Numerical and experimental study on the falling film flow characteristics with the effect of co-current gas flow in hydrogen liquefaction process

Liquid hydrogen storage and transportation is an effective method for large-scale transportation and utilization of hydrogen energy. Revealing the flow mechanism of cryogenic working fluid is the key to optimize heat exchanger structure and hydrogen liquefaction process(LH2). The methods of cryogenic visualization experiment, theoretical analysis and numerical simulation are conducted to study the falling film flow characteristics with the effect of co-current gas flow in LH2spiral wound heat exchanger.The results show that the flow rate of mixed refrigerant has a great influence on liquid film spreading process, falling film flow pattern and heat transfer performance. The liquid film of LH2mixed refrigerant with column flow pattern can not uniformly and completely cover the tube wall surface. As liquid flow rate increases, the falling film flow pattern evolves into sheet-column flow and sheet flow, and liquid film completely covers the surface of tube wall. With the increase of shear effect of gas-phase mixed refrigerant in the same direction, the liquid film gradually becomes unstable, and the flow pattern eventually evolves into a mist flow.

Numerical Investigations on Harbor Oscillations Induced by Falling Objects

In this paper,the open-sourced computational fluid dynamics software,OpenFOAM~?,is used to study the fluctuation phenomenon of the water body inside a horizontally one-dimensional enclosed harbor basin with constant water depth triggered by falling wedges with various horizontal falling positions,initial falling velocities and masses.Based on both Fourier transfo rm analysis and wavelet spectrum analysis for the time series of the free surface elevations inside the harbor basin,it is found for the first time that the wedge falling inside the harbor can directly trigger harbor resonance.The influences of the three factors(including the horizontal falling position,the initial falling velocity,and the mass)on the response amplitudes of the lowest three resonant modes are also investigated.The results show that when the wedge falls on one of the nodal points of a resonant mode,the mode would be remarkably suppressed.Conversely,when the wedge falls on one of the anti-nodal points of a resonant mode,the mode would be evidently triggered.The initial falling velocity of the wedge mainly has a remarkable effect on the response amplitude of the most significant mode,and the latter shows a gradual increase trend with the increase of the former.While for the other two less significant modes,their response amplitudes fluctuate around certain constant values as the initial falling velocity rises.In general,the response amplitudes of all the lowest three modes are shown to gradually increase with the mass of the wedge.

Influencing factors of fear of falling among glaucoma patients in west China:a cross-sectional study

AIM:To investigate the current situation and influencing factors of fear of falling in glaucoma patients in western China.METHODS:In this cross-sectional study,glaucoma patients treated in the Ophthalmology Department of West China Hospital of Sichuan University were conducted to investigate the demographic data,visual acuity,visual field,activities of daily living,risk of falling,fear of falling and psychological states.Generalized linear model was used for multivariate analysis with fear of falling as dependent variable and other factors as independent variables.RESULTS:The mean score of the Chinese version modified Fall Efficacy Scale(MFES)was 7.52±2.09 points.Univariate analysis and multivariate analysis showed that the history of falls within one year,visual acuity,visual field,risk of falling,activities of daily living and psychological states had statistically difference on fear of falling(P<0.05).CONCLUSION:Glaucoma patients in west China have relatively high risk of fear of falling.History of falling within 1y,severe visual function impairment,high risk of falling,incapable of independence of daily living,and abnormal psychological state are risk factors of fear of falling among glaucoma patients.

Fish Swimming amid Falling Flowers中的中国绘画元素

中国传统文化传播深刻影响了欧美诗人的诗歌创作,如霍华德·奈莫洛夫受中国传统绘画《落花游鱼图》的影响创作了美国现代诗歌Fish Swimming amid Falling Flowers。霍华德·奈莫洛夫受中国传统绘画的影响主要体现在诗歌创作中对物象移用、意境营造、重返自然、诗意栖居、万物相融、和谐共存的哲思。

Falling Tree or Fallen Tree?

