Siphon Phenomenon Research Articles

Coupling effect of nano-tribology and biomechanics based on siphon phenomenon

Coupling effect of nano-tribology and biomechanics based on siphon phenomenon

Analysis of Economic Development in Urban Agglomerations by High-Speed Rail Network: Taking Beijing-Tianjin-Hebei City Cluster as an Example

With the increasing impact of the opening of high-speed railway on the inner city, many indicators within the city have changed significantly, which plays an important role in the impact of the city's economy. Therefore, this paper explores how the high-speed railway network affects intra-city economic development based on the changes in three indicators of city size, per capita disposable income of residents and the structure of the three industries, as reflected by the population flow in the Beijing-Tianjin-Hebei city cluster. It is found that the opening of high-speed railway has led to a "siphon phenomenon" in the Beijing-Tianjin-Hebei urban agglomeration, which has both advantages and disadvantages for the development of large cities and small and medium-sized cities; it has a positive effect on the increase of disposable income of the residents; and it also has a positive effect on the development of tertiary industry.

A siphon-based spatial evaporation device for efficient salt-free interfacial steam generation

Solar-driven interfacial evaporation is an emerging alternative for alleviating the water crisis due to its sustainability and eco-friendly, but it still required efficient strategies to address the major obstacle of salt accumulation during high-rate evaporation processes. Herein, a spatial solar evaporation device with hydrogel-based evaporator and 3D printing module was fabricated to achieve excellent evaporation performance based on siphon phenomenon, in which carbon nanotubes were used as light absorber and coated on cotton fabrics via polyvinyl alcohol as binder. The 3D evaporator structure captured ambient energy efficiently to accelerate water vaporization. Coupling with the low evaporation enthalpy of intermediate water in PVA-hydrogel matrix, the evaporator exhibited fascinating evaporation rate of 4.55 ± 0.06 kg m−2 h−1 in siphon mode under 1.0 sun, which was ~3.2 times and ~1.8 times higher than the 2D floating and 2.5D hanging mode. Moreover, the design of siphon effect prevented the salt accumulation on the spatial evaporation device. Even for 20.0 wt% brine, there was no salt precipitating on the evaporator surface during a long-term evaporation (8 h), demonstrating the excellent stability and durability. In addition, the concentrated brine can be separated from the feed timely, avoiding the declined evaporation performance from increased feed salinity.

Analysis of the influence of siphon hole spacing on soft-soil drainage effect

In soft-soil siphon drainage, due to the siphon phenomenon, groundwater is discharged from the soil without the need for power and this increases the effective stress in the soil. A significant part of the drainage effect is determined by the spacing of the siphon holes. According to model tests carried out in this work, the decrease in the groundwater level was more pronounced for a smaller siphon hole spacing. Compared with a single-hole test, a spacing of 0.4 m resulted in an improvement of 107.6% in the minimum groundwater level. Based on subsequent numerical simulations it was found that when the hole spacing was 1.0 m, the decrease in the groundwater level on day 60 reached the limit value of 10 m for soft soil with a permeability coefficient of 10−9 m/s. In addition, field tests indicated that the average decrease in the water level for a 0.9 m hole spacing was 75.9% greater than that for 1.8 m, while the time required to reach the same decrease in the water level was 63.6% less.

Viscoelastic Fluid-Inspired Swarm Behavior to Reduce Susceptibility to Local Minima: The Chain Siphon Algorithm

We present a novel distributed robotic swarm algorithm inspired by the open channel siphon phenomenon displayed in certain viscoelastic fluids. Self-siphoning viscoelastic fluids are often able to mitigate the trapping effects of local minima in the environment. Using a similar strategy, our algorithm enables a robot swarm to mitigate the trapping effects of local minima in potential fields. Once a robot senses the goal, local communication between robots is used to propagate path-to-goal gradient information through the swarm's communication graph. This information is used to augment each agent's local potential field, reducing the local minima traps and often eliminating them. We perform hardware experiments using the Georgia Tech Miniature Autonomous Blimp (GT-MAB) aerial robotic platforms as well as Monte Carlo simulations conducted in the Simulating Collaborative Robots in Massive Multi-Agent Game Execution (SCRIMMAGE) simulator. We compare the new method to other potential field based swarm behaviors that both do and do not incorporate local minima fixes. The distributed algorithm generates self-siphoning behavior within the robotic swarm, and this reduces its susceptibility to local minima.

