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垂直軸効力型の風車のひとつにサボニウス風車がある。サボニウス風車には、低速回転、高トルクという特徴があるため、風力発電に用いられることはほとんどなく、揚水や粉挽きなどに用いられる。一方、最近注目されている海流発電は、大きな潜在力をもちながらも、研究例は少なく、実用化はなされていない。海流は比較的低速であるため、サボニウス型回転装置を用いた発電は大きな可能性をもっている。サボニウス型回転装置の性能を調べる上で数値シミュレーションが効果的であるが、数値シミュレーションを行う上で、回転装置を含む領域を格子分割する必要がある。サボニウス風車は幾何学的には単純な形状をしているが、解析に適した格子をつくることはあまり容易ではない。本報告では、複数の回転装置が独立して回転する場合にも適用できる差分格子の生成法についてひとつの提案をおこなう。, One of the vertical axis wind turbines that utilize drag force is the Savonius wind turbine. Savonius wind turbines are characterized by low speed rotation and high torque, so they are rarely used for wind power generation and are used for pumping and milling. On the other hand, ocean current power generation, which has been attracting attention recently, has great potential, but there are few research examples and it has not been put into practical use. Since the ocean current is relatively slow, power generation using the Savonius type rotating device has great potential. Numerical simulation is effective for investigating the performance of the Savonius type rotating device, but in performing the numerical simulation, it is necessary to divide the area including the rotating device into a grid. Although the Savonius wind turbine has a simple geometric shape, it is not so easy to generate a grid suitable for analysis. In this report, we propose a grid generation method that can be applied even when multiple rotating devices rotate independently.

A CFD (Computational Fluid Dynamics) workshop was held in the 44th Aircraft Symposium, October 2006, in order to evaluate domestic CFD technology for civil transport aircrafts in high-lift configurations. JAXA provided an experimental data for comparison obtained in the JAXA large low-speed wind tunnel using a half model equipped with high-lift devices, fuselage, nacelle-pylon, slat tracks and Flap Track Fairings (FTF). This paper briefly presents the experimental model, objectives and test cases of the CFD workshop, summary of comparison, and obtained knowledge and issues on CFD and wind tunnel testing for high-lift configuration., 資料番号: AA0063742027, レポート番号: JAXA-SP-07-016

Flow around JAXA HLD (High Lift Devices) wind tunnel model is analyzed by RANS (Reynolds Averaged Navier Stokes) CFD (Computational Fluid Dynamics) method and compared with the experimental data obtained by JAXA. Unstructured mesh with overset technique is used for mesh generation around realistic configuration with small parts such as slat clip. It was shown that the slat clip made a difference in the flowfield especially around the edge of the slat. Baldwin-Barth and Spalart-Allmaras one equation models are used for turbulence model and the former gives better agreement with the experiment., 資料番号: AA0063742031, レポート番号: JAXA-SP-07-016

An aerodynamics simulation code using high-order Spectral Volume (SV) method has been developed, and flow simulations around JAXA high-lift configuration model were conducted on the Earth Simulator. The obtained results of the Euler computation are compared with those of a conventional unstructured method and the available wind-tunnel data. The computed pressure profiles fairly agree with the experimental data on the relatively coarse mesh, although viscous effects were all neglected in the calculation. In particular, trailing vortices from various high-lift devices are clearly captured even in the down stream region where they are likely to be vanished due to inherent numerical viscosity in the conventional unstructured mesh methods. This demonstrates that the present high-order unstructured mesh method will be capable of capturing various flow features accurately while it retains the desired geometrical flexibility. It is also shown that the developed code achieves high computing performance on the Earth Simulator., 資料番号: AA0063742032, レポート番号: JAXA-SP-07-016

A pointwise relaxation implicit Discontinuous Galerkin (DG) method developed in our study is extended to unstructured hybrid grids comprised of hexahedral, pyramidal, prismatic and tetrahedral cells. The mathematical formulation of the present method is first shown. The scalar advective equation in 3D space is then solved using hybrid grid. The accuracy of the scheme as well as the convergence rate is examined for illustrating the characteristics of the present numerical method. Finally, the pointwise relaxation implicit DG method for 3D Euler equations is constructed to solve inviscid compressible flowfield over ONERA-M6 isolated wing using hybrid mesh systems., 資料番号: AA0063742011, レポート番号: JAXA-SP-07-016

