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Numerical investigation of reflected shock/vortex interaction near an open-ended duct

AIAA JOURNAL 2005年第2期43卷 349-356页

作者： Liang, SM Chung, WT Chen, H Shyu, SH Natl Cheng Kung Univ Inst Aeronaut & Astronaut Tainan 701 Taiwan Wu Feng Inst Technol Chia I 621 Taiwan

The problem of planar reflected-shock/spiral-vortex interactions near an open-ended duct is considered. The reflected shock is formed after exiting the duct and impinging on a vertical wall that is located downstream or the duct. Two cases associated with the shock diffraction around the duct exit are investigated for understanding the detailed flow structure and acoustic waves due to the reflected shock/spiral-vortex interaction. One is a 90-deg diffraction;the other is a 180-deg diffraction. An Euler solver with a high-resolution scheme of weighted essential nonoscillation is used to study these complicated flow problems. The Euler solver is validated to be reasonably accurate by comparing the computed solution with experimental data. For the study of reflected-shock/spiral-vortex interactions, the techniques of computational shadowgraph, computational schlieren image, and computational interferometry are used. Detailed flow structures of reflected shock/vortex interactions are reported for different incident shock Mach numbers. An interesting result of stagnant reflected shock waves downstream of the duct is found for an incident shock Mach number equal to or greater than 1.4. For the incident shock Mach number below this critical value, the reflected shock RE will eventually enter the duct. The mechanism for the formation of acoustic waves generated by reflected-shock/vortex interactions is analyzed.

关键词： Vortex Rings Curved Shocks Blunt Bodies Flow Visualization Techniques Courant Friedrichs Lewy Flow Conditions Euler Equations Shear Layers integration algorithm Navier Stokes Solver

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Computing differential equations for integrals associated to smooth Fano polytope

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JAPAN JOURNAL OF INDUSTRIAL AND APPLIED MATHEMATICS 2013年第2期30卷 307-319页

作者： Nakayama, Hiromasa Takayama, Nobuki Kobe Univ Grad Sch Sci Dept Math Nada Ku Kobe Hyogo 6578501 Japan JST Crest Hibi Team Nada Ku Kobe Hyogo 6578501 Japan

We give an approximation algorithm of computing holonomic systems of linear differential equations for definite integrals of rational functions with parameters. We show that this algorithm gives a correct answer in finite steps, but we have no general stopping condition. We apply the approximation method to find differential equations for integrals associated to smooth Fano polytopes. These are interesting in the study of K3 surfaces and the toric mirror symmetry. In this class of integrals, we can apply Stienstra's rank formula to our algorithm, which gives a stopping condition of the approximation algorithm.

关键词： Grobner Basis D-modules integration algorithm Period map Calabi-Yau variety

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Development of hereditary model for deformation and failure of salt rocks

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JOURNAL OF MINING SCIENCE 2004年第1期40卷 45-56页

作者： Konstantinova, SA Chernopazov, SA Ural Sci Res & Design Inst Halurgy Perm Russia

A model is proposed for hereditary elasticity and viscoplasticity of salt rocks. The features of rock sample deformation to be connected with loosening and original damaged state are considered in construction of nucl... 详细信息

关键词： shear creep constitutive relations creep parameters integration algorithm

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A micromechanics-based elasto-plastic model for granular media combined with Cosserat continuum theory

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ACTA GEOTECHNICA 2022年第6期17卷 2259-2285页

作者： Tian, Jianqiu Lai, Yuanming Liu, Enlong Yang, Yunming Sichuan Univ Coll Water Resource & Hydropower State Key Lab Hydraul & Mt River Engn Chengdu 610065 Peoples R China Chinese Acad Sci Northwest Inst Ecoenvironm & Resources State Key Lab Frozen Soil Engn Lanzhou 730000 Peoples R China Univ Nottingham Ningbo China Ningbo Nottingham New Mat Inst Ningbo 315100 Peoples R China

This paper is devoted to the micromechanical model of granular materials based on the Cosserat continuum theory. The generalised stress-strain relationships of a representative element volume are closely related to the micro elasto-plastic force-displacement and moment-rotation laws. With the help of generalised micro-macro relations, a micromechanical model is presented by aggregating the generalised micro elasto-plastic inter-particle contact laws in each contact orientation. A corresponding implicit multiscale integration algorithm for integrating the micromechanical model is proposed. Furthermore, the micromechanical model and implicit multiscale integration algorithm are simplified to consider a two-dimensional condition, and the Romberg integration of the numerical quadrature formula is also introduced in this condition. Compared with the data of Hostun sand and the results of DEM simulations for different particle shapes, it is demonstrated that the proposed micromechanical model can describe both the macro and micro responses of granular materials relatively well, such as strain softening/hardening, volumetric compaction/dilatancy, particle rotation, and evolution of the coordination number.

关键词： Constitutive model Cosserat theory Granular materials integration algorithm Microstructure Multiscale responses

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Numerical Evaluation of Dynamic Response by Using Modified Newmark's Method

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JORDAN JOURNAL OF CIVIL ENGINEERING 2019年第1期13卷 30-43页

作者： Alnahhal, Wael Aref, Amjad Qatar Univ Doha Qatar SUNY Buffalo Buffalo NY USA

It is well known that the Newmark's method is considered one of the most popular methods for structural dynamic analysis. In this study, starting from the basic Newmark's method, a new accurate method is investigated and developed. The basic idea of the proposed method is to use Richardson's extrapolation to improve the basic Newmark's method. To observe the accuracy of the proposed method, several numerical tests are performed for a single degree-of-freedom (SDM) dynamic system and the results are compared with results from Newmark's method and the exact solution. The results show that the proposed method improves the solution accuracy of the structural dynamic problems compared to the Newmark's method. Moreover, the results of the free oscillating case show that the modified Newmark's method has more computational efficiency compared to the Newmark's method.

