numerical simulation
در نشریات گروه مواد و متالورژی-
This research focuses on identifying optimal design modifications to enhance the fatigue characteristics of a diaphragm spring in a clutch system. A diaphragm spring from an Iranian Saipa automotive clutch, widely used as taxis in Iran and Iraq, was selected for practical testing and numerical analysis due to its frequent malfunctions and maintenance requirements during service. The load-deflection relationship of the selected spring was experimentally tested under compressive loading. Design modifications were explored by varying the spring thickness and finger configuration. Fatigue strength analysis was conducted using SolidWorks and ANSYS software to model and simulate the spring's performance under critical experimental loads. The results revealed that increasing the spring thickness improves fatigue life but adversely impacts deflection and other design requirements. Conversely, increasing the number or length of the fingers reduces fatigue life. The most effective modification for enhancing fatigue life while maintaining design requirements was increasing the finger root radius.Keywords: Design Diaphragm Spring, Experimental Load Deflection Testing, Numerical Simulation, Von Mises Stress, Fatigue Life, Damage
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پانل های ساندویچی معمولا به دلیل نسبت استحکام به وزن مناسب و جذب انرژی بالا، کاربرد وسیعی در صنایع مختلف از جمله صنایع هوافضا، صنایع دریایی و صنایع خودروسازی دارند. در این مقاله، رفتار بالستیکی پانل های ساندویچی با رویه های آلومینیوم- پلی اوره و هسته های آلومینیومی به شکل موج های نیم استوانه ای یا دارای حفره های نیم کروی (به صورت تک لایه یا چند لایه) بررسی شده است. با هدف افزایش مقاومت بالستیکی پانل های ساندویچی اثرات هندسه و چیدمان هسته، رویه پلی اوره، چند لایه بودن هسته و محل برخورد پرتابه سرتخت (استوانه ای) در سرعت های بالا (50 تا 400 متر بر ثانیه) شبیه سازی شده است. نرم افزار دینامیکی غیرخطی ال اس داینا برای شبیه سازی عددی و تحلیل مورد استفاده قرار گرفته است. تعداد 12 حالت متفاوت از نظر نحوه قرارگیری رویه ها و لایه های هسته مورد بررسی قرار گرفت. نتایج بررسی نشان دادند که در هسته های تک لایه با تغییر هندسه هسته از نیم استوانه ای به نیم کروی سرعت حد بالستیک 16 درصد افزایش پیدا کرده است. در هسته های دو لایه با جابجایی لایه ها با موج های مختلف (از نیم استوانه ای - نیم کروی به نیم کروی - نیم استوانه ای) سرعت حد بالستیک 4 درصد افزایش یافته است. استفاده از رویه پلی اوره در پانل ساندویچی سرعت حد بالستیک را 15درصد افزایش داد. با افزایش تعداد لایه های هسته نیم استوانه ای و نیم کروی سرعت حد بالستیک به ترتیب 32 و 29 درصد زیاد شد. در بین پانل های ساندویچی بررسی شده، مقادیر حد بالستیک و نسبت انرژی مستهلک شده بر واحد جرم بهترین پانل SP2 (پانل ساندویچی با رویه های آلومینیوم و پلی یوریا به ضخامت 1میلی متر و هسته نیم استوانه ای (دو لایه) به ضخامت 5/0 میلی متر و شعاع قوس 10 میلی متر) نسبت به ضعیفترین آن ها SP5 (پانل ساندویچی با رویه های آلومینیوم و پلی یوریا به ضخامت 1میلی متر و هسته نیم کروی (تک لایه) به ضخامت 5/0 میلی متر و شعاع قوس 20 میلی متر) به ترتیب، 3/92% و 4/254% اختلاف دارد.