《英语辅导报》2000-2001学年度第14期(高二版),7—9单元阶段验收题,笔试部分Ⅱ课本要点A)单项选择题,第9小题: The roof was badlydamaged by a——tree inthe great storm last night. A.fall B.fallen C.fallingD.failed 原参考答案为:B 到底是falling tree还是fallen tree?我们先来分析一下现在分词与过去分词作定语时之语意表达功能: 1.现在分词作定语现在分词作定语从其语意功能看:a)

Residence time distribution of high viscosity fluids falling film flow down outside of industrial-scale vertical wavy wall: Experimental investigation and CFD prediction

The flow behavior of gravity-driven falling film of non-conductive high viscosity polymer fluids on an industrial-scale vertical wavy wall was investigated in terms of film thickness and residence time distribution by numerical simulation and experiment.Falling film flow of high viscosity fluids was found to be steady on a vertical wavy wall in the presence of the large film thickness.The comparison between numerical simulation and experiment for the film thickness both in crest and trough of wavy wall showed good agreement.The simulation results of average residence time of falling film flow with different viscous fluids were also consistent with the experimental results.This work provides the initial insights of how to evaluate and optimize the falling film flow system of polymer fluid.

Viscous falling film instability around a vertical moving cylinder

The present work discusses both the linear and nonlinear stability conditions of a viscous falling film down the outer surface of a solid vertical cylinder which moves in the direction of its axis with a constant velocity. After studying the linear conditions, a generalized nonlinear kine- matic model is then derived to present the physical system. Applying the boundary conditions, analytical solutions are obtained using the long-wave perturbation method. In the first step, the normal mode method is used to characterize the linear behaviors. In the second step, the nonlinear film flow model is solved by using the method of multiple scales, to obtain Ginzburg-Landau equation. The influence of some physical parameters is discussed in both linear and nonlinear steps of the problem, and the results are displayed in many plots showing the stability criteria in various param- eter planes.

Homing Guidance Law with Falling Angle and Flying Time Control

In this paper,a new homing guidance method is used to control the flying time and falling angle for guided missiles. Through this approach,it finds the approximate solution to the quadratic equation of time-togo,which is used for the formula derivation of the flying time control command. In this guidance law design,the acceleration rate control command is adopted. The guidance law is composed of a PN guidance command and a flying time control command. Firstly,it obtains a desired falling angle with accurate guidance. Secondly,it introduces to satisfy the constraint of flying time. The flying time control requires an assumption on the future evolution of missile,which is called time-to-go. To cope with the time-varying speed of missiles,a method of compensating the estimation of time-to-go is presented. The new guidance law is evaluated by using a simulation of typical terminal guidance for rocket-propelled torpedo. The simulation results show that the guidance achieves excellent control performance and exhibits insensitivity to initial trajectory parameter over a widen flight envelope.

Numerical study on falling film flowing characteristics of R113 inside vertical tube under different structural conditions

To develop an appropriate falling film evaporation device for organic fluid cogeneration, a numerical study on the gas–liquid two-phase counter-current flow characteristics of R113 inside a vertical tube under different structural conditions was conducted using the Fluent software. The effects of the tube length, tube diameter, and annular gap on the falling film flow characteristics were determined, respectively. The results indicated that under a certain spray density, the falling film thickness in the region of the steady section was almost constant with different structural parameters for the tube diameter, tube length, and annular gap. In addition, a smaller tube diameter resulted in a steadier film flow. When the tube diameter decreased to a specific value, the film thickness showed a uniform distribution along the wall surface. This indicated that a best falling tube diameter exists. Meanwhile, the film fluctuation was enhanced with an increase in the tube length. When the tube length was greater than 1.2 m, the falling film splashed and could not completely wet the wall surface. The film fluctuation was enhanced by decreasing the annular gap, and the film could not be formed when the annular gap was smaller than 1.2 mm.

Simulation of the hydrodynamics and mass transfer in a falling film wavy microchannel

The flow in a liquid falling film is predominantly laminar,and the liquid-side mass transfer is limited by molecular diffusion.The effective way to enhance the mass transfer is to improve the liquid film flow behavior.The falling film behaviors of water,ethanol and ethylene glycol in nine different wavy microchannels were simulated by Computational Fluid Dynamics.The simulation results show that the falling film thickness exhibits a waveform distribution resulting in a resonance phenomenon along the wavy microchannel.The fluctuation of liquid film surface increases the gas-liquid interface area,and the internal eddy flow inside the liquid film also improves the turbulence of liquid film,the gas-liquid mass transfer in falling film microchannels is intensified.Compared with flat microchannel,the CO_(2) absorption efficiency in water in the wavy microchannel is improved over 41%.Prediction models of liquid film amplitude and average liquid film thickness were established respectively.

