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Stability analysis method considering non-parallelism:EPSE method and its application 被引量:3
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作者 Gaotong YU Jun GAO Jisheng LUO 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2016年第1期27-36,共10页
The e-N method is widely used in transition prediction. The amplitude growth rate used in the e-N method is usually provided by the linear stability theory (LST) based on the local parallel hypothesis. Considering t... The e-N method is widely used in transition prediction. The amplitude growth rate used in the e-N method is usually provided by the linear stability theory (LST) based on the local parallel hypothesis. Considering the non-parallelism effect, the parabolized stability equation (PSE) method lacks local characteristic of stability analysis. In this paper, a local stability analysis method considering non-parallelism is proposed, termed as EPSE since it may be considered as an expansion of the PSE method. The EPSE considers variation of the shape function in the streamwise direction. Its local characteristic is convenient for stability analysis. This paper uses the EPSE in a strong non-parallel flow and mode exchange problem. The results agree well with the PSE and the direct numerical simulation (DNS). In addition, it is found that the growth rate is related to the normalized method in the non-parallel flow. Different results can be obtained using different normalized methods. Therefore, the normalized method must be consistent. 展开更多
关键词 parabolized stability equation (PSE) expansion of PSE (EPSE) linear stability theory (LST) normalized method non-parallel
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Effective transmittance of Fabry–Perot cavity under non-parallel beam incidence
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作者 吕寅生 谢品华 +2 位作者 徐晋 李友涛 张华荣 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第1期449-457,共9页
The Fabry–Perot(FP) resonant cavity is widely used in laser and spectroscopic measurements due to its unique interference transfer function(ITF). In the ideal case of parallel incident light, the ITF of the FP resona... The Fabry–Perot(FP) resonant cavity is widely used in laser and spectroscopic measurements due to its unique interference transfer function(ITF). In the ideal case of parallel incident light, the ITF of the FP resonant cavity can be expressed by the Airy function. However, in reality, it is difficult to achieve perfect parallelism with collimated beams. In this article, a theoretical model is established for non-parallel light incidence, which assumes that the non-parallel incident light is a cone-shaped beam, and the cone angle is used to quantify the non-parallelism of the beam. The transmittance function of the FP resonant cavity under non-parallel light incidence is derived. The accuracy of the model is experimentally verified. Based on this model, the effects of divergence angle, tilt angle and FP cavity parameters(reflectivity, cavity length)on the ITF are studied. The reasons for the decrease in peak value, broadening and asymmetry of the interference peak under non-parallel light incidence are explained. It is suggested that a fine balance between the interference peak and the collimation effect of the incident light should be considered in the design and application of FP resonant cavities, especially for tilted applications such as angle-scanned spectroscopy. The research results of this article have certain significance for the design and application of FP resonant cavities. 展开更多
关键词 Fabry–Pérot(FP)resonant cavity interference transfer function Airy function non-parallel beam incidence
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Experimental study on cracking behaviour of moulded gypsum containing two non-parallel overlapping flaws under uniaxial compression 被引量:10
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作者 Lekan Olatayo Afolagboye Jianming He Sijing Wang 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2017年第2期394-405,共12页
Failure of rock mass that is subjected to compressive loads occurs from initiation, propagation, and linkage of new cracks from preexisting fissures. Our research investigates the cracking behaviour and coalescence pr... Failure of rock mass that is subjected to compressive loads occurs from initiation, propagation, and linkage of new cracks from preexisting fissures. Our research investigates the cracking behaviour and coalescence process in a brittle material with two non-parallel overlapping flaws using a high-speed camera. The coalescence tensile crack and tensile wing cracks were the first cracks to occur from the preexisting flaws. The initiation stresses of the primary cracks at the two tips of each flaw were simultaneous and decreased with reduced flaw inclination angle. The following types of coalescence cracks were identified between the flaws: primary tensile coalescence crack, tensile crack linkage, shear crack linkage, mixed tensile-shear crack, and indirect crack coalescence. Coalescence through tensile linkage occurred mostly at pre-peak stress. In contrast, coalescence through shear or mixed tensile-shear cracks occurred at higher stress. Overall, this study indicates that the geometry of preexisting flaws affect crack initiation and coalescence behaviour. 展开更多
关键词 Crack coalescence Moulded gypsum non-parallel flaws Primary cracks Uniaxial compression test
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Non-parallel double-crack propagation in rock-like materials under uniaxial compression 被引量:4
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作者 Weidong Pan Xin Wang +2 位作者 Qiming Liu Yongkang Yuan Baodong Zuo 《International Journal of Coal Science & Technology》 EI 2019年第3期372-387,共16页
