MIPT researchers have discovered a method to reduce turbulence in supersonic aircraft.

The study has been published in the journal Fluid Dynamics. The research focuses on investigating the interaction of weak shock waves, known as N-waves, with the laminar boundary layer formed on a flat plate with a rounded leading edge at a Mach number of 2.5. This number indicates that the flight occurs at a speed of approximately 3000 kilometers per hour, which is 2.5 times the speed of sound. The results of the numerical modeling were compared with known experimental data.

Aerodynamic characteristics of high-speed aircraft are heavily influenced by the turbulence of compressible boundary layers, which can significantly increase viscous drag and heat transfer to the streamlined surface.

“Accurate identification of the location of the laminar-turbulent transition is crucial for predicting the thermal regime of the surface and ensuring flight safety,” noted Ivan Yegorov, Corresponding Member of the Russian Academy of Sciences and Professor of Computer Modeling at MIPT. “Our results show that by altering the shape of the surface, we can greatly influence the behavior of the boundary layer.”

A key aspect of the work was the examination of the interaction between the N-wave and the bluntness of the leading edge, which opens new horizons for analyzing laminar-turbulent transition processes. Previous studies have indicated that N-waves can induce significant disturbances, which in turn lead to the formation of turbulent wedges near the wing surface. These disturbances can substantially alter the aerodynamic flow scenario.

The new study employed an original modeling technique based on the full Navier-Stokes equations. The boundary conditions and flow parameters in the model corresponded to an experimental study conducted in a low-turbulence supersonic wind tunnel T-325 at the Institute of Theoretical and Applied Mechanics of the Siberian Branch of the Russian Academy of Sciences.

In the numerical modeling of the N-wave, the researchers replaced the thin two-dimensional rectangular roughness with a parabolic arc for computational convenience. They simulated two cases: a sharp edge and a blunt edge. Calculations were performed on four different grids with varying degrees of refinement to demonstrate their convergence with each other.

The scientists found that behind the sharp edge, a single stationary wake forms, consisting of a pair of vortices, while the blunt edge creates two distinct wakes. Each of these wakes, as the results showed, has a significantly higher amplitude of stationary disturbances, indicating an increase in flow instability and a potentially earlier transition to turbulence.

Experiments in the wind tunnel demonstrated that the results of numerical modeling satisfactorily align with the experimental data. They also showed that the lines of transition from laminar to turbulent flow are distorted in the area affected by the N-wave. This discovery could have significant practical applications, for instance, in aerodynamic design, where understanding the transition to turbulence is critical for enhancing the efficiency and safety of aircraft.

Although the results represent a significant advancement, the authors emphasize that further parametric studies are needed for a deeper understanding. Specifically, it will be necessary to adapt the characteristics of disturbance generators for analyzing the boundary layer on blunt plates.

This research has made an important contribution to the field of aerodynamics and opens new avenues for further investigations into the interaction of flows and structures, which may aid in addressing a range of engineering challenges in various fields of science and technology.

The results of this work will assist engineers and designers in more accurately predicting the characteristics of high-speed aircraft, laying the groundwork for improving their design and enhancing flight safety.