Fraunhofer Institute for Industrial Mathematics ITWM
Fraunhofer Institute for Industrial Mathematics ITWM

Versatile Software Tool VISPI – Simulate Virtual Spinning

Our software tool VISPI simulates stationary, viscous filaments or fibers in flows and originated from a BMBF project of the same name. VISPI is used to model the dynamics of viscous and cross-section-averaged filaments. The software also considers the interactions of the filaments on the flow – both the dynamics and the energy between the filaments and the flow.

Our software tool is used in a wide range of application and it is of particular interest to companies in the construction of textile machines and for the production of technical textiles. This is because it is only through our built-in feedback of the filaments to the flow that VISPI makes it possible to simulate realistic results for industrial applications.

Industrial Applications: Design and Optimize with VISPI

VISPI is already successfully being used by our industrial partners for the construction of textile machines. They use the software to design the geometry of their machines and determine the optimum arrangement of spinnerets in the spinning package.

With VISPI we optimize:

  • BCF processes (Bulk Continuous Filament)
  • Spunbond processes (viscous drafting)
  • Rotational spinning processes (e.g. for the production of glass wool)

Companies use our software VISPI to optimize the geometry of their line, especially in order to identify turbulence and avoid dead zones so that filaments fluctuate as little as possible in the flow. Another application VISPI is to identify the ideal process parameters to improve product quality while saving energy and material costs.

VISPI also supports the optimal design of spinneret positions to ensure uniform cooling of all filaments, and, therefore, to produce filaments of the same quality.

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 flow through the filament bundle. The blowing speed is varied from 0.01 m/s to 2 m/s and the other parameters are fixed. For low velocities, the air is entrained vertically downward through the filaments. At high blowing velocities, the air flows horizontally through the bundle. This cools the bundle faster and more homogeneously.

Influence of the Blowing Speed on the Flow Through the Filament Bundle.

Different Drafting of the Various Filaments Depending on the Hole Position in the Spin Pack

Video Matlab: Velocities of All 200 Polymer Filaments Along the Spinning Length

In this video we see the different stretching of different filaments depending on the hole position in the spin pack. The filaments close to the blowing surface are cooled faster and, thus, are stretched faster. The rear filaments in the bundle, on the other hand, are cooled more slowly and, therefore, can be stretched longer. All filaments are wound on the same godet, so although the final speed and diameter are the same, the cooling history is different. These are later reflected in the final product. This is because the different cooling histories have an influence on brittleness, post-drawing, rice strength, dyeability, crystallization and other characteristics.

Further Technical Information about the Software

  • VISPI is platform independent and can be used under Windows or Linux.
  • ANSYS FLUENT and SU2 are available for coupling with the flow.
  • The specification of the boundary conditions of SU2 is done directly in VISPI.
  • Some typical polymers are already integrated in the database of VISPI.
  • The visualization can be done directly in VISPI. However, it is also possible to export data in CSV or in EnSight Gold Case format.

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