Starting point of the development of the software tool FIDYST was the simulation of nonwoven and spinning processes like spunbond or meltblown. By further developments FIDYST became more and more flexible. FIDYST is developed to simulate the dynamics of line shaped objects, e.g.

•     fibers (e.g. cotton or glass wool),
•     filaments (in spinning processes),
•     yarns and also
•     cables.

In the following text these objects are called fibers for simplification.

Modeling of the Fiber Dynamics

The dynamics of the fibers are described by Newtonian equation of motion with internal and external forces. With the internal forces the

•     elastic,
•     viscous or
•     viscoelastic

properties of the fibers are modeled. The external forces describe the

•  
•     air drag of the (turbulent) air flow,
•     contacts of fibers with (moving) machin parts (e.g. belt,...),
•     contacts between fibers,
•     gravity or
•     electrostatic forces.

In some processes the influence of the turbulence onto the fiber dominates the process. Therefor, a stochastic air drag model was developed which adequately accounts for the characteristic turbulent scales.

Simulation of the Air Flow

The fluid dynamics simulations are done by commercial CFD tools, such as ANSYS-FLUENT or ANSYS-CFX. The fluid data are input data for FIDYST. If a full coupling of the fiber dynamics and the fluid dynamics is necessary, the simulation tools for fluid and fibers are coupled iteratively. The fibers are integrated into the fluid dynamics by source terms for mass, momentum and energy.

Flexibility of FIDYST

FIDYST is developed as a general simulation tool for slender bodies. Thus FIDYST is not restricted to a special application. To apply FIDYST within a new complex industrial process FIDYST can be adapted and extended to the process.

Examples for Applications

spunbond, meltblown, BCF, staple fibers, electro spinning, processing of natural fibers, glass wool production, air weaving,...

https://www.itwm.fraunhofer.de/FIDYST_EN