کلید واژگان: پانل ساندویچی، ضربه سرعت بالا، مقاومت بالستیکی، پلی اوره، شبیه سازی عددیIn this paper, the ballistic behavior of sandwich panels with aluminum-polyurea face sheets and aluminum cores in the form of semi-cylindrical waves or with hemispherical cavities (single or multi-layer) has been investigated. To increase the ballistic resistance of sandwich panels, the effects of core geometry, core layout, polyurea plates, number of core layers, and projectile impact location at high velocities (50 to 400 m/s) have been simulated. A number of 12 different modes were examined in terms of the placement of the face sheets and core layers. The results of the investigation showed that in single-layer cores, by changing the geometry of the core from semi-cylindrical to hemispherical, the ballistic limit velocity increased by 16%. In two-layer cores, by shifting the layers with different waves (from semi-cylindrical -hemispherical to hemispherical- semi-cylindrical), the ballistic limit velocity increased by 4%. The use of polyurea in the sandwich panel increased the ballistic limit velocity by 15%. By increasing the number of semi-cylindrical and hemispherical core layers, the ballistic limit velocity increased by 32 and 29%, respectively. Among the investigated sandwich panels, the values of the ballistic limit and the ratio of expended energy per unit of mass are the best for SP2 panel (sandwich panel with aluminum and polyurea face sheets with a thickness of 1 mm and a semi-cylindrical core (double layer) with a thickness of 0.5 mm and radius arc 10 mm) compared to the weakest ones SP5 panel (sandwich panel with aluminum and polyurea face sheets with a thickness of 1 mm and a hemispherical core with a thickness of 0.5 mm and an arc radius of 20 mm); 92.3% and 254.4% respectively.
Keywords: Sandwich Panel, High Velocity Impact, Ballistic Resistance, Polyurea, Numerical Simulation -
The predictive accuracy of the finite element (FE) based packages are broadly based on the compatibility of adopted non-linear numerical procedures and incorporated material models. However, the routine way to define concrete material is not applicable to the concretes containing substitute materials in place of conventional concrete ingredients. Therefore, in this work, appropriate definition of materials in terms of stress-strain relations have been utilized to simulate the experimental work of RC beams containing coarser fractions of recycled concrete aggregates (RCA). The entire work has been carried out into two phases; an experimental work and the simulation of experimental work using FEA package, ABAQUS. In the experimental part, three number of full-scaled beam specimens were tested to failure through four-point monotonous loading. The replacement level of natural coarse aggregates was taken as 0.0, 50 and 100% by direct substitution. In the simulation phase, in addition to laboratory evaluated properties like compressive stress, tensile stress and elastic modulus, the measured stress-strain relationship for reinforcing steel and constitutive relationship for recycled aggregate concrete (RAC) reported in the literature have been considered as an input. The stress-strain relationships of RAC selected from the literature has been treated as user defined model. Besides the strength, serviceability in terms of deflections, crack patterns and load deformation characteristics of simulated beams have been investigated and compared with those of laboratory tested beam specimens.
Keywords: Recycled Concrete Aggregate, Normal Strength Concrete Beam, Flexural Behavior, Numerical Simulation -
افزایش تقاضا برای مواد بلوری خالص با توزیع اندازه ی بلوری باریک منجر به بهینه سازی بلورسازهای لوله مکش بافلی در صنایع وابسته شده است. اندازه ی توزیع بلورهای تولیدی به طور قابل ملاحظه ای با افزایش اختلاط درون بلورساز تغییر می کنند، بنابراین دستیابی به درک درست و دقیقی از هیدرودینامیک بلورساز می تواند در زمینه ی طراحی و افزایش مقیاس بلورساز کمک بسیاری نماید. تا کنون مطالعات گسترده ای در زمینه ی میدان جریان درون بلورسازها انجام شده است، اما هیچکدام از این تحقیقات تاثیرات و برهمکنش پارامترهای چیدمان داخلی بلورساز را بررسی نکرده اند. در این پژوهش، مقادیر عددی بهینه ی سه پارامتر هندسی (قطر لوله، نسبت قطر لوله به قطر بافل، و همچنین عرض ناحیه حلقوی ته نشینی بلورها) به کمک شبیه سازی عددی میدان جریان در 18 بلورساز لوله مکش بافلی مورد مطالعه قرار گرفت. برهمکنش پارامترها نیز با استفاده از روش فاکتوریل کلی بررسی شد. برای تجزیه و تحلیل بهتر نتایج مختلف مانند توزیع سرعت محوری، انرژی جنبشی متلاطم، و خطوط جریان، هرکدام از بلورسازها به پنج بخش تقسیم شده اند. نتایج شبیه سازی حاکی از آن است که بلورسازی با قطر لوله ی 5/17 سانتیمتر، نسبت قطر لوله به قطر بافل 5/0، و عرض ناحیه ی حلقوی ته نشینی بلورها برابر با قطر لوله، شرایط هیدرودینامیکی بهینه در هرکدام از بخش های بلورساز را فراهم می کند.
