检索结果-南通市图书馆

Self-consistent parabolized stability equation(PSE) method for compressible boundary layer

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2015年第7期36卷 835-846页

作者： Yongming ZHANG caihong su Department of Mechanics Tianjin University Tianjin Key Laboratory of Modern Engineering Mechanics Tianjin University

The parabolized stability equation （PSE） method has been proven to be a useful and convenient tool for the investigation of the stability and transition problems of boundary layers. However, in its original formulation, for nonlinear problems, the complex wave number of each Fourier mode is determined by the so-called phase-locked rule, which results in non-self-consistency in the wave numbers. In this paper, a modification is proposed to make it self-consistent. The main idea is that, instead of allowing wave numbers to be complex, all wave numbers are kept real, and the growth or decay of each mode is simply manifested in the growth or decay of the modulus of its shape function. The validity of the new formulation is illustrated by comparing the results with those from the corresponding direct numerical simulation （DNS） as applied to a problem of compressible boundary layer with Mach number 6.

关键词： parabolized stability equation (PSE) boundary layer direct numericalsimulation (DNS) self-consistent

Interaction of weak free-stream disturbance with an oblique shock： validation of the shock-capturing method

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2017年第11期38卷 1601-1612页

作者： caihong su Jinlei GENG Department of Mechanics Tianjin University Tianjin 300072 China

Transition prediction is of great importance for the design of long distance flying vehicles. It starts from the problem of receptivity, i.e., how external disturbances trigger instability waves in the boundary layer. For super/hypersonic boundary layers, the external disturbances first interact with the shock ahead of the flying vehicles before entering the boundary layer. Since direct numerical simulation （DNS） is the only available tool for its comprehensive and detailed investigation, an important problem arises whether the numerical scheme, especially the shock-capturing method, can faithfully reproduce the interaction of the external disturbances with the shock, which is so far unknown. This paper is aimed to provide the answer. The interaction of weak disturbances with an oblique shock is investigated, which has a known theoretical solution. Numerical simulation using the shock-capturing method is conducted, and results are compared with those given by theoretical analysis, which shows that the adopted numerical method can faithfully reproduce the interaction of weak external disturbances with the shock.

关键词： shock high speed flow free-stream disturbance shock-capturing

Transition prediction of the supersonic boundary layer on a cone under the consideration of receptivity to slow acoustic waves

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2011年第10期54卷 1875-1882页

作者： su caihong ZHOU Heng Department of Mechanics Tianjin University Tianjin 300072 China Tianjin Key Laboratory of Modern Engineer Mechanics Tianjin 300072 China

Transition prediction of the supersonic boundary layer on a cone with small angle of attack and Mach number 3.5 is investi-gated under the consideration of receptivity to slow acoustic waves, as the acoustic waves are the main environmental distur-bances in a conventional, i.e. non-quiet, wind tunnel. It is shown that the e-N method can still yield fairly satisfactory results incomparison with those obtained in wind tunnel experiments, provided that the boundary layer receptivity to slow acousticwaves is properly taken into account, including the dependence of the amplitude of disturbances on the frequency andstream-wise location. Neither the conventional e-N method nor the improved e-N method can yield correct result of transitionprediction, because the receptivity mechanisms considered there are not in accord with the real situation in the wind tunnel.

关键词： receptivity boundary layer transition cone e-N method

Response of a hypersonic blunt cone boundary layer to slow acoustic waves with assessment of various routes of receptivity

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2018年第11期39卷 1643-1660页

作者： Bingbing WAN Jisheng LUO caihong su Laboratory for High-Speed Aerodynamics School of Mechanical Engineering Tianjin University

The hypersonic boundary-layer receptivity to slow acoustic waves is investigated for the Mach 6 flow over a 5-degree half-angle blunt cone with the nose radius of 5.08 mm. The plane acoustic wave interacts with the bow shock, and generates all types of disturbances behind the shock, which may take various routes to generate the boundarylayer unstable mode. In this paper, two routes of receptivity are investigated in *** is through the disturbance in the entropy layer. The other is through the slow acoustic wave transmitted downstream the bow shock, which can excite the boundary-layer mode due to the synchronization mechanism. The results show that, for a low frequency slow acoustic wave, the latter route plays a leading role. The entropy-layer instability wave is able to excite the first mode near the neutral point, but its receptivity efficiency is much lower.

关键词： receptivity entropy layer blunt cone hypersonic boundary layer

Extraction,chemical components,bioactive functions and adulteration identification of walnut oils:A review

在线全文

学校读者我要写书评

暂无评论

Grain & Oil Science and Technology 2024年第1期7卷 30-41页

作者： Yuan Gao Jia Hu Xia su Qi Li caihong su Yongling Li Gaiqin Ma Siyu Zhang Xiuzhu Yu Engineering Research Center of Grain and Oil Functionalized Processing College of Food Science and EngineeringNorthwest A&F UniversityShaanxi 712100China Animal Products and Animal Medicine Feed Quality Inspection Center Hebei 050041China

Walnut oil is a functional wood oil known to researchers that may potentially be a large source of Chinese edible *** are various extraction methods for walnut oil,including traditional(pressing,solvent-and enzymeassisted extraction)and novel methods(microwave,ultrasound,supercritical CO_(2),subcritical and other extraction technologies).Walnut oil is rich in nutrients,including phytosterols,tocopherols,polyphenols,squalene and *** provides many health benefits,such as antioxidant,antitumor,anti-inflammatory,antidiabetic and lipid metabolism-related *** addition,the authentication of walnut oil has received much research *** present review provides detailed research on walnut oil extraction,composition,health benefits and adulteration identification *** path toward further walnut oil improvement in the context of the market value of walnut oil is also discussed.

