Viscous Flow Field Function Reference

The following primitive field functions become available with the activation of viscous flow models. The models required are noted in each entry.

ActiveForce: The total hydrodynamic force $f$ that a fluid exerts on a wall boundary. $f = n_{Γ} \cdot (- p I + T)$ , where $n_{Γ}$ is the unit normal vector on boundary $Γ$ , $p$ is pressure, and $T$ is the stress tensor. Active Force is calculated as a nodal vector of force. Only the sum of the vertex values is conservative. Any re-distribution of the sum back to element faces or cell values using the data mapper or the non-smooth representation is not conservative. (Viscous Flow)
Boundary Displacement: The displacement of a free surface or exterior interface, given to the morphing function for mesh adaptation. (Free Surface)
Conformation Tensor: The tensor $C$ used in the square-root conformal form to define the stress tensor $T = G (C - I)$ in Eqn. (710). The conformation tensor is defined for each individual mode and is available whether or not the square-root conformal mode is activated.
Extra Stress n: The terms Extra Stress 1, Extra Stress 2, ... that sum to $T^{p}$ in Eqn. (706). There is a term for each viscoelastic mode used. (Viscoelastic)
Fiber Stress Tensor1: The contribution of the short fibers to the total hydrodynamic stress of a suspension of short fibers. Corresponds to $T_{f i b e r}$ in Eqn. (754). (Fiber-Flow Interaction)
Filled: The fraction of volume in a region occupied by the viscous flow, expressed as a value between 0 and 1. (Partial Fill)
Flow Type Parameter: Parameter $ξ$ , used to indicate the type of flow field: shear, extension, or solid body rotation.
$ξ = \frac{| D | - | Ω |}{| D | + | Ω |}$
$D$ is the deformation or strain rate tensor and $Ω$ is the vorticity tensor. $ξ$ = –1 for pure rotation, 0 for pure shear, and 1 for pure extension. See Lee et al. [186].
Grid Flux: The rate at which a face sweeps out volume due to grid motion. $G_{f} = v_{g} \cdot a_{f}$ , where $v_{g}$ is the grid velocity and $a_{f}$ is the face area. (Free Surface)
Morpher Displacement: Vector value of the distance by which the morpher has moved the mesh vertices (not face centers) in the current time-step. As this field is a vector field function, you can plot the x-, y-, z- components, and magnitude. (Free Surface)
Orientation Tensor: Tensor $a_{2}$ in Eqn. (749) describing the mean orientation of the short fibers suspended in a viscous flow. (Short Fiber Orientation)
Pressure: The pressure of the viscous flow $p$ which is a factor in the stress tensor $σ$ in Eqn. (655). (Viscous Flow)
Rate of Deformation: The rate of deformation tensor $D$ in Eqn. (695). (Viscoelastic)
SavedCoord: This field contains the coordinates before the morphing. (Free Surface)
Shear Rate: Flow shear rate $\dot{γ}$ in Eqn. (701). (Viscous Flow)
Specific Heat: The specific heat of the viscous fluid. (Viscous Energy)
Temperature: The temperature of the viscous fluid. (Viscous Energy)
Thermal Conductivity: The thermal conductivity of the viscous fluid. (Viscous Energy)
Total Viscosity: The sum of the solvent viscosity $μ_{s}$ in Eqn. (707) and the ViscoelasticEquivalentViscosity (see below). Use TotalViscosity for shear driven flows or elongational flows where there are non-zero shear strain rates. Do not use it in flows with free surfaces or axes of symmetry. In complex flows where the shear strain rates drop to very small values, TotalViscosity becomes very high and can result in singularities. (Viscoelastic)
Velocity: The velocity of the viscous flow. (Viscous Flow)
Viscoelastic Equivalent Viscosity: The ratio $\frac{{I I}_{T}}{{I I}_{D}} = \frac{{(t r [T])}^{2} - t r (T^{2})}{{(t r [D])}^{2} - t r (D^{2})}$ of the second invariants of the stress tensor $T$ and the rate of deformation tensor $D$ , providing an estimate of the shear resistance of the viscoelastic material with respect to the local shear rate in the system. See Eqn. (708) and Eqn. (709). (Viscoelastic)