Partial microperforated panel and its acoustic siphon effect

Partial microperforated panel (MPP) structures have been proposed for MPP with low sound absorption properties. Its purpose is to improve the sound absorption performance of the MPP in certain frequency bands. The structure was studied by the transfer matrix method, finite element simulation and experimental test. The results show that the three kinds of curves, that is, theoretical and simulation and experimental curves, are in good agreement. In the parallel structure of partial MPP and the cavity, the MPP structure occupying three-quarters of the total area makes perfect sound absorption at 1076 Hz. The sound absorption peak of the MPP structure which occupies half of the total area is 0.89 at 980 Hz. The theory of calculating the partial MPP, which is accurate for fast prediction of sound absorption peaks, is proposed. The sound absorption performance of the multi-partial MPP structure has also been theoretically verified. The acoustic siphon phenomenon of partial MPP is discussed. On this basis, a multi-Helmholtz resonance structure is designed to achieve high sound absorption effect. The sound absorption coefficient is greater than 0.87 at 488–712 Hz.

Comparison of enhanced geothermal system with water and CO2 as working fluid: A case study in Zhacanggou, Northeastern Tibet, China

In the study, we analyzed the hot dry rock geothermal field of the Guide Basin in Qinghai Province, China. We used T2Well software—a coupled wellbore–reservoir simulator—to build a “wellbore–reservoir” coupled model with a “three-spot” well pattern (one injection and two production wells). We simulated several fixed flow rate cases in which water or CO2 is injected. The objectives of our present work are (1) to investigate the fluid flow and thermal processes of water circulating at well bottoms, wellbores, and wellheads; (2) to identify the changing parameters at all physical fields; (3) to understand the influence of injection rates on heat extraction; and (4) to measure the maximum heat extraction capacity of the Guide area. Water extracts more heat than CO2 at the same flow rate. However, water consumes more pressure in reservoir, and its pressure decreases more quickly as the flow rate increases. In contrast, CO2 is in a sense a better working fluid. CO2 consumes less pressure when it flows and can circulate automatically due to the siphon phenomenon. In this way, a lower injection pressure is required in a higher CO2 flow rate case. The density of CO2 is sensitive to both temperature and pressure and vice versa. Inside a wellbore, such interactions are extremely complicated. When the fluid rate is slow, a system could operate for 30 years and remain stable, and there is only a small decrease in temperature. However, with higher flow rate scenarios—namely 50, 75, and 100 kg/s—the reservoir will exhibit greater heat loss. The reservoir’s production temperature and extraction efficiency will drop dramatically. Therefore, for the Guide area, if a “three-spot” well pattern is used for geothermal extraction either with water or CO2 as the working fluid, the most appropriate flow rate is 50 kg/s.

Study of Siphon Breaker Experiment and Simulation for a Research Reactor.

Under the design conditions of a research reactor, the siphon phenomenon induced by pipe rupture can cause continuous outward flow of water. To prevent this outflow, a control device is required. A siphon breaker is a type of safety device that can be utilized to control the loss of coolant water effectively. To analyze the characteristics of siphon breaking, a real-scale experiment was conducted. From the results of the experiment, it was found that there are several design factors that affect the siphon breaking phenomenon. Therefore, there is a need to develop a theoretical model capable of predicting and analyzing the siphon breaking phenomenon under various design conditions. Using the experimental data, it was possible to formulate a theoretical model that accurately predicts the progress and the result of the siphon breaking phenomenon. The established theoretical model is based on fluid mechanics and incorporates the Chisholm model to analyze two-phase flow. From Bernoulli's equation, the velocity, quantity, undershooting height, water level, pressure, friction coefficient, and factors related to the two-phase flow could be obtained or calculated. Moreover, to utilize the model established in this study, a siphon breaker analysis and design program was developed. The simulation program operates on the theoretical model basis and returns the result as a graph. The user can confirm the possibility of the siphon breaking by checking the shape of the graph. Furthermore, saving the entire simulation result is possible and it can be used as a resource for analyzing the real siphon breaking system. In conclusion, the user can confirm the status of the siphon breaking and design the siphon breaker system using the program developed in this study.

