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Underwater explosion in centrifuge partⅠ:Validation and calibration of scaling laws

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Science China(Technological Sciences) 2017年第11期60卷 1638-1657页

作者： HU Jing CHEN ZuYu ZHANG XueDong WEI YingQi LIANG XiangQian LIANG JianHui MA GuoWei WANG QiuSheng LONG Yuan China Institute of Water Resources and Hydropower Research Beijing 100048China School of Transportation Science and Engineering Beihang UniversityBeijing 100083China Key Laboratory of Urban Security and Disaster Engineering of Ministry of Education Beijing University of TechnologyBeijing 100124China College of Field Engineering PLA University of Science and TechnologyNanjing 210007China

Centrifuge is a promising tool for underwater explosion(UNDEX) research as both Mach and Froude similitudes could be satisfied with hyper-gravity in models, which would result in similarities in both shock wave and bubble oscillation. scaling laws for UNDEX in centrifuge have been proposed based on dimensional analysis. Two dimensionless numbers, i.e.,π_3 and π_4, are used to characterize shock wave and bubble oscillation, respectively. To validate scaling laws, 17 UNDEX tests are designed by varying accelerations or explosive weights and positions in centrifuge. The tests are classified into different groups to validate scaling laws as well as calibrate coefficients in empirical formulae for both shock wave and bubble oscillation. The results show that changes of gravity acceleration or hydrodynamic pressure almost has no influence on shock wave peak pressure and time constant as long as π3 is constant. The dimensionless bubble period and maximum radius agreed with each other when π4 is constant. Based on the research, an example is exhibited to suggest method for the computation of initial loading conditions for a submerged obstacle subjected to UNDEX.

关键词： underwater explosion (UNDEX) centrifuge scaling laws shock wave bubble oscillation

Intra-and inter-specific scaling laws of plants and animals

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Acta Mechanica Sinica 2021年第2期37卷 321-330页

作者： Jiahang Li Hao Wu Ghassan S。Kassab Wenchang Tan Yunlong Huo Department of Mechanics and Engineering Science College of EngineeringPeking UniversityBeijing 100871China PKU-HKUST Shenzhen-Hongkong Institution Shenzhen 518057China California Medical Innovations Institute San DiegoCA 92121USA Shenzhen Graduate School Peking UniversityShenzhen 518055China Institute of Mechanobiology&Medical Engineering School of Life Sciences&BiotechnologyShanghai Jiao Tong UniversityShanghai 200240China

The allometric scaling laws of metabolism in 447 animal and 1200 plant species showed convex and concave curvatures between mass and metabolic rate,*** objective of the study is to explain the difference of curvatures between animals and plants based on fractal *** intraspecific scaling laws were derived from an asymmetric vascular tree with the fractal dimension(i.e.,a in k^(a)_(1)+k^(a)_(2)+…-=1,where k_(i)refers to the ratio of daughter to mother diameters).Based on the intraspecific scaling laws,the allometric scaling exponent of metabolism(i.e.,an interspecific scaling law)was shown to be equal to one-third of fractal ***,a novel piecewise-defined function in conjunction with the intraspecific scaling laws was proposed to explain the diverse metabolic scaling in animals and *** intraspecific and interspecific scaling laws showed good agreement with morphometric *** experimentally-validated scaling models predict the diversity of intraspecific and interspecific scaling seen in *** our knowledge,this is the first study to use fractal models to explain the convex and concave forms of metabolic scaling in animals and *** study resolves the long-term controversies to use the resource-transport network models for explanation of the allometric scaling law of metabolism.