کلید واژگان: شبیه سازی عددی، بلورسازهای لوله مکش بافلی، طراحی آزمایش و تجزیه داده ها، طراحی فاکتوریل، توزیع اندازه بلورThe increasing demand for highly pure crystalline materials with narrow Crystal Size Distribution (NCSD) leads related industries to utilize the Draft Tube Baffle (DTB) Crystallizers. The product Crystal Size Distribution (CSD) significantly alters by enhancing the mixing characteristics inside crystallizer, therefore acquiring a precise vision of hydrodynamics will help in designing and scaling up the DTB crystallizer. There are numerous studies on the flow field in the DTB crystallizers, but none of them investigates the interactions and effects of the internal arrangement of DTB crystallizers. In this study, the optimal configuration of three geometrical parameters (tube diameter, the ratio of tube diameter to baffle diameter, and the width of the annular settlement zone) was obtained by numerical simulation of the flow field in 18 DTB crystallizers. The interaction of parameters was studied by employing the general factorial method. Each crystallizer was divided into five compartments where various results such as the distribution of axial velocity, the turbulent kinetic energy, and streamlines were considered for data analysis. The results demonstrate that the hydrodynamics requirements in each compartment will be satisfied in crystallizer with 17.5 cm tube diameter, the ratio of tube diameter/baffle diameter=0.5, and the width of the annular settlement zone equal to the tube diameter.
Keywords: Numerical Simulation, Draft Tube Baffle Crystallizer, Experimental Design, Data Analysis, GeneralFactorial Design, Crystal Size Distribution -
Through this paper, a 3D simulation together with experimental observation was conducted to study two-phase flow in a vertical tube. OpenFOAM software was employed to analyze air and water. Main flow stream was downward which was considered to be within a vertical pipe of 10 mm in diameter. Study included two inputs for flows: upper input for water and side input for air. Several states with various mass fluxes for both water and air were studied. Based on physics of the issue, numerical simulation was considered to be time-dependent. Obtained results showed that when air velocity occupied lower values, air momentum cannot overcome water momentum leading in small slugs. When airflow velocity was more than water flow rate, it dominated water flow and consequently could affect mainstream direction. Also, velocity graphs on centerline represented that going forward in time, velocity magnitude experiences a significant value of fluctuations and large oscillations occur next to outlet. Comparing experimental and numerical results, approximately 9% differences can be found which showed suitable agreement. Results showed that at initial steps, void fraction faces a significant jump in values. Intensity of this change in void fraction values was higher in lower water velocity. Indeed, by increment of water velocity, inertial forces associated with liquid phase find a dominant role in overall hydrodynamics of the gas-liquid flow. Also, it is obvious that flowing manner in cases 1, 2, and 3 are similar but after case 4, flow pattern varies. These changes are more considerable in cases 5 and 6.
Keywords: Two-phase Flow, Downward Flow, Numerical Simulation, Level Set Method -
مهمترین هدف در آزمایش ضربه سقوطی که در صنایع نظامی، فولاد و لوله سازی استفاده می شود، بدست آوردن مقدار انرژی شکست است. با نصب تجهیزات مناسب می توان نیروی ضربه دینامیکی را بر حسب تغییر مکان چکش دستگاه ضربه سقوطی اندازه گیری کرد و به کمک آن پارامترهای زیادی نظیر انرژی شروع و رشد ترک و انرژی کل شکست را محاسبه نمود. بدین منظور با استفاده تحلیل عددی بوسیله نرم افزار آباکوس، محل مناسب نصب کرنش سنج ها روی چکش تعیین شد. سپس مدار نیروسنج نصب و به کمک روش های تحلیلی و تجربی، رفع عیب و کالیبره شد. جهت بدست آوردن انرژی، باید ولتاژ را به مقادیر نیرو در هر لحظه تبدیل کرد. برای بدست آوردن ضریب مورد نظر از دو روش تحلیلی و تجربی استفاده شد. دو عدد حاصل از دو روش مذکور اختلاف قابل قبولی داشتند. همچنین، جهت افزایش دقت تکرارپذیری تجهیزاتی مانند میکروسوییچ و شابلون استفاده شدند. آزمایش های انجام شده با دستگاه نشان از تکرارپذیری نتایج داشت.