SST-CFDワークショップ.次世代超音速機の数値シミュレーション利用技術に関する国際ワークショップ 航空宇宙技術研究所 20011203-20011205 東京 日本, SST-CFD Workshop. International Workshops on Numerical Simulation Technology for Design of Next Generation Supersonic Civil Transport National Aerospace Laboratory 20011203-20011205 Tokyo Japan, An automated and robust unstructured hybrid mesh generation method comprised of tetrahedra, prisms, and pyramids has been developed. The hybrid grid generation starts with isotropic tetrahedral grids to enhance the robustness of the algorithm. The user-specified number of prismatic layers is then added keeping the mesh validity. The tetrahedra near no-slip walls are shifted inward and the resulting gap between the tetrahedra and the walls is filled up with prismatic elements step by step. The addition of prismatic elements is stopped if a local mesh has incorrect topology. The method is applied to the experimental supersonic airplane model designed at NAL. Computed results by solving the Navier-Stokes equations are compared with wind tunnel data and the validity of the method is demonstrated., 資料番号: AA0063609060, レポート番号: JAXA-SP-06-029E

SST-CFDワークショップ.次世代超音速機の数値シミュレーション利用技術に関する国際ワークショップ 航空宇宙技術研究所 20011203-20011205 東京 日本, SST-CFD Workshop. International Workshops on Numerical Simulation Technology for Design of Next Generation Supersonic Civil Transport National Aerospace Laboratory 20011203-20011205 Tokyo Japan, This paper provides CFD (Computational Fluid Dynamics) flow analysis results of the NAL NEXST-1 (National EXperimental Supersonic Transport-1) for the 3rd NAL SST (SuperSonic Transport) CFD workshop. A hybrid unstructured grid system was employed for viscous aerodynamic analysis. Computations were conducted for both wind tunnel test condition and Flight Test condition. The CFD results showed very good correlation with wind tunnel test results., 資料番号: AA0063609059, レポート番号: JAXA-SP-06-029E

SST-CFDワークショップ.次世代超音速機の数値シミュレーション利用技術に関する国際ワークショップ: Toward the Future form NEXST-1 Flight Trial 宇宙航空研究開発機構 20061012-20061013 東京 日本, SST-CFD Workshop. International Workshops on Numerical Simulation Technology for Design of Next Generation Supersonic Civil Transport: Toward the Future form NEXST-1 Flight Trial Japan Aerospace Exploration Agency 20061012-20061013 Tokyo Japan, 資料番号: AA0063609068, レポート番号: JAXA-SP-06-029E

SST-CFDワークショップ.次世代超音速機の数値シミュレーション利用技術に関する国際ワークショップ: Toward the Future form NEXST-1 Flight Trial 宇宙航空研究開発機構 20061012-20061013 東京 日本, SST-CFD Workshop. International Workshops on Numerical Simulation Technology for Design of Next Generation Supersonic Civil Transport: Toward the Future form NEXST-1 Flight Trial Japan Aerospace Exploration Agency 20061012-20061013 Tokyo Japan, This paper provides CFD (Computational Fluid Dynamics) flow analysis results of the JAXA NEXST-1 (National EXperimental Supersonic Transport-1) for the 4th JAXA SST (SuperSonic Transport) CFD workshop. A hybrid unstructured grid system was employed for viscous aerodynamic analysis. Computations were conducted for the flight test condition, then computed and measured results are compared. Effects of some computational conditions, such as, choice of turbulence modeling, mesh density and numerical scheme, are studied., 資料番号: AA0063609075, レポート番号: JAXA-SP-06-029E

