Simulation Glass Mixing and Stirring

The simulation of glass mixing and stirring in the glass industry can perfectly be performed with our simulation software NOGRID points. This CFD software offers detailed insights into the homogenization process, allowing engineers to optimize stirrer designs and significantly enhance product quality. 

The purpose of stirring and mixing in the glass industry is to achieve uniform, homogeneous glass. Since stirring equipment operates under high temperatures and significant mechanical stress, the components must be highly durable and are often made from large quantities of platinum or platinum alloys. Although stirrers, stirrer bars, blenders, homogenizers, screw plungers and plunging stirrers currently used are generally effective in operation, reliable and with predictable lifetime, lower cost and improved operational efficiency are main targets for the future.

Simulation for optimal stirrer design and best product quality 

The stirrer application in NOGRID points CFD software analyzes continuously batch-operated stirrer systems,  helping to determine the optimal stirrer design for achieving the highest glass quality. Our research has shown that the most effective indicator of a stirrer's performance is the deformation of a body as it moves through the stirring system. To assess this, we integrated the local deformation of a body along the entire path through the mixing cell. The amount of the deformation indicates how much the body is  stretched. A greater deformation means that striae passing through the stirrer are stretched into a very long body and thus disappear and no longer impact the product quality.

Capabilities of NOGRID points CFD software

NOGRID points unites the capabilities to handle free surface flow and moving parts within the domain and allows the simulation of any conceivable geometry and operating mode, such as

• fully 3D computation solving the complete Navier-Stokes equations
• easy and intuitive setup
• freely definable material properties by equations or curves also for non-Newtonian fluids
• evaluation of chemical reactions and corresponding heat source terms
• open or closed domains including inflow and outflow areas (non-batch mode)
• moving of parts 

Whitepaper Nogrid points Technology

Stirrer systems can generate or remove glass defects

In the glass industry homogenization systems are used to improve the product quality. In practice it can be seen that, depending on the forming process, a stirrer system can both generate and remove glass defects. Looking at physical modeling of stirrer systems it can easily be shown, how particle tracers follow the flow and what happens, if the tracers run through the vicinity of the stirrer blades. The starting position of the tracers may vary, but iso-kinetic conditions must be applied. Supposing that density and viscosity of the tracers correspond to the fluid properties, physical modeling of stirrer systems shows a lot of effects, which help to understand the flow in stirrer systems.

By using simulation you get information about the glass mixing quality 

To obtain detailed information about the (glass) mixing quality of a certain stirrer system we use the mathematical simulation. By simulation we analyze particle tracers during their way through the mixing cell. Important simulation results are the length of the path, the dwell time and deformation of a mathematical volume. Especially the information about the stretching of a certain volume along the particle path indicates the quality of the mixing process.

However, the material properties of real striae could differ from that of the glass melt. To model this effect we developed a tool, which allows the computation of a volume with its own density and viscosity. This volume doesn't follow the streamlines of the fluid any longer but finds its own way through the stirrer system, depending on mechanical forces and wall distance.