Definition

Multiphysics is defined as a coupled modelling approach of studies that demand simultaneous addressing of hitherto separate physical disciplines and combining them to generate relational mathematical models and validate them with controlled experiments to enhance the understanding of natural behaviour. 

All problems arising from natural phenomena are of multiphysics nature, whereas most of the engineered solutions available today are not. Therefore, while all research is interrelated and is not conceivable anymore to neglect this fundamental issue within the scientific and industrial communities, most industrial solutions are simplified down to extremes to reduce the complexities of design. This is, of course, what engineering is all about, solution after simplification or divide and conquer. However, it also has consequences on the quality and cost of the products, which have now become central issues of simulations for researchers and engineers. 

During the last couple of centuries, solutions have been devised to everyday problems via simplified mathematical models. Once the computers became, more powerful, more complicated models have been built while still ignoring the “real-time” interactions between the different disciplines. As models became complicated, i.e., more mathematical and less engineering-oriented, largely due to the application of numerical methods such as finite elements, the physical complexities were more and more ignored. It can be best summarised for convenience by “boundary conditions” of a differential equation at the expense of “freezing” their impact on the quality of the solutions. Do these boundary conditions really exist in nature? Where are the boundaries of a physical object, and what happens if those limits conditions are extended a little bit further?

The problem is that even in this more realistic perception of boundary limits, the issue of physical complexity is still ignored, and often confused with complicated models. Recall that nearly all differential equations have “constant” terms, or model parameters, and these, in reality, represent the effects, or interactions, of another simultaneously present and important physical phenomena, which has been reduced to a simple, static effect. 

There is obviously much ground here to be covered, and it is believed that multiphysics modelling is a particularly strong tool allowing for complex features of physical interaction to be taken into account. It is known that the key to the treatment of sources of dispersion is in the field interaction, which can only be taken into account via a true multiphysics treatment of the physical problems. This progress in coupled field problems' treatment depends heavily on the success of solution methodologies to provide robust and reliable solution algorithms. 

Multiphysics analysis has hence been developed over the recent past to better represent the behaviour of complex processes by the use of simultaneous modelling of a number of systems. This development is driven by the industrial need to further the understanding of real physical phenomena in order to develop and design safer and more efficient products, which are environmentally friendly. 

Such analyses and investigations were impossible to perform a number of years ago due to a lack of powerful computing systems. However, the advances in computer hardware have led to more sophisticated investigations brought about by increased computation speeds. Since this has been accompanied by new software packages that exploit the improved architecture of new generation microprocessors, there have been dramatic improvements in the coupling of many mathematical simulation techniques. Many research establishments are comparing the results of such studies with experimental tests to improve modelling accuracy and validate the processes for future certification.

There are now many large science and engineering communities whose research is being customised towards multiphysics analytical and simulation methods to save costs and reduce time to market with the use of rapid prototyping. This is certainly true in more advanced technologies for the more innovative design of products to market. The examples include a new generation of nuclear reactors, precision design of airbags; and crashworthiness of aerostructures. Although these communities have been using different modelling techniques, the real coupling of various phenomena is still a big challenge in academic applications yet alone industrial real problems. The new methods are needed, and also indeed, the verifications and validations still remain the most challenging aspect of multiphysics analyses. 

The multiphysics simulations trend in academia and industry are mainly focused on the availability of appropriate techniques for coupling aspects and, indeed, their credibility, which can be verified and validated. Many are still implementing Lagrangian or Eulerian methods to simplify simulations of applications with assumptions and boundary conditions, but approaches such as Arbitrary Lagrangian-Eulerian (ALE), including penalty method, require robust validations. Therefore, it is essential to establish a clear direction for publications within the current need to provide appropriate reading materials accompanied by the latest techniques. 

The enhancement of the use of multiphysics analyses mainly depends on two aspects. First, on a better understanding of physics and physical representations of interactions, and second on advancements in computing facilities to ensure complex and large mathematical equations can be solved. 

The progress in both the above fields is of paramount importance. More research and developments are needed to ensure the accuracy of new tools for multiphysics simulations and the effectiveness of more significant and more stable and secure parallel computing facilities. 

Despite the importance of multiphysics modelling and analyses due to more accurate solutions for new products and problem-solving in industrial applications, compared to conventional one-way coupling, the cost of such analyses still plays an important role. Hence, it is essential to recognise the cost-effectiveness and identify the time and space to dedicate required modelling complexity in engineering and science applications. 

Over the past years, many studies have focused on various issues to address the importance of multiphysics analysis; however, some modelling and simulations were presented as a multiphysics approach but a multidisciplinary approach may simply describe it. 

Particular focus is recently given to virtual engineering and how the modelling and simulations in multiphysics may be able to help the introduction of a digital-twin to the world of production and maintenance. However, this may take a few more years to mature that by then, Elsevier Multiphysics Series will be in a position to offer volumes in such an area.

In the coming years, virtual multiphysics simulations and real-time modelling will be more applicable to address real-world problems.