Three dimensional vortex structures in the wake region behind two dimensional cylinder in the laminar flow are analyzed. In the wake-transition regime of Reynolds number between about 190 and 260, experiments show discontinuous changes of Strouhal number and the existence of two modes; Mode A and Mode B whose span wise characteristic wave length are about 4 D (D: diameter of cylinder) and D respectively. The compressible Navier-Stokes equations are solved with the finite difference method. 4th order penta-diagonal compact scheme with 4th order Runge-Kutta time integration scheme are used for high accuracy and resolution. NSCB which is generalized into the body fitted grid system is applied to the boundary condition. Numerical results show good agreements with experimental data of Strouhal number for both Mode A and B in the wake-transition regime. Span wise characteristic wave lengths for both modes are captured clearly. These results show the validity of effectiveness of highly accurate and resolution methods used here for the analysis of complex flow structures., 資料番号: AA0049212024, レポート番号: JAXA-SP-05-017

Research in automatic grid generation around realistic 3D geometry is being conducted in Japan Aerospace Exploration Agency. This research aims at reducing the time required to generate computational grid for inviscid as well as viscous flow simulations. The method is based on hexahedra grid method, as the extension of Cartesian grid method. As the result, the method inherits significant advantages of Cartesian grid: it is automatic and fast. Because an efficient viscous flow simulation requires grid with high aspect ratio near solid surface, a hybrid with prismatic grid is necessary. The hexahedra grid extends naturally to this approach, because there is consistency in grid topology (both Cartesian and prismatic grids have the same hexahedral shape). The main idea of the method is as follows: construct Cartesian grid, remove the cells near solid surface, and construct hexahedral cells based on the Cartesian cells' faces toward the surface. Note that both grids are not constructed from the solid surface. This leads to another advantage: the method is not sensitive to defects in solid surface (e.g. crack, overlap), because it actually reconstruct the solid surface grid. However, because of the way the hexahedral cells are constructed (simple projection from Cartesian grid cells' faces toward solid surface), there is a disadvantage: it can not capture sharp concave features. A method to overcome this problem is devised in the present research. This paper provides the summary of the method being developed as well as some current results., 資料番号: AA0048469043, レポート番号: JAXA-SP-04-012

Recently, a CFD technology has been widely applied to aerodynamic design. To generate a computational grid around a geometry easily and calculate a flow field with high order of accuracy helps to understand a flow field. However, the ease of the grid generation and the accuracy of the calculation are usually inconsistent. In this paper, to make a three-dimensional grid easily and efficiently, the grid generation method with a cartesian grid around a three-dimensional complex geometry was proposed to accelerate the computational grid generation process and a grid generation time was reduced to half. Furthermore, by making clear the relation between the accuracy of the computation and the grid property such as the minimum grid spacing and the dense of the grid, it was proved the latter is much more effective to the accuracy of the computation., 資料番号: AA0048469041, レポート番号: JAXA-SP-04-012

航空宇宙技術研究所 17-19 Jan. 2000 東京 日本, National Aerospace Laboratory 17-19 Jan. 2000 Tokyo Japan, NALのSST(超音速輸送機)プロジェクトにおいて、機体およびエンジンの周りの複雑な流れを高次の乱流モデルでシミュレートするためにUPACS(CFDコード共有化プロジェクト)コードが用いられることになっている。UPACSはマルチブロック構造格子法を採用したマルチプロセッサCFD(計算流体力学)ソルバである。このコードの基本的構想およびいくつかの論点を本報告で論ずる。構造格子法は、高次微分スキームと乱流モデルを効率的に精度良く実行することが容易であるという利点を持つ。形状に適合させた構造化格子を複雑な流路に適用するために、マルチブロック分解法を用いなければならない。ブロック間の接合は2種に区別でき、一方は4ブロックが1点で会する構造化接合であり、他方は構造化以外の接合である。マルチブロックソルバの必要条件は、ブロック分解により結果が劣化しないことである。これらの条件を満たすために、隣接するブロック間でのデータ移動がしばしば行われることになる。UPACSに対して2つの要求がある。1つはCFD研究者のためのツールであり、もう1つは流体機械設計者のための汎用流体ソルバである。これらの要求を満たすために、UPACSはCFDのためのプラットフォームまたは環境として発展している。, In the SST (Supersonic Transport) project of NAL, UPACS (Unified Platform for Aerospace Computer Simulation) code is going to be used for the simulation of complicated flow around an airframe and engine with higher order turbulence models. The UPACS is a multiprocessor CFD (Computational Fluid Dynamics) solver employing the multiblock structural grid method. The basic concept of the code and some of its features are discussed in this report. The structured grid method possesses the advantages of ease in implementing higher order differential schemes and turbulence model with efficiency and accuracy. To apply body-fitted structured grids to a complicated flow passage, a multi-block decomposition method must be used. The connection between blocks is categorized into two types, one of which is the structured connection, defined as the connection where four blocks meet at one point and the other is the unstructured one. The requirement for a multiblock solver is that the result is not adversely affected by block decomposition. In order to satisfy these requirements, extensive data transfer between adjacent blocks has to be performed frequently. There are two requirements for UPACS; that it be a tool for CFD researchers and that it be a general-purpose flow solver for fluid-machine designers. To satisfy these requirements, UPACS is developing into a platform or an environment for CFD., 資料番号: AA0028638031, レポート番号: NAL SP-49T

