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Adaptive mesh refinement(AMR) is a powerful tool to efficiently solve multi-scaled problems. However, the vanilla AMR method has a well-known critical demerit, i.e., it cannot be applied to non-local problems. Although multi-grid iteration (MGI) can be regarded as a good remedy for a non-local problem such as the Poisson equation, we observed fundamental difficulties in applying the MGI technique in AMR to realistic problems under complicated mesh layouts because it does not converge or it requires too many iterations even if it does converge. To cope with the problem, when updating the next approximation in the MGI process, we calculate the precise total corrections that are relatively accurate to the current residual by introducing a new iteration for such a total correction. This procedure greatly accelerates the MGI convergence speed especially under complicated mesh layouts.

An experimental investigation on compound heat transfer enhancement by a combination of ribbed tubes with wire coil inserts was performed. Two wire coils with different geometries were inserted in smoothed, straight ribbed and helically ribbed tubes to make six variations of enhanced tube, and the effects of heat transfer enhancement were examined. The heat transfer coefficient was obtained for Reynolds numbers ranging from 300 to 30,000 by means of Wilson’s method. The friction factor was also obtained from the measurement of pressure drop between both ends of the tube. Moreover, the performance of enhanced tubes were evaluated by comparing the heat transfer coefficient with that of the smoothed tube under the condition of the same pumping power. All enhanced tubes exhibit higher performance in the laminar region than in the turbulent region. The highest performance is accomplished by the helically ribbed tube with a wire coil having a pitch ratio P/e = 10.0 and a clearance NDC = 0.04 due to much higher heat transfer enhancement in comparison to the other five enhanced tubes and the smaller friction factor increase in comparison to the straight ribbed tubes.

An experimental investigation on compound heat transfer enhancement by a combination of a helically ribbed tube with twisted tape inserts was performed. The measurement of heat transfer coefficient as well as the pressure drop was performed in order to evaluate the performance of enhanced tubes using the equal pumping power evaluation method. The heat transfer coefficient was obtained by means of Wilson’s method for the Reynolds number ranging from 300 to 30,000. The combination of smoothed tube and twisted tape having a clearance NDC = 0.07 accomplished the highest performance in the laminar region. On the other hand, the combination of helically ribbed tube and twisted tape having a clearance NDC = 0.02 gave the highest performance in the turbulent region. The reasons for these results are discussed well in terms of the compound effect and clearance effect.

本研究ではNa2CO3水溶液の2層の濃度成層を側方加熱冷却したときに発生する二重拡散対流に対して，レーザホログラフィー実時間干渉法を適用し，得られる干渉縞から局所濃度の算出を試みた．それには，干渉縞は等屈折率線と一致すること，屈折率は温度と濃度によって決まることが利用され，その結果，擬定常状態における任意時間の局所濃度分布が干渉縞と実測された局所温度分布から算出された．また，干渉縞より求められた濃度と別途行ったサンプリング法により求めた濃度との比較を行ったところ，両者の一致は非常に良好であり，本結果による濃度計測の信頼性は高く，十分実用的であることが明らかとなった．

水溶液を2層に濃度成層させ側方から加熱, 冷却を行った場合に発生する二重拡散対流について数値解析を行い, 本研究室において行われてきた実験結果との比較検討を行った. 計算条件はPr=6.67, Le=184, RαT=2.43×107, Rac=3.13×107, 容器アスペクト比A=1.1とした. 実験結果と計算結果の比較から, 流れ場と温度場の推移において定性的一致が, また上下層間濃度差Δcおよび溶質移動流束jの時間変化において定量的一致が得られた. これらの結果より本数値解析プログラムは二重拡散現象を忠実に再現できる事が確認された. 次に実験では測定が困難な濃度場について数値解析により調査した. その結果, 層境界面崩壊までの一連の現象は, (A) 層境界面が形成する期間, (B) 擬定常状態となり溶質が一定の速度で移動する期間, (C) 層境界面が不安定となり溶質移動が促進される期間, と3つの期間に分けられそれぞれの期間において特徴的な溶質移動機構が存在する事が分かった.

