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متن کامل


عنوان: 
نویسنده: 

عقبائی مسلم

اطلاعات دوره: 
  • سال: 

    1394
  • دوره: 

    1
تعامل: 
  • بازدید: 

    308
  • دانلود: 

    1908
چکیده: 

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نشریه: 

GAS PROCESSING

اطلاعات دوره: 
  • سال: 

    2016
  • دوره: 

    4
  • شماره: 

    1
  • صفحات: 

    53-61
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    246
  • دانلود: 

    0
چکیده: 

Different Flow patterns of downward gas-liquid two-phase Flow using simple mixer are studied in an experimental manner. An experimental setup is designed and fabricated to allow the visual observation of downward two-phase Flow patterns and their transitions. The Flow patterns are recorded by a 1200 frames per second high speed video camera. The quality of downward two-phase Flow patterns photos are improved through image processing. The setup includes a transparent vertical pipe of 50 mm diameter and the (L/d) aspect ratio of 80. Flow patterns are obtained through 374 test cases during which air and water superficial velocities changed. In order to assess the performance of the mixer, all expected Flow patterns are obtained. The four observed Flow regimes are: of falling film, bubbly, slug and froth. The Flow map is plotted and transitions among different Flow patterns are compared with previous finding in specified conditions indicating a good agreement was observed.

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اطلاعات دوره: 
  • سال: 

    2010
  • دوره: 

    13
تعامل: 
  • بازدید: 

    311
  • دانلود: 

    0
چکیده: 

LABORATORY INVESTIGATION HAS BEEN CARRIED OUT ON MIXING POWER CONSUMPTION AND Flow REGIME transition IN A FULLY BAFFLED STIRRED TANK REACTOR EQUIPPED WITH DUAL SIX-BLADE RUSHTON TURBINES BY ELECTRICAL MEASUREMENT TECHNIQUE. AN EMPIRICAL CORRELATION HAS BEEN DERIVED USING PREDICTED EXPERIMENTAL DATA, WHICH PRESENTS A NEW RELATION IN ESTIMATION OF POWER CONSUMPTION IN STIRRED TANKS WITH DUAL RUSHTON IMPELLERS. RESULTS HAVE BEEN COMPARED WITH DATA AVAILABLE IN TECHNICAL LITERATURE. A REASONABLE AGREEMENT BETWEEN THE EXPERIMENTAL AND TECHNICAL LITERATURE RESULTS HAS BEEN OBSERVED.

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اطلاعات دوره: 
  • سال: 

    1401
  • دوره: 

    54
  • شماره: 

    7
  • صفحات: 

    1533-1552
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    38
  • دانلود: 

    13
چکیده: 

شبیه سازی عددی پدیده گذار یکی از چالش ها در شبیه سازی جریان های آشفته در هر دو نوع از جریان های داخلی و خارجی است. در مطالعه حاضر، ضرایب مدل گذار چهار معادله ای γ-Reθ بر اساس فیزیک گذار در جریان داخلی به نحوی اصلاح می شود که طول ورودی در جریان داخلی بدرستی پیش بینی شود. برای اعتبارسنجی، جریان داخلی در شش هندسه متفاوت شبیه سازی شد تا جامعیت مدل در پیش بینی پدیده گذار در فیزیک های مختلف مشخص شود. جریان درون مجرای سه بعدی، دو لوله متقارن محوری، یک لوله تنگ شونده-بازشونده، دو صفحه موازی و پله معکوس در محدوده اعداد رینولدز 103×2 تا 105×3 شبیه سازی گردید. متغیرهای جریان نظیر سرعت متوسط، ضریب اصطکاک پوسته ای، ضریب اصطکاک در ناحیه توسعه یافته و طول بازچسبانی با نتایج تجربی، تئوری و نتایج حاصل از شبیه سازی گردابه های بزرگ مقایسه شد. با مقایسه نتایج سرعت متوسط با روابط نیمه تجربی و داده های تجربی، مشاهده شد که مدل اصلاح شده توانایی تخمین مناسبی از طول ورودی در جریان داخلی را در مقایسه با داده های تجربی دارد. علاوه براین، مقدار خطا در پیش بینی ضریب اصطکاک در ناحیه توسعه یافته و طول بازچسبانی با استفاده از ضرایب اصلاح شده به ترتیب بیش از 7/6 و 26/7درصد در مقایسه با مدل های پیشین کاهش یافت.

