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Transient thermal response behavior of hypersonic reentry flight test vehicle HYFLEX (Hypersonic Flight Experiment) was investigated. The iterative CFD (Computational Fluid Dynamics)/FEM (Finite Element Method) coupling analysis was carried out. In this study, flow field around the body is computed by the finite volume Navier-Stokes equation solver FIVAD. On the other hand, heat conduction behavior is calculated by the finite element solver THAP. The NWT (Numerical Wind Tunnel) system and CMS (Common work Station) system of NAL are used for simulation, with the data file transfer by LAN (Local Area Network)., 極超音速で大気圏に再突入する実験機HYFLEX(極超音速飛行実験)について、空力加熱解析と構造熱伝導解析を連成させて、非定常熱応答の数値シミュレーションを試みた。対象をHYFLEX機体前胴部とし、空力解析は有限体積法コードFIVADを用い、熱伝導解析は有限要素法コードTHAPを用いた。計算には航空宇宙技術研究所の大規模並列ベクトルコンピュータシステムである数値風洞(NWT)と構造計算用ワークステーションシステム(CMS)を用い、データファイル転送による分散処理を行った。

Transient thermal response behavior of hypersonic reentry flight test vehicle HYFLEX (Hypersonic Flight Experiment) was investigated. The iterative CFD (Computational Fluid Dynamics)/FEM (Finite Element Method) coupling analysis was carried out. In this study, flow field around the body was computed using the finite volume Navier-Stokes equation solver FIVAD. On the other hand, heat conduction behavior was calculated using the finite element solver THAP. The NWT (Numerical Wind Tunnel) system and CMS (Common Work Station) system of NAL were used for simulation, with the data file transfer by LAN (Local Area Network)., 極超音速で大気圏に再突入するHYFLEX(極超音速飛行実験)実験機について、過渡熱応答挙動を研究した。ここでは反復CFD/FEM(計算流体力学/有限要素法)結合解析を実施した。本研究では機体周りの流れ場をナビエ・ストークス方程式有限体積法コードFIVADを用いて計算した。熱伝導挙動は有限要素法コードTHAPを用いて計算した。シミュレーション計算には航空宇宙技術研究所の数値風洞(NWT)と共通ワークステーションシステム(CMS)を用い、データファイル転送は局地ネットワーク(LAN)を使用した。

The following subjects on CFD (Computational Fluid Dynamics) are discussed: (1) SST (Supersonic Transport), scaled high-speed experimental aircraft, aerodynamic design of a SST wing, bleed and bypass effects of nacelles; (2) high enthalpy flows, chemical reaction model of aerodynamic heating, shock wave induced unsteady aerodynamic heating; (3) aircraft engine/space propulsion, three dimensional unsteady flow analysis in turbomachinery; (4) rotor, flowfields around main rotor, development of rotor CFD codes, and (5) turbulence, turbulence of compressible flows, turbulent heat transfer in a channel between parallel plates., CFD(数値流体力学)に関する次の主題を論じている。(1)SST(超音速輸送)、小型高速実験機、SSTの主翼空力設計、ナセルのブリード流/バイパス流効果、(2)高エンタルピー流れ、空力加熱の化学反応モデル、衝撃波誘起非定常空力加熱、(3)航空エンジン/宇宙推進、航空機エンジン内の3次元非定常流れ解析、(4)回転翼、ヘリコプタ・メインロータ周りの流れ、ロータCFDコードの開発、および(5)乱流、圧縮性流体の乱流、平行平板間の乱流熱伝達。

National Aerospace Laboratory (NAL) is scheduled to become an independent administrative agency. In order to reinforce the relation with other organizations, three technology development centers will be constructed, one of which is CFD (Computational Fluid Dynamics) technology development center. The CFD center is going to conduct a new research program concerning the numerical simulation technology on multidisciplinary problem. The program is composed of the development of multi-disciplinary simulation codes, verification and standardization of the codes, development of the key technology and the super computer system. This paper summarizes the role of the CFD technology development center and its planned activities in the coming four years., 航空宇宙技術研究所(NAL)は独立行政法人となる予定であるが、他組織機関との関係を強化するために3つの技術開発センターが設立される予定であり、そのひとつがCFD(計算流体力学)技術開発センターである。CFDセンターは、多学問分野の問題での数値シミュレーション技術に関する新しい研究プログラムを実施する予定である。本プログラムは、多学問分野シミュレーションコードの開発、コードの検証と標準化、基幹技術の開発およびスーパコンピュータからなる。本稿では、CFD技術開発センターの役割と今後4年間の活動予定について概要を述べた。