矩形容器内で階段状に2層に濃度成層するNa2CO3水溶液を側方から加熱冷却したときに発生する二重拡散対流を対象に, 広い初期浮力比N0=0.54～7.17のもと, 感温液晶とポリスチレン粒子を用いた温度場と流れ場の同時可視化実験を行なった.加熱冷却後, 間もなく熱と溶質の二重拡散により2層のセル対流構造が形成され, それは比較的長い擬定常状態を経て崩壊した. 崩壊前に界面の波打ち現象が確認されたが, このときの界面近傍の流れ構造, 温度場形状は非常に複雑であり, その現象のスケールは熱レイリー数に依存した. また, 界面崩壊時間は条件により10～600分まで変化するが, それは初期浮力比に大きく依存した. さらに, 本結果と溶液・条件が異なる既往の研究結果との間で界面崩壊時間の比較を行ったところ, 2つ研究で得られた界面崩壊時間は無次元時間FomScを用いて良好に相関できることがわかった.

As a basis for the development of energy storage systems utilizing crystallization/dissolution of chemical substances, an experimental study is performed for crystallization of ammonium sulfamate from an aqueous solution confined in a rectangular vessel. A molded polycrystal adhering to one of the vertical walls in the vessel was made to grow by cooling the opposite wall. The behavior of natural convection in the solution was visualized using granulated tracers. In addition, local changes in solution temperature were also measured.In the neighborhood of the growing polycrystal, upward flows develope through the decerase in concentration of solution due to crystal growth, as well as by the increase in temperature due to the latent heat of crystallization. Dilute solution transferred upward is retained at the top of the vessel to form a horizontal rolling cell there. After that, ascending dilute solution is retained above the cell, and forms a second cell. Finally, horizontal multi-layers are established in the liquid phase. Moreover, the effects of cooling rate and flow structure on the crystal growth is discussed.

An experimental investigation to obtain heat transfer correlation in a Votator type scraped surface heat exchanger with two-blades was performed by an electro-chemical method. Measurements were carried by mass transfer under diffusion control in a ferricyanide/ferrocyanide redox electrochemical reaction. The heat transfer correlation was obtained from an analogy of heat and mass transfer. Local heat transfer coefficients on the wall of the outer column of the exchanger was measured by varying the rotational Reynolds number, flow rate of fluid, Prandtl number and equivalent diameter in order to obtain the unity thermal design equation. The time averaged local Nusselt number in a high Prandtl number fluid was found to be correlated by the following equation: Nu = 1.53Re r 2.51 Pr 0.33 (D o /D e ) 0.44 (1320

Heat transfer enhancement in a rectangular duct with a semicylindrical turbulence promoter was experimentally studied for a high Prandtl number fluid. The measurements of mass transfer coefficient and wall shear stress as well as flow visualization were performed in order to investigate how the performance of a heat transfer enhancement promoter is influenced by its inclination angle and by the clearance between the promoter and the wall surface. When the inclination angle is 0°, the variation of performance with clearance is closely related to the extent of heat transfer enhancement in the region of slipping flow. In this case, the clearance exhibiting the maximum performance is almost equal to the film thickness for a smooth duct without a promoter. As the inclination angle increases, what influences the variation of performance with clearance gradually shifts to the extent of heat transfer enhancement in the region of circulating and reattaching flows, and the clearance exhibiting the maximum performance decreases. There is no remarkable difference in the maximum performance between inclination angles examined here. It is, however, desirable to set the inclination angle to 30°, since the distribution of the local mass transfer coefficient for this angle is less curved than those for other angles.

