CFD-Based Methodology for Float Design Evaluation in Filling Systems

Abstract

This thesis presents a simulation-driven methodology for evaluating float design in aseptic filling machines, with the objective of reducing surface instabilities and air entrainment that contribute to splashing during the filling of viscous food products. The study was conducted in collaboration with Tetra Pak and focuses on understanding how float geometry, particularly mass and radius, affects liquid surface behaviour in two machine configuration formats: TCA65C and TCA50.

Computational Fluid Dynamics (CFD) models were developed in Simcenter STAR-CCM+ using the Volume of Fluid (VOF) method to capture free-surface dynamics. Three model types, 2D axisymmetric, pseudo-3D, and full 3D, were compared. Experimental validation was performed using a custom test rig and a proxy non-Newtonian fluid. The 3D model best captured key behaviours such as float motion and surface depression, while the 2D model provided useful trend predictions with significantly lower computational cost.

A parameter study revealed that both float mass and radius influence surface depression. In the TCA65C case, float masses above 110 g were necessary to prevent air entrainment, while in TCA50, 100 g was sufficient. Float radius also had a large effect; smaller radii were generally more effective in maintaining surface stability. The results also showed that the 3D model is essential for accurately capturing threshold behaviours near critical mass-radius combinations. Float radius had a strong effect on surface behaviour in the TCA65C case, where the liquid had a significantly higher viscosity than the TCA50 format. For TCA50, intermediate mass/radius values had minimal impact on surface stability, while extremes showed significant changes.

The findings support the use of CFD as a tool for guiding float design optimization. Increased float mass and appropriate radius selection were shown to mitigate the risk of splashing and improve surface stability across different product viscosities. The developed modelling approach provides a robust foundation for future design iterations and can be further extended by incorporating fluid-structure interaction, six-degree-of-freedom float motion, and higher-fidelity turbulence modelling.

Popular Abstract

What causes food to splash inside packaging machines? This thesis explores how the shape and weight of a tiny floating part can reduce waste, cut cleaning time, and keep the process flowing smoothly.

When filling packages with thick food products like soups, creams, or condensed milk, even a small splash can cause serious trouble. A droplet landing in the wrong place can lead to hygiene issues, wasted product, or a bad seal, which in turn means cleaning, stoppages, and lost productivity. At the heart of this is a small floating object used in Tetra Pak’s filling machines. This float helps control the liquid level inside a tube, but when the machine is running and the float starts to move, it can disturb the surface and cause splashing.

In this thesis, I used computer simulations, a method known as Computational Fluid Dynamics (CFD), to understand how different float designs behave under real-world conditions. I created virtual models of the
filling process in two machine types and tested how changes in the float’s mass or diameter influenced the liquid surface. These simulations were validated with physical experiments using a specially designed test rig and a liquid that mimicked the thick, non-Newtonian flow of real food products.

The results showed that a heavier float helps to let the float sit lower in the liquid, preventing it from drawing in air or rebounding sharply, two effects that can lead to splashing. Interestingly, the shape of the float also mattered: smaller radii led to more stable behaviour, likely because they allowed the float to sit deeper in the liquid and reduced sharp flow disturbances.

Another discovery was that 2D simulations, while useful for spotting general trends, could not accurately predict when the float would start to pull air underneath it. For that, a full 3D model was necessary, even though it required more computational time. Still, the 3D model revealed clear “tipping points,” where just a 10-gram increase in float mass could shift the behaviour from unstable to potentially splash-free.

These findings are useful for engineers working to improve filling lines for viscous food products. They show that with minor adjustments to float design, without changing the rest of the machine, it’s possible to reduce cleaning time, avoid waste, and ensure better product quality. Perhaps most importantly, this work demonstrates how digital simulation tools can play a powerful role in improving everyday industrial processes long before a prototype hits the factory floor.

A curious insight? In some cases, changing the float mass by just 10 grams could make the difference between a clean fill and a messy splash, a small tweak with a big impact

• author: Persson, Max
• supervisor: Fatehi Hesameddin
• organization: Department of Energy Sciences
• course: MVKM01 20251
• year: 2025
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• report number: ISRN: LUTMDN/TMPH-25/5638-SE
• ISSN: 0282-1990
• language: English
• id: 9204823
• date added to LUP: 2025-06-24 08:35:30
• date last changed: 2025-06-24 08:35:30