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نشریه: 

هیدرولیک

اطلاعات دوره: 
  • سال: 

    1401
  • دوره: 

    17
  • شماره: 

    4
  • صفحات: 

    99-107
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    44
  • دانلود: 

    22
چکیده: 

در شبکه انتقال و توزیع آب به طور معمول از روزنه های جانبی در بدنه ی کانال اصلی به منظور انحراف جریان از کانال اصلی استفاده می شود. در روزنه جانبی زمانی که لبة بالایی روزنه هیچ تأثیری بر روی جریان نداشته باشد جریان وضعیت سرریز جانبی دارد. جریان انتقالی در محدوده ی کوچکی زیر لبه بالایی روزنه تا اندکی بالای این لبه رخ می دهد. در این تحقیق به مطالعه آزمایشگاهی این ناحیه انتقالی بین دو رژیم جریان روزنه و سرریز جانبی پرداخته شده است و تلاش شده تا این محدوده مشخص گردد، بدین منظور از رابطه دبی اشل و پروفیل سطح آب استفاده شده است. دقت معادلات موجود برآورد دبی سرریز و روزنه جانبی نیز در این محدوده بررسی شده است. فلوم مورد استفاده دارای طول 8متر و عرض 8/0 متر با دیواره شیشه ای و کف فلزی است. چهار طول روزنه جانبی، سه ارتفاع روزنه جانبی و دو آب پایه بررسی شده است. نتایج نشان داد که نسبت ارتفاع به طول روزنه جانبی مستطیلی و فاصله نصب روزنه تا کف کانال مهمترین پارامترها بر رخداد جریان انتقالی است. در نسبت ارتفاع به طول کمتر از 2/0 جریان انتقالی مشاهده نشد. بررسی معادلات برآورد دبی نشان داد که حتی در حضور جریان انتقالی برآورد دبی این معادلات دارای حداکثر خطای حدود 7% است که خطای قابل توجهی نیست و برای کاره های اجرایی نیازی به استخراح معادله جدید در محدوده جریان انتقالی نیست.

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نویسندگان: 

Hanaee Toktam | Farhangdoust Hadi

اطلاعات دوره: 
  • سال: 

    1402
  • دوره: 

    11
  • شماره: 

    2
  • صفحات: 

    133-152
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    202
  • دانلود: 

    30
چکیده: 