The Systems Modeling Language (SysML) is a standard, general-purpose, modeling language for model-based systems engineering (MBSE). SysML supports the specification, analysis, and design of a broad range of complex systems such as control systems. The authors demonstrate how they can integrate a SysML modeling tool (IBM Rational Rhapsody) with a proprietary simulation tool (MathWorks Simulink) and a Computer Algebra System (CAS) to validate system specification. The integration with Simulink enables users to perform systems engineering process in a SysML model, while designing continuous control algorithms and plant behavior in Simulink, and to validate the behavior by simulating the overall composition in Simulink. The integration with a CAS enables the evaluation of mathematical constraints defined in SysML parametric diagrams. The authors also show the overall approach using a Dual Clutch Transmission (DCT) and a Cruise Control System as examples.

To investigate the mechanism of heat transfer augmentation, numerical computations of turbulent flow and heat transfer in a parallel plate channel, attached transversely with turbulence promoters at regular intervals on the lower surface, have been performed by using a simple turbulence model and the Galerkin finite element method. It has been revealed that, in the optimum case, a vortex of peculiar structure is formed behind each turbulence promoter, and it plays a significant role in enhancing the heat transfer rate; and the maximum augmentation effect reaches about 13% when taking the pumping power into account, while it is 67% when neglecting the pumping power. It also turns out that the optimum interval of turbulence promoters is about 10 times the promoter diameter, and the optimum Reynolds number is about 9000.

矩形流路内に単独設置された半円柱乱流促進体による伝熱促進において促進体の傾斜角や壁面-促進体間クリアランスが促進効果に及ぼす影響を解明するため, 高プラントル数流体を用いて物質移動係数と壁面剪断応力の測定及び流れの可視化を行った.傾斜角0° の場合, 伝熱促進性能はスリップ流れ域における伝熱係数の増減に大きく左右され, 最大性能を示すクリアランス (最適クリアランス) は平滑流路での境膜厚さとほぼ等しくなる.傾斜角の増加に伴って伝熱促進性能は再付着・循環流域での伝熱係数の増減の影響を受けるようになり, 最適クリアランスは減少していく.また本実験の範囲では各傾斜角が示す最大性能に顕著な違いはみられないが, 伝熱係数の分布が最も均一となる傾斜角30°の場合が促進体形状として最適である.

MSMPR (Mixed Suspension Mixed Product Removal) 型晶析器を用いた連続多段晶析プロセスを対象に, 各段の結晶滞留時間および滞留量が異なり, 前段で生成した結晶スラリーがそのまま次段に供給されるという実際的な場合について各段の結晶成長速度と核化速度を算出する方法を提案した.本法では先ず各段におけるポピュレーションバランス式を誘導しその解析解を求めた後, 各段の結晶重量, 滞留時間, 粒度分布のデータのみから, パーソナルコンピューターを用いて1段目から順に各段の結晶成長速度と核化速度を区別して同時に求めるものである.本法を日産式メラミン製造プロセスにおける連続三段晶析工程に適用したところ, 満足すべき操業解析結果を得た.本解析結果と基礎実験で別途測定したメラミンの過溶解度および結晶線成長速度係数のデータを用いて各晶析器の操作過飽和度や相対操作過飽和度を算出し, 操業状況を検証した.

This paper describes the occurrence and development of double-diffusive convection in the liquid phase during solidification of NH 4 Cl−H 2 O system in a confined cavity with lateral cooling. Multiple point measurements of concentration show a step change in the vertical direction, and temperature visualizations reveal an S-shaped profile of isotherms, which indicate the existence of time-dependent horizontally-stacked roll cells separated by diffusive interfaces. The cells are generated in a sequential fashion, rather than simultaneously and the thickness of each cell increases with progression of solidification. The concentration in each cell is found to remain nearly constant, except for the initial development of cells. Convection within each cell is largely controlled by the temperature field, and diffusion is dominant in the diffusive interface between two cells due to the solute field with a vertical concentration gradient. The fluid in the diffusive interface is initially stagnant, but the interface changes into a new cell under a certain condition. The criteria for cell generation are determined by the buoyancy ratio and the thermal Rayleigh number in the diffusive interface.

