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A model for the mean velocity of debris flow movement based on the minimum energy dissipation principle

Journal of Mountain Science 2024年第12期21卷 3961-3970页

作者： LI Xiangning CHEN Jiangang CHEN Xiaoqing ZHAO Wanyu CHEN Huayong ZHANG Shaoxiong Key Laboratory of Mountain Hazards and Earth Surface Process Institute of Mountain Hazards and EnvironmentChinese Academy of Sciences(CAS)Chengdu 610041China University of Chinese Academy Sciences Beijing 100049China Shijiazhuang Tiedao University Shijiazhuang 050043China

The geomorphic minimum energy dissipation principle is important in the development of gully evolutionary *** impact of debris flows on channels during movement also adheres to this theory.A minimum energy dissipation model for debris flows has been obtained from previous studies,which is derived from the flow rules of runoff along a channel under rainfall or ice-snow meltwater ***,the lack of consideration for erosion characteristics has hindered a comprehensive understanding of the movement characteristics of debris *** this paper,the phenomenon of volume increase resulting from the entrainment along debris flow movement is considered in order to derive a model for the mean velocity,reflecting the minimum energy dissipation *** entire expression of the mean velocity model is determined through 38 typical glacial and rainstorm debris flow *** evaluate the reliability of the proposed model,we employed 164 monitoring data from 1995 to 2000 in the Jiangjia gully,Yunnan,*** results show that the velocity calculated by the proposed model are highly correlated with those obtained from the monitoring ***,a comparison is made between the mean velocities calculated by the proposed model and those obtained from previous studies,highlighting the exceptional applicability of the proposed *** study will contribute to reveal the movement laws of debris flow along the channel.

关键词： Debris flow Minimum energy dissipation principle Longitudinal profile evolution mean velocity

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Slowing down critical transitions via Gaussian white noise and periodic force

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Science China(Technological Sciences) 2019年第12期62卷 2144-2152页

作者： MA JinZhong XU Yong XU Wei LI YongGe KURTHS Jirge Department of Applied Mathematics Northwestern Polytechnical UniversityXi'an 710072China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical UniversiyXi'an 710072China Center for Mathematical Sciences&School of Mathematics and Statistics Huazhong University of Science and TechmologyWuhan 430074China Potsdam Institute for Climate Impact Research Potsdam 14412Germany Department of Physics Humboldt UniversityBerlin 12489Germany

Stochastic perturbations and periodic excitations are generally regarded as sources to induce critical transitions in complex systems. However, we find that they are also able to slow down an imminent critical transition. To illustrate this phenomenon, a periodically driven bistable eutrophication model with Gaussian white noise is introduced as a prototype class of real *** residence probability(RP) is presented to measure the possibility that the given system stays in the oligotrophic state versus Gaussian white noise and periodic force. Variations in the mean first passage time(MFPT) and the mean velocity(MV) of the first right-crossing process are also calculated respectively. We show that the frequency of the periodic force can increase the MFPT while reduce the MV under different control parameters. Nevertheless, the noise intensity or the amplitude may result in an increase of the RP only in the case of control parameters approaching the critical values. Furthermore, for an impending critical transition, an increase of the RP appears with the interaction between the amplitude and noise intensity or the combination of the noise intensity and frequency, while the interaction of the frequency and amplitude leads to an extension of the MFPT or a decrease of the MV. As a result, an increase of the RP and MFPT, and a decrease of the MVobtained from our results claim that it is possible to slow down an imminent critical transition via Gaussian white noise and periodic force.

关键词： critical transition slowing down bistable eutrophication model Gaussian white noise periodic force residence probability mean first passage time mean velocity

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Experiment on the Effect of Sediment Concentration on Flow Structure

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四川大学学报（工程科学版） 2005年第S1期37卷 41-45页

作者： Chen, Li Wu, Menwu Deng, Xiaoli Huang, Rongmin Lab. of Water Resources and Hydropower Eng. Sci. Wuhan Univ. Wuhan 430072 China

The paper studies on the sediment-laden flow by using *** calibration has been conducted to determine the relationship between backscattered signal strength and sediment concentration. Based on the experimental data,the interactions between sediment and fluid in open channel flow are investi- *** experiment shows that there exist inner relation between sediment concentration and turbulence, and the relationship is distinctry related to the diameter of particle as well as the flow co...

