检索结果-内蒙古大学图书馆

computational fluid dynamics Analysis of Nozzle Plume Effects on Sonic Boom Signature

JOURNAL OF AIRCRAFT 2011年第2期48卷 368-380页

作者： Bui, Trong T. NASA Dryden Flight Res Ctr Res Aerodynam Prop & Performance Branch Edwards AFB CA 93523 USA

A computational fluid dynamics study is conducted to examine nozzle exhaust jet plume effects on the sonic boom signature of a supersonic aircraft. A simplified axisymmetric nozzle geometry, representative of the nozzle on the NASA Dryden NF-15B Lift and Nozzle Change Effects on Tail Shock research airplane, is considered. The computational fluid dynamics code is validated using available wind-tunnel sonic boom experimental data. The effects of grid size, spatial order of accuracy, grid type, and flow viscosity on the accuracy of the predicted sonic boom pressure signature are quantified. Grid lines parallel to the Mach wave direction are found to give the best results. Second-order-accurate upwind methods are required as a minimum for accurate sonic boom simulations. The highly underexpanded nozzle flow is found to provide significantly more reduction in the tail shock strength in the sonic boom N-wave pressure signature than perfectly expanded and overexpanded nozzle flows. A tail shock train in the sonic boom signature is observed for the highly underexpanded nozzle flow. Axisymmetric computational fluid dynamics simulations show the flow physics inside the F-15 nozzle to be nonisentropic and complex.

关键词： Sonic Booms Axisymmetric Nozzles computational fluid dynamics simulation One Dimensional Flow Supersonic Aircraft Wind Tunnel Tests computational fluid dynamics Code Viscosity Static Pressure Lift Distribution

来源：评论

学校读者我要写书评

暂无评论

Micro-particle deposition and lobar distribution of mass flow in human upper respiratory tract model

引用

Science Bulletin 2011年第Z1期 380-385页

作者： HUANG JianHua1 & ZHANG LianZhong1,2 1 School of Physics,Nankai University,Tianjin 300071,China 2 State Key Laboratory of Loess and Quaternary Geology,Institute of Earth Environment,Chinese Academy of Sciences,Xi’an 710075,China

A representative human upper respiratory tract model consisting of oropharyngeal and asymmetric tracheobronchial(TB) airways from the trachea(G0) to the main lobar bronchi(G2) was constructed. Laminar-to-turbulent airflow for typical inhalation modes as well as micro-particle transportation,wall deposition and mass flow to lobes was simulated using the CFX10.0 software from Ansys Inc. The numerical particle deposition efficiency of the oropharynx region and two generations(G1 and G2) of TB airways shows great agreement with the experimental data obtained from realistic casts. The particle deposition pattern indicates that inertial impaction is the primary mechanism in the human upper airway,and turbulence dispersion performs crescent influence especially for small particles. The initial positions of particles with different fates are confined to specifically concentrated zones. The particle mass distributions of five lobes are close to airflow distributions. The upper lobes receive fewer particles than lower lobes and the right middle lobe receives the least.

关键词： upper respiratory tract asymmetric tracheobronchial airways transportation and deposition lobar differences computational fluid dynamics simulation

来源：评论

学校读者我要写书评

暂无评论

Design and Feasibility of ExoMars Supersonic Parachute Scirocco Test

引用

JOURNAL OF SPACECRAFT AND ROCKETS 2010年第6期47卷 981-993页

作者： Votta, R. Marini, M. De Filippis, F. Di Vice, M. Sabatano, R. Ctr Italiano Ric Aerosp Aerosp Prop & Reacting Flows Unit I-81043 Capua CE Italy Ctr Italiano Ric Aerosp Space Syst Unit I-81043 Capua CE Italy Ctr Italiano Ric Aerosp Aeronaut Syst Unit I-81043 Capua CE Italy

A feasibility study of ExoMars parachute supersonic experiment to be possibly performed in the Centro Italiano Ricerche Aerospaziali Plasma Wind-Tunnel Scirocco facility has been analyzed. To verify the test feasibility, some test conditions in terms of facility reservoir conditions have been simulated by means of computational fluid dynamics computations of a modified nozzle, and verified with respect to testing requirements mainly in terms of test article size, Mach number, and dynamic pressure. The proper functioning of the wind tunnel has also been checked. In particular, the facility makes available a 80-MW power vacuum system that guarantees inside the test chamber the low-pressure conditions of the Mars atmosphere into which the parachute is foreseen to be opened. The possibility to introduce an air heater and/or burner would assure also the matching of temperature requirement, and reduce the request of mass flow rate. computational fluid dynamics simulations of the complete facility configuration (nozzle, test chamber, diffuser) with the test article inside have verified the right functioning of the diffuser (occurrence of tunnel blockage) and the effects of the interaction between the bow shock wave in front of the capsule and the flow exiting from the nozzle, and the pressure that establishes inside the test chamber.