Flow and mass transfer characteristics in tube banks are investigated in the transitional flow regime at intermediate Reynolds numbers. The tube arrays considered are a staggered tube array and an in-line tube array with longitudinal and transverse pitch-to-diameter ratios of two. The flow is steady at the entrance of the tube banks, but becomes oscillatory downstream of an onset location of vortex shedding. This location moves upstream with increasing Reynolds number, and the upstream development of flow transition is much faster for the staggered array than the in-line array. Therefore, the row-by-row variation of the mass transfer rate is small for the staggered array but considerable for the in-line array. The mass transfer for the staggered array is sensitive to the unsteady wakes of the preceding row tubes, while the surface shear stress is insensitive to such wakes. However, for the in-line array the mass transfer and shear stress are both sensitive to the unsteady wakes.

This article presents a simple technique for temperature visualization using liquid crystals in an aqueous solution during the process of cooling and solidification. This method provides a clear picture of the role of double-diffusive convection in producing vertical compositional and density stratification in an initially homogeneous liquid during solidification.

矩形流路内の伝熱面上に連続設置された半円柱乱流促進体が伝熱の促進に及ぼす効果を解明するため, 高Pr数流体を用いて流れの可視化および電極反応法による物質移動係数の測定を行った.さらに平滑面上の境膜厚さを基準に促進体の位置を表す変数NTFを導入して性能比ηとの関連を検討し, 円弧を壁面に向けて設置した場合 (Bタイプ) に強い相関のあることを明らかにした.Bタイプでは促進体がわずかだけ境膜内に入るようなクリアランスを設けた時に最も高い促進効果を得ることができる.また半円柱はこれまでに実験を行った促進体形状の中で最も高い促進効果を示した.

Pulsatile laminar flow is examined experimentally in a two-dimensional furrowed channel with varying flow parameters. We present flow diagrams in which five flow modes are classified in terms of the Womersley number and oscillatory fraction of the flow rate for each net flow Reynolds number, on the basis of the process of vortex formation, growth and subsequent disappearance. A striking feature of pulsatile flow in the wavy-walled channel is that after the vortex ejects from the furrow, the vortex does not always disappear in the mainstream, but reattaches to the wall and eventually disappears under certain conditions, in contrast to oscillatory flow. We also show the transition to three-dimensional flow and a new flow structure in which a wave appears in the mainstream during the flow deceleration phase due to a shear layer instability.

An experimental study of solidification is performed for a super-eutectic sodium carbonate solution (Na 2 CO 3 -H 2 O) in a confined cavity with varying initial concentrations and temperatures. We show important features of transport processes of heat and species during horizontal solidification by quantitative measurements of temperature and concentration. The development of the vertical density stratification that forms as a result of solidification can effectively damp thermal convection in the liquid region, and leads to the establishment of either a stagnant fluid region or double-diffusive cells. Initial superheat is found to be responsible for the initiation of the double-diffusive cells

Oscillatory flow is examined experimentally in a two-dimensional furrowed channel. We show the transition of two-dimensional to three-dimensional flow due to instability of the flow at moderate Reynolds numbers. The critical value of the Reynolds number at the onset of three-dimensional flow strongly depends on the Strouhal number. The fluid motion is found to be most unstable in the limited Strouhal number range of 0.02 to 0.03. Two distinct three-dimensional flows are discovered and their boundary is determined only by the Strouhal number, i. e. St≒0.02.

乱流促進体の設置による矩形流路内の伝熱促進の効果を解明するため, 流れの可視化および電気化学的方法による物質移動係数の測定を行い, 促進体間ピッチや壁面-促進体間クリアランスが促進効果に及ぼす影響について検討した.実験に用いた促進体の形状は矩形と2種類の三角柱である.本実験では三角柱促進体を逆に配置した場合 (B-type) が最も高い促進効果を示し, クリアランスが無い場合に性能比ηは最大を示した.