کلید واژگان: دستگاه ضربه سقوطی، مدار نیروسنج، شیبه سازی عددی، انرژی شکستThe most important objective in the drop weight tear test (DWTT) is obtaining the fracture energy. DWTT use in the military, steel and pipeline industries. By installing the proper equipment, the dynamic impact load can be measured in terms of the hammer displacement of the DWTT machine and it can calculate many parameters such as initiation energy, propagation and total fracture energy. For this purpose, numerical analysis by ABAQUS software was used to determine the proper location of the strain gauge on the hammer. Then, the strain gauge circuit (load-cell) was installed and calibrated using analytical and experimental methods. In order to use the circuit, the voltage must be converted to the load values. The analytical and experimental methods were used to obtain the desired coefficient. The two coefficient had an acceptable difference. In addition, in order to increase the accuracy and repeatability, other equipment such as guide and micro-swich were used in the DWTT machine. Experiments with the DWTT machine showed the repeatability of the results.
Keywords: DWTT, Load-cell Circuit, Numerical Simulation, Fracture Energy -
In the present paper, the numerical modelling to predict the interface damage of weld defect in a steel pipeline was studied. This work focused on determination of the maximum operating pressure and the characterisation of mechanical behaviour at a weld-base metal interface. The operating pressure can fluctuate leading to the phenomenon of fatigue and consequently to the failure of pipeline. Experimental investigations were carried out using non-destructive test (NDT) in order to locate and determine size of defects. A bilinear interface decohesion model is used to simulate the damage behaviour considering a stress-relative displacement laws. Numerical simulations based on the finite element method were used to study the influence of size defects and young's moduli ratio on the operating pressure as well as interfacial damage between the weld and base metal. The obtained results showed that the interface damage depending on shape and material properties of defects has an impact on pipeline safety and integrity.Keywords: Welding defect, Hydrostatic Test, Non-destructive test, interface, Damage, numerical simulation
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The many benefits of ultra-fine grained (UFG) tubes in the industry have led researchers to devise methods to increase the strength of tubes. Tubular channel angular pressing (TCAP) process is a new severe plastic deformation (SPD) technique to produce UFG tubes. In this research, at first, one pass of tubular channel angular pressing process with trapezoidal channel geometry is applied on Al-6061 samples. Then, mechanical properties such as yield strength, ultimate strength, hardness, and microstructure of the TCAPed samples are compared with the initial ones. In addition, effective strain and stress, processed load and deformation geometry during different stages of the tubular channel angular pressing process were investigated by finite element modeling. Finally, the results of the analytical model with finite element simulation were compared. It should be noted that the trapezoidal channel geometry has been used due to the high strain homogeneity and low force required for this channel geometry compared to other channel geometries. The microstructural results showed that the grain size of the initial samples was reduced from 92 µm to 785 nm in the TCAPed samples. The results of compression test showed that the yield strength and ultimate strength of the samples increased by 90% and 52%, respectively. The hardness of processed samples was also increased by 56% compared to the initial ones.Keywords: TCAP, Trapezoidal channel geometry, Microstructure, Mechanical properties, Numerical simulation
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In this research, steady-state Mixture and Eulerian-Eulerian method for liquid-gas parallel flow ejector have been examined. The simulation demonstrated that the Mixture model simulation represents better and efficient. The Eulerian-Eulerian model needed longer computational time and had a complexity to achieve the optimal convergence. However, both methods' performances were shown slightly similar. The models indicated a difference of about 6% in the flow rate ratio, their pressure diagrams nearly coincide, and their velocity parameter varies by 7% by comparing to the existing experimental data. Additionally, the Mixture model results appropriately conformed much better to the experimental data. So, the Mixture model was chosen for futher parametric study. Simulation results indicated that the flow rate ratio decreases by increasing the throat's cross-sectional area, and the flow rate ratio increases by increasing the nozzle's cross-sectional area. In this regard, e.g., the flow rate ratio of ejector by increasing pressure from 70 to 80 kPa, the air inlet increases up to 94%, and by increasing ejector outlet pressure, the flow rate ratio reduces such that no suction can be observed at 160 kPa. Consequently, in the 150 kPa pressure ratio, the flow rate ratio was reduced by almost 100%.
