# Simulations and calculations

# The offer

- Structural mechanics calculations (FEM), flow calculations (CFD), kinematic and dynamic simulations of mechanisms
- Control systems modelling
- Hybrid modelling of physical phenomena and processes
- Techniques of numerical optimisation of process parameters and design variables

One can change conditions in which the phenomenon takes place and study influence of ambience geometry on it. Computer simulations are a powerful tool which has found different applications in science. They are also invaluable in the industry – they allow a significant decrease of project design and implementation costs by shortening design time and reduction in the number of necessary prototypes.

This particular concept, called „virtual prototyping” is implemented in SKA Polska for our customers. It is used ever since the earliest design stage – testing the principle behind mechanism operation, a device or a measurement station. Of course, nothing will replace checking the principle of operation „live”, however, simulations allow us to limit the number of performed experiments and configurations to the ones which have the chance to be successful. Also, during other stags of design, everywhere where something needs to be checked physically (for example, select a better framework variation), it may be done virtually. Only then, if it is necessary, it may be confirmed using a physical model.

The problems solved by us may be divided into three most important categories:

## Structural mechanics

solved using FEM type methods (Finite Elements Method), which enable determination of stress and deformation states in solids subjected to loads. These methods are excellent, for example, for determination of resistance of key elements of the designed system.

## Fluid mechanics

solved using CFD (Computational Fluid Dynamics) methods, which enable determination of fluid or gas flow in a given system: velocity field, pressure, temperature on the basis of defined starting conditions and boundary conditions. Depending on the complexity of the task we are modelling, we may take into account things like: viscosity, compressibility, chemical reactions or multiphase flows.

## Rigid body kinematics and dynamics (mechanism simulations)

By solving the constraint equations or motion equations for the considered system of bodies one can study mechanisms as a whole: define trajectories, velocities and motion scopes for particular elements and forces acting on them during motion including control. All of this in order to evaluate how well the system meets design assumptions and how well it will work.

In case of more complicated and demanding issues, we use multiphisics methods to test how different phenomena taking place within the same system are influencing one another – e.g. how does air flow change in a duct undergoing deformations.

We also employ different methods of numerical optimisation (e.g.: gradient based algorithms, genetic algorithms), so after running a number of simulations we may find such system configuration which meets the requirements in the best way. An example of optimisation use may be the problem of finding optimal geometry for the mechanism of an articulated quadrangle which would realize the desired trajectory or finding valve control which meets the desired shape of flow rate.

The most important aspect of computer modelling (simulations) is adequate model simplification in comparison to reality. Too detailed description of a system may result in a system impossible to calculate within a reasonable timeframe. On the other hand, simplifications going too far may lead to involuntary omission of elements which in reality could have been important.. Experience of our engineers allows creation of optimal, virtual representation of reality.