Effects of ABA Content on the Development of Abscission Zone and Berry Falling After Harvesting of Grapes

The commodity price of grape reduces as berry falling after harvest. It is crucial to prevent grape from berry falling during storage. In this article, the structure change of grape cells in the abscission zone was observed, the ABA content and the activities of cellulase and polygalacturonase （PG） were measured, and the relationship of ABA and berry falling was investigated. The results suggest that cells in the abscission zone grow into a separation layer soon after the grapes are cut off. According to the level of development, we designed 6 grades to sort the different development stages. The grade 3 plays an important role in berry falling. ABA enhances the activities of cellulase and polygalacturonase, and accelerates the decomposition of cellulose and pectin, which determines the level of development of abscission zone and berry falling. If ABA ratio is less than 20 ng g-i flesh weight （FW）, the abscission zone is not developed to the grade 3, and the berry falling is effectively stopped. We treated grape bunches with nine plant growth regulators and two chemicals. The results indicated that 2,3,5-triiodobenzoic acid （TIBA） can （a） inhibit the generation of ABA significantly, （b） inactivate the activities of cellulase and PG, （c） delay the development of the grade 3 of abscission zone, and （d） stop berry falling. Indole acetic acid （IAA）, gibberellic acid （GA3）, naphthalene acetic acid （NAA）, 6-benzylaminopurine （6-BA）, calcium chloride （CaCl2）, and potassium permanganate （KMnO4） caused similar results as TIBA. Chlorocholine chloride （CCC）, dimethyl amino succinamic acid （B9）, chloroethylphosphonic acid （CEPA） and exogenous ABA showed opposite effects.

浅析fault, defeat, falling, flaw, shortcoming

Fault, defeat, falling, flaw, shortcoming,这组词(n．)都指人或物在某方面有缺陷，不够完善，以faulI和defeat为常用。

Heat transfer characteristics of molten plastics in a vertical falling film reactor

The heat transfer efficiency during the pyrolysis process is a key factor to be considered in the design of pyrolysis reactors. In this study, the average apparent heat transfer characteristics of molten plastic pyrolysis in a vertical falling film reactor were explored by experiments and numerical simulation and the apparent heat transfer coefficients were determined. In addition, the temperature distribution and the thickness of the liquid film in the reactor were predicted and the influences of pyrolysis temperatures on the average apparent heat transfer coefficients were discussed.

Numerical simulation of a falling droplet surrounding by air under electric field using VOF method:A CFD study

This is a numerical study of a falling droplet surrounding by air under the electric field modeled with finite volume method by means of CFD.The VOF method has been employed to model the two-phase flow of the present study.Various capillary numbers are investigated to analyze the effects of electric field intensity on the falling droplet deformation.Also,the effects of electric potential on the heat transfer coefficient have been examined.The obtained results showed that by applying the electric field at a capillary number of 0.2 the droplet tends to retain its primitive shape as time goes by,with a subtle deformation to an oblate form.Intensifying the electric field to a capillary number of 0.8 droplet deformation is almost insignificantwith time progressing;however,further enhancement in capillary number to 2 causes the droplet to deform as a prolate shape and higher values of this number intensify the prolate form deformation of the droplet and result in pinch-off phenomenon.Ultimately,it is showed that as the electric potential augments the heat transfer coefficient increases in which for electric potential values higher than 2400 V the heat transfer coefficient enhances significantly.

Research on the falling film flow and heat transfer characteristics of FLNG spiral wound heat exchanger under sea conditions

As the key equipment of floating liquefied natural gas(FLNG)process,the performance of spiral wound heat exchanger(SWHE)influences operation costs and reliability of the whole system.The sea conditions destroy the falling film flow state of the refrigeration and then affect the heat transfer performance of FLNG SWHE.In order to design and optimize the SWHE,a cryogenic experimental device of FLNG process and a numerical model of falling film flow have been constructed to study the effects of sea conditions on the falling film flow and heat transfer characteristics of SWHE.The cryogenic experimental results show that the pitching conditions have larger effects on the heat transfer performance than yawing.Under the pitching angle of 7°,the natural gas temperature and gaseous refrigerant temperature increase by 3.22°C and 7.42°C,respectively.The flow rates of refrigerant and feed natural gas have a great impact on the heat transfer performance of SWHE under pitching and compound sloshing conditions.When the tilt angle increases to 9°,the tube structure with outer diameter D=8 mm and pipe spacing S=4 mm is recommended to reduce the drying area of the pipe wall surface.

Partial Bell Polynomials, Falling and Rising Factorials, Stirling Numbers, and Combinatorial Identities

In the paper,the authors collect,discuss,and find out several connections,equivalences,closed-form formulas,and combinatorial identities concerning partial Bell polynomials,falling factorials,rising factorials,extended binomial coefficients,and the Stirling numbers of the first and second kinds.These results are new,interesting,important,useful,and applicable in combinatorial number theory.

