Simulation Glass Mixing and Stirring

Figure 1: Glass striae can disappear by diffusion, chemical reaction or by mechanical stretching

Figure 2: Animation glass mixing over many mixer periods

The simulation of glass mixing and stirring in the glass industry can perfectly be performed with the simulation software NOGRID pointsThe function of stirring (mixing) is to create uniform, homogeneous glass (homogenization in glass industry). Stirring equipment operates at high temperatures and under high mechanical stresses, so stirring devices have to be robust and often involve large amounts 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.

Receive optimal stirrer design and best product quality with simulation

The stirrer application in NOGRID points CFD software analyzes continuously, batches operating stirrer systems and finds the optimal stirrer design to reach the best product (here: glass) quality. We found out that the best measure of quality for a certain stirrer device is the deformation of a body, which flows through the stirrer system. We integrated the local deformation of a body over the complete path through the mixing cell. The amount of the deformation indicates how this body was stretched. A high deformation means that striae, which pass the stirrer, are stretched to a very long body and as a result disappear and don't influence the product quality anymore.

NOGRID unites abilities to handle free surface flow and moving parts in the domain and allows the simulation of any conceivable geometry and operation modes such as

  • computation is in full 3D solving complete Navier-Stokes-Equations
  • easy and intuitive setup
  • free 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 

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.

Nogrid's strengths

Particular strengths of NOGRID's fluid flow CFD software are the rapid preprocessing (no fluid grid needs to be generated, only the boundary mesh, inner finite points are generated automatically depending on User setting initially and during computation), and the outstandingly short computation time even for complicated cavities.
As you can see in the image below, the boundary of the geometry still requires a mesh to allow the interior finite points to detect the boundary. The boundary must therefore be meshed and the finite points inside are automatically generated during the simulation controlled by User specifications.
Easy Modelling

Easy and fast modelling: Build geometry, mesh boundary, setup the case and start computation

What is CFD from NOGRID?


CFD solves the fundamental equations that define the fluid flow process. With CFD software from NOGRID every engineer makes better decisions by predicting, analyzing and controlling fluid flow, heat and mass transfer or chemical reaction. By using NOGRID software for flow modeling you receive information on essential flow characteristics as for example flow distribution. Using it additional to testing and experimentation NOGRID software helps to improve the evaluation of your design – resulting in better construction and operation parameters, increasing planning security and money savings due to faster time to the marketplace for your product or process.




With NOGRID, you choose professional CFD software and services – our aim is helping you to be successful. When you decide to work with NOGRID you choose close cooperation with a dynamic, flat hierarchies-organization. Short information channels result in quick and accurate professional support and service. Our team consists of highly qualified employees, who are experts in fields such as numerical simulation or computational fluid dynamics. Based on our know-how, we are pleased to offer the following services, responding to your individual requirements:




In our two-days training courses you will learn, how to use NOGRID CFD software efficiently. Our technical support team will teach you how to handle and solve different cases.

For more details please refer to Training Courses →


Technical Support


We offer full professional support from the minute you start using our software, by telephone or by email. Contact us, when ever needed.

For more details please refer to Software Support




Lack of time or resources and other constraints often make outsourcing an attractive solution. We help you with your flow modeling needs. Based on our engineering expertise in this field we offer individual numerical simulation services matching the unique needs of your organization.

For more details please refer to Simulation Services →


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Simulation Software from Nogrid

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