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A theoretical study on the unsteady aerothermodynamics for attached flow models

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

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Prediction of fish body's passive visco-elastic properties and related muscle mechanical performance in vivo during steady swimming

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Science China(Physics,Mechanics & Astronomy) 2014年第2期57卷 354-364页

作者： ZHANG Wei YU YongLiang tong binggang School of Physics University of Chinese Academy of Sciences

For attaining the optimized locomotory performance of swimming fishes,both the passive visco-elastic properties of the fish body and the mechanical behavior of the active muscles should coordinate with the fish body’s undulatory motion pattern.However,it is difficult to directly measure the visco-elastic constitutive relation and the muscular mechanical performance in vivo.In the present paper,a new approach based on the continuous beam model for steady swimming fish is proposed to predict the fish body’s visco-elastic properties and the related muscle mechanical behavior in vivo.Given the lateral travelling-wave-like movement as the input condition,the required muscle force and the energy consumption are functions of the fish body’s visco-elastic parameters,i.***.the Young’s modulus E and the viscosity coefficient in the Kelvin model.After investigating the variations of the propagating speed of the required muscle force with the fish body’s visco-elastic parameters,we analyze the impacts of the visco-elastic properties on the energy efficiencies,including the energy utilization ratios of each element of the kinematic chain in fish swimming and the overall efficiency.Under the constraints of reasonable wave speed of muscle activation and the physiological feasibility,the optimal design of the passive visco-elastic properties can be predicted aiming at maximizing the overall efficiency.The analysis is based on the small-amplitude steady swimming of the carangiform swimmer,with typical Reynolds number varying from 2.5×104to 2.5×105,and the present results show that the non-dimensional Young’s modulus is 112±34,and the non-dimensional viscosity coefficient is 13 approximately.In the present estimated ranges,the overall efficiency of the swimming fish is insensitive to the viscosity,and its magnitude is about 0.11±0.02,in the predicted range given by previous study.

关键词：肌肉力量机械性能鱼体体内游泳预测粘弹特性稳定

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An analytical study on nonequilibrium dissociating gas flow behind a strong bow shockwave under rarefied conditions

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Science China(Physics,Mechanics & Astronomy) 2013年第4期56卷 671-679页

作者： WANG ZhiHui BAO Lin tong binggang School of Physics University of Chinese Academy of Sciences

In this paper, an explicitly analytical shock mapping relation is approximately deduced based on the theoretical modeling of the chemical nonequilibrium stagnation flow towards a slightly blunted nose. Based on the relation, the complex reacting stagnation flow problem can be discussed under the framework of the simplest normal shockwave flow. Therefore, a quantita- tively meaningful criterion for dissociation nonequilibrium flow, that is a specific Damk hler number Da d , is naturally intro- duced as the ratio of the mapping length of the stagnation streamline and the characteristic nonequilibrium scale. Da d is found to be dependent on the flow's rarefaction criterion W r , that is a specific Knudsen number. Then, based on Da d , a normalized analytical formulation is obtained to quantitatively predict the actual degrees of dissociation at the outer edge of the stagnation point boundary layer (SPBL). At last, the direct simulation Monte Carlo (DSMC) method is employed to validate the analytical results, and the related flow mechanism is discussed. The present study not only shows nonequilibrium features of the flow problem, but also provides an indispensable basis for the following study on the nonequilibrium SPBL heat transfer.

关键词：稀薄不平衡 Knudsen数化学非平衡激波气体游离映射关系

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Theoretical modeling of chemical nonequilibrium stagnation point boundary layer heat transfer under rarefied conditions

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Science China(Physics,Mechanics & Astronomy) 2013年第5期56卷 866-874页

作者： WANG ZhiHui BAO Lin tong binggang School of Physics University of Chinese Academy of Sciences