Parallel performance with CFD (Computational Fluid Dynamics) programs on the NWT (Numerical Wind Tunnel) and the PARAGON installed National Aerospace Laboratory was already reported. In this paper, the characteristics of Laplace equation solver programs, number of operations, amount of memory and sequence of operations are analyzed. And also the effective performance of execution, memory access latency and network bandwidth of these parallel computers are analyzed. The suitability of parallel programs and parallel computers with their characteristics of operations and network communications are reported., 航空宇宙技術研究所に設置のNWT(数値風洞)およびPARAGON(パラゴン)でのCFD(数値流体力学)プログラムによる並列性能については、既に報告した。本報告では、ラプラス方程式ソルバプログラムの特性、演算数、メモリ量および演算シーケンスを解析した。また、これら並列計算機の実行の効率的性能、メモリアクセス待ち時間およびネットワーク帯域幅も解析した。オペレーション特性およびネットワーク通信での並列プログラムおよび並列計算機の適合性を報告した。

In 1993, National Aerospace Laboratory (NAL) introduced a very high performance distributed parallel-vector supercomputer called Numerical Wind Tunnel (NWT-1). In the seven years since the NWT-1 system was established, many achievements have been made with it, particularly in Computational Fluid Dynamics (CFD). Contrary to expectations, however, the high data productivity comparable to wind tunnel testing has not yet been attained. The next generation supercomputer NWT-2 aims to meet the demands to apply CFD techniques to design processing, with its high data-productivity and increased system-operability making possible multidisciplinary analysis and design optimization. The following points are focused on: (1) high computing performance for use in multidisciplinary analysis and optimization; (2) the total system integration including data storage integration, visualization and storage-region-networking; and (3) environment for developing seamless user-friendly software. Developing a CFD-based aerodynamic design method using an inverse analysis is one of the major goals in the NAL SST (Supersonic Transport) project, and the NWT-2 is considered to play an important role as the computing foundation., 1993年に、NALは数値風洞(NWT)という高性能の分散型並列ベクトル・スーパコンピュータを導入した。NWT-1システムが設置されてから既に7年が経過し、特に計算流体力学(CFD)において多くの業績をあげてきた。しかし、風洞試験と比較し得るデータ生産性などの性能については、期待に反して未だ満足いくものではなかった。次世代のスーパコンピュータNWT-2は、高データ生産性とシステム操作性の向上を実現し、CFD技術が複合領域解析と設計最適化を通して設計過程に適用可能にすることなどの要求を満たすように計画されている。以下の点に焦点を合わせた。(1)複合領域解析と最適化が行える高計算性能、(2)データ記憶、視覚化、記憶領域ネットワークを含めた全システム統合化、(3)ユーザフレンドリーな使用を可能にする環境を開発する統一ソフトウェア。逆解法を用いたCFDに基づく航空力学設計法を開発することが、NALのSST(超音速機)プロジェクトの大きな目標の1つであり、NWT-2は計算基盤として重要な役割を果たすと考えられる。

An unsteady Euler code for rotor blade aerodynamics is developed. A moving overlapped grid method is employed to treat rotating blades. This code has an ability to analyze rotor blade aerodynamic characteristics without modeling wake and tip vortex. Two grid systems are employed to solve the Euler equations. One of the grid systems wraps the rotor blade using Boundary Fitted Coordinates (BFC). The other is the Cartesian background grid covering the whole calculation region including the entire rotor. The calculation is carried out on Numerical Wind Tunnel (NWT) in National Aerospace Laboratory (NAL) to perform large scale and accurate computations. This method is applied for the calculations of hovering and forward flight conditions. The capability of capturing tip vortex is shown by some visualized iso-surfaces of the vorticity magnitude in both cases. In the hover case, the reasonable agreements are obtained between computed and measured pressure distributions on the blade surface and tip-vortex trajectories., ロータブレードの空気力学のために非定常オイラーコードを開発した。移動複合格子法を用いて、ロータブレードを取り扱った。本コードは伴流および翼端渦のモデル化しないで、ロータブレードの空力特性を解析することができる。2つの格子システムを用いて、オイラー方程式を解いた。1つの格子システムはBFC(境界適合調整法)を用いてロータブレードを覆う。もう1つの格子システムでは全ロータにわたる計算領域全体を覆う背景計算格子である。計算はNAL(航空宇宙技術研究所)のNWT(数値風洞)で行い、大規模かつ正確な計算をした。本手法をホバリングおよび前進飛行条件の計算に適用した。両方の場合について、翼端渦を捉えることができることを可視化した等渦度面により示した。ホバーの場合、翼面圧力分布および翼端渦軌跡の計算と計測はかなり良く一致した。