Impact of CO2 injection rate on heat extraction at the HDR geothermal field of Zhacanggou, China

CO2 is now considered as a novel heat transmission fluid to extract geothermal energy. It can achieve the goal of energy exploitation and CO2 geological sequestration. Taking Zhacanggou as research area, a “Three-spot” well pattern (one injection with two production), “wellbore–reservoir” coupled model is built, and a constant injection rate is set up. A fully coupled wellbore–reservoir simulator—T2Well—is introduced to study the flow mechanism of CO2 working as heat transmission fluid, the variance pattern of each physical field, the influence of CO2 injection rate on heat extraction and the potential and sustainability of heat resource in Guide region. The density profile variance resulting from temperature differences of two wells can help the system achieve “self-circulation” by siphon phenomenon, which is more significant in higher injection rate cases. The density of CO2 is under the effect of both pressure and temperature; moreover, it has a counter effect on temperature and pressure. The feedback makes the flow process in wellbore more complex. In low injection rate scenarios, the temperature has a dominating impact on the fluid density, while in high rate scenario, pressure plays a more important role. In most scenarios, it basically keeps stable during 30-year operation. The decline of production temperature is <5 °C. However, for some high injection rate cases (75 and 100 kg/s), due to the heat depletion in reservoir, there is a dramatic decline for production temperature and heat extraction rate. Therefore, a 50-kg/s CO2 injection rate is more suitable for “Three-spot” well pattern in Guide region.

Development of siphon breaker simulation program for investing loss of coolant accident of a research reactor

Under the design conditions of a research reactor, the siphon phenomenon induced by pipe rupture can cause continuous efflux of water. In order to prevent water efflux, an additional facility is necessary. A siphon breaker is a type of safety facility that can resist the loss of coolant effectively. However, analysis of siphon breaking is complex since it comprises two-phase flow and there are many inputs to be considered. For this reason, in order to facilitate the analysis and design of the siphon breaker, a simulation program based on fluid mechanics was developed using MFC (Microsoft Foundation Class) programming. From Bernoulli’s equation, the velocity and quantity as well as undershooting height, water level, pressure, friction coefficient, and factors related to the two-phase flow could be calculated. The Chisholm model, which was included in the program to analyze the two-phase flow, can predict the results in a manner similar to those obtained from a real-scale experiment. By modifying the values of the input parameters and analyzing the results with respect to loss of coolant accident (LOCA) locations, the size of pipe and coefficients could be compared easily. Since simulation results are shown in the form of a graph, the user is able to confirm the total breaking situation. Furthermore, it is possible to save the entire simulation results. The simulation results were shown to be similar to those obtained from the real-scale experiment and the program functioned correctly. By using the program, the user is easily able to confirm the status of the siphon breaking, and the program is also helpful in the design of the siphon breaker.