Keywords: Liquid-gas ejector, Two-phase flow, Mixture method, Eulerian-Eulerian method, numerical simulation -
The performance characteristics of InGaN Double-Quantum-Well (DQW) Laser Diodes (LDs) with different barrier structures were studied numerically by Integrated System Engineering Technical Computer-Aided Design (ISE TCAD) software. Three different kinds of structures of barriers including quaternary AlInGaN and AlInGaN/AlGaN superlattice barriers were used and compared with conventional GaN in InGaN-based laser diodes. Replacing the traditional GaN barriers with quaternary AlInGaN increased holes and electrons flowing in the active region and thus, the radiative recombination enhanced the output power. However, it did not reduce the threshold current due to hole and electron overflowing. To investigate the ways of greatly reducing the threshold current, the structure consisting of AlInGaN/AlGaN superlattice barriers was proposed. The simulation showed that electrical and optical characteristics such as output power, Differential Quantum Efficiency (DQE), and slop efficiency were significantly enhanced for LDs containing superlattice barriers compared to the basic structure. This is while the threshold current was considerably reduced. The enhancement was mainly attributed to the improvement of hole injection and also the blocking hole and electron overflowing caused by the reduction of polarization charges at the interface between the barriers, the well, and the Electron Blocking Layer (EBL).Keywords: InGaN quantum well laser, superlattice barriers, Electrical, Optical Properties, numerical simulation
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در بسیاری از حملات انفجاری، علیرغم تحمیل نشدن آسیب جدی به المانهای سازهای، عناصر غیرسازهای ازجمله دیوارهای بنایی دچار آسیب جدی شدهاند. همچنین سازهی بسیاری از ساختمانهای موجود در مراکز نظامی از دیوارهای آجری میباشد. لذا بررسی عملکرد این دیوارها در برابر بارگذاری انفجار ضروری است. برخی از تحقیقات صورت گرفته به بررسی آزمایشگاهی این موضوع پرداختهاند. ازآنجاکه مطالعات آزمایشگاهی ازلحاظ مسایل امنیتی، ایمنی و هزینهای مشکلاتی به همراه دارد استفاده از شبیهسازی عددی بهعنوان مکمل آن میتواند کار آیی زیادی داشته باشد. در این مقاله با استفاده از نرمافزار ANSYS AUTODYN شبیهسازی عددی دیوار آجری با ملات ماسه و سیمان با نگرش میکروی جزیی تشریح و مراحل شبیهسازی با معرفی المانها، مدلهای ماده و حالت و مقادیر پارامترهای متناظر ارایهشده است. با راستی آزمایی نتایج تحلیل عددی با آزمایشها میدانی، نشان دادهشده است که این روش قادر به برآورد دقیق و سریع رفتار و آسیب دیوارها تحت بارهای انفجاری در سناریوهای مختلف تهدید است. همچنین الگوی منحنیهای هم آسیب برحسب متغیرهای بیش فشار و تکانه ارایه گردید که میتواند راهنمای ساخت بهینه دیوارها بر اساس نوع تهدید و هزینه متناسب باشد و نیز استراتژی تقویت دیوارهای موجود را برحسب سناریوهای تهدید محتمل تدوین کرد.
کلید واژگان: بارگذاری انفجاری، دیوار بنایی، شبیه سازی عددی، میکرو مدلIn numerous explosive attacks, non-structural elements, including masonry walls, are severely damaged, although no serious damage is inflicted on structural elements. Besides, the structure of most buildings in military centers are made of masonry walls. Therefore, it is necessary to study the behavior of these walls subjected to blast load. In this regard, some research has focused on experimental studies. Because these experimental studies include difficulties in terms of security, safety and cost, using numerical studies as a complement can be very effective. In this paper, numerical simulation of masonry walls with mortar is described with a partial micro approach, using ANSYS AUTODYN software, and element characteristics, material models, equations of state and values of corresponding parameters are introduced step by step. By verifying the numerical analysis results with experimental data, it has been shown that this method is able to estimate the behavior and damage of masonry walls under blast loading, accurately and quickly. Moreover, the co-damage curves in terms of overpressure and impulse parameters is presented, which can be a helpful guide to the optimal design of walls based on different threat scenarios and cost. Finally, this model can be used to develop a corresponding retrofitting strategy for the existing walls in terms of possible threat scenarios.