Homogeneous isentropic turbulence is an idealized turbulent flow expected to appear in a flow being far from the solid boundary. A numerical simulation of decaying isotropic turbulence with a high resolution equal to 512 x 512 x 512 spatial mesh points was performed by using the Numerical Wind Tunnel, a parallel computer system, at National Aerospace Laboratory. The energy spectrum of the turbulence was served as a fundamental quantity, describing an important scaling characteristic of exited turbulent fluctuations. The simulation was started from an initial turbulent velocity, generated randomly from an assigned initial energy spectrum. The computation was done until the normalized time of 20, when the total magnitude of the turbulence energy decayed to some 15 percent of the given value at the initial time. As a result, the special fine structures, obtained by the simulation, have revealed that the intense regions of the turbulent velocity are concentrated into local fine vortex tubes, so called worms., 同次等方性乱れは、一種の理想化乱れであり、物体表面からの遠方流中に発生するものと見なすことができる。ここでは、このような乱れの崩壊過程の数値シミュレーションを実施した。計算は、高分解度を期待して、空間格子点を512の3乗にとり、航空宇宙技術研究所の数値風洞を使用した。計算方法は、初期擾乱を与える方法を採用したので、励起乱れの発達過程のスケール特性を記述できる乱れエネルギースペクトル方程式に準拠した。計算時間は、無次元時間20まで、また、乱れエネルギーが初期値の15%まで崩壊したとき打ち切った。結果は、乱れ渦度の空間的微細構造が、いわゆる線虫形構造と呼ばれる微細渦管となって集中的に局在する様子を描き出している。

A Genetic Algorithm (GA) has been applied to optimize a wing aerodynamic shape for generic subsonic transport aircraft using Navier-Stokes computations. Conventional optimization schemes are not suitable for aerodynamic optimization problems as they fall into a local optimum. Since a GA searches multi-directionally, the resulting aerodynamic optimization algorithm finds a global optimum. Moreover, as the algorithm itself is very simple and thus very robust. However, a GA needs enormous computational time. Previous study indicated that 2-D optimization of airfoil shape with GA and Navier-Stokes calculation needs several hundred CPU time on CRAY C90 single processor. From this study, it was realized that 3-D optimization with GA will require unacceptable CPU time even on a supercomputer. Thus, any 3-D optimization of wing shape has never been done before with a GA and Navier-Stokes calculation though Navier-Stokes calculation is necessary to evaluate L/D (Lift to Drag ratio) of a wing precisely. In this study, to overcome enormous CPU time necessary for this optimization: (1) spanwise maximum thickness and twist angle distributions are selected as design variables; (2) the multigrid technique is applied to the 3-D Navier-Stokes computation; and (3) the computation is parallelized on numerical wind tunnel at National Aerospace Laboratory, which is a parallel vector machine with 166 processing elements. The objective of the present optimization is to maximize L/D of wing shape. To avoid apparent solution of zero thickness wing for low drag in high speed, a structural constraint is considered. In the optimum design obtained from the present GA, the design principles for the wing developed by existing theory and experience are found to be materialized. This indicates feasibility of the present approach for the aerodynamic optimization in advanced computational environments., ナビエ・ストークス数値計算を用いた一般亜音速輸送機用の空力翼形状の最適化に遺伝的アルゴリズム(GA)を適用した。通常の最適化スキームは局所的な最適解にとどまるので空力最適化問題には適していない。GAは多方向的に探索するので、結果的に空力最適化アルゴリズムは大域的な最適解を見つけ出す。さらに、アルゴリズム自体が極めて単純で、非常にロバストである。しかし、GAは膨大な計算時間を必要とする。前回の研究で、GAとナビエ・ストークス計算による翼形状の2次元最適化計算にはCRAY-C90の単一プロセッサ当たり数百CPU時間を必要とすることを指摘した。この研究で、GAによる3次元最適化にはスーパーコンピュータでも受け入れがたいほどのCPU時間を必要とすることに気付いた。したがって、翼のL/D(揚抗比)を正確に評価するのにナビエ・ストークス計算を必要とするにもかかわらず、これまでGAおよびナビエ・ストークス計算による翼形状の3次元最適化を行わなかった。この最適化に必要な膨大なCPU時間を克服するために、(1)スパン方向の最大翼厚分布とねじり角分布を設計変数として選定し、(2)多重格子法を3次元ナビエ・ストークス計算に適用し、(3)166の処理素子を有する並列ベクトル機である航空宇宙技術研究所の数値風洞を用いて計算を並列化した。本研究の最適化目的は翼形状のL/Dを最大にすることである。高速度中の低い抗力に対し翼厚さゼロという見掛け上の解が出るのを避けるために、構造上の制限を考案した。本研究のGAから得た最適設計の中で、既存の理論と経験から開発した翼に対する設計原理が具体化されることが分かった。このことは高次コンピュータ環境にあって、空力最適化に対する現在の研究法が実現可能であることを示している。

