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TRUST 1.9.8
HPC thermohydraulic platform
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TRUST 1.9.8
HPC thermohydraulic platform
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This tutorial introduces the ICoCo coupling interface as implemented in the TRUST platform. It covers the full workflow from environment setup to bidirectional field exchange and Python-based coupling supervision.
The tutorial is structured as three progressive exercises:
Traditional numerical simulation codes are designed around a single physical domain: one code handles thermics, another handles mechanics, and so on. Real-world engineering studies, however, require the simultaneous simulation of several coupled physical phenomena. Nuclear reactor simulations, for example, must account for thermics, neutronics, and structural mechanics in a mutually consistent fashion.
The natural answer to this requirement is code coupling: allowing several specialized codes to communicate with one another while each remains responsible for its own physics domain.
Any coupled computation requires a central entity to drive the overall calculation: the supervisor. The supervisor is responsible for initializing all participating codes, advancing them through their respective time loops, and centralizing the data exchanges and unit conversions between them. In practice, the supervisor is typically implemented as a C++ program or a Python script.
In a naive approach, the supervisor must be aware of the internal API of every code it orchestrates. This quickly becomes unmanageable as soon as more than two codes are involved, or when a single supervisor is intended to operate with different pairs or groups of codes.
The standard solution is to define a unique coupling interface to which every participating code must conform. The interface acts as a contract: it specifies a fixed set of methods with standardized signatures, while leaving the implementation details entirely to each individual code. The supervisor then only needs to know this common interface, regardless of which specific codes are being coupled.
This design provides versatility: any code that correctly implements the interface can be substituted into an existing supervisor with minimal or no modification. The trade-off is that the interface must be implemented once for each new code that is to be coupled.
ICoCo (Interface for Code Coupling) is the standard coupling interface used within the TRUST ecosystem. Its key characteristics are the following.
It is written in C++ and, since TRUST 1.8.3, also wrapped via SWIG to allow use from Python scripts. It is designed specifically for simulation codes structured around iterative time loops. It defines a set of standard methods with fixed signatures and no default implementation; notable methods include initializeTimeStep(), validateTimeStep(), and abortTimeStep(). Data exchange between codes is performed through the notion of a field — a set of scalar or vector values defined on a mesh. The standard implementation relies on MEDCouplingFieldDouble from the SALOME MEDCoupling library.
1.16.1