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A symmetry-based length model for characterizing the hypersonic boundary layer transition on a slender cone at moderate incidence

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Advances in Aerodynamics 2022年第1期4卷 546-568页

作者： Wei-Tao Bi Zhou Wei Ke-Xin Zheng Zhen-Su She State Key Laboratory for Turbulence and Complex Systems and Department of Mechanics and Engineering Science College of EngineeringPeking UniversityBeijing100871China Science and Technology on Scramjet Laboratory China Aerodynamics Research and Development CenterMianyang621000China State Key Laboratory of Aerodynamics China Aerodynamics Research and Development CenterMianyang621000China Computational Aerodynamics Institute China Aerodynamics Research and Development CenterMianyang621000China

The hypersonic boundary layer(HBL)transition on a slender cone at moderate incidence is studied via a symmetry-based length model:the SED-SL model.The SED-SL specifies an analytic stress length function(which defines the eddy viscosity)describing a physically sound two-dimensional multi-regime structure of transitional boundary layer.Previous studies showed accurate predictions,especially on the drag coefficient,by the SED-SL for airfoil flows at different subsonic Mach numbers,Reynolds numbers and angles of attack.Here,the SED-SL is extended to compute the hypersonic heat transfer on a 7∘half-angle straight cone at Mach numbers 6 and 7 and angles of attack from 0∘to 6∘.It is shown that a proper setting of the multi-regime structure with three parameters(i.e.a transition center,an after-transition near-wall eddy length,and a transition width quantifying transition overshoot)yields an accurate description of the surface heat fluxes measured in wind tunnels.Uniformly good agreements between simulations and measurements are obtained from windward to leeward side of the cone,implying the validity of the multi-regime description of the transition independent of instability mechanisms.It is concluded that a unified description for the HBL transition of cone is found,and might offer a basis for developing a new transition model that is simultaneously of computational simplicity,sound physics and greater accuracy.

关键词： Hypersonic boundary layer transition Transition model cone Heat flux

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Anatomical Study of Cretaceous,Permineralized,Bennettitalean Fossils from Heilongjiang Province,NE China

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Acta Geologica Sinica(English Edition) 2022年第5期96卷 1495-1501页

作者： LIU Fengxiang YANG Xiaonan CHENG Yeming Department of Stratigraphy and Paleontology Department of Collection ManagementLaboratory of Geo-specimens Study and TestingGeological Museum of ChinaBeijing 100034China

Well-preserved Cretaceous trunk fragments of Cycadeoidea(Cycadeoidaceae)were recently found in Keshan County,Heilongjiang Province,Northeast China.These fossils represent important evidence of the distribution of this group of plants in East Asia.In these trunk fragments,the stem cortices and leaf bases with cones are preserved.The leaf bases are rhombic with cones infrequently distributed among leaf bases.The cortex is broad and consists of fundamental parenchyma cells,numerous secretory ducts and C-shaped leaf traces with adaxial secondary xylem and abaxial secondary phloem.The genus Cycadeoidea,which is widely distributed in the Cretaceous deposits of East Asia,North America and Western Europe,was an important component of Cretaceous floras.Bennettitalean trunk fossils with well-preserved anatomical structures are rarely known from China.These fossils are important for studies of the evolution of genus Cycadeoidea and for stratigraphic correlation.

关键词： secondary xylem cortex cone anatomy Cycadeoidaceae Songliao Basin Cretaceous

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Steady Compressible Euler Equations of Concentration Layers for Hypersonic-limit Flows Passing Three-dimensional Bodies and Generalized Newton-Busemann Pressure Law

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Chinese Annals of Mathematics,Series B 2023年第4期44卷 561-576页

作者： Aifang QU Hairong YUAN Department of Mathematics Shanghai Normal UniversityShanghai 200234China School of Mathematical Sciences and Shanghai Key Laboratory of Pure Mathematics and Mathematical Practice East China Normal UniversityShanghai 200241China

For stationary hypersonic-limit Euler flows passing a solid body in three-dimensional space,the shock-front coincides with the upwind surface of the body,hence there is an infinite-thin layer of concentrated mass,in which all particles hitting the body move along its upwind surface.By proposing a concept of Radon measure solutions of boundary value problems of the multi-dimensional compressible Euler equations,which incorporates the large-scale of three-dimensional distributions of upcoming hypersonic flows and the small-scale of particles moving on two-dimensional surfaces,the authors derive the compressible Euler equations for flows in concentration layers,which is a stationary pressureless compressible Euler system with source terms and independent variables on curved surface.As a by-product,they obtain a formula for pressure distribution on surfaces of general obstacles in hypersonic flows,which is a generalization of the classical Newton-Busemann law for drag/lift in hypersonic aerodynamics.