In this paper the concepts and detailed functions of the MSP View User Interfaces are presented. It is a distributed memory parallel computer with UNIX operating system and is developed for the Numerical Wind Tunnel (NWT). Users at the NAL however were very skilled in the use of MSP operating systems for general purposes, and it was necessary therefore to ensure continued usability by users and of user assets. For this reason Interfaces in NWT were made in MSP View. Catalogued procedures (NS-CATAPRO) and command procedures (NS-COMMAND) were developed as MSP View User Interfaces. In job processing with these Interfaces a number of the differences between UNIX and MSP can be discounted, and NWT used in the same manner as MSP. As a result, users can use NWT easily and with confidence. Moreover, there is no need to change resources from MSP to UNIX. Experiments have shown that the intended effectiveness of MSP View User Interfaces has been achieved., 主記憶分散型並列コンピュータである数値風洞(NWT)のジョブ処理に必要なユーザ・インタフェイスを開発した。NWTのオペレーティング・システム(OS)はUNIXであるが、航技研ユーザは長年運用されてきた汎用OSのMSPシステムの利用に長けていた。したがって、NWTにおいても、ユーザ利用性の継続とユーザ資産の継承を図る必要があった。この観点から、NWTのユーザ・インタフェイスはMSPビューとした。本稿では、MSPビュー・ユーザ・インタフェイスとして開発されたジョブ制御言語マクロ形式のNSカタプロと会話型マクロ・コマンド形式のNSコマンドを利用したジョブ処理について述べる。これらのユーザ・インタフェイスを利用したジョブ処理の中では、2つの異種OSの相違が自動吸収され、UNIXシステムのNWTを従来OSのMSPと等価な利用とすることが実現した。この結果、NWTの運用において、ユーザ利用性の継続とユーザ資産の継承という所期の目標を達成することができた。

NWT (Numerical Wind Tunnel) is a high performance parallel computer. It has served at the very high CPU (Central Processing Unit) utilization rate. To make the best use of NWT, the behaviors of Input/Output (I/O) on NWT jobs were investigated, and it was found that NWT jobs have a serious problem to deteriorate the performance. It is in the output process of Fortran unformatted sequential writing. The scheme that improves the performance has been found, and the importance of I/O performance on NWT jobs is recognized. In this paper the statistical and actual surveyed data of the I/O performance on NWT jobs, and the details of the method to solve this problem are shown., 数値風洞(NWT)は高処理性能並列計算機である。これは非常に高いCPU(中央処理装置)稼働率で運用されている。NWTを有効に使用するためにNWTジョブの入出力(I/O)の性能を調査し、NWTジョブが処理性能を低下する重大な問題を抱えていることが判った。その問題は書式なしフォートランレコードの出力性能にある。この処理性能の改善案を見出し、NWTジョブのI/O処理性能の重要性を認識した。本報では、NWTジョブのI/O処理性能の統計的および実測データ、ならびに本問題を解決する方法の詳細を示した。

The following topics on aerospace numerical simulation were discussed: computational fluid dynamics, development of super sonic transports, reusable space transportation systems, aero-engine simulation, computer development, numerical wind tunnels, the computational aerodynamics system for performance evaluation and research, airfoil stall, aerothermodynamic environments, transonic flow analysis, aerodynamic design, nozzle flow, fluid flow in rotating heated curve pipes, flow visualization, flap distortion, turbulence analysis, take-off characteristics, aeroelasticity analysis, tip leakage vortex breakdown, blade wake interaction, supersonic pulse jets impinging, mixing enhancement, and boundary layer thickness., 航空数値シミュレーションに関する、以下の主題を論じている。計算流体力学、超音速旅客機および宇宙往還機開発、航空用エンジンシミュレーション、計算機開発、数値風洞、航空機性能評価システム、翼型失速、熱空力環境、遷音速流解析、空力設計、ノズル流れ、回転曲管内流、流れの可視化、フラップ歪み、乱流解析、離陸時特性、空力弾性解析、翼端漏れ渦崩壊、翼後流相互作用、超音速パルスジェット衝突、混合促進、および境界層厚。

Numerical simulations of a flow around an HSCT (High Speed Civil Transport) model are carried out in order to establish reliability of CFD (Computational Fluid Dynamics). Multi block type structured grid and parallelization by message passing library are used to treat three dimensional complex configurations. Numerical results are compared with experimental data and they show good agreement. Numerical simulations are also carried out in order to check grid convergence., CFD(数値流体力学)の信頼性を確立するために、HSCT(高速民間輸送機)模型周りの流れの数値シミュレーションを実行した。3次元複合構成を処理するために、メッセージパッシング・ライブラリーによるマルチブロック型構造化格子と並列化を使用した。数値結果は実験のデータと比較され、それらはよい一致を示した。さらに、格子の収斂を確認するために、数値シミュレーションを実行した。

