Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - SSeMID (Stability and Sensitivity Methods for Industrial Design)

Teaser

The increasing environmental risks has been always present in the aeronautical community, industry and research centres, having a definite influence on the way the design of the aircraft of the future. In this line, the aeronautic community has defined a series of...

Summary

The increasing environmental risks has been always present in the aeronautical community, industry and research centres, having a definite influence on the way the design of the aircraft of the future. In this line, the aeronautic community has defined a series of environmental challenges for the new generation of aircrafts, which include halving perceived aircraft noise, and CO2 emissions per passenger-km and 80% cut in NOx emissions.

Most of these goals have a direct connection with the aerodynamic performance of the aircraft; mainly with aerodynamic technologies. Many of the elements of the aerodynamics of conventional aircraft are understood to some degree but reliable solutions for modelling are not available due to the new challenges appearing as the technology matures. One of the most common problems is related to the stability analysis for configurations in the limits of the flight envelope or when unsteady effects are dominant. Contribution to understanding these configurations is the main objective of the research proposed in SSeMID, and is the focus of the international training plan for the 16 PhD students employed within the network.

Stability analysis is a key element in understanding the current limitations of aircraft designs, and new numerical methodologies, and new technologies are required in order to apply innovative solutions by the aircraft manufacturing industry. SSeMID proposes to mature and industrialize the current technologies by obtaining the sensitivity maps of unstable features under the effect of design variables or external influence, such as noise, surface/shape deformation or surface irregularities. The direct application of this methodology is flow control. Flow control is an emerging technology that describes a variety of techniques by which aerodynamic performance can be enhanced to levels beyond those achieved by changes to external shape alone. The application of stability and sensitivity analysis can provide very valuable information to the design engineer about “how and where” are the key factor to achieve an optimal design. The proposed work program represents a combined effort of model developments, experimental validation and application to industrial practice.

Work performed

In order to achieve the defined objectives, the backbone of SSEMID is structured in four technical research lines:

1. Development of numerical tools.
2. Formulation of Direct and Adjoint methods.
3. Analysis of flow sensitivity under external perturbation.
4. Industrial applications of stability and sensitivity analysis

Work of the project is progressing at a good pace and preliminary results and significant advances in the following research lines are being obtained:
• Development of high order methods for turbulent flows.
This line covers the implementation of robust turbulent models and new schemes for under-resolved turbulence.
• Mesh generation and h/p adaptation, error estimation.
This subject covers research in error estimation, h/p mesh adaptation and implicit and multigrid methods for high-order schemes, development of robust schemes for unsteady problems and mode decomposition for analysis.
• Stability analysis of high detached flows or complex geometries.
Continuous and discrete approaches for stability analysis are matured in 3D highly detached flows at high Reynolds and Mach numbers: Biglobal, Triglobal. Eigenvalue methods for large dimensional and stiff problems and accurate numerical simulation of 3D wings.
• Analysis of hypersonic configurations with wall roughness, transition prediction under external and in particular acoustic perturbation. The study of acoustic and thermos-acoustic instabilities.
This line includes the study of the effect of surface irregularities or pulsating flows on laminar-turbulent transition, sensitivities of acoustic output with respect to base-flow modifications, and experimental investigation of unsteady flows.
• Shape optimization.
This research includes formulation of the sensitivity of the flow (modes) under external perturbations, in particular it considers the surface modifications, shape optimization and application to flow control.

Final results

Finalization of the tasks proposed in SSEMID will provide the advance in the state of the art of different technologies which, in the future, will contribute to design more efficient and environmentally friendly aircrafts.
In particular, it is expected to contribute to maturing of the new generation of numerical methods for simulation in engineering, as well as maturing and industrializing existing tools for feature detection and flow stability, shedding light on the complicated problems faced by industry at the limits of the flight envelope or when unsteady configurations are dominant. The aim is to discover new flow control strategies and new tools for shape optimization which would be routinely used by engineers. Finally, SSEMID project will generate new knowledge of the mechanics of transition from laminar to turbulent flow, which eventually will pave the way to manufacture the laminar aircraft.

All the research results will have a profound impact on the design of the aircraft. The development costs will be reduced as high performing aircraft design simulation tools will contribute to the transition of existing aircraft testing methods, which are mainly based on wind tunnel testing, into more automated process, relying on real time fast simulations. Accurate CFD tools can lead to millions of Euros in operational cost reduction per aircraft per year, and could save years of design process. The product will be delivered to the market in shorter time, and will have a much more mature design adding to its safety and stability. More efficient aircrafts will contribute to reducing CO2 and NOx emissions to the atmosphere since these emissions are directly related to the aircraft fuel burn, drag and airplane weight. Noise, which is a consequence of flow instabilities, which become especially evident in high lift configurations, can also be reduced with the more optimal design of the aircraft. In general, accurate predictions for the aircraft’s configurations will allow optimization of its technology and designing cheaper, and safer aircrafts with less negative environmental impact, ultimately benefiting the European society.