This paper theoretically studies the recombination-dominated nonequilibrium reacting flow inside the stagnation point boundary layer (SPBL) and the heat transfer characteristics under rarefied conditions. A general model is intuitively proposed to describe the energy transfer and conversion along the stagnation streamline towards a slightly blunted nose with non-catalytic wall surface. It is found that the atoms recombination effects inside the SPBL could be equivalent to a modification on the degree of dissociation in the external flow. As a result, a recombination nonequilibrium criterion Dar , that is a specific Damkhler number, is introduced to characterize the nonequilibrium degree of the reacting flow in the SPBL, and then, based on the general model and Dar , a bridging function indicating the nonequilibrium chemical effects on the SPBL heat transfer is established. By using the explicitly analytical bridging function, the flow and heat transfer mechanisms, including the real gas flow similarity law and the nonequilibrium flow regimes classification, are discussed. In addition, the direct simulation Monte Carlo (DSMC) method has also been employed to systematically validate the analytical results.

关键词：化学非平衡传热特性边界层理论建模驻点稀薄平衡反应桥接功能

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An experimental investigation into electromyography, constitutive relationship and morphology of crucian carp for biomechanical “digital fish”

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Science China(Physics,Mechanics & Astronomy) 2011年第5期54卷 966-977页

作者： ZHOU Meng YIN XieZhen tong binggang Department of Modern Mechanics University of Science and Technology of China Hefei 230027 China The Lab for Biomechanics of Animal Locomotion Graduate University of Chinese Academy of Sciences Beijing 100049 China

Currently, the integrated biomechanical studies on fish locomotion come into focus, so it is urgent to provide reliable and systematic experimental results, and to establish a biomechanical "digital fish" database for some typical fish species. Accordingly, based on the control framework of "Neural ControlActive Contraction of MusclePassive Deformation", the electromyography (EMG) signals, the mechanical properties and the constitutive relationship of skin, muscle, and body trunk, as well as morphological parameters of crucian carp, are investigated with experiments, from which a simplified database of biomechanical "digital fish" is established. First, the EMG signals from three lateral superficial red muscles of crucian carp, which was evolving in the C-start movement, were acquired with a self-designing amplifier. The modes of muscle activity were also investigated. Secondly, the Young's modulus and the reduced relaxation function of crucian carp's skin and muscle were determined by failure tests and relaxation tests in uniaxial tensile ways, respectively. Viscoelastic models were adopted to deduce the constitutive relationship. The mechanical properties and the angular stiffness of different sites on the crucian carp's body trunk were obtained with dynamic bending experiments, where a self-designing dynamic bending test machine was employed. The conclusion was drawn regarding the body trunk of crucian carp under dynamic bending deformation as an approximate elastomer. According to the above experimental results, a possible benefit of body effective stiffness increasing with a little energy dissipation was discussed. Thirdly, the distribution of geometric parameters and weight parameters for a single experimental individual and multiple individuals of crucian carp was studied with experiments. Finally, considering all the above results, generic experimental data were obtained by normalization, and a preliminary biomechanical "digital fish" database for crucian carp was established.

关键词：运动生物力学力学实验本构关系形态参数肌电图鲫鱼神经网络控制肌肉活动

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Unsteady aerothermodynamics:Proposal for the establishment of a new branch within the discipline of aerothermodynamics

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Chinese Science Bulletin 2010年第26期55卷 3072-3072页

作者： tong binggang College of Physical Sciences Graduate University of Chinese Academy of Sciences Beijing 100080 China

Researchers from the College of Physical Sciences, GUCAS, have proposed to establish a new branch, unsteady aerothermodynamics, within the discipline of aerothermodynamics. The principal objectives of this new branch,... 详细信息

关键词：气动热力学非定常中国科学院纪律瓷砖物理科学边界层流动研究生院

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A flow control mechanism in wing flapping with stroke asymmetry during insect forward flight

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Acta Mechanica Sinica 2005年第3期21卷 218-227页

作者： Yongliang Yu binggang tong Department of Physics Graduate School of the Chinese Academy of Sciences Beijing 100039 China Department of Modern Mechanics University of Science and Technology of China Hefei 230027 China