关键词： scaling laws Fractal models Asymmetric tree

Aeroelastic scaling laws for gust load alleviation control system

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Chinese Journal of Aeronautics 2016年第1期29卷 76-90页

作者： Tang Bo Wu Zhigang Yang Chao School of Aeronautic Science and Engineering Beihang University

Gust load alleviation （GLA） tests are widely conducted to study the effectiveness of the control laws and methods. The physical parameters of models in these tests are aeroelastic scaled, while the scaling of GLA control system is always unreached. This paper concentrates on studying the scaling laws of GLA control system. Through theoretical demonstration, the scaling criterion of a classical PID control system has been come up and a scaling methodology is provided and veri- fied. By adopting the scaling laws in this paper, gust response of the scaled model could be directly related to the full-scale aircraft theoretically under both open-loop and closed-loop conditions. Also, the influences of different scaling choices of an important non-dimensional parameter, the Froude number, have been studied in this paper. Furthermore for practical application, a compen- sating method is given when the theoretical scaled actuators or sensors cannot be obtained. Also, the scaling laws of some non-linear elements in control system such as the rate and amplitude sat- urations in actuator have been studied and examined by a numerical simulation.

关键词： Actuator Aeroelasticity Control Systems Froude number Gust loads alleviation scaling laws

A refinement of scaling laws in wall turbulence

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Journal of Chongqing University 2009年第3期8卷 195-200页

作者：张珂 School of Civil Engineering and Mechanics Huazhong University of Science and Technology

As a universal conclusion of turbulent scale, scaling laws are important to the research on statistic turbulence. We measured two-dimensional instantaneous velocity field in turbulent boundary layers of flat plate with the momentum thickness Reynolds number Reθ=2 167. scaling laws have different forms in different wall distance and scale. We proposed an expected scaling law and compared it with the She-Leveque (SL) scaling law based on the wavelet analysis and traditional statistical methods. Results show that the closer to the wall, the more the expected scaling law approached to the SL scaling law.

关键词： turbulent boundary layer probability density function particle image velocimetry scaling laws

NEW TYPES OF SEMI-INCLUSIVE PROCESSES OF MULTIPARTICLE PRODUCTIONS (Ⅰ)——scaling laws

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Science China Mathematics 1978年第5期 586-600页

作者：刘汉昭 Department of Physics Nankai University Tientsin

The seml-incluslve process is generalized as a process of measuring the momentum spectrum of one or more particles, when one knows the values of one or more of the four quantities n, k, u and △ (or any other four quantities possessing a one-to-one correspondence with n, k, u and △), where n, k, u and △ denote respectively the total number of charged particles, the left-right asymmerry of charged particles, the charge transfer and the maximum rapidity gap. The usual semiinclusive process corresponds to knowing the value of n only, and new types of semi-inclusive proecsses correspond to other cases. Experimental and theoretical studies on these new processes could greatly help us to improve and to discover mechanisms of multiparticle productions. Current experimental data can be used to determine some important, new types of semi-inclusive proceeses. The scaling laws of the new types of semi-inclusive processes are derived by means of a generalization of the model-independent KNO method.

关键词： NEW TYPES OF SEMI-INCLUSIVE PROCESSES OF MULTIPARTICLE PRODUCTIONS scaling laws SEMI

STIFFNESS AND EXCLUDED VOLUME EFFECTS ON CONFORMATION AND DYNAMICS OF POLYMERS:A SIMULATION STUDY

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Chinese Journal of Polymer Science 2012年第3期30卷 350-358页

作者：李安邦 Yuan-gen Yao Hong Xu Huazhong Normal Univ Coll Phys Sci&TechnolWuhan 430079Peoples R China Univ Paul Verlaine Metz LPMDICPMF-57078 Metz 3France

This work investigates the effects of the excluded volume and especially those of the chain stiffness on the structural and dynamical properties of a model polymer chain. The theoretical framework is the same as in the recent works by Steinhauser et al., where a Rouse approach is adopted. Our model differs in that our chains have a finite average bending angle. As in the works by Steinhauser et al., Langevin dynamic simulations were performed without hydrodynamic interactions. Whereas this doesn＇t impact the static properties we obtain, it also allows us to compare our results on dynamic properties to those predicted by Rouse theory, where hydrodynamic interactions are also neglected. Our results show that the structural properties are very sensitive to the chain stiffness, whereas the dynamic scaling laws remain the same as those by Rouse theory, with the prefactor depending on the persistence length.

