Regular Article

TRUST: the HPC open-source CFD platform – from CPU to GPU

Université Paris-Saclay, CEA, Service de Génie Logiciel pour la Simulation, 91191 Gif-sur-Yvette, France

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Received: 26 May 2025
Received in final form: 11 July 2025
Accepted: 4 August 2025
Published online: 22 September 2025

Abstract

Since 1993, the CEA has developed TRUST, an open-source CFD software platform designed to address a wide range of thermohydraulic problems. Initially focused on nuclear applications, the platform has progressively evolved to support incompressible single-phase flows, low-Mach-number reactive flows, and fully compressible multi-phase flows. TRUST incorporates a variety of numerical schemes and supports multiple mesh types, making it suitable for both academic and industrial applications, as well as for deployment on standard computing systems and high-performance computing (HPC) clusters. Notably, it has enabled one of the largest Direct Numerical Simulations (DNS) to date for hydrogen risk assessment, involving over 2 billion cells and more than 50,000 MPI processors. Recently, the development team has begun integrating GPU-based computing technologies–such as AmgX, rocALUTION, AMGCL and Kokkos–to develop a hybrid CPU/GPU version of the code capable of delivering high performance across diverse architectures. This article presents an overview of the TRUST platform, reviews the largest simulation performed to date with the CPU version, outlines the ongoing GPU integration strategy, and highlights selected results.