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A trigonometric series expansion method for the Orr-Sommerfeld equation

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Applied Mathematics and Mechanics(English Edition) 2019年第6期40卷 877-888页

作者： Ying TAN weidong su State Key Laboratory for Turbulence and Complex Systems Peking UniversityBeijing 100871China Department of Mechanics and Engineering Science College of EngineeringPeking UniversityBeijing 100871China

A trigonometric series expansion method and two similar modified methods for the Orr-Sommerfeld equation are presented. These methods use the trigonometric series expansion with an auxiliary function added to the highest order derivative of the unknown function and generate the lower order derivatives through successive integra- tions. The proposed methods are easy to implement because of the simplicity of the chosen basis functions. By solving the plane Poiseuille flow (PPF), plane Couette flow (PCF), and Blasius boundary layer flow with several homogeneous boundary conditions, it is shown that these methods yield results with the same accuracy as that given by the conventional Chebyshev collocation method but with better robustness, and that ob- tained by the finite difference method but with fewer modal number.

关键词： Orr-Sommerfeld equation spectral method trigonometric function parallel shear flow hydrodynamical stability eigenvalue problem

Local Reynolds number and thresholds of transition in shear flows

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Science China(Physics,Mechanics & Astronomy) 2013年第2期56卷 263-269页

作者： TAO JianJun CHEN ShiYi su weidong SKLTCS and CAPT Department of Mechanics and Aerospace EngineeringCollege of EngineeringPeking University

Recent experimental and numerical investigations reveal that the onset of turbulence in plane-Poiseuille flow and planeCouette flow has some similar stages separated with different threshold Reynolds *** on these observations and the energy equation of a disturbed fluid element,a local Reynolds number Re L is derived to represent the maximum ratio of the energy supplement to the energy dissipation in a cross *** is shown that along the sequence of transition stages,which include transient localized turbulence,"equilibrium" localized turbulence,spatially intermittent but temporally persistent turbulence and uniform turbulence,the corresponding thresholds of Re L for plane-Couette flow,Hagen-Poiseuille flow and plane-Poiseuille flow are consistent,indicating that the critical(threshold) states during the laminar-turbulent transition are determined by the local properties of the base flow and are independent of global features,such as flow geometries(pipe or channel) and types of driving forces(shear driving or pressure driving).

关键词： shear flow transition localized turbulence

SIMULATION AND ANALYSIS OF WAVE GROUPS IN A WAVE FLUME

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China Ocean Engineering 1989年第4期4卷 411-420页

作者： Yang, Zhengji Zuo, Qihua su, weidong Nanjing Hydraulic Research Inst China

Using the trial-error method, for a given wave spectrum, wave trains with different wave groupness, which is defined by the groupness factor GF have been simulated in a flume. The statistic characteristics are analyze... 详细信息

关键词： Data Processing Data Reduction and Analysis Probability

On the governing equations for the compressing process and its coupling with other processes

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Science China(Physics,Mechanics & Astronomy) 2011年第6期54卷 1154-1167页

作者： MAO Feng SHI YiPeng XUAN LiJun su weidong WU JieZhi State Key Laboratory for Turbulence and Complex Systems College of EngineeringPeking UniversityBeijing 100871China University of Tennessee Space Institute TullahomaTN 37388USA

As a continuation of a recent linear analysis by Mao et al.(Acta Mech Sin,2010,26:355),in this paper we propose a general theoretical formulation for the compressing process in complex Newtonian fluid flows,which covers gas dynamics,aeroacoustics,nonlinear thermoviscous acoustics,viscous shock layer,etc.,as its special *** principle on which our formulation is based is the maximally natural and dynamic Helmholtz decomposition of the Navier-Stokes equation,along with the kinematic Helmholtz decomposition of the velocity *** central results are the new dilatation equation and velocity-potential equation,which are the counterparts of vorticity transport equation and vector stream-function equation for the shearing process,*** couplings of the compressing process with shearing and thermal processes,including its physical sources,are carefully *** the possible applications and influences of the new formulation are yet to be explored,our preliminary discussion on the pros and cons of previous formulations pertain to acoustic analogy and that on the process splitting and coupling in highly compressible turbulence indicates that at least the formulation can serve as a new frame of reference by which one may gain some additional insight and thereby develop new approaches to the multi-process complex flow problems.

关键词： longitudinal (compressing) process transversal (shearing) process Helmholtz decomposition aeroacoustics compressible turbulence

MULTI-DIRECTIONAL WAVE suPERPOSITION OF WAVE DIFFRACTION

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China Ocean Engineering 1989年第2期4卷 165-175页

作者： Lou, Hongen Wang, Yongjun su, weidong Wang, Hong Nanjing Hydraulic Research Inst China

Characteristics of a natural wave cannot be successfully described by only using wave frequency spectra. In the laboratory, natural wave conditions cannot be simulated exactly by a harbor sheltering experiment with irregular long-crested waves, especially since the results of diffraction tests with reflection source are often inaccurate. Only a small number of laboratories in the world have possessed a directional spectrum wave producer because of its complication and expension. This paper describes the experiment for multi-directional wave superposition of wave diffraction, with the conventional regular wave producer and one-direction irregular wave producer. The test results are of equal value with that from a directional spectra wave. This method is suitable for rational design of harbor engineering projects and can be adopted in future practice.

