Simulation Structure-Structure Interaction Five Boxes on Stair

In this article, we present a structure-structure interaction (SSI) simulation between falling boxes on stairs. All boxes behave like rigid bodies and this is referred to as a so-called rigid body simulation (RBS).
The boxes are modeled as rigid bodies and are free to move unconstrained when forces act on them. The individual rigid bodies can collide with each other and can change their direction of movement. The collisions between the rigid bodies and the walls are assumed to be completely inelastic. An inelastic collision, unlike an elastic collision, is a collision in which kinetic energy is not conserved due to the effect of internal friction. The NOGRID software can compute both collision regimes controlled by a plasticity coefficient.

CAD five steps groups in NOGRID's COMPASS

Figure 1: CAD groups created in NOGRID's COMPASS

SSI five steps setup within the NOGRID points CFD software's GUI

Figure 2: Setup the SSI Five Steps case

SSI five steps results in NOGRID points CFD software's GUI

Figure 3: Result view of the SSI Five Steps case within NOGRID points' GUI

Animation SSI five steps in NOGRID points CFD software

Figure 4: Animation SSI Five Boxes on Steps

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 bodies 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, causing changes in its translational and rotational velocities. In addition, collisions between rigid bodies may occur. Such collisions lead to sudden changes in the translational and rotational velocities of the bodies involved.

In this 3D example, several boxes fall and interact with each other (see Figures 1 - 4). The simulation is solved in a fully coupled manner using the Lagrangian method. Fully coupled means that the stresses within the bodies are simultaneously resolved in a large solution matrix. Alternatively, the Eulerian method can also be applied to solve this case.

As with any rigid body in the FSI coupling, the boxes in this simulation are assigned a weight and a mass moment of inertia. Each rigid body therefore responds to the forces acting on it. When several rigid bodies are involved, the motion of one body may also be influenced by collisions with others.

NOGRID points can be effectively used for the design and problem solving for all kinds of FSI processes. The software helps to understand the flow by computing and visualizing the mass, momentum, and motion of single or multiple rigid bodies. It provides transient values that can be used to analyze and evaluate the efficiency of the components and processes.

Capabilities of NOGRID points CFD software

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

fully 3D computation solving complete Navier-Stokes equations
easy and intuitive setup also for SSI (Structure-Structure Interaction) cases
freely 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

Whitepaper Nogrid points Technology

Why choose Nogrid?

NOGRID provides professional CFD software for the simulation of fluid flow, heat and mass transfer, and chemical reactions. Its efficient modelling workflow helps engineers analyse flow behaviour, evaluate designs and make informed decisions without creating a conventional volume mesh.

Faster model preparation

With NOGRID, only the geometry boundary needs to be meshed. The finite points inside the fluid domain are generated automatically according to user-defined settings, both at the start of the simulation and during the calculation.

This approach reduces preprocessing effort and makes it easier to prepare complex geometries and cavities for simulation.

Efficient CFD workflow

The modelling process follows four straightforward steps:

Build the geometry. Mesh the boundary. Define the simulation. Start the calculation.

NOGRID is designed to provide short computation times, including for applications involving complex cavities. Engineers can use the resulting data to examine flow distribution and other relevant flow characteristics.

Better insight into fluid-flow processes

CFD solves the fundamental equations governing fluid flow. NOGRID software enables engineers to predict and analyse the behaviour of fluids and related physical processes before or alongside physical testing.

The simulation results can support:

evaluation and comparison of design alternatives
optimisation of construction and operating parameters
improved planning reliability
reduction of development time and testing effort
faster progression from design to market or operation

Steps from geometry generation to simulation results

TRAINING

Our two-day training courses teach participants how to set up, run and evaluate simulations efficiently with NOGRID CFD software. The courses include practical guidance for handling different types of simulation cases.

For more details please refer to Training Courses →

Technical Support

Professional support is available from the beginning of your work with NOGRID. Our technical team assists users by telephone and email with software operation, case setup and simulation-related questions.

For more details please refer to Software Support →

Simulation Service

When internal time, expertise or resources are limited, NOGRID can support your project with individual numerical simulation services. Our engineers develop and evaluate CFD models based on the specific requirements of your application.