检索结果-内蒙古大学图书馆

Computations of axisymmetric plug-nozzle flowfields: Flow structures and thrust performance

JOURNAL OF PROPULSION AND POWER 2002年第2期18卷 254-260页

作者： Ito, T Fujii, K Hayashi, AK Univ Tokyo Dept Aeronaut & Astronaut Bunkyo Ku Tokyo 1138654 Japan Inst Space & Astronaut Sci Kanagawa 2298510 Japan Aoyama Gakuin Univ Dept Engn Mech Tokyo 1578527 Japan

Plug-nozzle flowfields are analyzed by the numerical simulations. The method of characteristics is used to design the plug contour, and several types of plug nozzles are considered by truncating the length of the nozzle at different positions. Plug-nozzles' altitude-compensating features are confirmed by the computed results, and the base pressure turns out to play an important role to maintain the thrust performance of the nozzle for high-truncation configurations. The altitude clearly influences the base-pressure distributions under the assumption that the chamber pressure is constant during the ascent. The computed thrust difference between the contoured and the conical nozzle linearly increased as a function of the pressure ratio. The thrust performance of the contoured plug nozzle is estimated to be about 5-6% higher than the conical plug nozzle. Various conditions of external flows over the plug nozzle are also imposed, and the result shows that the external flow does not influence the pressure distribution on the nozzle surface for the pressure ratios higher than the designed point.

关键词： Contoured Plug Nozzle Mach Number Numerical Simulation Chamber Pressure Oblique Shock Wave Baldwin Lomax Turbulence Model Primitive Variable Navier Stokes Equations integration algorithm Propulsion System

来源：评论

学校读者我要写书评

暂无评论

Space-marching method on unstructured grid for supersonic flows with embedded subsonic regions

引用

AIAA JOURNAL 1997年第8期35卷 1280-1285页

作者： Nakahashi, K Saitoh, E Tohoku University Sendai 980-77 Japan

A space-marching algorithm on an unstructured grid to solve supersonic flows that may contain embedded subsonic regions is proposed. The method employs a domain-marching algorithm in which a bandlike computational subdomain is marched in the hyperbolic direction starting from the upstream boundary of the flowfield. A masking procedure is employed where the outside of the selected domain is masked during the flux computations to minimize the overall arithmetic operations. The unmasked domain is integrated in time to get a locally converged solution. If embedded subsonic regions are present, the unmasked region is enlarged to cover the entire subsonic regions surrounded by supersonic points. The method is applied to calculations of a fully supersonic flow in a scramjet and a supersonic flow with embedded subsonic regions around a blunt-nose body. It is demonstrated that the computational work can be reduced by as much as a factor of 10 as compared to conventional, time-marching unstructured grid methods.

关键词： Unstructured Grid Supersonic Flow Scramjet Primitive Variable Freestream Mach Number integration algorithm Angle of Attack Computing Supersonic Speed Total Energy

来源：评论

学校读者我要写书评

暂无评论

TEMPORAL AND ACOUSTIC ACCURACY OF AN IMPLICIT UPWIND METHOD FOR DUCTED FLOWS

引用

AIAA JOURNAL 1991年第11期29卷 1860-1867页

作者： RIDDER, JP BEDDINI, RA University of Illinois at Urbana-Champaign Urbana Illinois 61801

An implicit, time-accurate method for ducted-flow aeroacoustics is presented. The method is unfactored, using line Gauss-Seidel relaxation and multiple axial sweeps for convergence of each time step. First- or higher-order upwind spatial differencing is accomplished using either a modified form of van Leer's flux vector splitting or Roe's flux difference splitting on the inviscid terms of the governing equations. A general time integration algorithm is employed, which encompasses several schemes including the Euler implicit method used for the current work. Results are presented from three numerical tests with comparisons being made to both theory and experiment. These spatial and temporal accuracy tests show excellent tracking of the acoustic wave speed using Roe's flux difference splitting. The method is further seen to reflect waves properly as demonstrated by comparison of computed pressure amplitudes and acoustic mode shapes with experimental data. Additionally, no low mean-flow Mach number convergence limitation is observed. No Courant number stability restriction is displayed, as accurate results are obtained utilizing Courant numbers of order 10(2) for these tests.