关键词： Compressible Euler equations Hypersonic fow Concentration layer Ramp cone Radon measure solution Newton-Busemann law

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Existence of Triple Positive Solutions to a Four-Point Boundary Value Problem of a Fractional Differential Equations

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Wuhan University Journal of Natural Sciences 2022年第4期27卷 287-295页

作者： YANG Liu SHEN Chunfang ZHOU Hui College of Mathematics and Statistics Hefei Normal UniversityHefei 230061AnhuiChina

In this paper,the existence result of at least triple positive solutions to a boundary value problem of a fractional differential equations is achieved by means of the Avery-Peterson fixed point theorem and the careful analysis of the associate Green’s function in which the derivative of unknown function is involved in the nonlinear term explicitly.An example illustrating our main result is given.Our results complement the previous work in the area of the positive solutions of fractional differential equations.

关键词： fixed point positive solution cone Avery-Peterson fixed point theorem

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Positive Solutions of Fourth-Order Equations under Nonlocal Boundary Value Conditions of Sturm-Liouville Type

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Journal of Mathematical Research with Applications 2023年第1期43卷 91-100页

作者： Chunlei SONG Wei CHEN Guowei ZHANG Department of Mathematics Northeastern University

In this paper, we study the fourth-order problem with the first and second derivatives in nonlinearity under nonlocal boundary value conditions of Sturm-Liouville type involving Stieltjes integrals. Some inequality conditions on nonlinearity are presented that guarantee the existence of positive solutions to the problem by the theory of fixed point index on a special cone. Some examples are provided to support the main results under mixed boundary conditions containing multi-point with sign-changing coefficients and integral with sign-changing kernel.

关键词： positive solution fixed point index cone

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Design and experimental study of a practical Osculating Inward cone Waverider Inlet

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Chinese Journal of Aeronautics 2016年第6期29卷 1582-1590页

作者： He Xuzhao Zhou Zheng Qin Si Wei Feng Le Jialing Science and Technology on Scramjet Laboratory Hypervelocity Aerodynamics Institute of CARDC

A design method based on tip to tail streamline tracing and osculating inward cone methods is discussed for designing the integrated Osculating Inward cone Waverider Inlet(OICWI). A practical geometrical constrained experimental model of OICWI is designed based on the validated design method. It has a total contraction ratio of 4.61 and inner contraction ratio is 2.0. Wind-tunnel tests have been conducted for the OICWI model at free stream Mach number(Ma_∞) of 4.0, 3.5 and 3.0 respectively. The experimental results show that the OICWI has high flow capture ratio and compression abilities. It can self-start at Ma_∞= 3.5 and 4.0 and its flow capture ratio is 0.73 at Ma_∞= 4.0, and Angle of Attack(AOA) 0°. The research results show that the OICWI has advantages of inward cone waverider and streamline tracing inlet. Present OICWI is a novel approach for waverider inlet integration studies and it will promote the use of waverider inlet integration configuration in the studies of airbreathing hypersonic vehicles.

关键词： Inlet Integration design Inward turning cone Waverider Wind tunnel experiment

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Vertex angles effects in the energy absorption of axially crushed kenaf fibre-epoxy reinforced elliptical composite cones

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Defence Technology（防务技术） 2018年第4期14卷 327-335页

作者： Mohamed Alkateb S.M.Sapuan Z.Leman M.R.Ishak Mohammad Jawaid Department of Mechanical and Manufacturing Engineering Universiti Putra Malaysia Laboratory of Bio Composite Technology Institute of Tropical Forestry and Research Products (INTROP)Universiti Putra Malaysia Aerospace Manufacturing Research Centre (AMRC) Universiti Putra Malaysia Departments of Aerospace Engineering Universiti Putra Malaysia

Experimental quasi-static crushing tests were conducted by using a universal testing machine format kenaf-epoxy composite elliptical cones. The work focused on the vertex angle's effects on energy absorption capability; the vertex angles vary from 0° to 24° in 6 increments. The failure modes of the kenaf fibre epoxy composite elliptical cones were observed utilising delegate photos taken during the quasistatic crushing test. Load-deformation curves and deformation histories of typical specimens are presented and discussed. Moreover, the effects of cone vertex angles on the load carrying capacity and the energy absorption capability are also discussed. The results show that the energy absorption abilities significantly influence the ellipticity vertex angle as the load carrying capacity. We concluded that the quasi-static axial crushing behaviour of elliptical mat laminated composite cones is strongly affected by their structural geometry and the specific energy absorbed by the composite elliptical cones with vertex angles of 6°, 12°, 18°, and 24°, which is more than an elliptical cone with the vertex angle of 0°(the elliptical tube) at any given deformation. However, the specific energy absorption for the elliptical composite cone showed a positive correlation, i.e., the more the angle increased, the more energy was absorbed. In this regard, an elliptical composite cone with a 24° angle exhibited the best energy absorption capability.