关键词： Newmark's method Richardson's extrapolation Structural dynamic analysis Numerical analysis Modified Newmark's method integration algorithm

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DYNAMICS OF A SUBSATELLITE SYSTEM SUPPORTED BY 2 TETHERS

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1986年第1期9卷 12-16页

作者： MISRA, AK DIAMOND, GS McGill University Montreal Canada

The dynamics of a subsatellite system connected to a main orbiter by two extensible but massless tethers is studied. The points of attachment of these two tethers are offset from the center of mass of the orbiter. Both constant-length and retrieval cases are considered. Lagrangian formulation for constrained systems is used to derive the nonlinear equations of motion. These along with the constraint equations are solved numerically. It is noted that the rotational motion in the plane of the attachment points can be damped quite effectively using a simple control scheme. Comparisons are made with the single-tether case. A two-tether system has superior rotational behavior, but seems to have disadvantages as far as longitudinal oscillations are concerned.

关键词： Nonlinear Equation Young's Modulus Longitudinal Vibrations Earth Second Order Differential Equations Singular Value Decomposition Feedback Control Kinetic Energy Flight Testing integration algorithm

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Temporal evolution of three-dimensional vortex breakdown from steady, axisymmetric solutions

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AIAA JOURNAL 1996年第3期34卷 632-634页

作者： Tromp, JC Beran, PS USAF INST TECHNOLDEPT AERONAUT & ASTRONAUTWRIGHT PATTERSON AFBOH 45433

The emergence and consequences of asymmetries in swirling flows that are initially steady and axisymmetric are examined. The strength of an isolated vortex in a tube is increased in a parametric fashion through a critical value, where stability to three-dimensional disturbances is lost. The flow behavior undergoes a bifurcation at the critical value from steady and axisymmetric flow to unsteady and three-dimensional flow.

关键词： Vortex Breakdown Flow Visualization Two Dimensional Flow integration algorithm Composite Materials Plasticity Time Asymptotic Streaklines Navier Stokes Equations Composite Structures Vorticity Equations

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INVERSE SIMULATION OF LARGE-AMPLITUDE AIRCRAFT MANEUVERS

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1993年第4期16卷 733-737页

作者： GAO, C HESS, RA University of California Davis Davis California 95616

Inverse simulation techniques are computational methods that determine the control inputs to a dynamic system that will produce desired system outputs. Such techniques can be useful tools for the analysis and evaluation of problems associated with maneuvering night. As opposed to current inverse simulation methods that require numerical time differentiation in their implementation, the proposed technique is essentially an integration algorithm. It is applicable to cases where the number of inputs equals or exceeds the number of constrained outputs. The algorithm is exercised in determining the trim conditions and then the control inputs that force a nonlinear model of an F-16 fighter to complete large-amplitude maneuvers.

关键词： Aircraft Maneuvers Computational Methods integration algorithm Aerodynamic Angle Stability Derivatives Roll Control Stabilator Leading Edge Flap Inverse Problems Singular Value Decomposition

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Equivalency between strapdown inertial navigation coning and sculling integrals/algorithms

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2001年第2期24卷 201-205页

作者： Roscoe, KM KMR Associates Orono MN 55356 USA

This paper develops a generic equivalency between strapdown inertial navigation coning and sculling integrals and algorithms. The equivalency allows a previously derived coning algorithm to be converted to its corresponding sculling algorithm using a simple mathematical formula. Two examples are provided illustrating the coning-to-sculling algorithm conversion process. The results are verified by comparing them against previously derived coning and sculling algorithms.

关键词： Strapdown Inertial Navigation System integration algorithm Strapdown System Inertial Sensor Optimization algorithm Quaternions

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Evaluation of a real-time hybrid simulation system for performance evaluation of structures with rate dependent devices subjected to seismic loading

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ENGINEERING STRUCTURES 2012年 35卷 71-82页

作者： Chen, Cheng Ricles, James M. Karavasilis, Theodore L. Chae, Yunbyeong Sause, Richard ATLSS Engn Res Ctr Bethlehem PA 18015 USA San Francisco State Univ Sch Engn San Francisco CA 94132 USA Univ Warwick Sch Engn Coventry CV4 7AL W Midlands England

Real-time hybrid simulation is a viable experiment technique to evaluate the performance of structural systems subjected to earthquake loads. This paper presents details of the real-time hybrid simulation system developed at Lehigh University, including the hydraulic actuators, the IT control architecture, an integration algorithm and actuator delay compensation. An explicit integration algorithm provides a robust and accurate solution to the equations of motion while an adaptive inverse compensation method ensures the accurate application of the command displacements to experimental substructure(s) by servo-hydraulic actuators. Experiments of a steel moment resisting frame with magneto-rheological fluid dampers in passive-on mode were conducted using the real-time hybrid simulation system to evaluate the ability for the simulation method to evaluate the nonlinear seismic response of steel frame systems with dampers that are intended to enhance the response of the structure. The comparison with numerical simulation results demonstrates that the real-time hybrid simulation system produces accurate and reliable experimental results and therefore shows great potential for structural performance evaluation in earthquake engineering research. (C) 2011 Elsevier Ltd. All rights reserved.

关键词： Real-time Hybrid simulation integration algorithm Compensation

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