ABSTRACT The attention of contemporary planners to environmental factors and increasing awareness and communication of man with his surrounding environment has increased the layers and defining factors of design and planning concepts. In such a way, a common problem with the issue of environmental capabilities to respond was put in front of the planners. The collection of ideas presented in this era was in the form of responsive planning, focusing on the maximum use of environmental capabilities. The necessity of the emergence of a comprehensive discourse to overcome the plurality of factors, definitions and design methods in the environmental fields has been given less attention. Based on this, the current research aims to organize the leading theories in this field in a targeted manner and seeks to improve them based on their synergy. The structural question of this research is the meanings, examples and meaningful contexts of flexibility in various aspects and scales of urban planning. The research method used is qualitative thematic analysis with the help of artificial intelligence in MAXQDA software in a 6-step processing process. The important application of this research is to structure the minds of the planners of this field to reduce the scattered and interdisciplinary problems of the resources. The results of this research revealed dimensions such as identification and recognizability, diversity and changeability, adaptability and expandability, distribution, separation and continuity, organization and compatibility in the field of flexibility and related to the corresponding parts in urban planning   Extended Abstract Introduction Responsiveness-based design and planning emphasizing the maximum use of environmental capacities to meet users' needs implicitly cause a targeted improvement of environmental quality. As the environmental awareness of contemporary man has expanded and the platforms have become more diverse, many challenges are raised in the field of environment-oriented in the field of infrastructure quality and service provision. Urban developments and new developments in cities should be interpreted with integrated conceptualization. The conceptualization of interpretive flexibility in the planning and designing of public spaces in the city is used as an interdisciplinary perspective in urban space design to open and discuss its connection and potential as an approach to strengthening social cohesion and inclusion. The general definition of flexibility is that it can create places with new forms of meaning and be used for different groups to strengthen its coherence and multidisciplinary inclusion in terms of design and planning of space and body. On this basis, the concept of flexibility is proposed as a principle in the context of design and planning due to its wide range of effects on background phenomena. The history of such a role can be seen in the diversity of users' needs. In such a way, it is impossible to express the specific time and area of the need to pay attention to this concept. This is in line with Oldenburg's theory of "social public spaces," in which being in public space, communicating with people and the environment through observing the streets, sidewalks, squares, and parks of the city is a necessary step for people as a part of their social life. The meaningfulness of the design of the artificial environment was considered. In any case, in the contemporary era, on the one hand, at the same time as the quantitative and qualitative increase of human environmental awareness, there is no longer any phenomenon in the eyes of contemporary man arising from a unique aspect and range of factors. On the other hand, his life needs in the individual and collective dimensions have seen a high diversity, which has led to the formation of multiple semantic domains of past flexibility. The meaning of flexibility in such an interdisciplinary platform and basic design refers to the concept of understanding and responding quickly and efficiently to environmental changes. Such a holistic definition for this broad field of environmental design means the implicit acceptance of the role of scale in the meaningful domain of these concepts. On a macro scale, it means making design options to increase the presence, participation, and power of choices of users of the environment in participatory urban planning and design methods, and on a small scale, it means making design options to increase spatial quality and, as a result, the quality of activities. The daily activities of environmental users are through selection against the "dominant space." Flexibility at different scales is crucial for dimensional optimization, shaping, and structuring spatial features, leading to improved performance of space components and spaces. The development of the concept of "flexibility" from various studies in metropolitan to micro scales, such as interior architecture, allows it to pass the discourse of responsiveness to provide a broad approach to environmental design in which different values, interests, and priorities are prioritized. As a result, the issue of flexibility in environmental design has been raised as a multi-dimensional field in the design and planning of the basic environment. The breadth and complexity of this concept have made the researchers of this field deal with it in one or more ways, and it has been avoided to provide a comprehensive framework about the nature and structuring processes. The current research presents a structured view of flexibility in architecture and urban planning with an environmental approach.   Methodology The methodology to achieve this goal is to use the macro research method and achieve a comprehensive framework by combining categorized interpretations. In such a way that by sorting and categorizing these concepts and bases in a new way, he has found a new level of theoretical findings, which will be a suitable answer for the gaps in scientific knowledge and scientific methods created in this field. In this context, the research method "thematic analysis" has been used with a qualitative approach and the use of library resources. Also, to overcome the breadth and complexity of these concepts and the multi-layer networking of concepts in this research method, artificial intelligence has been used in MAXQDA research assistance software.   Results and discussion In the meantime, attention should also be paid to the fields of influence and application of the results of this research because designers refer to flexibility as the creator of environmental qualities, including dynamism. Also, since flexibility, along with the principles of readability and adaptability, affect the lifestyle and behavioral patterns of the audience of environmental design in architecture and urban planning, it will also be effective in dealing with the challenge of complexity in environmental design factors. One of the key questions for achieving research goals on this issue is how flexibility in environmental design impacts the relationship between flexibility and scale.   Conclusion The most important finding of this research suggests that first, it requires a focus on the conditions under which the processes of perceiving human abilities and discovering the needs of the human audience can manifest. The theoretical framework arises from a comparative approach between design disciplines. These conditions are independent of the final state of the design product, and strengthening the environmental capacities will lead to a direction and an area that includes environmental flexibility. By responding to new situations, the construction of the space and the body within a space building can be adapted to various configurations. Even though the environment may remain constant, the designed place will continue functioning as a strong living system over time.  It also seems that the nature of issues related to flexibility has complexity. Considering that the quality of flexibility in urban planning and architecture is significant in multilevel and multifaceted scales from micro to macro, it is important to pay attention to the scale of different variables. In order to reduce this problem, the consistency and adjustment of the scale of the variables measured in a specific analysis should be considered in the first step.   Funding There is no funding support.   Authors’ Contribution All of the authors approved the content of the manuscript and agreed on all aspects of the work.   Conflict of Interest Authors declared no conflict of interest.   Acknowledgments We are grateful to all the scientific.

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نویسندگان: 

Koc M. | Kandemir I. | Akkaya V.R.

اطلاعات دوره: 
  • سال: 

    2021
  • دوره: 

    14
  • شماره: 

    1
  • صفحات: 

    23-36
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    23
  • دانلود: 

    0
چکیده: 

Aim of this study is to investigate the properties of mono-atomic gas Flow through the porous medium by using Event-Driven Molecular Dynamics (EDMD) simulation in the transition regime. The molecules and the solid particles forming the porous structure were modelled as hard spheres hence molecule trajectories, collision partners, interaction times and post-collision velocities were calculated deterministically. The porous medium is formed of spherical particles suspended in the middle of the channel and these particles are distributed into the channel in a regular cubic array. Collisions of gas molecules with porous medium were provided by means of the specular reflection boundary condition. A negative pressure boundary condition was applied to the inlet and outlet of the porous media to ensure gas Flow. Porosity, solid sphere diameter and Knudsen number (Kn) were initially input to the simulation for different Cases. Thus, the effects of these parameters on mass Flow rate, dynamic viscosity, tortuosity and permeability were calculated by EDMD simulation. The results were compared with the literature and were found to be consistent.