关键词： Mars Science Laboratory Drag Coefficient Reynolds Averaged Navier Stokes Supersonic Wind Tunnels Mass Flow Rate computational fluid dynamics simulation Supersonic Nozzle Hypersonic Flows Boundary Layer Thickness Earth Atmosphere

来源：评论

学校读者我要写书评

暂无评论

Modeling of Fixed-Exit Porous Bleed Systems for Supersonic Inlets

引用

JOURNAL OF PROPULSION AND POWER 2010年第2期26卷 193-202页

作者： Slater, John W. Saunders, John D. NASA John H Glenn Res Ctr Inlet & Nozzle Branch Lewis Field Cleveland OH 44135 USA

A model has been developed to simulate porous bleed systems with fixed-area plenum exits in supersonic inlets. The fixed-exit bleed model computes the bleed plenum static pressure and bleed rates according to local flow conditions and the fixed-exit characteristics of the bleed system. The model was implemented into the Wind-US computational fluid dynamics code. The behavior of the model was demonstrated through computational fluid dynamics simulations of the flow through a Mach 3.0 axisymmetric, mixed-compression inlet. The model was able to capture the variation of bleed rates across a bleed region, especially variations due to shocks interacting with the bleed region. The model was able to accurately indicate the characteristic cane curves showing the variation of the engine-face total pressure recovery with respect to the total bleed rate or the engine-face flow ratio, which varied with the level of inlet backpressure. The fixed-exit model provided a more realistic simulation of the onset of inlet unstart than the existing bleed model, which assumed constant plenum pressures. The fixed-exit bleed model was less accurate in determining plenum pressures and indicated higher plenum pressures than observed in the inlet wind-tunnel test. The results highlight aspects of porous bleed models that require further research.

关键词： Supersonic Inlets computational fluid dynamics simulation Static Pressure Supercritical Flow Wind Tunnel Tests computational fluid dynamics Code Mach Numbers Reynolds Averaged Navier Stokes Laminar to Turbulent Transition Oblique Shock

来源：评论

学校读者我要写书评

暂无评论

Effects of Wavy Surface Roughness on the Performance of Micronozzles

引用

JOURNAL OF PROPULSION AND POWER 2010年第4期26卷 655-662页

作者： La Torre, Federico Kenjeres, Sasa Kleijn, Chris R. Moerel, Jean-Luc P. A. TNO Def Secur & Safety NL-2280 AA Rijswijk Netherlands Delft Univ Technol NL-2628 BW Delft Netherlands

Recent trends in small-scale (similar to 1 dm(3)) satellites motivate the further development of microscale propulsion subsystems. In the present paper, we focus on flow dynamics simulations of conical convergent divergent micronozzles and on the increased importance of wall effects due to the decrease in the characteristic length of such small systems. The inefficiency associated with viscous losses due to the developing boundary layer and the effect of sinusoidal surface roughness due to the employed microelectromechanical-system fabrication techniques are studied through computational fluid dynamics simulations for nonturbulent, nonrarefied flow conditions. Depending on the specific nature of the surface roughness, the formation and reflection of several weak shocks and, as a consequence, a decreased performance are observed.

