Wind tunnel test and computational fluid dynamics have been used for the aerodynamics design of the aircraft. Especially, in the case of wind tunnel test, the scale model which has various sensors inside has been installed in the wind tunnel, and 6 component force and moment, surface pressure and hinge moment of the control surface have been measured in the wind tunnel test. It is indispensable for the aerodynamics design to understand the flow phenomenon around the aircraft correctly. Therefore, the flow visualization techniques have been utilized in the aircraft development wind tunnel test since a long time ago. This paper summarizes the typical examples of traditional and latest flow visualization techniques in the aircraft development wind tunnel test. Also, the expected flow visualization technique in the future is described in this paper.

View full abstract

In this article, a drag breakdown approach is introduced which can decompose the aerodynamic drag of aircraft into physical drag components of wave, viscous and induced drag. In aerodynamic shape optimization problems, this approach allows to analyze drag reduction effect quantitatively, and to visualize drag source distribution in its flow-field intuitively. The drag breakdown approach is applied in aerodynamic shape optimization problems of two-dimensional airfoil as well as of wingtip device of a conventional transonic aircraft model, and then its effectiveness is clearly demonstrated. The visualization of design variables space and the extraction of engineering design knowledge by using the drag breakdown approach and a response surface model approach are also introduced in this article.

View full abstract

  Two quantitative optical measurements, which are Flight PSP measurement and wing deformation measurement for flight test, are introduced in this article.
  Flight PSP measurement is an extension of the PSP measurement in a wind tunnel. PSP sheets were installed on the main wing and they were measured by a CCD camera inside cabin. It could measure 2-3kPa pressure variation, which was relatively small as PSP measurement target, due to involve background subtraction and introduction of 2-color PSP with temperature compensation capability.
  Wing deformation measurement uses targets on a main wing and stereo cameras. It measures the 3-dimensional geometry of each markers, then calculates deformation from subtraction of ones between on ground and flight. It could measure about 50mm bending and 0.5° twist deformation in 1G flight quantitatively. It could also capture the deformation under 1.4G and 2G flight reasonably.

View full abstract

Combustion instability has become the primary technical challenge in the development of low-emission combustors for aero and land-based gas-turbine engines, since it has the capacity to cause catastrophic damage to the combustion chamber and other engine components. Despite a great deal of research regarding this issue over the past several decades, the problem is not yet fully solved, due to the attendant level of complexity. Understanding the driving mechanisms of combustion instabilities under practical conditions and configurations is definitely a critical issue in the development of low-emission jet engines, since a detailed understanding of these mechanisms allows one to consider the means by which to stabilize the combustor. Two recent studies on combustion stability diagnostics at Japan Aerospace Exploration Agency are introduced in this article.

View full abstract

Tensile fracture behaviour of CFRP laminate under varied strain rate is examined in this paper. In order to evaluate the fracture behaviour and surface strain distribution change, high-speed imaging technique and DIC (Digital Image Correlation) is applied in combination. CFRP specimen having stacking sequence of [+45°/-45°]_s and [90°]_6T shows strain rate dependence though [0º]_2T specimen doesn’t shows clear influence on tensile strength and failure strain. As a result of high-speed imaging, it is confirmed that fracture behaviour is scarcely affected by the strain rate despite of the strain rate dependency on strength and failure strain. By applying DIC to the high-speed photography taken just before the initiation of material failure, it is confirmed that the local strain concentration associated with inhomogeneous properties of the materials can be successfully captured.

View full abstract