关键词： Ports and Harbors Wave Effects

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深层煤岩气二氧化碳泡沫压裂压后评价方法

钻采工艺 2024年第3期47卷 97-101页

作者：陈海涌苏伟东武月荣徐洋王筱箐王历历中国石油长庆油田公司工程技术部中国石油川庆钻探工程有限公司钻采工程技术研究院低渗透油气田勘探开发国家工程实验室中国石油长庆油田公司油气工艺研究院

为了评价CO_(2)泡沫压裂对深层煤岩气的适用性及分析深层煤的压裂地质特征,文章以鄂尔多斯盆地深层煤岩气水平井X1井的CO_(2)泡沫压裂作业为例,通过采用压裂停泵压降速率分析、G函数压降曲线分析及压裂注入沿程管路摩阻分析等压力诊断方... 详细信息

为了评价CO_(2)泡沫压裂对深层煤岩气的适用性及分析深层煤的压裂地质特征,文章以鄂尔多斯盆地深层煤岩气水平井X1井的CO_(2)泡沫压裂作业为例,通过采用压裂停泵压降速率分析、G函数压降曲线分析及压裂注入沿程管路摩阻分析等压力诊断方法,评价了X1井的压裂地质特征、裂缝扩展特征及压裂液类型对压后效果的影响。研究结果表明:鄂尔多斯盆地的深部煤岩具有较好的渗透性;CO_(2)压泡沫压裂工艺能够满足鄂尔多斯盆地深层煤岩气水平井的压裂作业需要,增能助排优势突出,压后增产效果明显;与胍胶压裂液相比,CO_(2)泡沫压裂液改造后的停泵压降速率更快、渗透性更好;通过提高单簇进液强度、提高压裂的裂缝内压力能够改善地层的渗透性。此外,与砂岩相比,煤岩CO_(2)泡沫压后的CO_(2)喷势小、气体浓度低,见到了CO_(2)在地层中被吸附的预期。本研究可为深层煤岩气的压裂工艺优选及压裂参数优化提供经验及建议。

关键词：深部煤岩气 CO_(2)泡沫压裂压力诊断压后评价

Chaotic Phenomena Produced by the Spherical Vortices in the Beltrami Flows

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Chinese Physics Letters 1992年第10期9卷 515-518页

作者： SHI Changchun HUANG Yongnian ZHU Zhaoxuan su weidong DONG Yufei Department of Mechanics Peking UniversityBeijing 100871

We find a special type of Beltrami flows which has chaotic trajectories confined within a sphere or between two concentric spherical *** also find there exists the structure of chaotic manifold made from double-torus ... 详细信息

关键词： chaotic Beltrami shells

Effectiveness of hospital disinfection and experience learnt from 11 years of surveillance

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The Journal of Biomedical Research 2019年第6期33卷 408-413页

作者： Chun’ai Tao Yongxin Gan weidong su Zhutian Li Xiaolan Tang Center for Disease Prevention and Control of Guangxi Zhuang Autonomous Region

This survey was designed to assess the sanitation status of hospitals and the compliance of hospital staff to disinfection strategies within the past 11 years.A total of 199 provincial affiliated tertiary or secondary public hospitals from 2007 to 2017 were investigated and seven critical categories,namely indoor air,work surface,hand hygiene,ultraviolet(UV) irradiation intensity,use of disinfectants,sterilization of medical items,and effects of steam sterilizer,were *** average qualified rates were(94.74±3.54)%(810/855),(97.25±1.65)%(1 876/1 929),(87.57±4.60)%(2 508/2 864),(95.00±4.50)%(1 196/1 259),and(98.76±1.14)%(1 599/1 619) for indoor air,work surface,hand hygiene,UV irradiation intensity,and sterilization of medical items,*** terms of other categories,a few samples were not qualified:3/1 575 for use of disinfectants and 1/243 for effects of steam *** hospital disinfection monitoring and supervision program effectively improved the effectiveness of *** monitoring and supervision must be conducted to ensure a safe hospital treatment environment.

关键词： hospital disinfection indoor air hand hygiene work surface ultraviolet irradiation intensity surveillance program

2020—2023年不同等级医院医务人员手卫生和物体表面消毒质量的监测分析

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中国国境卫生检疫杂志 2024年第1期47卷 48-51页

作者：陶春爱甘永新卢桂宁苏伟东唐小兰广西壮族自治区疾病预防控制中心广西南宁530028

目的了解不同等级医院医务人员手卫生和物体表面消毒质量状况,为加强医院消毒质量控制提供依据。方法选择南宁市有代表性的三级、二级和一级医院各1家作为哨点医院,采集医务人员手及物体表面样品,检测菌落总数,评价消毒质量。结果2020—... 详细信息

目的了解不同等级医院医务人员手卫生和物体表面消毒质量状况,为加强医院消毒质量控制提供依据。方法选择南宁市有代表性的三级、二级和一级医院各1家作为哨点医院,采集医务人员手及物体表面样品,检测菌落总数,评价消毒质量。结果2020—2023年共采集医务人员手卫生消毒样品206份,合格133份,总合格率64.56%。三级医院的合格率为65.38%(51/78),二级医院为77.33%(58/75),一级医院为45.28%(24/53)。外科手消毒和卫生手消毒的样品合格率分别为100.00%(50/50)和53.21%(83/156),护理人员的卫生手消毒合格率(59.21%)高于医生的手卫生合格率(47.50%)。共采集物体表面消毒样品302份,合格率96.69%(292/302),不合格样品主要为诊疗仪器设备表面和门诊诊疗区物体表面。结论哨点医院物体表面消毒质量较好,医务人员手卫生合格率偏低,需提高医务人员的手卫生行为和质量水平,降低交叉感染的风险。

关键词：医院感染医院消毒手卫生物体表面