关键词： Surface Roughness Boundary Layer Thickness Conical Convergent Divergent Micronozzles Flow Conditions Microelectromechanical Systems computational fluid dynamics simulation Satellites Stagnation Pressure Mach Number Direct simulation Monte Carlo

来源：评论

学校读者我要写书评

暂无评论

The effect of aneurysm geometry on the intra-aneurysmal flow condition

引用

NEURORADIOLOGY 2010年第12期52卷 1135-1141页

作者： Tateshima, Satoshi Chien, Aichi Sayre, James Cebral, Juan Vinuela, Fernando Univ Calif Los Angeles David Geffen Sch Med Div Intervent Neuroradiol Los Angeles CA 90095 USA Univ Calif Los Angeles Sch Publ Hlth Dept Biostat Los Angeles CA 90095 USA George Mason Univ Dept Computat Sci Fairfax VA 22030 USA

Various anatomical parameters affect on intra-aneurysmal hemodynamics. Nevertheless, how the shapes of real patient aneurysms affect on their intra-aneurysmal hemodynamics remains unanswered. Quantitative computational fluid dynamics simulation was conducted using eight patients' angiograms of internal carotid artery-ophthalmic artery aneurysms. The mean size of the intracranial aneurysms was 11.5 mm (range 5.8 to 19.9 mm). Intra-aneurysmal blood flow velocity and wall shear stress (WSS) were collected from three measurement planes in each aneurysm dome. The correlation coefficients (r) were obtained between hemodynamic values (flow velocity and WSS) and the following anatomical parameters: averaged dimension of aneurysm dome, the largest aneurysm dome dimension, aspect ratio, and dome-neck ratio. Negative linear correlations were observed between the averaged dimension of aneurysm dome and intra-aneurysmal flow velocity (r = -0.735) and also WSS (r = -0.736). The largest dome diameter showed a negative correlation with intra-aneurysmal flow velocity (r = -0.731) and WSS (r = -0.496). The aspect ratio demonstrated a weak negative correlation with the intra-aneurysmal flow velocity (r = -0.381) and WSS (r = -0.501). A clear negative correlation was seen between the intra-aneurysmal flow velocity and the dome-neck ratio (r = -0.708). A weak negative correlation is observed between the intra-aneurysmal WSS and the dome-neck ratio (r = -0.392). The aneurysm dome size showed a negative linear correlation with intra-aneurysmal flow velocity and WSS. Wide-necked aneurysm geometry was associated with faster intra-aneurysmal flow velocity.

关键词： Hemodynamics Intracranial aneurysm computational fluid dynamics simulation Aneurysm shape Aneurysm size

来源：评论

学校读者我要写书评

暂无评论

Unsteady flow characteristics through a human nasal airway

引用

RESPIRATORY PHYSIOLOGY & NEUROBIOLOGY 2010年第3期172卷 136-146页

作者： Lee, Jong-Hoon Na, Yang Kim, Sung-Kyun Chung, Seung-Kyu Konkuk Univ Dept Mech Engn Seoul 143701 South Korea Sungkyunkwan Univ Sch Med Samsung Med Ctr Dept Otorhinolaryngol Head & Neck Surg Seoul South Korea

Time-dependent characteristics of the flow in a human nasal airway constructed from the CT image of a healthy volunteer were investigated using a computational fluid dynamics (CFD) technique. To capture the time-varying nature of the flow as well as pressure and temperature fields, the large eddy simulation (LES) technique instead of the RANS (Reynolds Averaged Navier-Stokes) approach was adopted. To make the present analysis more relevant to a real human breathing cycle, the flow was designed to be induced by the pressure difference and the time-varying pressure at the end of trachea was described to reproduce the flow rate data from the measurement. Comparison of the present results with those of typical steady simulations showed that the difference in flow characteristics is magnified in the expiration phase. This fact may suggest that the inertial effect associated with unsteady flow is more important during the expiration period. Also, the fact that the distribution of the flow rate in a given cross-section of the airway changes significantly with time implies the importance of unsteady data for clinical decision. The wall shear stress was found to have relatively high values at the locations near nasopharynx and larynx but the magnitude changes with time during the whole respiratory cycle. Analysis of the temperature field showed that most of the temperature change occurs in the nasal cavity when the air is incoming and thus, the nasal cavity acts as a very efficient heat exchanger during an inspiration period. (C) 2010 Elsevier B.V. All rights reserved.