Coalescence among fractures would have influence on the stability of rock masses. Deep understanding of mechanical behavior of fractured rock masses is an important mean to identify failure mechanism of geological dis... Coalescence among fractures would have influence on the stability of rock masses. Deep understanding of mechanical behavior of fractured rock masses is an important mean to identify failure mechanism of geological disaster. In this study, crack propagation processing was studied through loading pre-fractured specimens of concrete block, termed as rock-like material, in uniaxial compression tests. New non-parallel double-crack geometry was introduced to observe crack coalescence. The flaw combinations are different from the normally used flaw configurations. In addition, ultrasonic detection tests were performed on the test blocks. The stress and strain data of these tests and characteristic parameters of sound wave were recorded. The stress-strain curves of each test block under the uniaxial compression test were drawn, relations among deformation characteristics and crack angle of the crack specimens, and their overall strength were analyzed. It is found that strength of the specimen decreases as crack inclination increases under two crack inclinations. The highest uniaxial compressive strength is found in the specimen with the cracks at the same angle in different directions. Based on description of the crack initiation location, crack surface and the ultimate failure patterns, failure modes of eight subtype for test blocks are divided into three categories. It is expected that the study results could be beneficial for engineering application of jointed rock masses. 展开更多
关键词 Rock-like material non-parallel DOUBLE cracks CRACK-PROPAGATION path UNIAXIAL compression test
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Local receptivity in non-parallel boundary layer 被引量:1
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作者 Luyu SHEN Changgen LU 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2016年第7期929-940,共12页
The research on boundary-layer receptivity is the key issue for the laminarturbulent transition prediction in fluid mechanics. Many of the previous studies for local receptivity are on the basis of the parallel flow a... The research on boundary-layer receptivity is the key issue for the laminarturbulent transition prediction in fluid mechanics. Many of the previous studies for local receptivity are on the basis of the parallel flow assumption which cannot accurately reflect the real physics. To overcome this disadvantage, local receptivity in the non-parallel boundary layer is studied in this paper by the direct numerical simulation (DNS). The difference between the non-parallel and parallel boundary layers on local receptivity is investigated. In addition, the effects of the disturbance frequency, the roughness location, and the multiple roughness elements on receptivity are also determined. Besides, the relations of receptivity with the amplitude of free-stream turbulence (FST), with the roughness height, and with the roughness length are ascertained as well. The Tollmien- Schlichting (T-S) wave packets are excited in the non-parallel boundary layer under the interaction of the FST and the localized wall roughness. A group of T-S waves are separated by the fast Fourier transform. The obtained results are in accordance with Dietz's measurements, Wu's theoretical calculations, and the linear stability theory (LST). 展开更多
关键词 RECEPTIVITY non-parallel boundary layer free-stream turbulence (FST) wall roughness
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Secondary steady-state and time-periodic flows from a basic flow with square array of odd number of vortices
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作者 Zhimin CHEN W.G.PRICE 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2023年第3期447-458,共12页
In a magnetohydrodynamic(MHD)driven fluid cell,a plane non-parallel flow in a square domain satisfying a free-slip boundary condition is examined.The energy dissipation of the flow is controlled by the viscosity and l... In a magnetohydrodynamic(MHD)driven fluid cell,a plane non-parallel flow in a square domain satisfying a free-slip boundary condition is examined.The energy dissipation of the flow is controlled by the viscosity and linear friction.The latter arises from the influence of the Hartmann bottom boundary layer in a three-dimensional(3D)MHD experiment in a square bottomed cell.The basic flow in this fluid system is a square eddy flow exhibiting a network of N~2 vortices rotating alternately in clockwise and anticlockwise directions.When N is odd,the instability of the flow gives rise to secondary steady-state flows and secondary time-periodic flows,exhibiting similar characteristics to those observed when N=3.For this reason,this study focuses on the instability of the square eddy flow of nine vortices.It is shown that there exist eight bi-critical values corresponding to the existence of eight neutral eigenfunction spaces.Especially,there exist non-real neutral eigenfunctions,which produce secondary time-periodic flows exhibiting vortices merging in an oscillatory manner.This Hopf bifurcation phenomenon has not been observed in earlier investigations. 展开更多
关键词 two-dimensional(2D)Navier-Stokes equation non-parallel square vortex flow primary bifurcation secondary steady-state flow secondary time-periodic flow
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Improvement for expansion of parabolized stability equation method in boundary layer stability analysis 被引量:1
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作者 Yufeng HAN Jianxin LIU Jisheng LUO 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2018年第12期1737-1754,共18页
An improved expansion of the parabolized stability equation(iEPSE) method is proposed for the accurate linear instability prediction in boundary layers. It is a local eigenvalue problem, and the streamwise wavenumber ... An improved expansion of the parabolized stability equation(iEPSE) method is proposed for the accurate linear instability prediction in boundary layers. It is a local eigenvalue problem, and the streamwise wavenumber α and its streamwise gradient dα/dx are unknown variables. This eigenvalue problem is solved for the eigenvalue dα/dx with an initial α, and the correction of α is performed with the conservation relation used in the PSE. The i EPSE is validated in several compressible and incompressible boundary layers. The computational results show that the prediction accuracy of the i EPSE is significantly higher than that of the ESPE, and it is in excellent agreement with the PSE which is regarded as the baseline for comparison. In addition, the unphysical multiple eigenmode problem in the EPSE is solved by using the i EPSE. As a local non-parallel stability analysis tool, the i EPSE has great potential application in the eNtransition prediction in general three-dimensional boundary layers. 展开更多
