.0 - Nonlinear Reaction P(S) and Time-Dependent Source Q(t)

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@marek-ac marek-ac released this 06 Sep 08:20
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v2026.3.0
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Vanadis 3D v2026.3.0 — Nonlinear Reaction P(S) and Time-Dependent Source Q(t)

This release extends Vanadis 3D with a nonlinear concentration-dependent reaction formulation and generalized time-dependent emission sources.

New features

  • Added support for a nonlinear concentration-dependent reaction/decay coefficient P(S).
  • The nonlinear problem is solved using Picard iteration within each time step.
  • Added generalized time-dependent source handling Q(t).
  • Source strength is evaluated at both the previous and current time levels, allowing constant, switched, pulsed and other time-varying emission profiles.
  • The existing implicit time-integration formulation has been extended consistently to include the nonlinear reaction term and time-dependent source contribution.

Numerical implementation

The new nonlinear formulation preserves the existing Vanadis architecture:

  • HEX8 finite elements,
  • Directional Residual stabilization,
  • Element-by-Element matrix operations,
  • OpenMP CPU assembly,
  • CPU or CUDA DBCG linear solver,
  • diagonal preconditioning,
  • atomic and graph-coloring CUDA Element-by-Element variants.

The nonlinear coefficient is updated locally during the Picard iterations, while the CUDA solver continues to operate on the resulting linearized Element-by-Element system.

Verification

Regression testing showed that, when the concentration-dependent part of the reaction term is disabled, the new implementation reproduces the previous linear Vanadis results exactly for the corresponding test case.

The nonlinear test case converged successfully at every time step, and OpenMP runs using different thread counts produced equivalent results apart from normal floating-point round-off.

Notes

The current test configuration uses a constant source active from the initial time t=0, while the source-term implementation itself supports general time-dependent emission profiles.

This release represents the next development stage after v2026.2.1, which remains the reference version associated with the CMAS 2026 presentation.

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