Simulation 3D Fluid-Structure Interaction of Rigid Bodies in a Pipe Flow with a Water Filter

In this case study we show the 3D simulation of a fluid-structure interaction of rigid bodies that are in a pipe flow and can flow through a water filter or through a grid if they are small enough.

Rigid Body Simulation (RBS) is the simulation of the transient movement of rigid bodies. Rigid body mechanics is about physical bodies that are not deformable. During the simulation, the rigid body can move, but the shape or structure remains unchanged. Various types of forces can act on the rigid body: gravity, magnetic forces, frictional forces, etc. These forces accelerate the rigid body and the translational and rotational speeds change. In addition, there can be collisions between the rigid bodies. Collisions suddenly change the translational and rotational speeds of the bodies involved.

Figure 1: CAD groups created in NOGRID's COMPASS

Figure 2: Setup the FSI 3D Water Filter/Lattice Case

Figure 3: Result view of the FSI 3D Water Filter case within NOGRID points' GUI

Figure 4: Animation of the 3D Water Filter or Lattice in Pipe

The fluid-rigid body interaction simulated in this study is solved fully coupled with the Lagrangian method. Fully coupled means that the motion (translation and rotation) of the rigid bodies and the fluid variables for velocity and pressure are solved simultaneously in a large solution matrix (no need to iterate back and forth between the solution variables).
In engineering, Fluid-Structure-Interaction (FSI) refers to the consideration of the mutual influence of moving, not necessarily rigid bodies and a flow. The interaction between fluid flow and bodies occurs in many physical applications. Flow around a free rigid body causes both displacement and rotation of that body due to the forces and torques exerted on the body by the fluid. Conversely, the movement of the body causes changes in the flow. So if the flow also changes, there is a so-called real, two-sided fluid-rigid-body coupling. If several rigid bodies are involved, the movement of one body can of course also be influenced by collisions with other bodies.

A total of 12 spherical rigid bodies are considered in this case study, each rigid body having its own weight and moment of inertia. This means that every body behaves individually according to the forces that act on it from the fluid. Conversely, of course, the flow is also influenced by the rigid bodies. You can see, for example, that some spheres cannot pass through the filter because of their size and block the corresponding filter passage.

This model can act as basis for more complex structures and will give you a better understanding of the fluid structure coupling and helps to improve your design regarding efficiency and costs.

NOGRID points can perfectly be used for designing and problem solving for all kinds of FSI processes. The body movement and the flow pattern can be predicted. NOGRID points helps to understand the flow by visualization of the mass, momentum and rigid body movements. You receive transient quantities which you can use to analyze and evaluate the FSI process efficiency.

NOGRID unites abilities to handle FSI problems 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 also for FSI (Fluid-Structure-Interaction) cases
  • free definable material properties by equations or curves
  • evaluation of chemical reactions and corresponding heat source terms
  • open or closed domains including inflow and outflow areas (non-batch mode)
  • moving of parts 

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.

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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.

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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.

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