Details of research theme
[Title of research theme]
Research on turbulent transition and characteristics for actual subsonic aircraft
[Details of research theme]
Designing natural laminar flow (NLF) wings, which help maintain a laminar boundary layer around an aircraft, is crucial for enhancing aircraft environmental performance. The JAXA Aviation Technology Directorate has been actively engaged in NLF wing design and technology development to ensure their performance. In recent years, our focus has shifted towards investigating the impact of surface roughness, such as irregularities on the wing surface, on the transition between laminar and turbulent flow within the boundary layer, especially concerning the practical application of NLF wings on actual aircraft. To address these challenges, we have developed a multi-fidelity analysis system that integrates Reynolds-averaged Navier-Stokes (RANS), Direct Numerical Simulation (DNS), and stability analysis techniques for swept wings of infinite span. This system allows us to calculate high-fidelity roughness indices that closely resemble actual flight conditions at a reasonable computational cost. However, for accurate transition prediction in real-world environments, it is imperative to consider the influence of free-stream turbulence and acoustic disturbances. Therefore, our research aims to create a system that can investigate and analyze the effects of surface roughness, freestream turbulence, and acoustic disturbances simultaneously and we will evaluate the changes in the transition position due to these effects. Furthermore, we intend to elucidate the characteristics of turbulent flow fields, including energy budget, in actual flight conditions through DNS analysis. Ultimately, our goal is to develop a versatile tool for analyzing turbulent flow and laminar-to-turbulent transition in any region, not limited to wing areas but encompassing the entirety of subsonic aircraft. This will reveal turbulence and transition phenomena in regions with complex three-dimensional shapes, such as the wing root, wingtips, and nose. The knowledge gained from this research will significantly enhance the accuracy of transition indicators and transition analysis tools developed within the project.