WoT-Phyng-Sim: Integrating Physics Simulations with IoT Digital Twins using the Web of Things.

The high fragmentation in the IoT landscape necessitated the introduction of the Web of Things (WoT), a set of standards by W3C. Among other things, the WoT defines a standardized human-and machine-readable JSON document called the Thing Description (TD) that is able to describe the Application Programming Interface (API) provided by devices on a network. This description already provides enough information to generate a simulation that can mimic the cyber behavior of the Thing. However, the TD does not capture the physical properties and behavior of Things and, therefore, cannot be used to generate a cyber-physical simulation of a Thing. In this paper, we introduce a new method and an open-source framework for setting up and automatically generating WoT-compliant cyber-physical Digital Twins (DTs) in Computational Fluid Dynamics (CFD) simulators that can simulate physical processes, can be controlled in real-time and require minimal human effort. Such a simulation can be used to verify the behavior of cyber-physical systems before and after deployment. We demonstrate the viability of our method using a conjugate heat transfer simulation of a smart home environment with multiple devices running in real-time. Furthermore, we perform a scalability analysis and conclude that our approach is able to simulate multpile devices while maintaining real-time behavior. Using our proposed approach, the process of setting up physically realistic WoT-compliant DTs becomes fast, easy, which bridges the gap between cyber-physical systems and the WoT.