关键词： turbulence intensity mean velocity sediment concentration flow structure

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Experimental study of debris flow caused by domino failures of landslide dams

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International Journal of Sediment Research 2014年第3期29卷 414-422页

作者： Hua-Yong CHEN Peng CUI Gordon G.D.ZHOU Xing-Hua ZHU Jin-Bo TANG Key Laboratory of Mountain Hazards and Earth Surface Process CAS Institute of Mountain Hazards and Environment CAS

The formation of landslide dams is often induced by earthquakes in mountainous *** failure of a landslide dam typically results in catastrophic flash floods or debris flows *** attention has been given to the processes and mechanisms involved in the failure of individual landslide ***,the processes leading to domino failures of multiple landslide dams remain *** this study,experimental tests were carried out to investigate the domino failure of landslide dams and the consequent enlargement of downstream debris *** blockage conditions were considered,including complete blockage,partial blockage and erodible bed(no blockage).The mean velocity of the flow front was estimated by *** stress transducers(TSTs)and Laser range finders(LRFs) were employed to measure the total stress and the depth of the flow front,*** a complete blockage pattern,a portion of the debris flow was trapped in front of each retained landslide dam before the latter collapsed *** was accompanied by a dramatic decrease in the mean velocity of the flow ***,under both partial blockage and erodible bed conditions,the mean velocity of the flow front increased gradually downward along the sloping *** failures of the landslide dams were triggered when a series of dams(complete blockage and partial blockage) were distributed along the ***,not all of these domino failures led to enlarged debris *** modes of dam failures have significant impacts on the enlargement of debris ***,further research is necessary to understand the mechanisms of domino failures of landslide dams and their effects on the enlargement of debris flows.

关键词： Debris flow Landslide dams Domino failures Enlargement of debris flow mean velocity

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Characterization on the hydrodynamics of a covering-plate Rushton impeller

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Chinese Journal of Chemical Engineering 2018年第6期26卷 1392-1400页

作者： Tenglong Su Fengling Yang Meiting Li Kanghui Wu School of Mechanical Engineering Shandong University Key Laboratory of High Efficiency and Clean Mechanical Manufacture(Shandong University) Ministry of EducationShandong University

A modified Rushton impeller with two circular covering-plates mounted on the upper and lower sides of the blades was *** are gaps between the plates and the *** turbulent hydrodynamics was analyzed by the computational fluid dynamics(CFD) ***,the reliability of the numerical model and simulation method was verified by comparing with the experimental results from ***,the power consumption,flow pattern,mean velocity and mixing time of the covering-plate Rushton impeller(RT-C) were studied and compared with the standard Rushton impeller(RT) operated under the same *** show that the power consumption can be decreased about 18%.Compared with the almost unchanged flow field in the lower stirred tank,the mean velocity was increased at the upper half of the stirred *** in the impeller region,the mean axial and radial velocities were increased,the mean tangential velocity was *** addition,the average mixing time of RT-C was shortened about 4.14% than the counterpart of *** conclusions obtained here indicated that RT-C has a more effective mixing performance and it can be used as an alternative of RT in the process industries.

关键词： Covering-plate Rushton impeller(RT-C) Power consumption Flow pattern mean velocity Mixing time Computational fluid dynamics(CFD)

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Feasibility of the 2-point method to determine the load-velocity relationship variables during the countermovement jump exercise

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Journal of Sport and Health Science 2023年第4期12卷 544-552,F0003页

作者： Alejandro Pérez-Castilla Rodrigo Ramirez-Campillo John F.T.Fernandes Amador García-Ramos Department of Physical Education and Sport Faculty of Sport SciencesUniversity of GranadaGranada 18011Spain Human Performance Laboratory Department of Physical Activity SciencesUniversidad de Los LagosSantiago 5170000Chile Centro de Investigacion en Fisiologıa del Ejercicio Facultad de CienciasUniversidad MayorSantiago 8580745Chile Higher Education Sport Hartpury UniversityHartpury GL193BEUK Department of Sports Sciences and Physical Conditioning Faculty of EducationUniversidad Catolica de la Santısima ConcepcionConcepcion 4090541Chile

Purpose:This study aimed to examine the reliability and validity of load-velocity(L-V)relationship variables obtained through the 2-point method using different load combinations and velocity ***:Twenty men performed 2 identical sessions consisting of 2 countermovement jumps against 4 external loads(20 kg,40 kg,60 kg,and80 kg)and a heavy squat against a load linked to a mean velocity(MV)of 0.55 m/s(load_(0.55)).The L-V relationship variables(load-axis intercept(L_(0)),velocity-axis intercept(v_(0)),and area under the L-V relationship line(A_(line)))were obtained using 3 velocity variables(MV,mean propulsive velocity(MPV),and peak velocity)by the multiple-point method including(20-40-60-80-load_(0.55))and excluding(20-40-60-80)the heavy squat,as well as from their respective 2-point methods(20-load_(0.55)and 20-80).Results:The L-V relationship variables were obtained with an acceptable reliability(coefncient of variation(CV)≤7.30%;intra-class correlation coefficient>0.63).The reliability of L_(0)and v_(0)was comparable for both methods(CV_(ratio)(calculated as higher value/lower value):1.11-1.12),but the multiple-point method provided Al_(ine)with a greater reliability(CV_(ratio)=1.26).The use of a heavy squat provided the L-V relationship variables with a comparable or higher reliability than the use of a heavy countermovement jump load(CV_(ratio):1.06-1.19).The peak velocity provided the load-velocity relationship variables with the greatest reliability(CV_(ratio):1.15-1.86)followed by the MV(CV_(ratio):1.07-1.18),and finally the *** 2-point methods only revealed an acceptable validity for the MV and MPV(effect size≤0.19;Pearson s product-moment correlation coefficient≥0.96;Lin's concordance correlation coefficient≥0.94).Conclusion:The 2-point method obtained from a heavy squat load and MV or MPV is a quick,safe,and reliable procedure to evaluate the lower-body maximal neuromuscular capacities through the L-V relationship.