关键词： Explicit Methods Aerodynamics integration algorithm Aeroacoustics Axisymmetric Flow Crank Nicolson Method Navier Stokes Equations Conservation of Mass Boundary Layer Analysis Aspect Ratio

来源：评论

学校读者我要写书评

暂无评论

An algorithm for Computing the Optimal Control of Large Structural Systems *

引用

IFAC Proceedings Volumes 1987年第1期20卷 127-132页

作者： S. Utku M. Salama J. Garba Duke University Durham NC 27706 USA Applied Technologies Jet Propulsion Laboratory California institute of technology pasadena CA 91109 USA

In an alternate formulation to the Hamilton-Jacobi approach for finding the optimal control of linear systems with Quadratic cost functionals, one must solve a Volterra integral equation of the second kind. Using explicit expressions derived from the Volterra formulation, the paper describes an ilerative algorithm for the numerical computation of the optimal control at equally spaced & number of time stations in the control interval 0 ≤ t ≤ 1. It is assumed that the structural system with large number of degrees-of-freedom n is identified with fewer vibration modes 1 ≤ r ≤ n. the computational complexity of the algorithm is shown to be of order [4r (q max + r) ms +n 2 )], where m is the number of control variables, and q max is the required maximum number of iterations of Jacobi-type

关键词： optimal control Volterra equation large systems integration algorithm

来源：评论

学校读者我要写书评

暂无评论

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

引用

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

来源：评论

学校读者我要写书评

暂无评论

NUMERICAL INVESTIGATION OF SUPERSONIC FLOWS AROUND A SPIKED BLUNT-BODY

引用

JOURNAL OF SPACECRAFT AND ROCKETS 1995年第1期32卷 32-42页

作者： YAMAUCHI, M FUJII, K HIGASHINO, F INST SPACE & ASTRONAUT SCI SAGAMIHARAKANAGAWA 229JAPAN

In supersonic now, a spike attached to the nose reduces the drag of a blunt body. In this paper, supersonic flows around a spiked blunt body are numerically simulated to examine the effects of the spike length, Mach number, and angle of attack. Three-dimensional thin-layer compressible Navier-Stokes equations are solved using a high-resolution upwind scheme with LU-ADI time-integration algorithm. The computed results show that the drag of the spiked blunt body is significantly influenced by the spike length, Mach number, and angle of attack. Scales of the separated region are not significantly influenced by the freestream Mach number, For the spiked blunt body at angle of attack, the flowfield becomes complex with spiral flows. The computed results are in reasonable agreement with experimental data.

关键词： Axisymmetric Flow Freestream Mach Number Angle of Attack Navier Stokes Equations Numerical Simulation integration algorithm Conical Shock Wave Flow Separation Vortices Institute of Space and Astronautical Science

来源：评论

学校读者我要写书评

暂无评论

State of the art and development trends in numerical simulation for real-time hybrid simulation

EARTHQUAKE ENGINEERING AND RESILIENCE

引用

EARTHQUAKE ENGINEERING AND RESILIENCE 2022年第3期1卷 245-267页

作者： Dong, Xiaohui Tang, Zhenyun Du, Xiuli Beijing Univ Technol Key Lab Urban Secur & Disaster Engn Minist Educ Beijing 100124 Peoples R China

Real-time hybrid simulation (RTHS) is a novel testing method that combines numerical simulation and physical testing to evaluate the dynamic performance of engineering structures in large specimens using existing experimental facilities, thus eliminating the scaled effect. In recent years, studies on RTHS have expanded beyond traditional engineering structures, such as wind turbines, automobiles, and ocean structures. Thus far, the dimensions of physical substructures in RTHS are still relatively small, limited by the accuracy of system control for physical systems and the real-time calculation efficiency of numerical simulations. This study summarizes the achievements of real-time numerical simulations for RTHS, including the dimensions of the physical specimen, strategy of numerical simulation, and integral algorithms of RTHS. Meanwhile, two theoretically feasible methods based on parallel computing and surrogate models are discussed, which may be the development trends needed to improve the efficiency and accuracy of numerical solutions in real-time and enlarge the application scope of RTHS. This study summarized the achievement in real-time numerical simulation for RTHS. Two theoretically feasible solving methods respectively based on parallel-computing and surrogate model were discussed. image

关键词： integration algorithm numerical solution numerical substructure physical substructure real-time hybrid simulation

来源：评论

学校读者我要写书评

暂无评论

The Detection of breast cancer based on Dynamic Feature Selection with EM-Bayesian Ensemble Classifier

The Detection of breast cancer based on Dynamic Feature Sele...

