Material properties

Fluid properties

fluid_properties applies one material model to every fluid cell. Vanellus provides two built-in presets:

• air: humid air at sea level. Vanellus evaluates density from the simulation’s reference temperature and relative_humidity, and calculates thermal expansion as the inverse of the absolute reference temperature. Viscosity, specific heat capacity, and conductivity use values near 20 °C. Relative humidity is a fraction from 0 for dry air to 1 for saturated air, with a default of 0.3; Vanellus does not model moisture transport or condensation.
• water: fixed water properties near 20 °C.

For another fluid, custom requires five constant properties:

• density affects momentum and, with specific heat capacity, thermal energy transport.
• viscosity controls momentum diffusion through the fluid.
• specific_heat_capacity is the energy required to change the temperature of a unit mass.
• conductivity controls heat conduction through the fluid.
• thermal_expansion controls the buoyancy response when boussinesq is enabled.

Use a consistent set of custom properties at a representative operating temperature and pressure. Changing the fluid may also change the expected Reynolds number, boundary-layer resolution, pressure loss, and buoyancy response.

Solid properties

Only solid components using the conducting thermal model require bulk material properties. Insulating components and CTMs are excluded from the thermal domain.

A conducting solid requires:

• conductivity, either as one isotropic value or [kx, ky, kz], to control heat conduction;
• density; and
• specific_heat_capacity.

Density and specific heat capacity define the solid’s volumetric heat capacity for the energy solve. A conducting component can also provide optional power, which Vanellus distributes uniformly over its meshed volume.

See also

• Conducting and insulating domains explains where solid properties participate in the energy solve.
• Boussinesq buoyancy and reference temperature explains how fluid properties affect buoyancy.
• API reference lists the exact fluid and solid property fields.