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Flow equation and similarity criterion during centrifugal casting in micro-channel

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Transactions of Nonferrous Metals Society of China 2014年第5期24卷 1506-1511页

作者：任明星王国田李邦盛王振龙傅恒志哈尔滨工业大学微系统与微结构制造教育部重点实验室哈尔滨150001 哈尔滨工业大学材料科学与工程学院哈尔滨150001 哈尔滨工业大学机电工程学院哈尔滨150001

Liquid metal filling flow process in the microscale during the centrifugal casting process was studied by means of similar physical simulation. The research was focused on derived similarity criterion. Based on the traditional flow equations, the flow equation and the Bernoulli＇s equation for liquid metal flows in micro-scale space were derived, which provides a mathematical model for numerical simulation of micro-scale flow. In the meanwhile, according to the micro-flow equation and the similarity theory, the similarity criterion for the physical simulation of the mold filling behaviors was presented under centrifugal force field, so as to achieve the visual observation and quantitative analysis of micro-flow process.

关键词： micro-channel micro-flow centrifugal force field similarity criterion

Virtual flight test techniques to predict a blended-wing-body aircraft in-flight departure characteristics

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Chinese Journal of Aeronautics 2022年第1期35卷 215-225页

作者： Junquan FU Zhiwei SHI Zheng GONG Mark HLOWENBERG Dawei WU Lijun PAN Nanjing University of Aeronautics and Astronautics Nanjing 210016China University of Bristol Bristol BS81TRUnited Kingdom CO MAC Shanghai Aircraft Design and Research Institute Shanghai 201210China

As one of the promising configurations of the next generation of commercial aircraft,research on departure characteristics of the Blended-Wing-Body(BWB)is of great signification to safe flight limits.A three-degree-of-freedom(3-DOF)virtual flight test in a wind tunnel has been implemented for a candidate configuration to predict the departure *** support mechanism,the test model and the control law of the virtual flight test are *** order to show the relationship between virtual flight test and actual flight test,the similarity criterion is also *** open loop,the model has mild oscillations in the longitudinal and lateral directions,which are stable in *** effect of flight control has been verified in virtual flight and actual subscale flight *** analysis of system identification results indicate that the model has a good response to the excitation signal,and the response is in reasonable agreement with the flight ***,the virtual flight departure test results are compared with the flight *** shows that there is a good correspondence between the angle of attack and the elevator deflection at *** gives promising evidence of the practicability of virtual flight testing to predict departure of a BWB.

关键词： Blended-wing-body Departure Flight test similarity criterion Virtual flight test

Numerical studies on issues of Re-independence for indoor airflow and pollutant dispersion within an isolated building

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Building Simulation 2022年第7期15卷 1259-1276页

作者： Peng-Yi Cui Wei-Qiu Chen Jia-Qi Wang Jin-Hao Zhang Yuan-Dong Huang Wen-Quan Tao College of Environment and Architecture University of Shanghai for Science and TechnologyShanghaiChina Key Laboratory of Thermo-Fluid Science and Engineering of MOE School of Energy and Power EngineeringXi'an Jiaotong UniversityXi’anChina

This study conducted the numerical models validated by wind-tunnel experiments to investigate the issues of Re-independence of indoor airflow and pollutant dispersion within an isolated *** window Reynolds number(Re_(w))was specified to characterize the indoor flow and *** indicators of RRC(ratio of relative change)or DR(K_DR)(difference ratio of dimensionless concentration)<5%were applied to quantitatively determine the critical Rew for indoor flow and turbulent *** results show that the critical Re(Re_(crit)) value is position-dependent,and Re_(crit) at the most unfavorable position should be suggested as the optimal value within the whole areas of *** Re(H,orit)=27,000 is recommended for the outdoor flows;while Re_(w,crit)=15,000 is determined for the indoor flows due to the lower part below the window showing the most *** suggested Re_(w,crit)(=15,000)for indoor airflow and cross ventilation is independence of the window ***,taking K_DR≤5% as the indicator,the suggested Re_(w,crit) for ensuring indoor pollutant diffusion enter the independence regime should also be 15,000,indicating that indoor passive diffusion is completely determined by the flow *** contours of dimensionless velocity(U/U_(0))and concentration(K)against the increasing Re(w) further confirmed this critical *** study further reveals the Re-independence issues for indoor flow and dispersion to ensure the reliability of the data obtained by reduced-scale numerical or wind-tunnel models.