Theoretical study on loss of coolant accident of a research reactor

Under the design conditions of a research reactor, the siphon phenomenon induced by pipe rupture can cause continuous efflux of water. In order to prevent water efflux, an additional facility is necessary. A siphon breaker is a type of safety facility that can resist the loss of coolant effectively. However, analysis of siphon breaking is complex since it comprises two-phase flow and there are many inputs to be considered. For this reason, we analyzed the experimental results to develop a theoretical model of siphon breaking phenomena. Developed model is based on fluid mechanics and Chisholm model. From Bernoulli’s equation, the velocity and quantity as well as undershooting height, water level, pressure, friction coefficient, and factors related to the two-phase flow could be calculated. The Chisholm model, which is able to analyze the two-phase flow, can predict the results in a manner similar to those obtained from a real-scale experiment, and a general formula using Chisholm coefficient B was proposed in this study. Also, we verified the theoretical model and concluded that it is possible to analyze the siphon breaking. Moreover, the design conditions that can satisfy the safety requirements regarding a loss of coolant accident of research reactors could be found out by using the theoretical model. In conclusion, we propose the theoretical model which can analyze the siphon breaking as real, and it is helpful not only to analyze but also to design the siphon breaker.

Self-driven perfusion culture system using a paper-based double-layered scaffold

Shear stress caused by fluid flow is known to promote tissue development from cells in vivo. Therefore, perfusion cultures have been studied to investigate the mechanisms involved and to fabricate engineered tissues in vitro, particularly those that include blood vessels. Microfluidic devices, which function with fine machinery of chambers and microsyringes for fluid flow and have small culture areas, are conventionally used for perfusion culture. In contrast, we have developed a self-driven perfusion culture system by using a paper-based double-layered scaffold as the fundamental component. Gelatin microfibers were electrospun onto a paper material to prepare the scaffold system, in which the constant perfusion of the medium and the scaffold for cell adhesion/proliferation were functionally divided into a paper and a gelatin microfiber layer, respectively. By applying both the capillary action and siphon phenomenon of the paper-based scaffold, which bridged two medium chambers at different height levels, a self-driven medium flow was achieved and the flow rate was also stable, constant, and quantitatively controllable. Moreover, the culture area was enlargeable to the cm2 scale. The endothelial cells cultivated on this system oriented along the medium-flow direction, suggesting that the shear stress caused by medium flow was effectively applied. This perfusion culture system is expected to be useful for fabricating three-dimensional and large engineered tissues in the future.

사이펀 차단기 시뮬레이션 프로그램의 개발 및 활용

일부 연구용 원자로의 설계조건상 사이펀 현상은 배관 파단 사고 시 수조수의 지속적인 방출을 유발할 수 있다. 사이펀 차단기는 이러한 현상을 효과적으로 제한하기 위한 안전장치로, 유체역학적인 특성상 사이펀 차단 현상 해석을 위해 고려해야 할 변수가 많고 계산이 복잡하다. 이에 사이펀 차단 현상을 쉽게 분석할 수 있는 프로그램을 개발하게 되었다. 윈도우8 운영체제에서 비쥬얼 스튜디오 2012를 이용하여 MFC프로그래밍으로 개발되었으며, 사용자가 쉽게 사용할 수 있도록 GUI형식으로 개발되었다. 개발된 프로그램은 사용자가 입력한 값으로부터 유체역학적 관계식을 통해 3단계의 연산과정을 거쳐 시뮬레이션을 진행한다. 베르누이 방정식으로부터 유속과 유량을 구하여 수위, 언더슈팅, 압력, 손실계수, 그리고 이상 유동과 관계된 값들을 연산한다. 프로그램에 적용된 이상유동 해석모델은 Chisholm 모델이며, 실제와 유사하게 시뮬레이션이 가능함을 확인하였다. 시뮬레이션 결과는 그래프를 통해 나타나기 때문에 사용자는 전체적인 차단 현상을 쉽게 파악하는 것이 가능하며, 시뮬레이션 데이터의 저장 또한 가능하다. 따라서 사용자는 사이펀 차단기 시뮬레이션 프로그램의 사용을 통해 사이펀 차단 현상을 쉽게 확인할 수 있으며, 사이펀 차단기의 실제 설계에도 이용할 수 있을 것으로 기대된다. In the design conditions of some research reactors, the siphon phenomenon can cause continuous efflux of water during pipe rupture. A siphon breaker is a safety device that can prevent water efflux effectively. However, the analysis of the siphon breaking is complicated because many variables must be included in the calculation process. For this reason, a simulation program was developed with a user-friendly GUI to analyze the siphon breaking easily. The program was developed by MFC programming using Visual Studio 2012 in Windows 8. After saving the input parameters from a user, the program proceeds with three steps of calculation using fluid mechanics formulas. Bernoulli's equation is used to calculate the velocity, quantity, water level, undershooting, pressure, loss coefficient, and factors related to the two-phase flow. The Chisholm model is used to predict the results from a real-scale experiment. The simulation results are shown in a graph, through which a user can examine the total breaking situation. It is also possible to save all of the resulting data. The program allows a user to easily confirm the status of the siphon breaking and would be helpful in the design of siphon breakers.