A parallel numerical simulation code for three-dimensional spray combustion in an aircraft combustor has been developed. In this code, the Euler equations are used for the droplet phase assuming a continuous fluid, and the full Navier-Stokes equations are applied for the gas phase. Both phases are connected through mass, momentum and energy exchange equations, and solved simultaneously. The droplet phase has a radius distribution, and is divided into five groups of different initial radius, and they are treated as individual phases. And vaporization and combustion of fuel droplets are included in the calculation. Both phases are solved by the finite difference method, and the Harten-Yee's explicit non-MUSCL (Monotone Upwind Schemes for Conservation Laws) modified-flux type TVD (Total Variation Diminishing) scheme is applied to convective terms and the central difference scheme is to viscous terms of the gas phase. On the other hand, because the phenomena of spray combustion are complicated over the whole combustor, minute simulation requires fine calculation grid, and it takes large computational memory and time. So, to extend the code to three-dimension, parallel calculation method was used to divide calculation region and gas-liquid phases, and each calculation was treated on each Processor Element (PE). And a model flow field of liquid fuel combustor was numerically simulated by a parallel super computer NWT (Numerical Wind Tunnel) in the laboratory., 航空用燃焼器における3次元噴霧燃焼のための並列数値シミュレーションコードを開発した。本コードでは、液滴相を連続流体と仮定してオイラー方程式を用い、気相には完全ナビエ・ストークス方程式を適用した。質量、運動量およびエネルギー交換方程式により両相を結合し、同時に解を求めた。液滴相は粒径分布を有し、異なる5つの初期粒径グループに分割し、それぞれを個々の相として取り扱った。燃料液滴の蒸発および燃焼を計算に含めた。両相を有限差分法により解き、対流項にはHarten-Yeeの陽的非MUSCL(保存則に対する単調上流中心)改良流束型TVD(全変動減少)法(Harten-Yee's explicit non-MUSCL modified-flux type TVD scheme)を、気相の粘性項には中心差分法を適用した。一方、噴霧燃焼の現象は燃焼器全体にわたって複雑なので、精密なシミュレーションでは綿密な計算格子が必要となり、大きな計算メモリおよび時間を要した。そこで、コードを3次元に拡張するため、計算領域と気・液相を分割する並列計算法を用いて、それぞれをPE(プロセッサ要素)ごとに取り扱った。当研究所の並列スーパコンピュータNWT(数値風洞)を用いて、液体燃料燃焼器の流れ場モデルを数値シミュレーションした。

Three dimensional aerothermodynamic analyses of flows around re-entry vehicles, such as HYFLEX (Hypersonic Flight Experiment), Space Shuttle, and HOPE (H-2 Orbiting Plane), have been carried out on the Numerical Wind Tunnel (NWT) of the National Aerospace Laboratory. The simulations have been performed with a domain-decomposition parallel-processing approach. Comparison of the results with data from flight measurements and/or numerical simulation by other programs has been made., 航空宇宙技術研究所の数値風洞(NWT)を用いて、HYFLEX(極超音速飛行実験)機、スペースシャトルおよびHOPE(H-2ロケット打上げ型有翼回収機)のような再突入機の周りの流れを3次元熱空力解析した。領域分割並列処理法によりシミュレーションを実行した。ほかの計画で実施の飛行計測および/または数値シミュレーションからのデータとここでの結果を比較した。

In this work, three objectives and two constraints are considered for wing planform optimization: aerodynamic performance, wing weight and fuel weight. Aerodynamic performance is evaluated by Computational Fluid Dynamics (CFD). Wing weight and fuel tank volume are estimated by empirical formulae. To simplify the problem, only the leading-edge sweep angle and two chord lengths at the midspan and wingtip are used as design variables. The leading edge of the wing is kept straight. Thus, a tapered wing with a trailing-edge kink will be designed. As an optimizer, Genetic Algorithm (GA) is employed here. Because GA can find a more global optimum, it is expected to perform better than the conventional gradient-based methods. Major drawback of GA is that it requires a large number of function evaluations. Thus, FLO-22 code based on the full potential equation is used because of its efficiency instead of Euler or Navier-Stokes solver. Evaluations of GA population are parallelized an Numerical Wind Tunnel (NWT) at National Aerospace Laboratory (NAL). Planform optimization problems are considered for typical subsonic and transonic aircraft. The design results show the feasibility of the present approach for the initial sizing with optimization., 本研究では、空力性能、翼重量および燃料重量などの翼平面形状の最適化に関して、3つの目的関数ならびに2つの制限を考察した。CFD(数値流体力学)により空力性能を評価した。翼重量および燃料タンク容積を経験式により推定した。問題を単純化するため、前縁後退角および中央と翼端での2つの翼弦長のみを設計変数として用いた。翼前縁を直線とした。このようにして、後縁キンクを伴うテーパ翼の設計を試みた。ここでは最適化にGA(遺伝的アルゴリズム)を採用した。GAでは大域的最適化を見出せるので、従来の勾配法よりも良い性能設計が期待される。GAの大きな欠点は多数の関数評価を要することである。そこで、オイラーまたはナビエ・ストークスソルバに代えて、効率の良い完全ポテンシャル方程式に基づくFLO-22コードを用いた。NAL(航空宇宙技術研究所)のNWT(数値風洞)でGA個体集団の評価を並列処理した。翼平面形状最適化問題を典型的亜音速および遷音速航空機として考察した。設計結果は、初期形状を最適化するこの方法の実現可能性を示した。