航空宇宙技術研究所 16-18 Jun. 1999 東京 日本, National Aerospace Laboratory 16-18 Jun. 1999 Tokyo Japan, 3次元物体周りの非粘性流の高速な自動化解析のためのCartesian格子生成法を開発した。この方法は固体表面とCartesian格子の間の断面が簡単でない場合を考慮することができる。従って薄い物体や鋭角または複数固体領域などをセル内に含む場合を厳密に取り扱うことができる。このようなケースはしばしば超音速輸送機(SST)モデルの計算に現れてくる。計算効率を上げるために、セルの内側の物体表面を表すために擬似平面近似を行い、その結果この適用例では全物体表面の要素を約3分の1に減らすことができた。曲面のまわりの局所細分化格子について新アルゴリズムを使うことによってより高い計算効率を達成できる。, A Cartesian grid generation method has been developed for fast and automated analysis of inviscid flows around three dimensional bodies. It can take into account non-simple cases of intersection between a solid surface and a Cartesian grid, so that a cell containing a thin body, a sharp edge or multiple solid regions is properly handled. These cases appear frequently in the computation of a Supersonic Transport (SST) model. To increase the efficiency of computation, a pseudo-planar approximation is made to represent a body surface inside a cell, resulting in a reduction of total body surface elements by a factor of about three in this application. Higher efficiency is achieved using a new algorithm for local grid refinement around a curved surface., 資料番号: AA0001961042, レポート番号: NAL SP-44

航空宇宙技術研究所 12-13 Jun. 1997 東京 日本, National Aerospace Laboratory 12-13 Jun. 1997 Tokyo Japan, 超音速旅客機(HSCT)におけるエンジンナセル統合化のためのCFD(数値流体力学)による設計システムを述べた。システムは基本的に、少ない設計パラメータによる航空機形状モデリング、ユーザの最小限の介入により非構造表面および体積格子を生成する表面および体積のメッシングモジュール、および非構造格子を用いた効率的なCFD解析モジュールの3つで構成される。本システムの使用により、エンジンナセルをもつ完全なHSCT形状の数値解析を容易に行うことができる。HSCTの空力設計で高揚抗比(L/D)を達成するため、ナセル統合化形状は最も重要な設計因子の1つである。エンジンナセルを機体と統合化する場合、L/D比は一般に翼-ナセル干渉により劣化し、特に、超音速航行条件で著しい。しかしながら、良好な干渉により装着位置、ナセル形状および翼キャンバでL/D比を改善できる。本システムはエンジンの統合化形状の最適化研究に非常に有効である。種々のナセル形状および位置についてのオイラー計算結果も述べた。, A CFD (Computational Fluid Dynamics) based design system for the engine nacelle integration on a High Speed Commercial Transport (HSCT) is discussed. It consists of basically three modules, an airplane modeling which needs a small number of design parameters, a surface and volume meshing modules which generates unstructured surface and volume grids with minimum user's interventions, and efficient CFD analysis module using unstructured grids. Using this system, numerical analysis of complete HSCT configurations with engine nacelles can be easily carried out. In order to achieve a high Lift-to-Drag ratio (L/D) is HSCT aerodynamics design, a configuration of a nacelle integration is one of the most important design factors. When engine nacelles are integrated with an airframe, L/D is in general degraded due to the wing-nacelle interference, especially in the supersonic cruise condition. However favorable interference may enable L/D to be improved due to locations of installation, nacelle shapes and a wing camber. The present system is very effective to investigate engine integration configuration for the optimization. Results of the Euler calculations about various nacelle shapes and positions are also discussed., 資料番号: AA0001433012, レポート番号: NAL SP-37

