Search

In the framework of next supersonic transport airplane generation, the Japan Aerospace eXploration Agency (JAXA) has developed a new natural laminar flow highly swept wing. The design has been experimentally validated firstly in a supersonic wind tunnel and secondly accomplishing flight test. These experimental data were then analyzed and completed by numerical stability analyses in a joint research program between Onera and JAXA. At the design condition, for a Mach number M=2 at an altitude of h=18 km, results have confirmed the laminar design of the wing due to a strong attenuation of cross-flow instabilities ensuring an extended laminar zone. As the amplification of disturbances inside the boundary layer and transition process is very sensitive to external parameters, the impact of wall roughness of the models and the influence of Reynolds number on transition process have been carefully analyzed., Physical characteristics: Original contains color illustrations, 形態: カラー図版あり

Boundary layer transition characteristics of the scaled supersonic experimental airplane was numerically analyzed to confirm its Natural Laminar Flow (NLF) wing design. Using conventional incompressible and newly developed compressible transition prediction codes based on an e(sup N) method, the NLF characteristics were well confirmed though the following results. (1) The step function type target pressure distribution applied in the NLF wing design was found to be optimum (2) Comparing the transition N value estimated by the compressible code with experimental results obtained by NASA, wide laminar region of the NLF wing was expected. (3) Laminar boundary layer profiles estimated by a Navier-Stokes code led to smaller N value than one by the compressible boundary layer code. (4) No transition due to attachment-line contamination was predicted., JAXA Special Publication, 宇宙航空研究開発機構特別資料

In the aerodynamic design of the National EXperimental Supersonic Transport (NEXST) program, a supersonic Natural Laminar Flow (NLF) wing design concept was originally developed. Before the flight test of the NEXST-1 airplane, more detailed transition analysis should be performed in order to validate the NLF wing effect. Therefore, the NAL-ONERA cooperative research project started in April 2000, because ONERA had great ability of analyzing transition phenomena and NAL had some experimental transition data in supersonic flow. In the transition analysis on the sharp cone with a half angle of 5 degrees, the nose cone, and the NLF wing of the NEXST-1 airplane, almost good cross validation of both ONERA's and NAL's e(sup N) codes was obtained. Then, there was also high correlation between the S2MA wind tunnel test results and both laboratories' predictions under the assumption of a critical transition N value of 6. Moreover, about 40 percent chordwise region was estimated to be laminar at flight condition by NAL's code. In addition, a risk of transition due to attachment-line contamination was predicted at inner wing, using the well-known Poll's criterion., JAXA Special Publication, 宇宙航空研究開発機構特別資料

The aerodynamic design of an SST (SuperSonic Transport) configuration with some geometry requests at given flight condition in 3rd NAL-SST-CFD (Computational Fluid Dynamics) workshop competition subject 1 is conducted by following three design tools: a conventional linear theory design tool, a CFD-based optimization tool and a CFD-based inverse design tool. In order to increase a Lift to Drag ratio (L/D) of the airplane, several design concepts are adopted such as a warp wing design, linear and non-linear area-ruled fuselage designs and a supersonic NLF (Natural Laminar Flow) wing design. The non-linear area-ruled fuselage design shows that the CFD-based optimization design tool can improve the aerodynamic properties of the airplane designed by the conventional linear theory design tool. As for the NLF wing design, however, the CFD-based inverse design tool should be carefully coordinated in order to realize the target NLF pressure distributions., JAXA Special Publication, 宇宙航空研究開発機構特別資料

An experimental study was conducted to investigate transition process on 10-deg cone. There are two goals of this study. One is to validate transition prediction numerical code LSTAB, which is recently developed. Instability wave is detected by use of flush-mounted a pressure transducer and a hot-film sensor, and its frequency is confirmed to agree with the numerically predicted value. The second goal is to clarify the effects of freestream acoustic disturbances on the boundary-layer transition in supersonic flow. Intensity of freestream disturbances was controlled by a strip of sand paper or distributed roughness, which were attached on the floor or sidewall near the throat. High-frequency disturbance increased in freestream when sand paper was attached on the floor, though freestream disturbance was not affected by larger roughness on straight sidewall. The effect of roughness on the wind tunnel wall is pointed out to be different with the position and condition., Special Publication of National Aerospace Laboratory, 航空宇宙技術研究所特別資料

