Short Fiber Orientation Model Reference

The Short Fiber Orientation model describes the flow properties of short fibers suspended in a viscous fluid, including their change in mean orientation in response to the fluid flow. This model is supported for both single and multiphase flows.


Theory	See Short Fiber Suspensions.
Provided By	[physics continuum] > Models > Optional Models
Example Node Paths	Continua > Physics 1 > Models > Short Fiber Orientation Continua > Physics 1 > Models > Multiphase > Eulerian Phases > Phase 1 > Models > Short Fiber Orientation
Requires	Material: Liquid Flow: Viscous Flow Viscous Regime: Laminar
Properties	Key properties are: Fiber Aspect Ratio, Volume Fraction, Fiber-Fiber Interaction Model. See Short Fiber Orientation Model Properties.
Activates	Initial Conditions	`FiberOrientationTensorProfile`. See Short Fiber Orientation Model Initial Conditions.
	Boundary Inputs	See Short Fiber Orientation Model Boundary Settings.
	Monitors	OrientationTensor
	Field Functions	Orientation Tensor Fiber Stress Tensor See Viscous Flow Field Functions Reference.

The short fibers are modeled as spheroidal particles with an aspect ratio between 5 and 30.

Short Fiber Orientation Model Properties

Volume Fraction: $ϕ$ in Fiber Suspension Rheology, the fraction of the phase volume occupied by fibers.
Fiber Aspect Ratio: $r$ in Fiber Suspension Rheology, the ratio of length to width for the average fiber. The default is 20.
Slip Coefficient: $α$ in Eqn. (751), a value controlling the delay in orienting fibers to the steady-state value in the transient simulation. $0 < α \leq 1$ . The default is 1. When $α = 1$ , there is no delay.
Diffusion: The value of a numerical diffusion term introduced to enhance numerical stabilization. The default is 0.1. High values for this term assist convergence, but values higher than the default can result in lower accuracy.
Fiber-Fiber Interaction Model: The model that accounts for hydrodynamic interactions between fibers, either Phan-Thien Eqn. (753) or Bay Eqn. (752). The default is Bay.
SUPG: The value for the Streamline-Upwind-Petrov-Galerkin advection stabilization term. The default is 1.0.

Short Fiber Orientation Model Initial Conditions

FiberOrientationTensorProfile: The profile used for the tensor describing the initial mean orientation of fibers in the viscous fluid. Selection generally matches the format of the input data and depends on the processing condition. For example, if the inlet is at the beginning of the processing line, then random orientation suits the situation, but if some region in the downstream is used as the inlet, then the profile can be set to reflect conditions that affected the orientation in the course of the flow. See Tensor Quantities.

Short Fiber Orientation Model Boundary Settings

Mass Flow Inlet, Velocity Inlet

Fiber Orientation Option: When set to Fully Developed, treats the fibers as having a specific average orientation in the viscous fluid, calculated from fully developed values of the field variables such as pressure and velocity. The default is Random, in which orientation is arbitrary so that the diagonal cells of the orientation tensor are set to 1/3.