航空宇宙技術研究所 6-7 JUN. 1996 東京 日本, National Aerospace Laboratory 6-7 JUN. 1996 Tokyo Japan, 計算機性能の進歩と共に、数値流体力学(CFD)が良く発展し、航空機並びに宇宙機の開発に役立つ極めて有望な設計ツールとなっている。通常は機体形状を定めるのにCAD(コンピュータ支援設計)ツールを用いる。流れ場を解析するためにはその周りに格子システムを構成する必要がある。しかし、通常の汎用CADソフトウエアパッケージではCFD解析に適する表面格子の生成をサポートしないので、この部分が障害となっている。CADデータを基に表面格子生成の予備研究を報告した。CADツールからの変換形式はIGES(初期図面交換仕様)形式を用いた。まず断面データから形状を再構築した結果、アイソパラメトリック曲線は格子曲線として極めて適切なものとなった。ついで、必要な数の格子点を割り振ることにより表面格子を生成させた。, With the progress of computer performance, Computational Fluid Dynamics (CFD) is well developed and it is very promising to utilize as a design tool for the development of aircraft and spacecraft. It is usual to define a configuration by using a CAD (Computer Aided Design) tool. It is necessary to construct a grid system around it for analyzing the flow field. But this part is a bottleneck since the usual general-purpose CAD software packages do not support the generation of surface grids suitable for CFD analysis. In this paper, the preliminary work of surface gird generation based on the CAD data is reported. Conversion format from a CAD tool is the IGES (Initial Graphic Exchange Specification) format. The configuration from the section data is first reconstructed so that the isoparametric curves are quite suitable as the grid curves. Then a surface grid is generated by assigning the number of grid points needed., 資料番号: AA0000685035, レポート番号: NAL SP-34

並行ブレード／渦干渉(BVI: Blade-Vortex Interaction)についてパラメトリック研究を行った。渦を捕捉するために、高い精度のCFD(Computational Fluid Dynamics)スキームと細かい格子系を使用した。翼型の位置からかなり上流に初期渦を置き、下流に向けて一様流によって伝搬させることにより、渦糸が並行にブレードと干渉する流れ場をシミュレートした。迎え角がゼロの場合の結果については、既存の実験結果とも比較し、良い一致が見られた。初期ミス・ディスタンス、翼型の迎え角、渦の回転方向の3つがパラメータとして選ばれた。BVIの強さは初期ミス・ディスタンスによって大きく変化し、迎え角が変わると、その変化の特徴が違ってくる。翼型が迎え角をとると、BVIレベルの最大値は翼型の前縁の垂直位置よりも低い初期ミス・ディスタンスのところで発生することが分かった。その原因としては、迎え角がある場合は、翼の前方に上向きの速度(アップワッシュ)が存在するため、渦が下流へ運ばれるときに上方向にも移動していることが観測された。実際のBVIの最大値は最終的には渦が直接翼とぶつかる、いわれるヘッドオン状態で発生しているが確認された。, A parametric study on parallel Blade-Vortex Interaction (BVI) is carried out. A high accuracy CFD (Computational Fluid Dynamics) scheme and a fine grid system are employed to capture the vortex. By locating the initial vortex well upstream of the airfoil, a parallel vortex interaction is simulated. The results are compared with the existing experimental data with good agreement. The initial miss distance, airfoil incidence, vortex rotation directions are chosen as the parameters for this parametric study. The BVI strength shows a high dependency on the initial miss distance and the feature changes with the airfoil incidence. The maximum BVI level occurs at the initial miss distance lower than the leading edge of the airfoil when the airfoil has incidences. The cause of the maximum BVI location change is observed due to the upwash exists ahead of the incident airfoil, which moves the vortex upward while the vortex is convected by the flow. At the maximum BVI level, the final miss distance between the vortex and the airfoil is nearly zero, the head-on BVI as so-called., 資料番号: AA0063918000, レポート番号: JAXA-RR-07-051E