关键词： scaling laws Polymer Stiffness Excluded volume effects.

scaling Law of Exponents in Cosmological Clustering

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Chinese Physics Letters 2002年第2期19卷 280-282页

作者：张航李晓卿 DepartmentofPhysics NanjingNormalUniversityNanjing210097

The density ofN-clusters (the clusters which containNgalaxies) in the Universe is shown from observations to scale withNasnNN-with= 3/+ 1and the correlation exponent1.8. Correspondingly, a scaling relation= 29 - 9/12 - 4between the two exponents, which agrees with the observations, is found analytically in our naiveclustering model.

关键词： scaling laws Clusters Universe Exponent Cluster Analysis scaling relation

The nature of friction: A critical assessment

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Friction 2014年第1期2卷 1-26页

作者： Stephen HSU Charles YING Fei ZHAO George Washington University Washington DCUSA National Science Foundation ArlingtonVAUSA

Friction is an essential part of human *** need traction to walk,stand,work,and *** the same time,we need energy to overcome the resistance to motion,hence,too much friction costs excess energy to perform work,introducing *** the 21st century,we are facing the dual challenges of energy shortage and global warming from burning fossil ***,the ability to control friction has become a top priority in our world *** our understanding of the fundamental nature of friction is still *** has always been a subject of *** study of the origin of friction began in the 16th century,after the pioneering work by Leonardo da *** progress in understanding the nature of friction has been slow,hampered by the lack of instrument to measure friction *** experiments performed by Amontons,Coulomb,and others have yielded important insights to build the foundation of our *** in the late 1800s and early 1900s,the advent of steam engines,locomotives,followed by the automobiles airplanes,and space exploration demands a clear understanding of friction and the ability to control it for the machinery to *** progress on how to apply and control friction in engineering friction was made through trial and *** the beginning of the 21st century,a new dimension of nanoscale friction came into the picture in conjunction with the arrival of *** understanding of atomic and molecular friction has been expanding ***,integration of the new found knowledge of nanofriction into engineering practices has been ***?What is the scaling relationship between atomic friction and macro-friction?Is it possible to predict friction at the macro-level from nanoscale results?Why nanofriction values often do not agree with the macrofriction values given the same materials pair?Could it be there is a length scale dependent characteristic friction value?In eng

关键词： friction scaling laws molecular friction length scale dominant friction values

scaling of interaction lengths for hypersonic shock wave/turbulent boundary layer interactions

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Chinese Journal of Aeronautics 2021年第5期34卷 504-509页

作者： Yuting HONG Zhufei LI Jiming YANG Department of Modern Mechanics University of Science and Technology of ChinaHefei 230027China

The interaction length induced by Shock Wave/Turbulent Boundary-Layer Interactions(SWTBLIs)in the hypersonic flow was investigated using a scaling analysis,in which the interaction length normalized by the displacement thickness of boundary layer was correlated with a corrected non-dimensional separation criterion across the interaction after accounting for the wall temperature effects.A large number of hypersonic SWTBLIs were compiled to examine the scaling analysis over a wide range of Mach numbers,Reynolds numbers,and wall *** results indicate that the hypersonic SWTBLIs with low Reynolds numbers collapse on the supersonic SWTBLIs,while the hypersonic cases with high Reynolds numbers show a more rapid growth of the interaction length than that with low Reynolds ***,two scaling relationships are identified according to different Reynolds numbers for the hypersonic *** scaling analysis provides valuable guidelines for engineering prediction of the interaction length,and thus,enriches the knowledge of hypersonic SWTBLIs.

关键词： Hypersonic flow Interaction length scaling laws Separation criterion Shock wave/turbulent boundary layer interactions