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Supersonic flow over a pitching delta wing using surface pressure measurements and numerical simulations

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Chinese Journal of Aeronautics 2018年第1期31卷 65-78页

作者： Mostafa HADIDOOLABI Hossein ANSARIAN Aerospace engineering department Malek Ashtar University of Technology

Experimental and numerical methods were applied to investigating high subsonic and supersonic flows over a 60°swept delta wing in fixed state and pitching oscillation. Static pressure coefficient distributions over the wing leeward surface and the hysteresis loops of pressure coefficient versus angle of attack at the sensor locations were obtained by wind tunnel tests. Similar results were obtained by numerical simulations which agreed well with the experiments. Flow structure around the wing was also demonstrated by the numerical simulation. Effects of Mach number and angle of attack on pressure distribution curves in static tests were investigated. Effects of various oscillation parameters including Mach number, mean angle of attack, pitching amplitude and frequency on hysteresis loops were investigated in dynamic tests and the associated physical mechanisms were discussed. Vortex breakdown phenomenon over the wing was identified at high angles of attack using the pressure coefficient curves and hysteresis loops, and its effects on the flow features were discussed.

关键词： Delta wing Hysteresis loop Pitching oscillation Supersonic flow Vortex breakdown

Optimal design for split-and-recombine-type flow distributors of microreactors based on blockage detection

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Chinese Journal of Chemical engineering 2016年第7期24卷 897-903页

作者： Lin Wang Xianzuo Kong Yongsheng Qi department of Control engineering Inner Mongolia University of Technology

In order to increase the productivity of microreactors, the parallelization of the microreactors is required. The performances of flow distributors can affect the product yield and fault detection ability when blockage *** this research, an optimal design method to calculate the channel diameters and to determine the flow sensor location is derived based on mass balance and pressure balance models of split-and-recombine-type flow distributors(SRFDs). The model accuracy is verified by experiment data. The proposed method is applied to optimal design of SRFDs under constant flow rate operation conditions. The maximum angle difference between normal and blockage conditions at one sensor to those at the other sensors is set to be the objective function and the uniformity of flow distribution in microreactors under normal condition is also required. The diameters of each pipe in SRFDs are selected as the design variables. Simulated annealing algorithm is used to solve the optimization problem. The effectiveness of the optimal design results is demonstrated by fluid dynamics simulations. The results show that using the optimal channel diameters of SRFDs, the pressure drop in SRFD section is lower than that of the microreactor section. Meanwhile, in the case studies, only a few sensors that are located inside the SRFDs can easily detect the blockage abnormal condition in the parallelized microreactor system.

关键词： Optimal designSplit-and-recombine-type flow distributorsMicroreactorsMicrochannelsBlockage

Numerical simulation of mold-temperature-control solidification

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中国有色金属学会会刊：英文版 2007年第3期17卷 443-448页

作者：游东东邵明李元元周照耀 department of Mechanical engineering South China University of Technology

A finite element method(FEM) for the numerical simulation of the columnar part of the mould-temperature-control solidification(MTCS) process was presented. The latent heat was taken into account and 3D transient heat transfer analysis was carried out by using the developed FEM software. The relative errors between the numerical and experimental data are less than 6%. Three MTCS cases were computed with this method. The first case only opens the cooling channels in the bottom of the mold. The second case individually controls the separate 7 groups of cooling channels by giving 7 control points. When the temperature of a control point reaches the preset value of 400℃, the corresponding channel will be opened. The third case opens all the cooling channels at the same time. The results indicate that in the second case, the solid-liquid interface keeps near-planar. The growth velocity of the solid-liquid interface is 0.3-0.4 mm/s, which is greater than 0.1-0.3 mm/s of the first case, performing better than the others. Thus the forming quality and efficiency part interior can be improved by mold-temperature-control and the numerical model is validated. The numerical simulation of MTCS can provide an available tool for the advanced investigation on the defect improvement and the crystal’s quality.

关键词：数值模拟温度控制凝固固液界面

Flutter analysis of hybrid metal-composite low aspect ratio trapezoidal wings in supersonic flow

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Chinese Journal of Aeronautics 2017年第1期30卷 196-203页

作者： Shokrollahi Saeed Shafaghat Salman department of Aerospace engineering Malek Ashtar University of Technology

An effective 3D supersonic Mach box approach in combination with non-classical hybrid metal-composite plate theory has been used to investigate flutter boundaries of trapezoidal low aspect ratio wings. The wing structure is composed of two main components including aluminum material（in-board section） and laminated composite material（out-board section）. A global Ritz method is used with simple polynomials being employed as the trial functions. The most important objective of the present research is to study the effect of composite to metal proportion of hybrid wing structure on flutter boundaries in low supersonic regime. In addition, the effect of some important geometrical parameters such as sweep angle, taper ratio and aspect ratio on flutter boundaries were studied. The results obtained by present approach for special cases like pure metallic wings and results for high supersonic regime based on piston theory show a good agreement with those obtained by other investigators.

关键词： Assumed mode method Flutter Hybrid trapezoidal plateMach box method Supersonic flow

Seismic assessment of unanchored steel storage tanks by endurance time method

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Earthquake engineering and engineering Vibration 2011年第4期10卷 591-603页

作者： M. Alembagheri H.E. Estekanchi department of Civil engineering Sharif University of Technology (SUT)

Liquid storage tanks are essential structures that are often located in residential and industrial areas; thus an assessment of their seismic performance is an important engineering issue. In this paper, the seismic response ofunanchored steel liquid storage tanks is investigated using the endurance time （ET） dynamic analysis procedure and compared to responses obtained for anchored tanks under actual ground motions and intensifying ET records. In most cases, the results from ground motions are properly obtained with negligible differences using ET records. It is observed that uplifting of the tank base, which is closely related to the tank aspect ratio, has the greatest significance in the responses of the tank and can be predicted with reasonable accuracy by using currently available ET records.