Oscillatory flow in a two-dimensional symmetric furrowed channel is studied numerically and experimentally over wide ranges of flow parameters. Two-dimensional numerical computations show that the vortex strength has a peak at intermediate Strouhal numbers, regardless of the Reynolds number. Flow visualization experiments support the two-dimensional computational results at low Reynolds numbers, but deviations arise at moderate Reynolds numbers. We show the transition from two-dimensional to three-dimensional flow due to instability of the flow. The critical Reynolds number for the onset of three-dimensional flow strongly depends on the Strouhal number. The fluid motion is found to be most unstable in the limited Strouhal number range of 0.02–0.03, and this is in agreement with the prediction of the two-dimensional computation. Two distinct three-dimensional flows are discovered experimentally.

Freezing of superheated water in a rectangular enclosure cooled from below has been experimentally studied. Encapsulated thermochromic chiral nematic liquid crystals were used to visualize the isotherms near 4°C, where the density of water has the maximum value. In the supercooling and subsequent freezing process, mushroom-like vortices appear on the cold wall or the ice surface and grow through the unstable layer showing temperatures below 4°C due to density inversion. Two different critical Rayleigh numbers for the onset of convection were determined for the supercooling and freezing, respectively.

In this work, we examined the application of a new liquid crystal, a chiral nematic type, to water. It has been said that this liquid crystal is stable even in water. However, its usefulness has not been confirmed since its applications have been very few. Accordingly, visualization of the temperature field of transient natural convection heat transfer of water with maximum density effect was carried out as an example to confirm the practical applications

It is not surprising that rich Internet content, such as Flash and DHTML, is some of the most pervasive content because of its visual attractiveness to the sighted majority. Such visually rich content has been causing severe accessibility problems, especially for people with visual disabilities. For Flash content, the kinds of accessibility information necessary for screen readers is not usually provided in the existing content. A typical example of such missing data is the lack of alternative text for buttons, hypertext links, widget roles, and so on. One of the major reasons is that the current accessibility framework of Flash content imposes a burden on content authors to make their content accessible. As a result, adding support for accessibility tends to be neglected, and screen reader users are left out of the richer Internet experiences.Therefore, we decided to develop an automatic accessibility transcoding system for Flash content to allow users to access a wider range of existing content, and to reduce the workload for content authors by using an automatic repair algorithm. It works as a client-side transcoding system based on the internal object model inside the Flash content. It adds and repairs accessibility information for existing Flash content, so screen readers can present more accessible information to users. Our experiment using the pilot system showed that 55% of the missing alternative texts for buttons in the tested websites could be added automatically.

Multimedia content with Rich Internet Applications using Dynamic HTML (DHTML) and Adobe Flash is now becoming popular in various websites. However, visually impaired users cannot deal with such content due to audio interference with the speech from screen readers and intricate structures strongly optimized for sighted users.We have been developing an Accessibility Internet Browserfor Multimedia (aiBrowser) to address these problems. Thebrowser has two novel features: non-visual multimedia audiocontrols and alternative user interfaces using externalmetadata. First, by using the aiBrowser, users can directlycontrol the audio from the embedded media with fixed shortcutkeys. Therefore, this allows blind users to increase ordecrease the media volume, and pause or stop the mediato handle conflicts between the audio of the media and thespeech from the screen reader. Second, the aiBrowser canprovide an alternative simplified user interface suitable forscreen readers by using external metadata, which can evenbe applied to dynamic content such as DHTML and Flash.In this paper, we discuss accessibility problems with multimedia content due to streaming media and the dynamic changes in such content, and explain how the aiBrowser addresses these problems by describing non-visual multimedia audio controls and external metadata-based alternative user interfaces. The evaluation of the aiBrowser was conducted by comparing it to JAWS, one of the most popular screen readers, on three well known multimedia-content-intensive websites.The evaluation showed that the aiBrowser made the contentthat was inaccessible with JAWS relatively accessibleby using the multimedia audio controls and alternative interfaceswith metadata which included alternative text, headinginformation, and so on. It also drastically reduced thekeystrokes for navigation with aiBrowser, which implies toimprove the non-visual usability.

