What the Vanellus solver does
Vanellus is a steady-state finite-volume solver for fluid flow and conjugate heat transfer. It predicts the settled operating point produced by a fixed geometry, material set, and boundary conditions. It does not calculate how the system evolves through time.
Model summary
| Aspect | Vanellus representation |
|---|---|
| Flow | Steady-state, incompressible Navier–Stokes equations |
| Pressure–velocity coupling | SIMPLE algorithm |
| Turbulence | Laminar flow or steady-state RANS using the k–ω SST model |
| Heat transfer | Advection and conduction in the fluid, conduction in participating solids, and coupled temperatures and heat fluxes at their interfaces |
| Buoyancy | Optional Boussinesq coupling between temperature and momentum |
| Linear systems | BiCGSTAB, with equation-specific preconditioning |
The computational domain is divided into rectilinear finite-volume cells. Vanellus applies the conservation equations to those cells and couples fluid and solid regions where heat can cross an interface.
Steady-state solutions
Vanellus uses the SIMPLE algorithm to approach the steady-state solution iteratively. During each SIMPLE iteration, it updates the velocity and pressure fields, temperature, and, for a RANS case, the turbulence fields. It repeats this process until a convergence criterion or stopping limit is reached.
A SIMPLE iteration is a numerical correction, not a duration in seconds. Consequently:
iteration_info.csvrecords convergence history rather than a time history- an intermediate iteration is not the predicted state of the system during startup
- the final fields represent an equilibrium operating point, not the route taken to reach it
Laminar and RANS flow
With turbulence_model: "navier_stokes", Vanellus solves the flow without a turbulence model. With turbulence_model: "k_omega_sst", it solves Reynolds-averaged Navier–Stokes equations and models the effect of turbulence using the k–ω SST model.
RANS fields represent a steady, time-averaged flow. They can capture the engineering effect of turbulent mixing without resolving each instantaneous eddy. Selecting between these models changes the represented physics; it is not simply a numerical stability setting.
Temperature stability safeguard
After each energy-equation solve, Vanellus limits solved fluid and conducting-solid temperatures to within 500 K of the simulation’s reference temperature. The exported limits are therefore reference temperature - 500 °C and reference temperature + 500 °C.
This clipping prevents one unstable thermal update from immediately contaminating the remaining coupled equations. It is a numerical safeguard, not a physical boundary condition or material limit. A field that reaches either limit is not a valid result, even if the clipped value forms a stable-looking plateau.
Compact-thermal-model junction temperature is calculated separately from the resolved cell field, so the safeguard does not apply to that lumped value. Diagnose CTM behavior from its junction-temperature history.
Use Stabilize the energy solve when this safeguard appears in a result.
Convergence and physical validity
Vanellus solves the model you specify. Convergence of the residuals and monitors confirms that the numerical solution has met the requested tolerances. If the simulation has been correctly specified, this will typically align with the real-world physical system.
As the modeler, you are responsible for choosing geometry, material properties, boundary conditions, and physical models that represent your system and its operating conditions. Use sufficient mesh resolution to capture the features that matter, and assess your predictions through mesh-sensitivity studies and comparisons with measurements or reference results where available.
See also
- Turbulence inlet conditions and wall treatment explains Vanellus’s k–ω SST inputs and wall functions.
- Boussinesq buoyancy and reference temperature for temperature-driven flow.
- Residuals and linear-solver convergence for the two iterative convergence levels.
- How simulations stop for convergence criteria, limits, and external stops.