关键词： CFD simulation Re-independence similarity criterion indoor ventilation pollutant dispersion

Formation of defects in selective laser melted Inconel 718 and its correlation with mechanical properties through dimensionless numbers

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Science China(Physics,Mechanics & Astronomy) 2022年第5期65卷 58-74页

作者： Zhiwei Luo Zekun Wang Zhenyu Yan Jing Chen Shuguang Li Moubin Liu Capital Aerospace Machinery Co.Ltd. Beijing 100706China State Key Laboratory for Turbulence and Complex Systems Department of Mechanics and Engineering SciencePeking UniversityBeijing 100871China College of Engineering Peking UniversityBeijing 100187China Nanchang Innovation Institute Peking UniversityNanchang 330008China

This paper presents a profound study on the formation of three typical types of defects(i.e.,lack of fusion,keyholes,and gas pores)observed in selective laser melting(SLM)printed Inconel 718 samples,along with their correlations with mechanical properties of the *** tomography,scanning electron microscopy,and mechanical property tests revealed that the three types of defects fall into three stages of porosity evolution classified by recently-proposed dimensionless numbersηm(melting efficiency)andηv(vaporization efficiency).Meanwhile,experimental tests verified that the mechanical properties of products,such as strength and elongation,are remarkably sensitive to lack of ***,these properties are slightly affected by the keyholes and gas *** optimal process window characterized by dimensionless numbers is realized by adjusting the processing parameters and employing different *** process window allows products to have relatively low defects and high mechanical performances.A quantitative relation between processing parameters,dimensionless numbers,defects,and mechanical properties is established based on these *** relation,along with the optimal process window,is believed to enhance the quality of SLM products of Inconel 718 alloy and can be further extended to SLM with other metal materials.

关键词： selective laser melting defects formation mechanical properties similarity criterion

A theoretical study on the unsteady aerothermodynamics for attached flow models

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Science China(Physics,Mechanics & Astronomy) 2010年第8期53卷 1505-1514页

作者： CHEN Hao BAO Lin TONG BingGang Graduate University of the Chinese Academy of Sciences Beijing 100049China

The principle of the unsteady aerothermodynamics was theoretically investigated for the attached flow. Firstly, two simplified models with analytic solutions to the N-S equations were selected for the research, namely the compressible unsteady flows on the infinite flat plate with both time-varying wall velocity and time-varying wall temperature boundary conditions. The unsteady temperature field and the unsteady wall heat flux (heat flow) were analytically solved for the second model. Then, the interaction characteristic of the unsteady temperature field and the unsteady velocity field in the simplified models and the effects of the interaction on the transient wall heat transfer were studied by these two analytic solutions. The unsteady heat flux, which is governed by the energy equation, is directly related to the unsteady compression work and viscous dissipation which originates from the velocity field governed by the momentum equation. The main parameters and their roles in how the unsteady velocity field affects the unsteady heat flux were discussed for the simplified models. Lastly, the similarity criteria of the unsteady aerothermodynamics were derived based on the compressible boundary layer equations. Along with the Strouhal number Stu, the unsteadiness criterion of the velocity field, StT number, the unsteadiness criterion of the temperature field was proposed for the first time. Different from the traditional method used in unsteady aerodynamics which measures the flow unsteadiness only by the Stu number, present results show that the flow unsteadiness in unsteady aerothermodynamics should be comprehensively estimated by comparing the relative magnitudes of the temperature field unsteadiness criterion StT number with the coefficients of other terms in the dimensionless energy equation.

