# Comsol Multiphysics

Many problems in modern science or engineering are of multiphysics character. This means that they are governed by more than one type of physical problem, each represented by a set of partial differential equations. At Fire Research we can solve complex multiphysics problems to help product development or risk assessment for our customers.

COMSOL Multiphysics is a simulation software using finite element analysis to solve various problems in engineering, physics and chemistry. The uniqueness of COMSOL Multiphysics, over other FEA software packages is its ability to solve coupled phenomena. These are phenomena for which the solution of each individual physical problem cannot be obtained independently of the others. Examples of these include combined fluid dynamics/chemical engineering or heat transfer/mechanical engineering problems.

In order to achieve high quality models we can offer detailed measurements of the material properties to be used in the simulations, e.g. thermal and mechanical properties, chemical species analysis and combustion behaviour.

Heat transfer calculations

In many engineering applications it is of high interest to estimate the response of a product at elevated temperatures. In COMSOL Multiphysics the temperature in a product can be determined by using the heat transfer module where realistic boundary conditions are easily implemented.

A 2D model of the heat transferred from a heating pad into a fabric on top of a wooden board.

Coupled problem – self heating of wood pellets

An example of a coupled multiphysics problem is the self-heating in bulk storage of wood pellets. The wood pellets produce heat which leads to a temperature increase controlled by the heat diffusion equation. However, the amount of energy produced is controlled by the rate of chemical reactions, which is solved using Arrhenius type chemical engineering. The availability of oxygen for the reaction is controlled both by the mass diffusion laws as well as the Navier-Stokes equations of oxygen and other gases flowing in the volume. These flows are, in addition, controlled by the temperature distribution in the gas and solid state.

Example of air velocity field (arrows) and magnitude (colours) of a 1 m3 bulk pellets storage.

Mechanical behavior of fire exposes beams

Full 3D simulations of fire exposed steel beams can identify weaknesses and failure times of constructions. The COMSOL Multiphysics graphical interface offers many degrees of freedom in applying boundary conditions and varying the thermal properties of materials over time, temperature or spatial coordinates.

Stress and deflection of a fire exposed steel beam. The simulation only shows one half of the symmetric problem.

### Related Information

#### Contact Persons

Johan Anderson

Phone: +46 10 516 59 26

RISE Research Institutes of Sweden, Phone 010-516 50 00, E-mail info@ri.se

The RISE institutes SP, Innventia and Swedish ICT have merged in order to become a stronger research and innovation partner for businesses and society.