Application of Petri nets to deadlock avoidance in iPad-like manufacturing systems

The ever increasing sales of Apple’s iPad have created a tablet computer craze, attracting various manufacturers to invest and conduct researches in this sector. To obtain more production benefits and promote the business competitive strengths, we have proposed the Petri-net-based optimization algorithm. Based on the exceptional siphon phenomenon in the Petri net, the number of tokens in the siphon subnet never increases and the siphon subnet remains empty all the time. As usual, the deadlock occurs when one empty siphon subnet exists. To the end, the software tool PIPE-2 is used to verify the algorithm of finding the minimal siphon. The experimental results demonstrate the feasibility of the Petri-net-based optimization algorithm.

Wellbore–reservoir coupled simulation to study thermal and fluid processes in a CO2-based geothermal system: identifying favorable and unfavorable conditions in comparison with water

Using CO2 as a heat transmission fluid to extract geothermal energy is currently considered as a way to achieve CO2 resource utilization and geological sequestration. As a novel heat transmission fluid, the thermophysical properties of CO2 are quite different from those of water. CO2 has many advantages, such as larger mobility and buoyancy resulted from the lower density and viscosity. This will reduce the consumption of pressure driving the circulation, and save the energy of external equipment. The cycle even can be achieved by siphon phenomenon under a negative circulating pressure difference. However, there are still some disadvantages for CO2 as the heat transmission fluid, such as small heat capacity, leading to a less heat at the same mass flow rate. At the same time, because of the lager expansion and compression coefficient for CO2, changes in temperature and pressure may cause a more complex flow and thermodynamic processes. The lager compressibility makes it possible to get high temperature at the bottom of the injection well, whereas the lager expansion coefficient makes the temperature drop rapidly along the production well. Therefore, how to scientifically control the production pressure to guarantee sufficient high temperatures at the head of production well and, thereby, improve the efficiency of heat extraction are the key issues needed to be further addressed. The geological and geothermal conditions correspond to the central depression of the Songliao Basin located in the Northest of China. This depression has a high geothermal gradient and heat flow. In this article, a classic idealized “five-spot” reservoir model coupled with wellbores is used for simulations and analyses. The objectives of the present work are: (1) to investigate the fluid flow and thermal processes of supercritical CO2 along the wellbore and in the reservoir, (2) to understand the heat-extracting mechanism, (3) to identify advantages and disadvantages of using CO2 as the heat transmission fluid, and (4) to provide a theoretical basis for the selection of heat transmission fluid.

INVESTIGATION ON EFFECTS OF ENLARGED PIPE RUPTURE SIZE AND AIR PENETRATION TIMING IN REAL-SCALE EXPERIMENT OF SIPHON BREAKER

To ensure the safety of research reactors, the water level must be maintained above the required height. When a pipe ruptures, the siphon phenomenon causes continuous loss of coolant until the hydraulic head is removed. To protect the reactor core from this kind of accident, a siphon breaker has been suggested as a passive safety device. This study mainly focused on two variables: the size of the pipe rupture and the timing of air entrainment. In this study, the size of the pipe rupture was increased to the guillotine break case. There was a region in which a larger pipe rupture did not need a larger siphon breaker, and the water flow rate was related to the size of the pipe rupture and affected the residual water quantity. The timing of air entrainment was predicted to influence residual water level. However, the residual water level was not affected by the timing of air entrainment. The experimental cases, which showed the characteristic of partical sweep-out mode in the separation of siphon breaking phenomenon [2], showed almost same trend of physical properties.