关键词 parabolized stability equation(PSE) INSTABILITY non-parallelism boundary layer
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Comparison between the volumetric flow rate and pressure distribution for different kinds of sliding thrust bearing 被引量:4
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作者 O.Pourmehran M.Rahimi-Gorji +1 位作者 M.Gorji-Bandpy M.Baoub 《Propulsion and Power Research》 SCIE 2015年第2期84-90,共7页
In this paper a hydrodynamic journal sliding bearing,forming with two nonparallel surfaces that the lower surface moves with a unidirectional velocity and the upper surface is stationary shaped with exponential geomet... In this paper a hydrodynamic journal sliding bearing,forming with two nonparallel surfaces that the lower surface moves with a unidirectional velocity and the upper surface is stationary shaped with exponential geometry is verified mathematically.The values of volumetric flow rate and distribution of pressure for incompressible lubricant flow between two supports in several conditions of velocity with different variables are determined.The results indicate that by increasing the amount of constant(m),the maximum oil pressure in the bearing will face an extreme decrease,and also by increasing theαcoefficient,the rate of volumetric flow rate will decrease. 展开更多
关键词 non-parallel plate bearing Hydrodynamic sliding bearing Incompressible lubricant flow Volumetric flow rate Exponential geometry
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Finite-Time Stability for Interval Type-2 Fuzzy Nonlinear Systems via an Observer-Based Sliding Mode Control 被引量:2
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作者 LIU Yu'an XIA Jianwei +1 位作者 WANG Jing SHEN Hao 《Journal of Systems Science & Complexity》 SCIE EI CSCD 2022年第6期2223-2247,共25页
This work focuses on the design of a sliding mode controller for a class of continuoustime interval type-2 fuzzy-model-based nonlinear systems with unmeasurable state information over a finite-time interval.Aiming at ... This work focuses on the design of a sliding mode controller for a class of continuoustime interval type-2 fuzzy-model-based nonlinear systems with unmeasurable state information over a finite-time interval.Aiming at describing the nonlinearities containing parameter uncertainties that inevitably appear in practice,the interval type-2 fuzzy sets are employed to model the studied system.To improve the designing flexibility,a fuzzy observer model non-parallel distribution compensation scheme is designed to estimate the state information of the plant,i.e.,the observer is allowed to have a mismatching premise structure from the system.On this basis,the appropriate fuzzy sliding surface and fuzzy controller are constructed by following the same premise variables as the designed fuzzy observer.Then,by means of the sliding mode control theory and the Lyapunov function method,some novel sufficient criteria are established to ensure the finite-time boundedness for the studied systems via a partitioning strategy including the reaching phase,the sliding motion phase and the whole time interval.Furthermore,the designed gains are acquired by solving the matrix convex optimization problem.Finally,the effectiveness of the developed method is demonstrated by two simulation examples. 展开更多
关键词 Finite-time boundedness interval type-2 fuzzy model non-parallel distribution compensation observer-based sliding mode control
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A Water Strider Robot with Five Umbrella-Type Footpads 被引量:1
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作者 Chunyan Yao Tianwei Sheng +2 位作者 Yijun Zhu Kaixiang Xu Shiwu Zhang 《Journal of Bionic Engineering》 SCIE EI CSCD 2022年第2期331-342,共12页
The design of most water strider robots follows the principle that all supporting legs are in a plane,and each supporting leg bears a certain load and the water strider robot can float on the water.To meet this princi... The design of most water strider robots follows the principle that all supporting legs are in a plane,and each supporting leg bears a certain load and the water strider robot can float on the water.To meet this principle,the number of supporting legs and the spacing between each supporting legs of the water strider robot must be increased,which makes the shape of water strider robots look like octopus.This study proposed a novel water strider robot named 5S-robot,which used five new umbrella-type footpads and a centrifugal pump-based actuating mechanism.Motion analysis model and force analysis model of 5S-robot were built.The general consistency between the results of motion experiments and those of numerical simulation verified the former models.For this 5S-robot,the maximum load of 110.5 g and forward speed of 207.1 mm s^(-1)and rotational speed of 1.22 rad s^(-1)were measured,respectively. 展开更多
关键词 Umbrella-type footpad Water strider non-parallel arrangement Pump-based actuating mechanism
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A Classification of Long-Range Interactions between Two Stacks of p& p'-Branes
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作者 欧阳君 吴超 《Communications in Theoretical Physics》 SCIE CAS CSCD 2015年第2期195-208,共14页
We generalize the computations of the long-range interactions between two parallel stacks of branes to various cases when two stacks of branes are not placed parallel to each other. We classify the nature of interacti... We generalize the computations of the long-range interactions between two parallel stacks of branes to various cases when two stacks of branes are not placed parallel to each other. We classify the nature of interaction(repulsive or attractive) for each special case and this classification can be used to justify the nature of long-range interaction between two complicated brane systems such as brane bound states. We will provide explicit examples in this paper to demonstrate this. 展开更多
关键词 long-range interaction effective field theory computation non-parallel branes FLUX
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