Soak-back conditions are a crucial challenge for engine manufacturers to reduce the turnaround time between flights and improve engine durability and security. The natural convection conditions at stake make the numerical predictions of the flow and thermal behaviors rather difficult, when not prohibitively expensive. Consequently, the topic is still assessed with tests which can only be performed at a very late stage of the engine development and do not provide a good overview of the physics behind. Failures discovered so late are extremely expensive and complex to solve.

This paper presents the first phase of a methodology development to tackle the soak-back of an engine with the SIMULIA PowerFLOW Suite Computational Fluid Dynamics code. Comparisons for validation are made with the tests on one hand, and with ANSYS Fluent RANS (Reynolds Averaged Navier-Stokes) simulations whenever possible. The work conducted so far focuses on the engine bay only with coupled fluid-thermal simulations while the core flow is simplified into a 1D fluid nodes network.

A first simplified approach has proved to recover some of the phenomena observed in both the tests and RANS simulations. It failed however to match the initial temperatures of the soak phase, which is consistent with the choice of modelization made. Improvements to the model were therefore brought by adding more complexity and fidelity to the geometry, environment and tests scenario. The new results significantly improve the comparisons with the tests and RANS simulations. Some differences on absolute temperature levels and evolution rates remain here and there and highlight the necessity to improve the core flow modelization, which is what the next phase of the methodology development will focus on.

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