Keywords: masonry wall, blast load, numerical simulation, micro model -
هزینه های فراوان مطالعه تجربی امواج ناشی از انفجار پژوهشگران را به سمت تحلیل عددی آن به کمک دینامیک سیالات محاسباتی سوق داده است. تجربه نشان داده است که تحلیل عددی می تواند تا حد زیادی و با تقریب مناسب رفتار موج انفجار را پیش بینی کند. به منظور افزایش دقت تحلیل عددی پدیده انفجار تاکنون ترفندهای فراوانی مانند نوع مدل توربولانسی و روش اعمال انرژی انفجار مورد بررسی قرار گرفته است. اما یکی از عوامل مهم در افزایش دقت نتایج، معادله حالتی است که رفتار فیزیکی گاز ناشی از انفجار را توصیف می کند. در بیشتر پژوهش های پیشین از معادله گاز ایده آل به عنوان ساده ترین معادله حالت استفاده شده است. در پژوهش حاضر به بررسی اثر استفاده از معادلات حالت گاز حقیقی Jones–Wilkins–Lee (JWL) و Becker–Kistiakowski–Wilson (BKW) در مقایسه با مدل گاز ایده آل بر دقت نتایج تحلیل عددی مساله انفجار در نزدیکی یک دیواره پرداخته شده است. شبیه سازی عددی پدیده انفجار با استفاده از حلگر blastFoam از کد منبع باز openFoam صورت پذیرفته است و نتایج بدست آمده با نتایج پژوهش های قبلی مقایسه شده است. در نهایت ثوابت معادلات حالت گاز حقیقی JWL و BKW با استفاده از داده های تجربی و به کمک حل عددی کالیبره شده است.
کلید واژگان: موج بلست، انفجار، معادله حالت گاز حقیقی، کالیبراسیون، حل عددی، BKW، JWLThe high-expensive empirical analysis of blast waves motivates the researchers to investigate the explosion using numerical simulations. The literature shows that the computational fluid dynamics predicts the blast wave behavior accurately. Meanwhile, many methods such as the turbulence method, and the method of applying the explosion energy to the equations were presented to increase the accuracy of the numerical analysis. However, one of the most important factors in the results’ accuracy is the equation of state that describes the physical behavior of the explosion productions. The ideal-gas equation of state as the simplest equation of state was used in most of the previous researches. In this research the effect of using JWL and BKW, the real gas equations of state, on the results’ accuracy in comparison with the ideal-gas equation of state is investigated. To do this investigation, the problem of explosion close to a canopy is simulated. The numerical simulation of explosion phenomenon is done using the blastfoam solver of the openFoam open source code, and the results are compared with the previous studies. Finally, the constants of the BKW and JWL equations of state are calibrated using the empirical data.
Keywords: blast waves, explosion, real gas equation of State, Calibration, Numerical Simulation, BKW, JWL -
Blasting is the initial stage of development in mining operations. Therefore, the use of explosives requires a technical design to control its adverse effects on nearby structures. In that regard, the blast vibrations in Izeh-Karun 3 main road project were recorded using four 3-component Blast Recorder seismographs. The seismographs recorded a peak particle velocity of 8.8 mm/sec in the nearby oil pipe. The blast pattern and the resulting ground vibration are simulated. The numerical model is verified using the recorded seismic data and the empirical model. The stresses applied on the oil pipeline were measured by the static analysis of the stress induced by the oil pipeline's internal pressure and the dynamic analysis of ground vibration. The pipeline stress was equal to 271 MPa, lower than the pipeline yield stress (414 MPa). Therefore, the vibrations induced by the blasting operation did not damage the oil pipeline. Comparing the vibration induced in the oil pipeline (8.8 mm/sec) with the critical vibration level (50 mm/sec) showed that the pipelines near the blast operation were at a safe distance.Keywords: blasting, ground vibration, numerical simulation
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In this research, the effect of using the exhausted smoke of a cogeneration power plant as the working fluid of a solar chimney to increase power generation is studied by numerical methods. First, the cogeneration power plant is modeled using ASPEN HYSYS; then, the properties of the exhausted smoke including temperature, mass flow rate and etc. are entered to the model of solar chimney power plant, developed in ANSYS FLUENT. Using this hybrid model, the effect of solar radiation on power generation is compared for both air and smoke as working fluids. Furthermore, the effect of inlet temperature on power generation is also studied. The results showed that the power generation increases on average 4 times using smoke instead of air. It is also found that the optimum chimney height is 500 m using air and 600 m using the exhausted smoke of cogeneration power plant.Keywords: Solar Chimney Power Plant, Cogeneration power plant, Efficiency enhancement, Numerical simulation
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آغازگر الکتریکی یک جزء مهم زنجیره انفجار است که با تبدیل جریان الکتریکی به گرما توسط سیم پل، انرژی لازم برای شروع یک واکنش شیمیایی را فراهم می کند. این آغازگر به علت وزن پایین و قابلیت اطمینان بالا، در حوزه صنایع هوافضا کاربرد گسترده ای در موتورهای سوخت جامد، سیستم های جدایش و... دارد. در این تحقیق، یک مدل ریاضی برای بررسی عوامل موثر بر عملکرد آغازگر الکتریکی معرفی شده است. مقایسه نتایج شبیه سازی عددی با روش تفاضل محدود و داده های تجربی نشان داد که این مدل توانایی پیش بینی زمان آغازش و تعیین پروفایل دمای ناپایا در راستای محوری و شعاعی را دارد. مدل مذکور نشان داد که کاهش ضریب انتقال حرارت تماسی بین سیم پل و ماده آغازگر نسبت به افزایش آن تاثیر بیشتری بر نرخ انتقال حرارت دارد. هم چنین مشخص شد که با افزایش شدت جریان، تغییرات دما در راستای محوری کاهش و در راستای شعاعی افزایش می یابد