A theoretical modeling approach as well as an unsteady analytical method is used to study aerodynamic characteristics of wing flapping with asymmetric stroke-cycles in connection with an oblique stroke plane during insect forward flight. It is revealed that the aerodynamic asymmetry between the downstroke and the upstroke due to stroke-asymmetrical flapping is a key to understand the flow physics of generation and modulation of the lift and the thrust. Predicted results for examples of given kinematics validate more specifically some viewpoints that the wing lift is more easily produced when the forward speed is higher and the thrust is harder, and the lift and the thrust are generated mainly during downstroke and upstroke, respectively. The effects of three controlling parameters, i.e. the angles of tilted stroke plane, the different downstroke duration ratios, and the different angles of attack in both down- and up-stroke, are further discussed. It is found that larger oblique angles of stroke planes generate larger thrust but smaller lift; larger downstroke duration ratios lead to larger thrust, while making little change in lift and input aerodynamic power; and again, a small increase of the angle of attack in downstroke or upstroke may cause remarkable changes in aerodynamic performance in the relevant stroke.

关键词： Insect forward flight Wing flapping Stroke asymmetry Oblique stroke plane Theoretical modeling.

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An energetics analysis of fish self-propelled swimming

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Science China(Physics,Mechanics & Astronomy) 2018年第7期61卷 91-94页

作者： ZhongWei Wang YongLiang Yu binggang tong School of Engineering Science University of Chinese Academy of Sciences

Fishes can swim freely in water owing to the interaction between their deforming bodies and the surrounding fluid,as is called self-propelled swimming.Besides the experimental study,the numerical simulation can provide much more details of the flow structure,hydrodynamics and energetics of fish swimming.Since the pioneering study by Carling et al.[1],numerical simulation has become the primary method

关键词：游泳鱼数字模拟水动力学相互作用流动结构学习试验性

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Treatment of multisystem inflammatory syndrome in children

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World Journal of Pediatrics 2024年第4期20卷 325-339页

作者： tong tong Yi-Hua Jin Min Wang Fang-Qi Gong Department of Cardiology Children's HospitalZhejiang University School of MedicineNational Clinical Research Center for Child HealthNo.3333 Binsheng RoadHangzhou 310052China

Background Multisystem inflammatory syndrome in children(MIS-C),a relatively uncommon but severe pediatric complication,is associated with coronavirus disease 2019(COVID-19).A variety of treatment approaches,including intravenous immunoglobulins(IVIGs),glucocorticoids(GCs)and biologic agents,such as anakinra and infliximab,have been described for the management of COVID-19-related MIS-C.Anticoagulant therapy is also important.However,a well-developed treatment system has not been established,and many issues remain controversial.Several recently published articles related to the treatment of MIS-C have been released.Hence,in this review,we identified relevant articles published recently and summarized the treatment of MIS-C more comprehensively and systematically.Data sources We reviewed the literature on the treatment of MIS-C through 20 September 2023.The PubMed/Medline,Web of Science,EMBASE,and Cochrane Library databases were searched with the combination of the terms"multisystem inflammatory syndrome","MIS-C","PIMS-TS","therapy","treatment","drug","IVIG","GCs","intravenous immunoglobulin","corticosteroids","biological agent",and"aspirin".Results The severity of MIS-C varies,and different treatment schemes should be used according to the specific condition.Ongoing research and data collection are vital to better understand the pathophysiology and optimal management of MIS-C.Conclusions MIS-Cis a disease involving multiple systems and has great heterogeneity.With the accumulation of additional experience,we have garnered fresh insights into its treatment strategies.However,there remains a critical need for greater standardization in treatment protocols,alongside the pressing necessity for more robust and meticulously conducted studies to deepen our understanding of these protocols.

关键词： Coronavirus disease 2019-Corticosteroids Intravenous immunoglobulin Multisystem inflammatory syndrome in children-Treatment

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Selective nano-buckling improves the performance of graphene logic transistors

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National Science Review 2024年第2期11卷 95-96页

作者： tong Yang Ming Yang Department of Applied Physics The Hong Kong Polytechnic University Research Centre for Nanoscience and Nanotechnology The Hong Kong Polytechnic University

The massive integration of silicon-based transistors into modern electronic devices greatly increases power consumption and heat generation/dissipation[1]. In this concern, transistors based on atomically-thin graphene that exhibit high electric and thermoelectric conductivities with negligible contact resistance,

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