关键词： steel liquid storage tanks endurance time method seismic assessment intensifying dynamic excitation tank base uplifting

COVID-19 and Learning Styles: GCET as Case Study

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Computers, Materials & Continua 2021年第7期68卷 103-115页

作者： Mazhar Hussain Malik Sid Ahmed Amjed Sulaiman Al Hasani department of Computing and Information technology Global College of Engineering and TechnologyMuscatSultanate of Oman department of Electrical and Electronics engineering Global College of Engineering and TechnologyMuscatSultanate of Oman

The COVID-19 pandemic has caused higher educational institutions around the world to close campus-based activities and move to online *** aim of this paper is to present the case of Global College of engineering and technology(GCET)and how its practices including teaching,students/staff support,assessments,and exam policies were *** paper investigates the mediating role of no detriment policy impact on students’result along with the challenges faced by the higher educational institution,recommendations and *** investigation concludes that the strategies adopted for online delivery,student support,assessments and exam policies have helped students to effectively cope with the teaching and learning challenges posed by the COVID-19 pandemic without affecting their academic *** study shows that 99%of students were able to maintain the same or better level of performance during the 1st COVID-19 *** percent of students had shown a slight decrease in their performance(about 1%–2%)with respect to their overall marks *** no detriment policy has succoured those 1%of the students to maintain their overall performance to what it used to be pre-COVID-19 ***,the paper provides the list of challenges and suggestions for smooth conduction of online education.

关键词： Higher education learning styles COVID-19 challenges and strategies no detriment policy engineering and technology modules

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Acta Metallurgica Sinica(English Letters) 2018年第11期31卷 1183-1196页

作者： Farhad Bakhtiari Argesi Ali Shamsipur Seyyed Ehsan Mirsalehi department of Mining and Metallurgical engineering Amirkabir University of Technology

In this study, the dissimilar friction stir welding （FSW） butt joints between aluminum alloy 5754-H114 and commerciallypure copper were investigated. The thickness of welded plates was 4 mm and the aluminum plate was placed on theadvancing side. In order to obtain a suitable flow and a better material mixing, a 1-mm offset was considered for thealuminum plate, toward the butt centerline. For investigating the microstructure and mechanical properties of FSWedjoints, optical microscopy and mechanical tests （i.e., uniaxial tensile test and microhardness） were used, ***, the analysis of intermetallic compounds and fracture surface was examined by scanning electron microscopyand X-ray diffraction. The effect of heat generation on the mechanical properties and microstructure of the FSWed jointswas investigated. The results showed that there is an optimum amount of heat input. The intermetallic compounds formedin FSWed joints were A14Cu9 and AI2Cu. The best results were found in joints with 1000 rpm rotational speed and100 mm/min travel speed. The tensile strength was found as 219 MPa, which reached 84% of the aluminum base ***, maximum value of the microhardness of the stir zone （SZ） was attained as about 120 HV, which was greatlydepended on the grain size, intermetallic compounds and copper pieces in SZ.

关键词： Friction stir welding 5754-H114 aluminum alloy Pure copper Heat generation Microstructure Intermetallic compounds

New solvent blends for post-combustion CO2 capture

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Green Energy & Environment 2019年第4期4卷 439-452页

作者： Hanna K.Knuutila Rune Rennemo Arlinda F.Ciftja Norwegian University of Science and technology Department of Chemical Engineering

In the current work five different solvent blends are experimentally studied and the reboiler duties are calculated using the so-called short-cut *** amines,2-(diethylamino)ethanol(DEEA),3-(Diethylamino)-1,2-propanediol(DEA-12PD),2-[2-(Diethylamino)ethoxy]ethanol(DEA-EO),1-(2-Hydroxyethyl)piperidine(12HE-PP)are blended with 3-(Methylamino)propylamine(MAPA)and ethanolamine(MEA).The first results from simple solvent screening are given and the cyclic capacities are calculated based data at 40℃ and 80℃.Then,five solvent systems are chosen for vapor–liquid equilibrium *** vapor–liquid equilibrium data are then used to estimate cyclic capacities at more realistic temperatures,between 40℃ and 120℃ and by using a short-cut method proposed in the literature the reboiler duties of the characterized solvents are ***,the potential of the studied systems is *** of the characterized blends showed reboiler duties around 2.5 MJ kgCO2^-1.

关键词： CO2 capture Chemical absorption Vapor-liquid equilibria

Effect of multiple rings on side force over an ogive-cylinder body at subsonic speed

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Chinese Journal of Aeronautics 2018年第6期31卷 1181-1188页

作者： Priyank KUMAR J.K.PRASAD department of Space engineering & Rocketry Birla Institute of Technology

Experiments and computations were performed over an ogive-cylinder body having an lift-to-drag ratio of 16 at a diameter Reynolds number of 29000. The side force on the slender body augments with increasing angles of attack for the case without a ring. This increase was mainly due to the increase in the asymmetry of the existing vortex pair in the wake of the body. Attempts were made to completely reduce the existing side force at the angle of attack ranging from 35° to 45°.Three rectangular cross-sectioned circumferential rings having a height of 3% of the local diameter were placed at axial distances of 2.5, 3.5 and 4.5 times the base diameter from the tip of the body so as to reduce the side force. The results obtained indicate that inclusion of three rings completely alleviated the side force on the slender body at the angle of attack ranging from 0° to 45°. The presence of rings was found to alter the growth of the vortices that helped in the reduction of the side force. Computations performed were in reasonable agreement with the experiments.

关键词： Asymmetric vortex High angle of attack Ogive Side force Slender body Vortex lift