In order to achieve multidisciplinary analysis, not only must software be able to accurately analyze the effects of multiple physics problems, but the implementation of these analyses must be fast and effective. This is accomplished through the use of a multiphysics code that allows engineers to apply an unlimited number of physics analyses in a single simulation, without the need to worry about compatibility with the physics utilized by other design teams.
This involves the use of solvers that are both versatile and consistent across all physics types, and that allows for the easy implementation of additional physical effects.
When considering the multiphysics code necessary to achieve such an analysis, it is important to remember that a computer simulation is simply a translation of real-world physical laws into their virtual form. How much simplification takes place in the translation process determines the accuracy of the resulting model. There are several ways physics effects can be coupled while ensuring that the least amount of simplification takes place. Depending on the circumstances, the scope of the simulation, and the accuracy needed, a strongly or weakly coupled analysis, or a one-way coupled analysis, may be the most efficient way to compute a solution.
Figure 2: Modeling of the electrostatic behavior of a capacitive sensor system interacting with a finger dummy. Simulation results show the electric field distribution on the sensor surface and electric field lines between the sensor’s outer surface and the finger dummy.
An example where the strongly coupled approach applies is in the resistive heating of an electric conductor. When a current flows through a conductor, heat is produced. As a result, the temperature increases, and the electrical and thermal material properties change. This affects the current, and the electrical and thermal effects are interdependent and strongly coupled. Solving for a strongly coupled system provides the user with a self-consistent solution that simultaneously satisfies all physics effects involved according to the laws of nature.
In a one-way coupled analysis, where a physics variable or material property could be assumed constant or near constant, the simulation can be streamlined by computing this part of the simulation first, then using this solution as an input for analyzing the other physics problems involved. An example is the wind load on a solar panel. The fluid domain is largely independent of how much the structure bends in the wind, provided the wind is not too strong. Therefore, fluid flow can be computed once, and then used as an input to calculate the structural displacement and stress.
Innovative mechatronic devices are simulated at KOSTAL
Multiphysics simulation plays a key role in the conceptual phase, where analysis is used to explore cutting-edge innovations. Having accurate information about how certain physics effects will affect a product at this critical stage can help engineers make the right design decisions for their product.
Any oversimplifications applied, such as considering single physics only, can jeopardize the integrity of the product down the road with expensive design changes and even product recalls. Multiphysics simulation, when employed from the start of the design process, can provide a realistic model that comprises all relevant physics effects, allowing engineers to bring the right product to market on time and within budget.
This was seen by engineers at the German-based company KOSTAL, who found that employing the multiphysics approach from the start of the design process provided them with information that was vital to the success of their mechatronic roof modules for premium cars.
KOSTAL researchers faced a daunting task: How to simultaneously optimize the performance of the electrical, thermal, and electromagnetic components in their roof models. Typical roof modules can now house satellite navigation systems and antitheft capabilities, in addition to ambient lighting. Furthermore, since the automotive industry now typically uses LED displays instead of classic light bulbs, roof module designs must contain heat dissipation systems to remove the heat produced by the displays.
By using multiphysics software to predict thermal behavior, KOSTAL researchers restructured the space within the densely packed mechatronic roof modules. Optimizing the dimensions of each component from the beginning of the design process allowed KOSTAL engineers to develop a clear model of the final product right from the start. This understanding of the space allotted for each component facilitated further innovations, such as the capacitive sensor system shown in Figure 2.