Fraunhofer Institute for Industrial Mathematics ITWM
Fraunhofer Institute for Industrial Mathematics ITWM
Vielseitiges Softwaretool VISPI
© iStockphoto / Fraunhofer ITWM
Vielseitiges Softwaretool VISPI – Virtuelles Spinnen simulieren: Simulation virtueller Spinnprozesse zur Optimierung von Textilmaschinen und technischen Textilien

© iStockphoto / Fraunhofer ITWM

Versatile Software Tool VISPI – Simulate Virtual Spinning

Simulation of Virtual Spinning Processes for the Optimization of Textile Machinery and Technical Textiles

Our software tool VISPI simulates stationary, viscous filaments and fibers in airflow and originates from a BMBF project of the same name. VISPI models the dynamics of viscous, cross-section-averaged filaments and accounts for the interaction between filaments and airflow – including both dynamic effects and energy exchange.

VISPI is used across a wide range of applications. It is particularly relevant for companies specializing in textile machinery engineering and the production of technical textiles. By incorporating the feedback of filaments on the airflow, VISPI enables realistic simulation results under industrial conditions.

Revolutionize Your Spinning Process – with VISPI and SPOT!

Less waste. Less energy. Better product quality.

We present VISPI and SPOT – our innovative simulation tools for the virtual optimization of spinning processes.

With VISPI, we optimize the following processes:

  • BCF processes (Bulk Continuous Filament)
  • PDY and POY (Partially Drawn Yarn / Pre-Oriented Yarn)
  • Spunbond processes
  • Rotational spinning processes – e.g. for glass wool production
  • Dry Spinning & Wet Spinning
  • Air Gap Spinning – e.g. lyocell process
  • Electrospinning

What makes VISPI unique?

VISPI simulates realistic industrial conditions by modeling the full interaction between filaments and airflow. Turbulences and dead zones are identified early and systematically eliminated. Spinneret arrangements are optimally designed to ensure uniform cooling and consistent fiber quality.

The following example illustrates a typical spinning process with coupled airflow and fiber dynamics. The simulation shows how the airflow cools the fiber bundle while the fibers simultaneously heat the surrounding air. From the quench unit, a perpendicular airflow of approximately 1 m/s enters the fiber bundle; further downstream, the fibers accelerate the air in the draw-down direction.

VISPI with graphical user interface shows speed curves of filaments along the filament length
© Fraunhofer ITWM
VISPI with graphical user interface shows speed curves of filaments along the filament length.

Video Fluent: Air Velocity Curve for Different Blowing Speeds

The video shows the influence of the blowing speed on the through flow of the filament bundle. The blowing speed is varied from 0.5 m/s to 2 m/s while all other parameters are kept constant. At low blowing velocities, the air is entrained vertically downward by the filaments. At high blowing velocities, the bundle is cross-flowed in the horizontal direction. In this case, the bundle is cooled faster and more homogeneously.

Influence of the blowing speed on the flow through the filament bundle.

Best Practice: BCF Carpet Yarn Spinning – Van de Wiele
In BCF carpet yarn spinning at Van de Wiele, filaments in a circular spinneret are arranged in multiple rows. The front filament rows shield the rear rows from the cooling air. This leads to row-dependent temperature and flow profiles that directly affect the mechanical properties of the fibers.

VISPI-Simulation eines BCF-Prozesses (Van de Wiele): Temperaturverteilungen für mehrere Filamentreihen. Die vorderen Reihen werden stärker gekühlt als die abgeschirmten hinteren Reihen.
© Fraunhofer ITWM
VISPI-Simulation eines BCF-Prozesses (Van de Wiele): Temperaturverteilungen für mehrere Filamentreihen. Die vorderen Reihen werden stärker gekühlt als die abgeschirmten hinteren Reihen.
VISPI-Simulation eines BCF-Prozesses (Van de Wiele): Geschwindigkeitsverteilungen für mehrere Filamentreihen, was zu einer reihenabhängigen Ausdehnung führt und eine Optimierung des Lochmusters für eine gleichmäßigere Kühlung erforderlich macht.
© Fraunhofer ITWM
VISPI-Simulation eines BCF-Prozesses (Van de Wiele): Geschwindigkeitsverteilungen für mehrere Filamentreihen, was zu einer reihenabhängigen Ausdehnung führt und eine Optimierung des Lochmusters für eine gleichmäßigere Kühlung erforderlich macht.

Purely experimental access to the interior of such dense bundles is very limited. VISPI, by contrast, provides comprehensive information on the thermal and kinematic evolution of each individual filament. The front rows are directly exposed to the incoming airflow and therefore undergo a different cooling history than the partially shielded rear rows – differences that require targeted geometric optimization of the cooling configuration.

Best Practice: Hole Pattern Optimization with SPOT

Non-uniform cooling within the fiber bundle can be systematically addressed with SPOT, our in-house tool for spinneret design optimization. SPOT simulates the airflow around the fibers in detail and applies mathematical optimization methods to improve their arrangement within the spinneret. This ensures that all filaments achieve as uniform properties as possible.

The optimized fiber arrangement creates flow lanes through which the cooling air can reach even the rear filaments that are typically insufficiently cooled. The result is a clear and easy-to-implement recommendation: the spinneret holes only need to be drilled at the optimized positions. Despite the minimal hardware modification, the impact on product quality is significant.

Figure 1: Optimized Arrangement of Hole Positions
© Fraunhofer ITWM
An arrangement of hole positions before optimization.
Figure 2: Optimized Arrangement of Hole Positions
© Fraunhofer ITWM
An optimized arrangement of the hole positions improves the flow and thus significantly improves the cooling of the filaments.

Best Practice: Spinning-Duct Geometry Optimization

Dense filament bundles strongly interact with both the surrounding airflow and the local housing geometry. VISPI simulations of the coupled fiber–air dynamics show how certain flow channels promote dead zones and increased turbulence in the filament region. This leads to pronounced filament motion, commonly referred to »fiber dancing«.

By systematically adapting guiding elements and cross-sectional shapes, the duct geometry can be optimized such that turbulent fluctuations are significantly reduced and the filament bundle is stabilized.

An initial configuration with stronger turbulence and pronounced »fiber dancing«.
© Fraunhofer ITWM
An initial configuration with stronger turbulence and pronounced »fiber dancing«.
A geometrically optimized configuration with significantly reduced turbulent fluctuations and stabilized filament motion.
© Fraunhofer ITWM
A geometrically optimized configuration with significantly reduced turbulent fluctuations and stabilized filament motion.

Further Technical Information about the Software

  • VISPI is platform-independent and can be used under Windows or Linux.
  • For coupling with the flow, ANSYS FLUENT and SU2 are available.
  • The specification of boundary conditions for SU2 is carried out directly in VISPI.
  • Some typical polymers are already integrated in the VISPI database.
  • Visualization can be performed directly in VISPI. Data export in CSV or EnSight Gold Case format is also available.

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