A code of the 'Rarefied Gas Numerical Wind Tunnel (RGNWT)' developed for the Monte Carlo direct simulation of rarefied gas flows is paralleled to work on the Numerical Wind Tunnel (NWT) parallel vector computer system. Some simulation results indicate that the NWT is preferable to the Monte Carlo direct simulation of rarefied gas flows., 希薄気体流れのモンテカルロ直接シミュレーションのため開発した｢希薄気体数値風洞(RGNWT)｣コードを航空宇宙技術研究所の並列処理ベクトル計算機システム(NWT)上で動かすべく並列化した。シミュレーションを行った結果によれば、NWTは希薄気体流れのモンテカルロ直接シミュレーションに適している。

For the numerical investigation of the unsteady flow in turbomachinery components, a simulation system has been developed. In the paper, some of the key features of the code will be described and applications to unsteady turbomachinery flow will be presented. As a part of a common research project between the National Aerospace Laboratory (NAL) and the German Aerospace Research Establishment, this program system has been successfully implemented on NAL's Numerical wind tunnel. Concerning this, some performance tests will be also discussed., ターボ機械構成部品内の非定常流の数値研究として、シミュレーションシステムを開発した。コードの主要な特徴の幾つかを記述し、非定常ターボ機械流への適用を報告した。航空宇宙技術研究所(NAL)とドイツ航空宇宙研究所との間の共同研究プロジェクトの一環として、本プログラムシステムをNALの数値風洞において使用し、成功した。いくつかの性能試験についても論じた。

JAXA Special Publication, 宇宙航空研究開発機構特別資料

The Numerical Wind Tunnel (NWT) is a distributed memory parallel computer for research and development in numerical simulation. Effective utilization is a major consideration in the design of the NWT system. User interfaces in NWT were produced in the same manner as in the existing system (Fujitsu FACOM VP-2100), comprising shell-scripts (NS-Shell) and command procedures (NS-Command). Numerous job-processing functions were included, resulting in a system that may be used easily and with confidence and delivering high overall performance. Experiments confirmed that all goals for system effectiveness were achieved. In this paper concepts and detailed functions of system design for NWT jobs are presented, along with their availability., 数値風洞(NWT)は、航技研の研究開発における数値シミュレーション処理を目的とした主記憶分散型並列計算機システムである。NWTの高度有効利用を実現するために、ジョブ処理におけるシステム構築を行った。ジョブ処理のNSシェルとNSコマンドと呼称するユーザ・インタフェイスを開発し、これらにNWTのジョブ処理用に必要となる多くの機能を集約した。また、NSシェルとNSコマンドは航技研ユーザが利用に長けている従来システム(Fujitsu FACOM VP-2100)の形式とした。実運用において、NSシェルとNSコマンドは有効に活用され、UNIXに不慣れなユーザの容易かつ確実なジョブ処理を実現している。その結果、NWTは所期の目標どおり、高度有効利用を可能にするシステム運用を実現した。本稿では、NWTのジョブ処理におけるシステム構築とその有効性について報告する。

The experimental airplane R&D (Research and Development) program has been initiated in NAL of Japan in order to establish the advanced technologies including the sophisticated CFD (Computational Fluid Dynamics)-design for the next generation supersonic civil transport. CFD technology will be developed through developing the experimental airplanes in the program for the optimized and automated design technology, which should become the major technology for designing aerodynamically high performance aircraft. The un-powered and jet-propelled airplanes will be developed and tested in the flight to verify the fruits of the NAL's research work. The program term would be between 1997 and 2004. International and domestic institutes are invited to the research cooperation., JAXA Special Publication, 宇宙航空研究開発機構特別資料

CFD (Computational Fluid Dynamics) activity for hypersonic flow simulation has increased enormously due to the developments of Japanese re-entry spacecraft, OREX (Orbital Re-entry Experiment), HYFLEX (Hypersonic Fluid Experiment), and HOPE-X (H-2 Orbiting Plane-Experimental). HOPE-X will be launched in 2001 and several hundreds of numerical computations are being performed for the aerodynamic design of HOPE-X, by using NWT (Numerical Wind Tunnel) at NAL. With these design analyses, validation of CFD codes are made by comparing numerical results with several hypersonic wind tunnel experiments. Moreover, through these analyses, it is known that real gas effects are important design factors in the evaluation of aerodynamic and aerothermodynamic characteristics. Trim capability and efficiency of control surfaces, such as elevons and body flaps, are significantly influenced by these real gas effects. In this paper, recent CFD results and validation process for the study of hypersonic aerodynamics of HOPE-X are introduced., 日本の再突入宇宙機、OREX(軌道再突入実験)機、HYFLEX(極超音速飛行実験)機およびHOPE-X(宇宙往還機技術試験機)の開発に関連して、極超音速流シミュレーションのためのCFD(数値流体力学)解析の研究が大変盛んになってきた。HOPE-Xは2001年に打上げ予定であるが、HOPE-Xの空力設計のため、NAL(航空宇宙技術研究所)のNWT(数値風洞)を用いて、数100回の数値計算が行われている。これらの設計解析に伴い、数値結果と幾つかの極超音速風洞実験との比較により、CFDコードの検証がなされた。さらに、これらの解析を通して、空力および空熱力特性の評価において、実在気体効果が重要な設計ファクタであることが分かった。エレボンおよび機体フラップのような制御面のトリム能力および効率は、これら実在気体効果によって著しい影響を受ける。本論文では、HOPE-Xの極超音速空気動力学の研究に関する最近のCFD結果および検証プロセスを紹介した。

