Fluid model

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Fluid model#

The Fluid model represents the primary medium for CFD simulations in Flow360. It integrates several components that together govern the fluid dynamics behavior, including the Navier-Stokes solver, turbulence modeling, transition effects, and initial conditions. The Fluid model is applied to volume entities within your simulation domain.

Note

The freestream state (density, temperature, and velocity) is specified in the Operating Condition section, not in the Fluid model. The Fluid model’s Material section describes the substance itself (viscosity model, thermodynamics, and Prandtl numbers for a gas, or density and viscosity for a liquid). This separation allows the same Fluid model configuration to be used with different conditions.

Major Components#

The Fluid model consists of seven primary components, each documented in detail in its own section:

  1. Navier-Stokes Solver: Controls the core flow equations that govern momentum, continuity, and energy in the fluid. This component determines how the simulation resolves velocity, pressure, and density fields.

  2. Turbulence Model: Handles the modeling of turbulent flow structures through various approaches such as Spalart-Allmaras or k-Omega SST. This significantly impacts flow separation prediction and overall solution accuracy.

  3. Transition Model: Determines how and when flow transitions from laminar to turbulent within the simulation, which is critical for correctly predicting aerodynamic performance, especially at moderate Reynolds numbers.

  4. Initial Condition: Defines the starting flow state for the simulation, which can significantly impact convergence rates and stability, especially for complex flows.

  5. Stopping Criteria: Allows automatic termination of the simulation when monitored output fields (forces, probe values, or surface probe data) reach specified tolerance thresholds, providing efficient convergence control.

  6. Gravity: Applies a gravitational body force to the fluid momentum and energy equations, enabling simulation of buoyancy-driven flows. Disabled by default.

  7. Material: Defines the physical properties of the simulated fluid: the viscosity model, thermally perfect gas species, and Prandtl numbers for a gas, or the density and viscosity for a liquid.

See also

Knowledge base: NavierStokesSolver and TurbulenceModelSolver.

For how to define custom stopping criteria, see the Run Control user guide.

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