关键词： Respiratory airway Human nose computational fluid dynamics simulation Unsteady simulation Heat transfer

来源：评论

学校读者我要写书评

暂无评论

Numerical study of pressure drop for a new fibrous media model

引用

Journal of Southeast University(English Edition) 2010年第2期26卷 311-315页

作者：周斌 Paolo Tronville Richard Rivers 张小松东南大学能源与环境学院南京210096 Department of Energetics Politecnico di Torino EQS Inc. Louisville

An open-source computational fluid dynamics（CFD）code named OpenFOAM is used to validate the flow field characteristics（flow patterns and pressure drop）around a single *** show that OpenFOAM is suitable for simulating the low Reynolds number flow and Shaw＇s analytical expression is one of the solutions to Stokes＇ *** are performed on fibrous media and OpenFOAM simulation is carried out using the Tronville-Rivers two-dimensional random fiber model in terms of the characteristics of pressure *** is shown that the Kuwabara model predicts the pressure drop of fibrous filter media more accurately than the Happel model,and the experimental pressure drop is between simulated pressure drops with both non-slip and full-slip boundaries on fiber surfaces.

关键词： fibrous media diameter distribution pressure drop computational fluid dynamics simulation

来源：评论

学校读者我要写书评

暂无评论

Study on the combustion and emission characteristics of a diesel engine with multi-injection modes based on experimental investigation and computational fluid dynamics modelling

引用

PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART D-JOURNAL OF AUTOMOBILE ENGINEERING 2010年第D9期224卷 1161-1176页

作者： Shi, X-Y Qiao, X-Q Ni, J-M Zheng, Y-Y Ye, N-Y Tongji Univ Coll Automot Studies Shanghai 200092 Peoples R China Shanghai Jiao Tong Univ Sch Mech & Power Engn Shanghai 200030 Peoples R China Shandong Jiaotong Univ Dept Civil Engn Jinan Peoples R China

In this paper, experiments were carried out on a direct-injection diesel engine using a common-rail system, in order to study the effects of multi-injection modes on the combustion characteristics and pollutant emissions. A soot model was proposed for the post-injection mode, namely the Hiroyasu-Kodota averaged-reaction-rate soot model, which took into account both the chemical kinetics reaction and the turbulent mixing motion of the spray jet. Through integrating the revised soot model into a computational fluid dynamics (CFD) code, the combustion process and pollutants formation of the tested engine were simulated. The in-cylinder gas pressure and combustion heat release rate showed satisfactory agreement with measurements. The experimental data demonstrated that the pilot-injection mode was one of the most effective measures for reducing combustion noise. Meanwhile an optimum split-injection mode consisting of an appropriate pilot-injection fuel quantity combined with an optimal pilot-injection-main-injection interval could be achieved to decrease the nitrogen oxide (NOx) emission while not causing the particulate matter (PM) emission to deteriorate very much. Two innovative concepts of an active thermo-atmosphere and a passive inert atmosphere were presented from numerical simulation to discuss the effect of the pilot-injection mode on the combustion behaviour of the main injection. Regarding the post-injection mode, its prominent advantage was to decrease significantly the PM emission without an NOx emission penalty. Furthermore, by CFD modelling of the soot formation process, it can be observed that the turbulent mixing motion caused by the post-injection spray played a vital role in the soot oxidization process.

关键词： direct-injection diesel engine multi-injection mode combustion noise nitrogen oxide emission particulate matter emission computational fluid dynamics simulation active thermo-atmosphere passive inert atmosphere Hiroyasu-Kodota averaged-reaction-rate soot model

来源：评论

学校读者我要写书评

暂无评论

Influence of site selection on natural ventilation in Chinese traditional folk house

引用

Journal of Southeast University(English Edition) 2010年第2期26卷 161-164页

作者：徐峰解明镜张泉张国强王科湖南大学建筑学院长沙410082 湖南大学土木工程学院长沙410082 中南大学土木建筑学院长沙410083

The relationship between the site selection of a hilly terrain and the natural ventilation of the Dangdamen building complex,which is a traditional folk house,is revealed by a computational fluid dynamics（CFD）*** wind press and speed distributions around the building in four cases with different weather conditions and topographies are *** simulation results show that a hill can reduce the absolute values of the wind pressure at the windward and leeward sides of the *** encouraging effect of the patio on the natural ventilation in a terrain with a hill is greater than that without a *** same situation occurs when comparing the patio effects between summer and *** wind speed around the building can be reduced by the hill as it is an obstacle and the degrees of the influence of the hill in summer and in winter are quite different because of different wind *** analysis results show that this kind of site selection,with the hill to the north,is a suitable way to settle the conflict of the natural ventilation requirements in summer and in winter under subtropical climate conditions,especially in houses with patios.

关键词： site selection traditional folk house natural ventilation computational fluid dynamics simulation

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：