Conclusions and future work

Coupling of various massively-parallel computational algorithms is a challenging task, but a necessity in multi-physics simulations. The coupler developed during this project is a powerful resource. It has the format of a library, which can be invoked by various applications, which are executed independently. It is compartmentalised such that it does not affect the execution of any of the applications, and only manages data exchange between codes. In that respect, it follows the model of the MPI library and interfaces applications, as opposed to processes within one application.

The use of the coupling library does not require any modification of the client applications, except for a class of "socket" routines that manage the communication via the coupler library. This approach is least intrusive for interfacing independent, massively parallel applications. It also facilitates the developer's task since it is independent of the individual applications data structures and management, parallel implementation and scope.

The coupler library has been applied in simulations of coupled continuum-molecular flows. The continuum algorithm is $\mathcal {T}rans$ $\mathcal {F}low$, and the molecular dynamics were performed using $\mathcal {S}tream$$MD$. Both codes have been extensively validated and optimised for parallel scalability. Both Couette and Poiseuille flows were simulated using continuum-MD coupling for validation. Further simulations will be performed during the coming year of various physical phenomena that require MD-level detail near interfaces, coupled to large-scale continuum solution away from the interface. Some examples include the effect of outer macroscopic shear on polymeric surface coatings and the onset of cavitation in microscopic textures.

Finally, the coupler library will be hosted online for the benefit of the wider research community, in order to facilitate multi-physics simulations. In addition, the work will be disseminated at various conferences and consortia in an effort to maximise the uptake of the library.