Multiobjective genetic algorithms based on Fonseca-Fleming's Pareto-based ranking and fitness sharing techniques have been applied to aerodynamic shape optimization of compressor cascade airfoil design. Unlike the single objective optimization, the solution to Multiobjective Optimization (MO) is not a single point, but a family of points known as the Pareto-optimal set. By maintaining a population of solutions Genetic Algorithm (GA) can search for many Pareto-optimal solutions in parallel. Airfoil performance is evaluated by a Navier-Stokes code. Evaluation of GA population is parallelized on Numerical Wind Tunnel (NWT), a parallel vector machine, located at National Aerospace Laboratory. The present MO seeks high pressure rise, high turning angle and low total pressure loss at a low Mach number. Consequently, all of GA population became Pareto-solutions, and some of these solutions showed high pressure rise, high turning angle and low total pressure loss. The performance of the resulting airfoils is compared with that of the existing Controlled Diffusion Airfoil (CDA)., 圧縮機翼列翼型設計における空力形状最適化に、FonsecaとFlemingのパレートランキング法および適応度シェアリング技法に基づく多目的遺伝的アルゴリズムを適用した。単目的最適化とは異なり、多目的最適化(MO)での解は単一でなく、パレート最適セットとして知られる解の集合である。解集団を保持することにより、GA(遺伝的アルゴリズム)は多数のパレート最適解を同時に探索することが出来る。ナビエ・ストークスコードにより翼型性能を評価した。航空宇宙技術研究所の並列ベクトル計算機NWT(数値風洞)で、GA解集団の評価を並列処理した。ここで示したMOでは、低マッハ数での高圧縮比、高転向角および低全圧損失を目標とした。その結果、すべてのGA解集団はパレート解となり、これらの解の幾つかは高圧力上昇、高旋回角および低全圧損失を示した。結果として得られた翼型性能を既存の拡散制御翼(CDA)性能と比較した。

JAXA Special Publication, 宇宙航空研究開発機構特別資料

A Genetic Algorithm (GA) has been applied to optimize a transonic wing shape for generic transport aircraft. The extended Joukowski transformation as well as NACA five-digit series is used as airfoil definition of a wing to design a transonic wing geometry which maintains enough wing thickness to stand the bending moment due to the lift distribution. A three-dimensional compressible Navier-Stokes (N-S) solver is used to evaluate aerodynamic performance. The N-S evaluation is parallelized on Numerical Wind Tunnel (NWT) at National Aerospace Laboratory in Japan, a parallel vector machine with 166 processing elements. Designed wings show a trade-off between an increase of the airfoil thickness driven by a structural constraint and a reduction of the wave drag produced by a shock wave. Further investigations are necessary for the airfoil definitions as well as the GA operators., 一般的輸送機の遷音速翼形状の最適化にGA(遺伝的アルゴリズム)を適用した。NACA5桁方式のほかに、拡張ジューコフスキー変換を翼型定義として用いて、揚力分布による曲げモーメントに耐えられるほど十分な翼厚を保つ遷音速翼形状を設計した。3次元圧縮性N-S(ナビエ・ストークス)ソルバを用いて、空力性能を評価した。日本の航空宇宙技術研究所の166処理要素を有する並列ベクトル計算機NWT(数値風洞)を用いて、このN-S評価を並列処理した。設計翼では、構造的制約による翼型厚みの増加と衝撃波による造波抗力の減少との間でトレードオフを示した。GA演算子と同様に、翼型定義に関して更なる研究が必要である。

Direct Numerical Simulation (DNS) of decaying homogeneous isotropic turbulence with a high resolution (512(exp 3) spatial mesh points) is carried out using the numerical wind tunnel, and fully developed turbulent fields, such as the velocity, vorticity and temperature, are obtained. To search organized structures in the turbulent fields, the vorticity and temperature fields are visualized. As a result, the intense regions of vorticity concentrate into sheet-like layers at first. Then, the layers are rolled up by the Kelvin-Helmholtz instability, and ultimately, become to fine vortex tubes, which are called worms. On the other hand, the intense temperature gradient concentrates into local sheet-like layers., 数値風洞を用いて、減衰一様等方性乱流の高分解能(空間格子点数512(exp 3))直接数値シミュレーション(DNS)を行い、流速、渦度および温度などの発達した種々の乱流場を得た。乱流場の流れ構造を調べるため、渦度および温度場を可視化した。その結果、まず、渦度の強い領域がシート状に渦層として集中し、次に渦層がケルビン・ヘルムホルツの不安定性により巻き上げられ、最後に微細なみみずと称する渦管になる。一方、強い温度勾配は、局所的なシート状層に集中する。

