volume
در نشریات گروه مکانیک-
Sound is one of the important factors in creating a good feeling in a mosque and it can play a role as a sensory medium to communicate spiritually with God. Therefore, the acoustic standards have defined the optimal level for the mosque in the field of various variables. In order to compare the acoustic conditions of the use of the mosque with the standard limits, the present research has carried out field measurements and software analysis of the standing position in order to simulate the prayer position. Form and volume are the two considered architectural parameters and Background Noise (BN), Reverberation Time (RT), and Sound Pressure Level (SPL) are the three acoustic variables of the study. A total number of 15 historical mosques in Tabriz are divided into three large, medium, and small volume categories and five form categories have been tested. The reference of the study is ISO3382-1 and ISO3382-2 and the measurements were made with B&K equipment. In addition to the direct achievements, the results have been adapted to international standards and show that the acoustic situation in the historical mosques of Tabriz, regardless of their volume and form, produces sound in the range of 60 to 90 phones, and in terms of RT, have the suitable design from the volume point of view, but the lack of carpet flooring in some of them has increased the RT. The background noise in these examples is less than NC-25, which provides a quiet space for the user and provides the necessary concentration for individual worship.Keywords: Architectural Acoustics, Mosque, Form, Volume, Acoustic Standards
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Paying attention to the sound quality of mosques is one of the architectural fundamentals of Islamic societies because the mosque is the most prominent ritual place of Islam, and speech and hearing are considered its main characteristics. In this research, the analysis of the most effective form in optimal sound quality was defined as the primary goal, and for this purpose, the historical mosques of Tabriz city were subjected to field analysis. The initial analysis of the samples from the perspective of the variables affecting the acoustics led to the selection of 15 samples in three volume categories and five form groups, in which the selected standards for measurement are 3382-1 and 3382-2, and the measurement equipment are the 2260 B&K investigator and the SINUS Acoustic Camera. Among the acoustic variables, Background Noise, Sound Pressure Level, and Reverberation Time were analyzed, and the results of field measurement led to the framework becoming the final goal of the study. The results of this study show that acoustic behavior in samples regardless of their size and form is almost similar, which is due to the components such as materials and their implementation, as well as the overall formal frame within mosques, which were considered the same to reduce the interventional variables. The second achievement, which is the result of a visual data collection of the quality of sound playback, identifies the mentioned components and shows that the reflection and propagation of sound in selected mosques are from architectural elements that are common in all samples and form the overall frame of space. These two achievements framed the final goal of the study in the form of determining acoustic identification for historical mosques in Tabriz. The final result of this study is the analysis of data in MATLAB software which extracts the Background Noise, Sound Pressure Level, and Reverberation Time equation based on frequency in Tabriz historical mosques and spaces with a similar model.
Keywords: Architectural Acoustics, Mosque, Form, Volume, Proportions -
صدا یکی از عوامل مهم در ایجاد حس مطلوب در یک مسجد است و می تواند به عنوان واسطه ای حسی برای برقراری ارتباط روحی با خدا باشد. از سویی دیگر فاکتورهای معمارانه متعددی بر کیفیت آکوستیک تاثیر می گذارند و لذا می توان صدا را عامل ارتباط دهنده معماری به عملکرد مسجد دانست. پژوهش حاضر به منظور ارزیابی شرایط آکوستیکی کاربری مسجد، دو حالت ایستاده و نشسته را به منظور شبیه سازی حالات نمازگذار اندازه گیری میدانی نموده است. فرم و حجم دو پارامتر معماری مدنظر و نوفه زمینه[i]</sup>، زمان واخنش[ii]</sup> و تراز فشار صدا[iii]</sup> سه متغیر آکوستیکی مطالعه بوده و 15 مسجد تاریخی تبریز در 4 رده حجمی و 5 دسته فرمی مورد آزمون قرار گرفته اند. استناد مطالعه استاندارد [iv]</sup>3382 بوده و سنجش ها با تجهیزات شرکت B&K و دوربین صوتی انجام یافته است. نتایج پژوهش نشان می دهد دسته بندی فرمی مورد نظر مطالعه تاثیر چندانی در وضعیت آکوستیکی ایجاد نمی کند و عمده تفاوت ها ناشی از تغییرات حجمی است. همین امر وجود شناسه صوتی مشخصی را برای مساجد تاریخی در تبریز به اثبات می ر ساند که منبعث از ساختار اجرایی مصالح است. نمونه ها عناصر ساختاری مشترکی همچون قوس ها، جداره های برآمده، گوشه سازی ها، تزییناتی چون کاربندی، سطح ستون ها و... با مصالح یکسان دارا هستند که با پخش و پراکنش صدا سبب ایجاد بازخوردهای آکوستیکی مشابه می شوند.