关键词： Force-velocity relationship mean velocity Multiple-point method Peak velocity velocity-based training

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Perturbation analysis for pulsatile flow of Carreau fluid through tapered stenotic arteries

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International Journal of Biomathematics 2016年第4期9卷 259-283页

作者： D. S. Sankar Engineering Mathematics UnitFaculty of Engineering Universiti Teknologi Brunei Gadong BEI~IO Brunei Darussalam

The pulsatile flow of blood in a tapered narrow artery with overlapping time-dependent stenosis is mathematically analyzed, modeling blood as Caxreau fluid. Perturbation method is employed for solving the resulting nonlinear system of equations along with the appropriate boundary conditions. The analytic solutions to the pressure gradient, velocity distribution, flow rate, wall shear stress and longitudinal impedance to flow axe obtained in the asymptotic form. The variation of the aforesaid flow quantities with respect to various physical parameters such as maximum depth of the stenosis, angle of tapering of the artery, power law index, Reynolds number, pulsatile amplitude of the flow and Weissenberg number is investigated. It is found that the wall shear stress and longitudinal impedance to flow increase with the increase of the angle of tapering of the artery, the maximum depth of the stenosis and pulsatile Reynolds number and these decrease with the increase of the amplitude of the flow, power law index and Weis- senberg number. The mean velocity of blood decreases significantly with the increase of the artery radius, maximum depth of the stenosis, angle of tapering of the artery.

关键词： Pulsatile flow Carreau fluid overlapping stenosis mean velocity longitudinalimpedance to flow.

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Incorporating boundary constraints to predict mean velocities in turbulent channel flow

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Science China(Physics,Mechanics & Astronomy) 2012年第9期55卷 1691-1695页

作者： WU You CHEN Xi SHE ZhenSu HUSSAIN Fazle State Key Laboratory for Turbulence and Complex Systems and Department of Mechanics College of Engineering Peking University Beijing 100871 China Department of Mechanical Engineering University of Houston Houston TX 77204-4006 USA

We derive exact near-wall and centerline constraints and apply them to improve a recently proposed LPR model for finite Reynolds number(Re) turbulent channel *** analysis defines two constants which are invariant with Re and suggests two more layers for incorporating boundary effects in the prediction of the mean velocity profile in the turbulent *** results provide corrections for the LPR mixing length model and incorrect predictions near the wall and the ***,we show that the analysis,together with a set of well-defined sensitive indicators,is useful for assessment of numerical simulation data.

关键词： turbulence channel flow mean velocity asymptotic analysis

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Forest Canopy Flow Analysis Using Turbulence Model with Source/Sink Terms

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Journal of Donghua University(English Edition) 2015年第4期32卷 588-593页

作者：杨会付海明 College of Environmental Science and Engineering Donghua University

A computational fluid dynamics( CFD) model was presented to simulate wind flow over a forest canopy for analyzing the wind flow within and above forest canopies. Unlike previous studies on the canopy flow,the effect of canopy contour on the canopy was considered to develop the simulation method into a more general but complex case of wind flow over a forest canopy,using cedrus deodara and cinnamomum camphora. The desire of this work is mainly motivated to provide a rational way for predicting the wind flow within and above vegetation canopies. The model of canopy is not incorporated in the geometrical model,and it uses a porous domain combined with k-ε two-equation turbulence model with source / sink terms. The objectives of this paper are to analyze the contour of pressure and velocity and compare the simulation results with other works and field measurements. Results are encouraging,as the model profiles of mean velocity( u) qualitatively agree well with other works compared with and quantitatively have similar explanations as several authors. In conclusion, it is demonstrated that the adoption turbulence model with source / sink terms for forest canopies is proved to be a physically accurate and numerically robust method. The model and method are recommended for future use in simulating turbulent flows in forest canopies.

关键词： k-ε source / sink terms mean velocity forest canopy

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Investigation on Eccentric Agitation in the Stirred Vessel Using 3D-Laser Doppler Velocimeter

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Chinese Journal of Chemical Engineering 2006年第5期14卷 618-625页

作者：王波张捷宇贺友多安胜利 Material and Metallurgical School Inner Mongolia University of Science & Technology School of Materials Science and Engineering Shanghai University

The spatial structure of the velocity field in a stirred vessel with water has been measured and analyzed using the laser Doppler velocimeter technique, with the immersing depth and agitation speed of the impeller re-maining approximately constant. The experimental results were provided such as the mean velocity field, fluctuat-ing velocities, turbulent kinetic energy, Reynolds shear stress and time series of the velocity in the stirred tank. These results probably provided the valuable basis to further optimize and enlarge the stirred tank in the industrial process.

关键词： stirred vessel laser Doppler velocimeter eccentric agitation mean velocity

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