关键词： unsteady aerothermodynamics transient heat transfer similarity criterion

Hydraulic experiment on mushroom head in bottom-blown smelting furnace

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Journal of Iron and Steel Research International 2017年第5期24卷 490-494页

作者： Fu-yong Su Zhi Wen School of Energy and Environmental Engineering University of Science and Technology Beijing Beijing 100083 China

There are many bottom-blown smelting furnaces in metallurgical industry. When oxygen or air sprays from the jet nozzle into the bottom of the furnace, the melting phase will be frozen and a hemispherical porous zone with a mushroom head shape will be formed around the nozzle. The mushroom head can pro- tect the jet nozzle and mitigate the liquid spray on the surface of melt. In order to analyze the formation process of a mushroom head in the bottom-blown smelting furnaces, a hydraulic experiment system was designed and the formation of the mushroom head was investigated by hydraulic experiment. The hydrau- lic experiment results show that the formation process is mainly divided into generating crushing genera- ting process and stable mushroom head generation process. The formation of stable mushroom head re- quires certain thermodynamic condition and water splash is more intense without a mushroom head than with a mushroom head. The size, porosity and diameter of the mushroom head are affected by the flow rate, temperature and heat capacity of the bottom-blowing gas and the temperature of the superheat and the physical parameters of the melt.

关键词： Bottom-blown smelting furnace Mushroom head Hydraulic experiment Thermal equilibrium similarity criterion

SITMILARITY LAW FOR HYDRAULIC DISTORTED MODEL

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Journal of Hydrodynamics 2003年第1期15卷 67-71页

作者： Wang Yong taoDepartment of Environmental Science and Engineering, University of Science and Technology of Suzhou, Suzhou 215011, ChinaCui Li Department of Civil Engineering, Dalian University of Technology, Dalian 116024, China Dept. of Environ. Sci. and Eng. Univ. of Sci. and Technol. of Suzhou Suzhou 215011 China Dept. of Civil Eng. Dalian Univ. of Technol. Dalian 116024 China

Newton's general similarity criterion was applied to the distorted model. Theresults for the similarities of gravity force, drag force and pressure force are identical withthose derived from relevant differential equations of fluid flow. And the selected limits of thedistorted ratio were studied and the simulation of roughness coefficient of distorted model wasconducted by means of hydraulic test.

关键词： distorted model similarity criterion distorted ratio simulation ofroughness coefficient

Laboratory experiments of well testing for fracture-cave carbonate gas reservoirs

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Petroleum 2017年第3期3卷 301-308页

作者： Yu Xiong Wanli Xiong Mingjin Cai Chengxi Hou Chong Wang The State Key Laboratory of Oil&Gas Reservoir Geology and Exploitation Engineering Southwest Petroleum UniversityChengdu 610500China Exploration and Development Research Institute PetroChina Tarim OilfieldKorla 841008China

It is well known that the flowing of oil and gas in fracture and cave does not obey Darcy law,which makes it unable to interpret parameters correctly when doing well testing for those kinds of formation for having no flowing test used to correct corresponding flowing *** on similarity criterion,a physical experimental method for gas flowing from cave to wellbore through fracture has been built *** characteristics of fluid flowing in fracture and cave can be seen clearly according to logelog curves with the measured data,which was obtained from the experimental model test and dealt with Savitzky-Golay filtering *** addition,a new mathematical model reflecting those transient-flow behaviors as well as its solution has been presented in this *** curves obtained from our new model could reflect the characteristics of flowing in fracture and *** results showed that test experiments can reflect the influence of large-scaled cave and fracture on the flowing characteristics and the new model can be applied to explain parameters of fracture and cave for similar cases.

关键词： Fractured-cave reservoir Well testing Mathematical model similarity criterion

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