کلید واژگان: آغازگر الکتریکی، انتقال حرارت، شبیه سازی عددی، شدت جریان، دما، سیم پلThe electric initiator is an important component of the explosive train which provides requiered energy to initiate a chemical reaction by converting the electric current to the heat via a bridgewire. This initiator is widely used in the field of aerospace industry in the solid rocket propellant motors, separation systems and etc due to its low weight and high reliability. In this research, a mathematical model has been introduced to investigate the effective parameters on the electric initiator performance. Comparison of numerical simulation results by finite difference method and experimental data showed that this model has the ability of the prediction of the ignition time and determine the transient temperature profile in axial and radial direction. The model showed that the reduction of the contact heat transfer coefficient between the bridgewire and the primer compared to its increase has a greater effect on the heat transfer rate. It was also found that with increasing the current, the temperature changes decreased along the axial direction and increased in radial direction.
Keywords: Electric Initiator, Heat Transfer, Numerical Simulation, Current, Temperature, Bridge Wire -
Co-Continuous Ceramic Composites, referred to as C4, have bi-continuous, interconnected and interpenetrating phases of a metal and ceramic. This bestows such composites with a higher strength to weight ratio compared with traditional composites. In this research work, a C4 composite of AA5083/SiC is fabricated for personal body armour, using gravity infiltration technique. A numerical simulation model of the C4 specimen is developed. This finite element model is utilized to simulate the DoP of a subsonic bullet into the C4 and is estimated as 1.47 mm. The C4 specimen is then, subjected to ballistic tests. A medium velocity projectile with a rated velocity of 326 m/s is used to impact the C4 specimen. The ballistic tests validate the numerical simulation with a DoP of 1.5 mm. Visual inspection reveals brittle cracks and interfacial debonding in the impacted C4. The results indicate that, such composites can potentially be utilized as low cost body armour.Keywords: Co-continuous Ceramic Composite, depth of penetration, Impact testing, numerical simulation
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This work presents a numerical Simulation of an underwater glider to investigate the effect of angle of attack on the hydrodynamic coefficients such as lift, drag, and torque. Due to the vital role of these coefficients in designing the controllers of a glider, and to obtain an accurate result, this simulation has been carried on at a range of operating velocities. The total length of the underwater glider with two wings is 900 mm with a 4-digits NACA0009 profile. The fluid flow regime is discretized and solved by computational fluid dynamics and finite volume method. Since the Reynolds number range for this study is in a turbulent flow state (up to 3.7e06), the κ-ω SST formulation was used to solve Navier-Stokes equations and continuity and the angles of attack ranging are from - 8 to 8 degrees. The main purpose of this research is to study the effect of each of the dynamics parameters of glider motion such as velocity and angle of attacks on the hydrodynamic coefficients. Based on the results, the drag and lift coefficients are enhanced with increasing the angle of attack. In addition, the drag coefficient enhanced with increasing the velocity however, when the glider velocity is increased, the lift coefficient does not change significantly except at the highest angle of attack that decreases. The highest drag coefficient is 0.0246, which corresponds to the angle of attack of -8 and the Reynolds number of 3738184. In addition to simple geometry, the glider studied in this paper shows relatively little resistance to flow.Keywords: Underwater gliders, numerical simulation, finite volume method, Hydrodynamic coefficients, Angle of attack
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Numerical simulation is a powerful tool to predict the physical behavior of the designed devices. This method provides detailed information about the investigated phenomenon for each point of the device, which is generally challenging by experiments. Comsol Multiphysics can be utilized in a wide range of engineering fields. This software employs the finite element method (FEM) to solve the physical governing equations. Due to the importance of the heat transfer in advanced ceramics and the potential of the numerical methods to solve the related problems, the present article aims to provide a comprehensive review of the performed numerical research works using Comsol Multiphysics.