The focus of this research is on the development of a new approach for simulating vortex induced vibrations on marine risers at high Reynolds numbers. This method considers the span-wise variation of the lift and drag forces, and determines the moment acting on the cylinder. The predicted motion then consists of a rotational component to accompany the traditional cross-stream and stream-wise translations normally associated with vortex induced vibrations. This was accomplished by describing the motion of the cylinder using a set of springs and dampers. A moment acting on the cylinder causes the springs on one end to compress, and stretch on the other, thus rotating the cylinder. A Large Eddy Simulation (LES) computational fluid dynamics code running on 16 3Ghz processors was used to calculate the unsteady flow and at each time step the hydrodynamic forces acting on the cylinder were calculated in a separate routine based on the pressure distribution around the cylinder. This information was then used to solve two second-order ordinary differential equations, which gave the velocity and displacement of the cylinder in cross-flow and rotational planes. This information was transferred back to the code where the cylinder was displaced and another cycle of calculations was started. The simulated results showed that the correlation length was higher for a cylinder subject to pure translation compared to a cylinder free to translate and rotate in the cross-stream direction. This has implications for current numerical and experimental techniques since it has been traditionally assumed that the flow around a circular cylinder becomes two-dimensional during vortex induced vibrations. Consequently, empirical,numerical and experimental models have generally only considered cross stream and/or stream-wise translation. The extent to which the experimental apparatus or harmonic model may have influenced the behavior of the riser by eliminating span-wise amplitude variation is imp

The focus of this research is on the development of a new approach for simulating vortex induced vibrations on marine risers at high Reynolds numbers. This method considers the span-wise variation of the lift and drag forces, and determines the moment acting on the cylinder. The predicted motion then consists of a rotational component to accompany the traditional cross-stream and stream-wise translations normally associated with vortex induced vibrations. This was accomplished by describing the motion of the cylinder using a set of springs and dampers. A moment acting on the cylinder causes the springs on one end to compress, and stretch on the other, thus rotating the cylinder. A Large Eddy Simulation (LES) computational fluid dynamics code running on 16 3Ghz processors was used to calculate the unsteady flow and at each time step the hydrodynamic forces acting on the cylinder were calculated in a separate routine based on the pressure distribution around the cylinder. This information was then used to solve two second-order ordinary differential equations, which gave the velocity and displacement of the cylinder in cross-flow and rotational planes. This information was transferred back to the code where the cylinder was displaced and another cycle of calculations was started. The simulated results showed that the correlation length was higher for a cylinder subject to pure translation compared to a cylinder free to translate and rotate in the cross-stream direction. This has implications for current numerical and experimental techniques since it has been traditionally assumed that the flow around a circular cylinder becomes two-dimensional during vortex induced vibrations. Consequently, empirical,numerical and experimental models have generally only considered cross stream and/or stream-wise translation. The extent to which the experimental apparatus or harmonic model may have influenced the behavior of the riser by eliminating span-wise amplitude variation is imp

The focus of this research is on the development of a new approach for simulating vortex induced vibrations on marine risers at high Reynolds numbers. This method considers the span-wise variation of the lift and drag forces, and determines the moment acting on the cylinder. The predicted motion then consists of a rotational component to accompany the traditional cross-stream and stream-wise translations normally associated with vortex induced vibrations. This was accomplished by describing the motion of the cylinder using a set of springs and dampers. A moment acting on the cylinder causes the springs on one end to compress, and stretch on the other, thus rotating the cylinder. A Large Eddy Simulation (LES) computational fluid dynamics code running on 16 3Ghz processors was used to calculate the unsteady flow and at each time step the hydrodynamic forces acting on the cylinder were calculated in a separate routine based on the pressure distribution around the cylinder. This information was then used to solve two second-order ordinary differential equations, which gave the velocity and displacement of the cylinder in cross-flow and rotational planes. This information was transferred back to the code where the cylinder was displaced and another cycle of calculations was started. The simulated results showed that the correlation length was higher for a cylinder subject to pure translation compared to a cylinder free to translate and rotate in the cross-stream direction. This has implications for current numerical and experimental techniques since it has been traditionally assumed that the flow around a circular cylinder becomes two-dimensional during vortex induced vibrations. Consequently, empirical,numerical and experimental models have generally only considered cross stream and/or stream-wise translation. The extent to which the experimental apparatus or harmonic model may have influenced the behavior of the riser by eliminating span-wise amplitude variation is imp