ロータの回転や6自由度の機体運動などの複雑な動きのため、メイン／テールロータおよび胴体からなるヘリコプタの数値シミュレーションにおいて、正確で速い補間アルゴリズムの重要性が高まってきている。本報告では、直交格子と曲線格子で構成される移動重合格子を利用したCFD(Computational Fluid Dynamics)コードに対して、より正確で早い補間法を提案した。新しい補間法では、(1)直交格子の特性、(2)ヘリコプタ・ブレードの特殊な幾何学的配置、および(3)並列計算時の計算負荷バランスなどを十分有効に利用できるアルゴリズムが考案されている。第1章では、Alternating Index Searching(AIS)アルゴリズムを提案し、従来のLinear Searchingアルゴリズムに対し、2次元の簡単なケースと実際のヘリコプタを模擬した3次元計算のケースで補間計算の速度を比べた。第2章では、並列計算における各計算ノードの負荷バランスを考慮したReverse Index Searching(RIS)アルゴリズムを提案した。この補間法を利用することによって、ヘリコプタのより効果的な大型計算を実現することができた。, The importance of accurate and fast interpolation algorithm is growing up for multi-body configuration with arbitrary overlap. One of the critical cases can be a helicopter simulation because of the complex relative movement of rotor-rotation and body motion. In this paper, new searching algorithms are implemented for the interpolation between two different grids, Cartesian grid and curvilinear grid, of which the overlapped grid system consists for the massive computation of the full helicopter configuration. These searching algorithms are proposed to make full use of (1) the characteristics of Cartesian grid, (2) special geometric configuration of helicopter, and (3) load balancing in parallel computation. In the first stage, Alternating Index Searching (AIS) algorithm, which alternates a searching direction by jumping the grid index to the searching point, is constructed to compare the iteration speed with a conventional Linear Searching (LS) algorithm. Simple two dimensional problems and three dimensional helicopter simulations are conducted to compare the efficiency of these searching algorithms. The result shows a considerable enhancement in computing time for whole computation domain. In the second stage, Reverse Index Searching (RIS) algorithm, which is developed to consider the load balance among each Processing Element (PE) during parallel computation, is proposed. By applying these searching algorithms, efficient massive computation can be achieved for the helicopter configuration., 資料番号: AA0063881000, レポート番号: JAXA-RR-07-024E

SST-CFDワークショップ.次世代超音速機の数値シミュレーション利用技術に関する国際ワークショップ: Toward the Future form NEXST-1 Flight Trial 宇宙航空研究開発機構 20061012-20061013 東京 日本, SST-CFD Workshop. International Workshops on Numerical Simulation Technology for Design of Next Generation Supersonic Civil Transport: Toward the Future form NEXST-1 Flight Trial Japan Aerospace Exploration Agency 20061012-20061013 Tokyo Japan, CFD (Computational Fluid Dynamics) analyses of a flow field around supersonic transport, NEXST-1 (National EXperimental Supersonic Transport-1) are conducted. The CFD results are compared with flight test data. In this paper, C(sub D) and C(sub p) discrepancies between them are mainly discussed with consideration of the effects of transition and local geometry change by protuberances of measuring instruments. As for the C(sub D) discrepancies, CFD results have more (4-9 cts) profile drag, which could be the sum of spurious numerical error and turbulence model mismatch. As for the C(sub p) discrepancies, C(sub p) values at local points are definitely influenced by protuberances. Through the discussion, we also demonstrate how the CFD simulation can augment the validity of the flight test data., 資料番号: AA0063609073, レポート番号: JAXA-SP-06-029E