Keywords: Advanced ceramics, Numerical simulation, Comsol Multiphysics, Heat transfer -
In this paper, a mesh-free approach called smooth particle hydrodynamics (SPH) is proposed to analyze the seepage problem in porous media. In this method, computational domain is discredited by some nodes, and there is no need for background mesh; therefore, it is a truly meshless method. The method was applied to analyze seepage flow through a concrete dam foundation. Using the SPH method, the computational boundary being coincident with the physical boundary, was numerically acquired by solving seepage flow govern in equations. The numerical results of the presented method were compared with ones calculated by the Geostudio-SEEPW (finite element based software). The water head values were calculated through the dam foundation, and there was a good agreement between results. Moreover, results showed that the SPH method is efficient and capable of analyzing seepage flow particularly in complex geometry problems.Keywords: seepage flow, Concrete Dam Foundation, Smooth Particle Hydrodynamics, numerical simulation, Geostudio-SEEPW
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در این پژوهش تاثیر روش پرکردن هسته های موجدار ذوزنقه ای شکل دو لایه، با فوم های پلی یورتان از نوع سخت با وزن سبک، مورد مطالعه قرار گرفته است. پنج نوع هسته موجدار از جنس آلمینیوم به صورت خالی و پر شده از فوم، تحت بارگذاری شبه استاتیکی به صورت، فشاری تک محوره قرار گرفته اند. در ادامه با استفاده از شبیه سازی عددی توسط نرم افزار آباکوس به بررسی پارامترهای ضربه پذیری، شامل جذب انرژی ویژه، بعنوان اهداف آزمایش می پردازیم. این نوع سیستم جاذب انرژی، می تواند در صنایع هوایی، کشتی سازی، خودروسازی، صنایع ریلی و آسانسورها جهت جذب انرژی ضربه مورد استفاده قرار گیرد. مقایسه ی نتایج حاصل از تحلیل عددی و آزمایشگاهی، نشان از همپوشانی بالا و تطابق خوب دو روش با هم دارد. نتایج تحلیل های اجزاء محدود و آزمایشگاهی نشان داد، که به کارگیری فوم در هسته، می تواند ظرفیت جذب انرژی را به صورت قابل ملاحضه ای افزایش دهد. در انتها پارامترهای هندسی مناسب، و بهترین نمونه ها از لحاظ معیارهای در نظر گرفته شده با توجه به اهداف طراحی، معرفی می شوند.کلید واژگان: جذب انرژی، هسته ذوزنقه ای مرکب، بارگذاری شبه استاتیک، فوم پلی یورتان سخت، شبیه سازی عددیThe aim of this research work is to investigate the mechanical properties of double layer trapezoid-shape corrugated core sandwich structures under quasi-static loading conditions and to determine the failure mechanisms and energy-absorbing characteristics of the corrugated cores. In this investigation, influence of foam filling technique in double layer trapezoid-shape corrugated core by using lightweight rigid polyurethane foam is investigation. Five types of Aluminum corrugated cores both bare and foam-filled were subjected to unidirectional quasi-static compression. In the following, using numerical simulation by Abaqus software to evaluation the impact parameters, including Specific Energy Absorption (SEA) as discussed testing purposes. the energy absorbing system can be used in the aerospace industry, shipbuilding, automotive, railway industry and elevators to absorb impact energy. The FEM results are compared with Experimental results which reveal a good conformity. FEM and experimental results showed that foam filling technique can significantly increase specific absorbed energy. Finally, appropriate geometric parameters and the best examples of criteria considered with respect to the objectives, are introduced.Keywords: energy absorption, Trapezoidal Compound core, quasi-static loading, rigid polyurethane foam, numerical simulation
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