کلید واژگان: آکوستیک معماری، مسجد، فرم، حجمSound is one of the important factors in creating the desired feeling in a mosque and can be used as a sensory inductor to establish a spiritual relationship with God. On the other hand, several architectural factors affect the acoustic quality and therefore sound can be considered as a link between architecture and mosque performance. In order to evaluate the acoustic conditions of the mosque, the present study has measured the two standing and sitting positions in order to simulate the prayer positions. form and volume are the two considered architectural parameters and Background Noise, Reverberation Time and Sound Pressure Level are the three acoustic variables studied and 15 historical mosques of Tabriz have been tested in 4 volumetric and 5 formal categories. The study was cited in ISO 3382 and the measurements were performed with B&K equipment and Acoustic Camera. The results show that the formal classification of the study does not have much effect on the acoustic status and the main differences are due to volume changes. This proves the existence of a specific sound ID for historical mosques in Tabriz, which originates from the executive form of materials. Samples have common structural elements such as arches, protruding walls, corners, decorations such as ‘karbani’, column surface, etc. with the same materials that cause similar acoustic feedback by sound propagation.
Keywords: Architectural acoustics, mosque, form, volume -
Numerical solutions of high-speed microdroplet impact onto a smooth solid surface are computed, using the interFoam VoF solver of the OpenFOAM® CFD package. Toward the solid surface, the liquid microdroplet is moving with an impinging gas flow, simulating the situation of ink droplets being deposited onto substrate with a collimated mist jet in the Optomec Aerosol Jet® printing process. For simplicity and computational efficiency, axisymmetric incompressible flow is assumed here for the free-surface fluid dynamic problem. The computed values of maximum spread factor ξ, for the range of parameters relevant to Aerosol Jet® printing, are found in good agreement with some of the correlation formulas proposed by previous authors in the literature. A formula of improved accuracy is then obtained for evaluating ξ of Aerosol Jet® deposited droplets, by combining selected formulas from different authors with appropriate modifications. The computational results also illustrate droplet impact dynamics with lamella shape evolution throughout the spreading, receding-relaxation, and wetting equilibrium phases, consistent with that observed and described by many authors. This suggests a scale-invariant nature of the basic droplet impact behavior such that experiments with larger droplets at the same nondimensional parameter values may be applicable for studying microdroplet impact dynamics. Significant free surface oscillations can be observed with low viscosity droplets. The border line between free surface oscillations and aperiodic creeping to the capillary equilibrium shape appears at Oh ∼ 0.25. Droplet bouncing after receding is prompted with large contact angles at solid surface (as consistent with findings reported in the literature), but can be suppressed by increasing the droplet viscosity.Keywords: Drop impact, Microdroplet, Aerosol Jet®, Volume, of, fluid (VoF), Computational analysis
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Investigation of Magneto Hydrodynamic Natural Convection Flows in a 3-D Rectangular EnclosureThe article deals with magnetic field of free convective flows in cavities similar to those used in artificial growth of single crystals from melts (horizontal Bridgman configurations) and having aspect ratios an equal to 4. The combined effect of wall electrical conductivity and vertical direction of the magnetic field on the buoyancy induced flow of mercury was investigated numerically. The validation of the numerical method was achieved by comparison with both experimental and analytical data found in the literature. The plotted results for variation of velocity, temperature and Nusselt number in terms of the Hartmann number Ha and Rayleigh number Ra showed a considerable decrease in convection intensity as the magnetic field is increased, especially for values of Gr situated around 107. The calculations also showed that the vertically directed magnetic field (perpendicular to the x-z plane) is the most effective in controlling the flow and hence the speed of growth of the crystal. Also, wall electrical conductivity enhances damping by changing the distribution of the induced electric current to one which augments the magnitude of the Lorentz force.Keywords: Natural convection, Magnetic field, Cavity, Liquid metal, finite, volume, Lorentz force, tridimensional