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نویسندگان: 

REN H. | ZHANG G.X. | GUAN H.S.

اطلاعات دوره: 
  • سال: 

    2016
  • دوره: 

    9
  • شماره: 

    5
  • صفحات: 

    2299-2309
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    229
  • دانلود: 

    0
چکیده: 

Instability and fl w transition of a vortex ring impinging on a wall were investigated by means of large-eddy simulation for two vortex core thicknesses corresponding to thin and thick vortex rings. Various fundamental mechanisms dictating the fl w behaviours, such as evolution of vortical structures, instability and breakdown of vortex rings, development of modal energies, and transition from laminar to turbulent state, have been studied systematically. Analysis of the enstrophy of wrapping vortices and turbulent kinetic energy (TKE) in fl w fiel indicates that the formation and evolution of wrapping vortices are closely associated with the fl w transitionto turbulent state. It is found that the temporaldevelopmentof wrapping vortices and the growth rate of axial fl w generated around the circumference of the core region for the thin ring are faster than those for the thick ring.The azimuthal instabilities of primary and secondary vortex rings are analysed and the development of modal energies reveals the fl w transition to turbulent state. The law of energy decay follows a characteristic k -5/3 law, indicating that the vortical fl w has become turbulent. The results obtained in this study provide physical insight into the understanding of the instability mechanisms relevant to the vortical fl w evolution.

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اطلاعات دوره: 
  • سال: 

    2023
  • دوره: 

    8
  • شماره: 

    4
  • صفحات: 

    1111-1123
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    24
  • دانلود: 

    0
چکیده: 

The purpose of this study is a new understanding behaviour and net cash Flow forecasting. The data of this research contains the daily trial balance for one year, which has been received from 48 bank branches. For this purpose, the optimal model out of 4 models; Geometric Brownie, Arithmetic Brownie, Vasicek and Modified Square Root at three levels of microscopic, mesoscopic and macroscopic have been investigated and the Geometric Brownie model has been approved as the optimal model in microscopic level . The results show that Geometric Brownian Motion model can simulate the net cash Flow highly accurate in accordance with the criteria of mean absolute percentage error. also forecasting net cash Flow for each under study time series has been done in various forecasting horizons involved 7, 14, 21, 30, 60, 90 and 180 day time period accordance with the criteria of mean absolute percentage error. Also The other results obtained from this study is that according to 8 different prediction accuracy criteria, By increasing the forecast hori-zon, ability of the GBM model in simulation and forecasting the net cash Flow de-creases.

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اطلاعات دوره: 
  • سال: 

    1399
  • دوره: 

    24
  • شماره: 

    3
  • صفحات: 

    83-95
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    364
  • دانلود: 

    124
چکیده: 

دریچه های سالونی با مزایای قابلیت نصب آسان، خودکارسازی و امکان عبور راحت رسوبات و اجسام شناور، از جمله سازه های جدید تنظیم سطح آب و کنترل دبی در کانال های آبیاری هستند. تبدیل شکل دریچه از مستطیلی به بیضوی، امکان افزایش دبی عبوری با یک رقوم سطح آب را فراهم می کند. در تحقیق حاضر تاثیر تبدیل ناگهانی بر مقدار دبی و افت انرژی دریچه سالونی-بیضوی در شرایط جریان مستغرق به صورت آزمایشگاهی مورد ارزیابی قرار گرفته است. نتایج بیانگر آن است که مقدار دبی و افت انرژی دریچه سالونی-بیضوی با تبدیل ناگهانی نسبت به شرایط هم عرض کانال به ترتیب در حدود 28 تا 86 درصد کاهش و 11 تا 35 درصد افزایش می یابد. در پایان روابط آماری برای برآورد دبی با حداکثر خطای 16± درصد و افت انرژی دریچه دریچه سالونی-بیضوی با تبدیل ناگهانی در شرایط جریان مستغرق با حداکثر خطای 16± درصد ارایه شد. . .

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