关键词： Kenaf fibres Composite materials Elliptical cone Vertex angle Collapsible Energy absorption

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Modeling natural convection boundary layer flow of micropolar nanofluid over vertical permeable cone with variable wall temperature

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Applied Mathematics and Mechanics(English Edition) 2017年第8期38卷 1171-1180页

作者： S.E.AHMED Department of Mathematics Faculty of ScienceSouth Valley UniversityQena 83523Egypt

This paper discusses the natural convection boundary layer flow of a micropo- lax nanofluid over a vertical permeable cone with variable wall temperatures. Non-similax solutions are obtained. The nonlineaxly coupled differential equations under the boundary layer approximations governing the flow axe solved numerically using an efficient, itera- tive, tri-diagonal, implicit finite difference method. Different experimental correlations for both nanofluid effective viscosity and nanofluid thermal conductivity are considered. It is found that as the vortex-viscosity parameter increases, both the velocity profiles and the local Nusselt number decrease. Also, among all the nanoparticles considered in this investigation, Cu gives a good convection.

关键词： micropolar nanofluid non-similar solution cone finite difference method,non-uniform heating

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Prediction of the effectiveness of rolling dynamic compaction using artificial neural networks and cone penetration test data

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岩石力学与工程学报 2019年第1期38卷 153-170页

作者： R.A.T.M.Ranasinghe M.B.Jaksa F.Pooya Nejad Y.L.Kuo School of Civil Environmental and Mining EngineeringUniversity of Adelaide

Rolling Dynamic Compaction(RDC),which is a ground improvement technique involving non-circular modules drawn behind a tractor,has provided the construction industry with an improved ground compaction capability,especially with respect to a greater influence depth and a higher speed of compaction,resulting in increased productivity. However,to date,there is no reliable method to predict the effectiveness of RDC in a range of ground conditions. This paper presents a new and unique predictive tool developed by means of artificial neural networks(ANNs) that permits a priori prediction of density improvement resulting from a range of ground improvement projects that employed 4-sided RDC modules;commercially known as"impact rollers". The strong coefficient of correlation(i.e. R>0.86) and the parametric behavior achieved in this study indicate that the model is successful in providing reliable predictions of the effectiveness of RDC in various ground conditions.

关键词： soil mechanics rolling dynamic compaction artificial neural networks cone penetration test ground improvement

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Transition prediction for supersonic and hypersonic boundary layers on a cone with angle of attack

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Science China(Physics,Mechanics & Astronomy) 2009年第8期52卷 1223-1232页

作者： SU CaiHong1 & ZHOU Heng1,2 1 Department of Mechanics,Tianjin University,Tianjin 300072,China 2 Liu-Hui Center of Applied Mathematics,Nankai University and Tianjin University,Tianjin 300072,China Department of Mechanics Tianjin University Tianjin China Liu-Hui Center of Applied Mathematics Nankai University and Tianjin University Tianjin China

Transition prediction for boundary layers has always been one of the urgent problems waiting for a solution for the development of aero-space technology,yet there is no reliable and effective method due to the complexity of the problem.The eN method has been regarded as an effective method for the transition prediction of boundary layers.However,it heavily relies on experiment or experience.And in cases with three-dimensional base flow,for instance,the boundary layer on a cone with angle of attack,the result of its application is not satisfactory.The authors have found its cause and proposed the method for its improvement,which did yield the fairly satisfactory result for a given test case,and also did not rely so much on experiment or experience.However,before people can really apply this method to practical problems,more test cases have to be studied.In this paper,more test cases for the application of the improved eN method to problems of transition prediction of supersonic and hypersonic boundary layers on cones with angle of attack will be studied.The results are compared with those obtained by experiments and/or direct numerical simulations,confirming that the improved eN method is effective and reliable.We also find that there may be more than one ZARF for each meridian plane,and which one should be chosen for the eN method has been clarified.

关键词： angle of attack cone boundary layer transition eN method

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