Influence of Proxies on the Reported Frequency of Falls, Fear of Falling and Activity Restriction in Older People

Introduction: In older populations, the help of a third person may be necessary for a certain number of individuals in order to fill in questionnaires. The influence of this assistance on the collected information can raise questions, among others concerning the concordance between the information provided by the persons themselves and by their proxies, or the introduction of a potential bias. Our study’s objective is to examine, among older people, the differences in the reported frequency of falls, fear of falling and activity restriction due to fear of falling, according to the fact that people had filled in a questionnaire with or without the help of a third person. Methods: The data used come from the secondary analysis of a cross-sectional survey using a self-administered questionnaire and conducted in 2006 in a Belgian semi-rural town among non-institutionalised persons aged 65 years and over. Results: Among the 501 questionnaires, 16.4% were filled in with the help of another person. In bivariate analysis, the persons who needed help reported fall history, fear of falling and activity restriction significantly more often. In multivariable analysis, when considering concurrently the covariates (sex, age, living alone and fall history for fear of falling and for activity restriction), the influence of having received help to fill in the survey was only significant for activity restriction. Conclusion: Our study shows that it is important to know whether or not a person has received help to fill in a questionnaire. This can actually influence the reported frequency of certain outcomes, even, for activity restriction, when considering simultaneously the effect of other covariates. Given the current and future ageing of our populations, it seems that more extensive exploration is needed of the influence of proxies on the collected information about falls, fear of falling and activity restriction among older people.

Physical Activation of Elderly and the Decrease of Falling Risk

A Physical Activation Program was designed and implemented with a particular emphasis in recovering of motor independence, and in an indirect manner;the increase of activities was carried out in a social context in such a way that it allowed isolated elderly to develop their ability to perform daily activities diminishing the burden on their caregivers. 30 people were randomly selected: 15 subjects in the experimental group and 15 in the control group;7 women and 8 men each group. Subjects aged between 60 - 84 years with a mean age of 78 years and a standard deviation of 6.5 were applied in a three-month Physical Activation Program with a 45-min daily sessions. Results obtained showed that physical activity in elderly, systematically improved their amplitude and joint mobility which impact directly and indirectly their quality of life, reducing their risk of falling.

Developed Numerical Simulation of Falling and Moving Objects in Viscous Fluids under the Action of a Reynolds Lubrication Theory and Low Reynolds Numbers

The development work focuses on the numerical simulations of free body movement in viscous fluid. The aim is to make the simulation of very slow motion of the small body in viscous fluid. We developed bodies’ immersed dynamics simulations in viscous fluid by seeking numerical solutions for appropriate field variables. We developed the methods for vertically and spherically cylindrical objects’ motions, the forces on bodies close to a plane stationary wall are computed from the velocity and pressure fields using the Stokes equation through COMSOL Multiphysics finite element software. The Navier-Stokes equation is reduced to Stokes equation there is independence of time which means object will have an effect only on the motion and the slightly compressible flow assumption is made in order to obtain smooth solution numerically. The forces on an object in slightly compressible Stokes flow have been exerted on the falling objects. The resulting forces have compared with analytical results from the Reynolds Lubrication Theory, and achieved significant results from the development method in Matlab and achieved significant numerical simulations in COMSOL. In addition, an investigation has been made to an object swimming at low Reynolds number. At low Reynolds number moving is possible when object scale is small and flow pattern is slow and sticky. We have developed a system for a thin two-dimensional (2D) worm-like object wiggle that is passing a wave along its centreline and its motion has simulated by the Ordinary Differential Equations (ODE) system and by the Arbitrary Lagrangian-Eulerian (ALE) moving mesh technology. The development method result shows that it is possible for the small object to have a motion from one position to another through small amplitudes and wavelengths in viscous fluid.

Slight free falling impact test for assessing guava maturity

A non-destructive method for assessing the maturity of guava was developed based on the mechanical properties of the fruit under the slight falling impact test. The levels of maturity were classified with cluster and discriminant analyses on the primitive impact measurements and their derivatives. The accuracy of classification was improved with linear discriminant analysis and the number of indices being processed was reduced with stepwise regression analysis. The accuracy of classification is 84.21%. The performance shows that slight falling impact together with linear discriminant analysis provides a promising non-destructive approach in assessing the maturity of guavas.