关键词： Extraction technology Chemical composition Bioactive Authentication

The variation of transition location in response to the variation of the amplitudes of initial disturbances

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2010年第6期53卷 1109-1115页

作者： su caihong & ZHOU Heng Department of Mechanics,Tianjin University,Tianjin 300072,China 1. Department of Mechanics Tianjin University Tianjin 300072 China

The transition location of a boundary layer depends on the amplitude and characteristic of initial disturbances. The larger the amplitude and the amplification rate of the initial disturbances are,the more upstream the transition location is. However,the environment surrounding the flying vehicle is variable,so the amplitude and characteristic of the disturbances triggered in the boundary layer through receptivity are also variable. In this paper,how the transition location varies in response to the variation of the initial disturbance amplitudes is studied by using direct numerical simulation. The results show that if the initial disturbance amplitudes become smaller,the transition location moves downstream correspondingly,but there is a time delay compared to the time of arrival of the disturbances with reduced amplitudes. Moreover,the speed of moving downstream is appreciably lower than the propagation speed of the disturbances. On the other hand,if the amplitudes of the initial disturbances recover their original value,the transition would immediately take place whenever the disturbances reach the former transition location,but the laminar flow between the new and old transition locations would not become turbulent immediately. Theoretical explanations are provided based on the transition mechanism found by our group.

关键词： transition boundary layer stability modification of mean flow direct numerical simulation

TENTATIVE EXPLANATION OF THE MECHANISM OF NOISE REDUCTION FOR JET ENGINE WITH CHEVRON AT ITS TRAILING EDGE

在线全文

学校读者我要写书评

暂无评论

TENTATIVE EXPLANATION OF THE MECHANISM OF NOISE REDUCTION FO...

The reliability of the improved e^N method for the transition prediction of boundary layers on a flat plate

2016年度全国气动声学学术会议

作者： caihong su Department of Mechanics Tianjin University

Modern jet engines may have chevrons at their trailing *** is believed to a measure for noise ***, its mechanism is still not fully *** this paper, based on theory of flow instability a simplified model is proposed to explore the possible cause of the noise reduction by chevron at the trailing edge of commercial aircraft jet engines.

关键词：

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2012年第5期55卷 837-843页

作者： su caihong1,2 1 Department of Mechanics,Tianjin University,Tianjin 300072,China 2 Tianjin Key Laboratory of Modern Engineering Mechanics,Tianjin 300072,China 1. Department of Mechanics Tianjin University Tianjin 300072 China2. Tianjin Key Laboratory of Modern Engineering Mechanics Tianjin 300072 China

The transition criterion in the improved eN method is that transition would occur whenever the velocity amplitude of disturbance reaches 1%-2% of the free stream velocity,while in the conventional eN method,the N factor is an empirical *** this paper the reliability of this key assumption in the improved eN method is checked by results of transition prediction by using the Parabolized Stability Equations(PSE).Transition locations of an incompressible boundary layer and a hypersonic boundary layer at Mach number 6 on a flat plate are predicted by both the improved eN method and the PSE *** from both methods agree fairly well with each other,implying that the transition criterion proposed in the improved eN method is reliable.

关键词： transition prediction boundary layer eN PSE

在线全文

学校读者我要写书评

暂无评论

发动机外罩波纹形尾缘降噪机理初探

空气动力学学报 2018年第3期36卷 410-416页

作者：苏彩虹天津大学机械工程学院高速空气动力学研究室天津300072

喷气发动机的射流是起飞过程中主要的噪声源之一。发动机外罩外的流动和外涵道内的环形射流在尾缘下游形成一个强剪切层。由剪切层的不稳定性产生的大尺度结构是一个重要的噪声源。近年发现,一些现代航空发动机外罩采用了波纹形尾缘的设... 详细信息

喷气发动机的射流是起飞过程中主要的噪声源之一。发动机外罩外的流动和外涵道内的环形射流在尾缘下游形成一个强剪切层。由剪切层的不稳定性产生的大尺度结构是一个重要的噪声源。近年发现,一些现代航空发动机外罩采用了波纹形尾缘的设计,被认为是一种降噪的措施。本文采用简化模型,即一个分割两层流体的平板后缘形成的剪切层,从流动稳定性的角度探讨其降噪的机理。研究发现,对于平直尾缘的情况,尾缘后会产生二维的非定常涡,对应的是剪切层中最不稳定的模态。而对于波纹形尾缘的情况,则不存在二维模态。对三维平均流的全局稳定性分析显示,所得三维最不稳定模态的增长率显著小于平滑尾缘的情况。数值模拟结果也证实了这一结论。因此,波纹形尾缘降噪的机理可以归结为,波纹形设计降低了平均流的不稳定性,从而降低了大尺度结构的增长率和幅值,使得Lighthill声源项中雷诺应力的二阶导数项也相应大幅减小,从而降低了噪声。

关键词：发动机气动噪声稳定性波纹形尾缘