Practices supporting Web accessibility are spread out all over the world. However, the accessibility of multimedia content and rich Internet applications has been little discussed. These types of content are using a lot of visual cues and developing new techniques to make their visual interfaces richer. Therefore, it is generally believed that they are not accessible for people with visually disabilities. However, since there is neither objective data nor tools to measure the accessibility of such content, as a first step to tackle these new accessibility issues we focused on the Flash content. A survey was conducted using five metrics based on the problems faced by screen reader users. We developed a survey tool to assess their severity. Our results showed a complete lack of alternative texts from the developers in the sampled pages. Also, more than half of tested pages were hidden to screen reader users. We conclude that most of existing Flash content is not accessible and there is an emerging need to encourage the use of practices that make Flash content accessible.

Rich and multimedia content is increasing rapidly on the Web. It is very attractive for sighted people, but it brings severe problems to screen reader users. Once the audio starts playing, it becomes hard for blind users to listen to the screen reader because there is physically only one volume control that cannot control the separate audio streams. Though there are often software-controlled buttons to control the audio, they are often controllable only with a mouse and are not associated with alternative text. Because of the audio conflicts and inaccessible control buttons, the multimedia content is often inaccessible to blind users. In addition, the use of dynamically changing interactive user interfaces is also a critical issue, since existing screen readers cannot detect such dynamic content changes.We developed an accessible Internet browser for multimedia to address these problems and offer multimedia content as an information resource for the blind. It is characterized by three major features. First, it allows users to control the audio, such as the volume, play/stop, pause, and even the speed. Second, a dynamically adaptable metadata function is added to simplify complicated multimedia pages and to track dynamic changes and effectively inform users about the changes. Third, an audio description function supports Internet movies with a text format described by the metadata. In this paper, after briefly discussing the existing accessibility problems of multimedia content, we describe our accessible Internet browser for multimedia.

Although multimedia content containing streaming media is now widely used on the World Wide Web, there exist considerable difficulties for blind users to access such content, due to its dynamic changes, keyboard inoperability, and audio interference with the speech from assistive software. In particular, the third problem of audio interference is serious for blind users, since multimedia content often contains streaming media such as video and music which continuously play sounds, and thus they cannot hear the speech, which is masked by the loud media. In this paper, we propose a new accessible browser that can directly manipulate such multimedia content. In order to control Flash contents, our browser relies on a transcoding HTTP proxy to inject special scripts into the Flash content and then manipulates the embedded streaming media and sound objects via the injected scripts. By using our browser, users can easily turn the volume up or down, play, stop, or pause the streaming media with shortcut keys. Since the users do not need to focus on buttons or sliders for these operations, they can immediately stop or fade out the intrusive media when listening to speech from assistive software.

XML (Extensible Markup Language) processing can incur significant runtime overhead in XML-based infrastructural middleware such as Web service application servers. This paper proposes a novel mechanism for efficiently processing similar XML documents. Given a new XML document as a byte sequence, the XML parser proposed in this paper normally avoids syntactic analysis but simply matches the document with previously processed ones, reusing those results. Our parser is adaptive since it partially parses and then remembers XML document fragments that it has not met before. Moreover, it processes safely since its partial parsing correctly checks the well-formedness of documents. Our implementation of the proposed parser complies with the JSR 63 standard of the Java API for XML Processing (JAXP) 1.1 specification. We evaluated Deltarser performance with messages using Google Web services. Comparing to Piccolo (and Apache Xerces), it effectively parses 35% (106%) faster in a server-side use-case scenario, and 73% (126%) faster in a client-side use-case scenario.

An experimental study of electroosinotic dewatering was carried out, using a kneaded clay bed. By investigating the experimental results, the following conclusions were obtained. (1) After a long time, a final moisture distribution is formed in the clay bed where the electric current flows but electroosinotic flow does not occur. (2) The gradient of the final moisture distribution curve increases with increasing voltage applied to the clay bed. (3) The minimum moisture content on the final moisture distribution curve can reach a lower value than either experimental data published in the literature or the critical moisture content for dewatering shrinkage of the clay bed.