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Steady, laminar, natural-convection flow in the presence of a magnetic field in an inclined rectangular enclosure heated from one side and cooled from the adjacent side was considered. The governing equations were solved numerically for the stream function, vorticity and temperature using the finite-volume method for various Grashof and Hartman numbers and inclination angles and magnetic field directions. The results show that the orientation and the strength and direction of the magnetic field have significant effects on the flow and temperature fields. Counterclockwise inclination induces the formation of multiple eddies inside the enclosure significantly affecting the temperature field. Circulation inside the enclosure and therefore the convection become stronger as the Grashof number increases while the magnetic field suppresses the convective flow and the heat transfer rate.Keywords: Natural convection, Magnetic field, Inclined rectangular enclosure finite, volume, Lorentz force
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در این تحقیق، پدیده ی کاویتاسیون روی هندسه های متقارن محوری کاویتاتورها و بدنه ی پرتابه ها با استفاده از روش نسبت حجمی سیال)V O F(با الگوریتم یانگز و روش جریان تعادلی همگن به صورت عددی مدل سازی شده است. کاربرد اصلی روش نسبت حجمی سیال در تحلیل جریان های مایع با سطح آزاد است. در این تحقیق قابلیت حل جریان گاز به الگوریتم V O F افزوده شد و سپس با اعمال مدل های تحلیلی عددی انتقال جرم کاویتاسیون در معادله ی انتقال سطح آزاد، پدیده ی کاویتاسیون شبیه سازی شد. نتایج حاصله نشان می دهد که الگوریتم عددی مورد استفاده، پارامترهای هندسی کاویتاسیون توسعه یافته ٓمانند ابعاد، نحوه ی بسته شدنٓ و پارامترهای جریانی آن ٓمانند ضریب پسا، ضریب فشار، سرعت روی مرز کاویتی و رفتار جت بازگشتیٓ را با دقت بالایی مدل سازی می کند. همچنین ماهیت غیردائمی الگوریتم عددی حاضر امکان مدل سازی مشخصه های رژیم کاویتاسیون ابری، مانند جدایش ساختارهای بخار از ناحیه ی کاویتی، را نیز فراهم می کند.
کلید واژگان: کاویتاسیون توسعه یافته، کاویتاسیون جزئی، سیالات با سطح آزاد، روش نسبت حجمی سیال (V O F)، روش جریان تعادلی همگن، مدل انتقال جرم، ضریب پساIn this study, transient cavitating flows over 2D-axisymmetric geometries of cavitators and projectile bodies were simulated using the Volume of Fluid (VOF) method and Young's free surface reconstruction algorithm. To predict the shape of the cavity, Navier-Stokes equations, in addition to an advection equation for the liquid volume fraction, are solved. The main application of the Volume of Fluid method is on the simulation of free surface flows. In this work, another capability has been added to the original Volume of Fluid model to solve, simultaneously, the gas and liquid phases. After this step, by applying an analytical-numerical mass transfer algorithm, the cavitation henomenon has been simulated. The mass transfer between the liquid and vapor is modeled using Kunz's method. Simulation of the cavitation is based on a homogenous equilibrium flow model. The main features of the developed model compared to available work in the literature are in the use of Young's algorithm to construct the cavity region and in the consideration of surface tension, which becomes important in the prediction of the cavity closure region. The developed model was used for different geometries in a wide range of cavitation numbers from cloud cavitation to a super cavitation regime. The developed numerical model can accurately predict the geometrical parameters of a super cavity, such as its length, diameter, and the closure region. In addition, the flow parameters of a supercavity, such as its drag coefficient, pressure coefficient, and re-entrant jet, were simulated with very high accuracy. The model can also simulate the characteristics of cloud cavitation, such as the separation of large vapor structures from the main cavity region. Totally, the developed model accurately captured the cavity closure region with its transient features of re-entrant jet movement and bubble detachment. In comparison with other available models for cavitation (such as the commercial software, Fluent) the developed algorithm is more efficient and needs far less CPU time and memory.Keywords: Supercavitation, partial cavitation, free, surface flows, volume, of, fluid (VOF) method, homegenous equilibrium flow, mass transfer model, drag coefficent
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