引用

Chinese Conference on Pattern Recognition/1st CJK Joint Workshop on Pattern Recognition

作者： Fu, Qiang Feng, Jun Wang, Huiya Northwest Univ Xian Sch Informat Sci & Technol Xian 710069 Peoples R China Northwest Univ Xian Dept Math Xian 710069 Peoples R China

ISBN: (纸本)9781424441990

When solving the problem in Computer Assisted Detection by the approach of Pattern Recognition, the lesion data always exhibited high-dimensional and inhomogeneous, which makes most of the traditional classifiers can not performance very well. In this paper, a novel approach based on the Dynamic Feature Subset Selection and the EM algorithm with Naive Bayesian classifier integration algorithm (DSFS+EMNB) is proposed. The experimental results demonstrated that this method significantly outperforms the other methods like SVM and other traditional classification methods in terms of average accuracy, as well as generality.

关键词： Dynamic Feature Subset Selection algorithm EM algorithm Naive Bayesian Classifier integration algorithm

来源：评论

学校读者我要写书评

暂无评论

DESIGN AND IMPLEMENTATION OF A VISUAL LOGGING AND AUTOMATIC MODELING TOOL FOR CAMP DISTRIBUTION CONNECTION BASED ON DEEP LEARNING algorithmS

引用

SCALABLE COMPUTING-PRACTICE AND EXPERIENCE 2024年第6期25卷 5593-5602页

作者： Jia, Yong Zhang, Junwei Suo, Siyuan Xiao, Chun Liang, Yue Zhang, Shiyi State Grid Shanxi Mkt Serv Ctr Taiyuan 4164025 Shanxi Peoples R China

This particular offers a visual logging and automatic modelling apparatus for camp distribution connection employing state-of-the-art deep learning techniques. The gadget that emerged from an interdisciplinary approach inspired by ideas related to data security, quantum computing, and environmental monitoring points to an upward trajectory in increasing the accuracy and efficiency of compassionate coordination in settings for camp distribution. Experiments on the dataset show how successfully connection modelling, anomaly detection, as well as semantic segmentation, are done to generate a more cohesive model. Its reputation is further highlighted by the corresponding study of works from various domains, which finds that it has accuracy, precision, and F1 score measurements above 0.88 per task. As a directed investigation area in non-stipulated regions turns into significant scientific research, it contributes an ever-more significant role in leading authorities through which to make some administrative efforts to optimise such research, as disciplined researchers currently have sufficient knowledge of contemporary trends. Compared to present use, the equipment is more accurate and has superior review values. The research can achieve unprecedented computing efficiency, as seen by its 12-hour setup time and processing velocity measurement of 20 milliseconds per recorded picture.

关键词： Visual Logging Deep Learning Humanitarian Logistics Object Detection integration algorithm

来源：评论

学校读者我要写书评

暂无评论

Research of optical coherence tomography microscope based on CCD detector

Research of optical coherence tomography microscope based on...

引用

2008 International Conference on Optical Instruments and Technology

作者： Hua,ZHANG~(1,2) Zhongbao,XU~(1,2) Shuomo,ZHANG~(1,2) (1.School of Mechanical Engineering,Hubei University of Technology,Wuhan 430068,China 2.The Key Laboratory of Modern Manufacturing Quantity Engineering of Hubei Province, Wuhan 430068,China)

The reference wave phase was modulated with a sinusoidal vibrating mirror attached to a Piezoelectric Transducer(PZT), the integration was performed by a CCD,and the charge storage period of the CCD image sensor was one-quarter period of the sinusoidal phase *** the frequency- synchronous detection technique,four images(four frames of interference pattern)were recorded during one period of the phase *** order to obtain the optimum modulation parameter,the values of amplitude and phase of the sinusoidal phase modulation were determined by considering the measurement error caused by the additive noise contained in the detected *** PZT oscillation was controlled by a closed loop control system based on PID *** ideal discrete digital sine function at 50Hz with adjustable amplitude was used to adjust the vibrating of PZT,and a digital phase shift techniques was used to adjust vibrating phase of PZT so that the phase of the modulation could reach their optimum *** CCD detector was triggered with software at *** on work above,a small coherent signal masked by the preponderant incoherent background with a CCD detector was obtained.

关键词： full-field optical coherence tomography combination light source frequency-synchronous detection technique phase modulation integration algorithm

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：