THESE CIFRE - Body Force Modeling of Open Rotors for RANS Simulations F/H

Job description

The aviation industry is pursuing significant reductions in fuel consumption and emissions through advanced propulsion concepts. Among these, open rotors in a rotor-stator configuration represent a promising solution for achieving high propulsive efficiency, and up to 20% reduction in both CO₂ emissions and fuel consumption. However, their highly non-traditional, unshrouded blade arrangement brings aerodynamic complexity that introduces challenges in accurately modeling, simulating, and optimizing their performance during early and advanced design phases.

A critical technical challenge accompanying Open Fan designs is the accurate representation of propulsor-airframe interaction. Open rotors with a rotor-stator configuration generate complex aerodynamic effects that interact strongly with the airframe, influencing overall aircraft efficiency and performance. Installed effects — such as modifications in thrust, load distribution, and possible flow disturbances — must be accurately evaluated from the onset of the design process to avoid late-phase corrections and to maximize the benefits of this architecture.

While detailed unsteady RANS (URANS) simulations with meshed blades can capture these effects accurately, their computational cost is restrictive, particularly for extensive parametric and design-space investigations. In contrast, Body Force Modeling within steady RANS frameworks provides a highly efficient tool for the rapid assessment of open rotor design variants and installed effects. This technique substitutes physical blade geometry with distributed force sources, allowing the reproduction of essential aerodynamic characteristics —such as flow turning and energy addition/removal — at a fraction of the computational expense.

Body force models for open rotor systems must be robust enough to capture important physical phenomena specific to rotor-stator interactions and installation effects under varying operating conditions. The development of such generalized and reliable modeling tools is of high strategic value for research and industrial deployment. Research Program The thesis will address three primary objectives:

• Evaluating and extending body force approaches for open rotors: Investigate relevant flow physics, modeling assumptions, and limitations of current body force methods as applied to open rotor systems.
• Developing a generalized body force model for open rotors: Build and calibrate new model formulations based on an extensive RANS simulation database covering representative open rotor architectures and operational conditions.

Assessing and enhancing installed effect predictions

• Focus on representing propulsor-airframe interactions within the body force modeling framework, and establish the capability of this method to reliably estimate installation penalties or benefits, compared with costlier URANS references.

The novel body force models will be implemented in SAFRAN's in-house BFMToolBox library. This ensures alignment with internal numerical workflows and supports continuous method development within the company's ecosystem.

Main stages

• Literature review of body force modeling for propellers and open rotors, emphasizing rotor-stator configuration and installation effects.
• Development and analysis of test cases for model enhancement, in both isolated and installed environments.
• Creation of a dedicated RANS simulation database focusing on rotor-stator open rotor and installation scenarios.
• Formulation and implementation of new reduced-order models in the BFMToolBox environment.
• Validation of the models in both isolated and installed cases, through comparison with high-fidelity and, where available, experimental results.
• Dissemination of research findings through publications and international conferences. Practical Information

Duration

• 3 years, starting Beg 2027

CIFRE funding

• PhD student hired as a SAFRAN employee under a 3-year contract
• The candidate will spend most of the time at ISAE-SUPAERO, with regular travels at SAFRAN (1 per trimester for a day or two). Frequent travels to Gennevilliers or Corbeil are possible, and also Saclay (Safran Tech).

The ideal candidate should have:

• Strong background in fluid mechanics and aerodynamics, ideally with experience in turbomachinery or rotor-stator systems
• Good understanding of CFD and numerical methods
• Initiative, analytical thinking, and problem-solving skills