基準形状に正弦波状，あるいは局在する波状の変形を加えることで，超音速自然層流機首を設計することを試みた．変形のパラメータだけでなく，一様流に関するパラメータも変化させ，最も自然層流効果の大きくなる形状を調査した．その結果，変形によって周方向と軸方向の圧力勾配比が減少すると，側面の境界層遷移を支配する横流れ不安定を抑制し自然層流効果をもたらすことがわかった．また，この圧力勾配比を小さくするには，圧力分布のピーク位置，すなわち圧力係数が負圧側で極大となる位置をトップラインとボトムラインで適切に配置することが重要であることがわかった．そして，そのような自然層流効果をもたらす変形形状の設計指針を獲得し，自然層流機首となる形状例が得られた．正弦波変形における自然層流効果は，実験的にも検証できた．一方，全抵抗の増加を抑制するには，局在波変形の方が有効であることが示された．, The transition characteristics were examined numerically on candidate shapes in order to design a natural laminar flow nose for a supersonic transport. Two types of deformation from a baseline shape were examined. One is sinusoidal type, and another is localized type. Not only parameters of geometry which define the deformation, but also the conditions of uniform flow were varied to obtain the largest effect of natural laminar flow. In results, the crossflow instability, which dominates the boundary-layer transition at the side area, was found to be suppressed from the small ratio of pressure gradients in azimuthal and axial directions at the side area. Moreover it was found that the relative location of bump in pressure distribution along leeward and windward rays is a key to yield small ratio of pressure gradient in azimuthal direction. The effect of natural laminar flow for sinusoidal deformation was confirmed experimentally. On the other hand, the localized deformation was found to be more effective in order to suppress increasing of total drag than the sinusoidal deformation., 形態: カラー図版あり, Physical characteristics: Original contains color illustrations

A database for aerodynamic design of the supersonic transport (NEXST-DB) was constructed by JAXA. Many kind of aerodynamic data uploaded on the NEXST-DB were accumulated from the NEXST program. The uploaded data on the NEXST-DB consisted by aerodynamic results, airplane geometries, aerodynamic design tools and publications. A fl ight test, CFD analysis, wind tunnel test and the boundary layer transition analysis results obtained from the NEXST-1 project were mainly uploaded as the aerodynamic results. The aerodynamic design tools were developed on the project and used for designing of the NEXST-1 airplane. All of the aerodynamic data and tools uploaded on the NEXST-DB can freely be downloaded from the website. The detail information of the publications related to the NEXST program was also introduced., 次世代超音速旅客機の研究開発として進められた小型超音速実験機(NEXST)プログラムにおいて蓄積された空力データを収録した超音速機空力設計データベース(NEXST-DB)を構築した．インターネット公開型のデータベースであり，Web上で図示機能やテキストデータのダウンロード機能を充実させ，正確なデータが迅速に利用できるようにした．本NEXST-DBには空力データ，機体形状データ，空力設計ツール，そして対外発表資料を掲載・公開している．空力データには，NEXST-1の飛行実験や，CFD解析，風洞試験，境界層遷移解析結果を掲載し，機体形状データはCAD形式の形状ファイルが利用できるようにした．空力設計ツールは，NEXST-1の空力設計に用いた抵抗低減設計ツールやCFD逆問題設計ツールを掲載し，利用の多様化を図った．掲載内容や機能，利用方法の詳細についてまとめた．, Physical characteristics: Original contains color illustrations, 形態: カラー図版あり

Stability analysis on a supersonic natural laminar flow (NLF) wing designed by JAXA was performed at both flight and wind tunnel test conditions as a joint research program between ONERA and JAXA. Both parties validated the NLF wing effect by confirming suppression of crossflow instability at design point, using an e(N) method with fixed β strategy proposed by ONERA. Although JAXA’s flight test vehicle and wind tunnel test model had almost same averaged roughness height of about 1micrometer, it was shown that surface roughness had little influence on measured transition location at both flight and wind tunnel test conditions. Furthermore, JAXA found that the pressure distribution measured in flight test did not completely coincide to the target pressure distribution (Cp (Target)) for the NLF wing design. It revealed that measured transition location at outer wing region was not delayed in flight test, compared with the transition location predicted with the Cp (Target) which had large gain to delay the transition. Influence of Reynolds number on transition location was also studied for the target pressure distribution Cp (Target). Consequently, chordwise transition location, (x/c)Tr., rapidly moves from mid-chord location to forward location (near leading edge) for increasing Reynolds numbers, according to the change of instability of boundary layer from Tollmien-Schlichting instability to crossflow instability., 形態: カラー図版あり, Physical characteristics: Original contains color illustrations

In the aerodynamic design of the National EXperimental Supersonic Transport (NEXST) program, a supersonic natural laminar flow (NLF) wing design concept was originally developed. Before the flight test of the NEXST-1 airplane, more detailed transition analysis should be performed in order to validate the NLF wing effect. Therefore, the JAXA-ONERA cooperative research project started in April 2000, because ONERA had great ability of analyzing transition phenomena and JAXA had some experimental transition data in supersonic flow. In the transition analysis on the sharp cone with a half angle of 5 degrees, the nose cone, and the NLF wing of the NEXST-1 airplane, good cross validation of both ONERA's and JAXA 's e(N) codes was obtained. There was also high correlation between the experimental results in ONERA's continuous circuit-flow type supersonic wind tunnel and both laboratories' predictions under the assumption of a critical transition N value of 6. In addition, a risk of transition due to attachment-line contamination was predicted at inner wing, using the well-known Poll's criterion., Original contains color illustrations, 形態: カラー図版あり