고절수형 위생도기 개발을 위한 이상유동 수치해석 연구

물 부족 시대에 양변기 절수는 물을 절약하는데 가장 효과적인 방법 중 하나이다. 본 연구에서는 고절수형 양변기 개발을 위한 이상유동 해석을 위해 VOF 기법을 이용하였다. VOF를 이용한 전체 모델의 해석은 많은 시간이 요구되므로 전체모델의 일부분만 고려하는 부분모델도 해석시간 단축을 위해 사용하였다. 유량배분 해석을 위해 4개의 서로 다른 림 모델을 고려하였는데 림 홀의 위치나 개수보다는 림 홀의 크기가 유량배분을 효과적으로 달성하기 위한 인자임이 본 연구를 통해 밝혀졌다. 또한, 전체모델 해석을 통해 사이펀 현상에 따른 이상유동의 속도 및 압력도 분석하였다. 따라서 본 연구는 고절수형 양변기 모델 개발을 위한 다양한 기초 데이터를 제공한다. In the era of water scarcity, saving toilet water is one of the most effective ways to save water. In this study, two-phase flow for the development of highly-efficient toilet has been analysed with VOF(Volume Of Fluid) method. Since the whole model requires extensive computing time, part of the whole model has also been adopted to reduce the analysis time. Four different rim models were considered for flow distribution analysis and sizes of rim holes were found to become more important rather than locations or numbers of rim holes in achieving flow distribution effectively. In addition, velocity and pressure of two-phase flow due to siphon phenomenon have been studied through the analysis of whole model. Therefore, this study provides a variety of fundamental data for the development of highly-efficient toilet.

Mass transfer and mixing by pulsatile three-dimensional chaotic flow in alternating curved pipes

We present an experimental and numerical study of three-dimensional pulsatile flow in a twisted pipe in order to show the effects of chaotic advection on mixing in this flow configuration. The numerical study is done by CFD code with a pulsatile velocity field imposed as an inlet condition. The experimental setup is composed principally of a “Scotch-yoke” pulsatile flow generator and a twisted duct. The twisted duct consists of six 90° bends of circular cross-section; the plane of curvature of each bend is at 90° to that of its neighbors. The secondary flow, generated by centrifugal force, the pulsating velocity field and also due to the change in curvature plane, leads to irregular fluid particle trajectories. Velocity measurements were made for a range of stationary Reynolds numbers (300 ⩽ Re st ⩽ 1200) and frequency parameters (1 ⩽ α < 20) and for two velocity-amplitude ratios ( β); agreement between the numerical and experimental results is satisfactory. In the first bend, for certain control parameter values, the secondary flow becomes more complex due to the pulsation, and in some cases Lyne instability and a siphon phenomenon appear. However, in the other bends, one passes from four cells (Lyne instability) in the first bend with two cells in the other bends. The numerical and experimental study revealed modifications in the trajectories’ evolution due to pulsation. The superposition of an oscillating flow on a stationary curved-pipe flow, in some cases, causes the destruction of the trapping zones (KAM structures). The number of regular zones that disappear with an increase in the number of bends decrease with pulsation frequency and velocity-amplitude ratio. Both these phenomena contribute to the mixing and mass transfer enhancement in the flow.

G108 水流ジェットによって誘起されるサイフォン現象の数値的及び実験的研究(1)(GS-1-2 様々な流動現象,GS-1 様々な流動現象,一般セッション)

G108 水流ジェットによって誘起されるサイフォン現象の数値的及び実験的研究(1)(GS-1-2 様々な流動現象,GS-1 様々な流動現象,一般セッション)

G108 水流ジェットによって誘起されるサイフォン現象の数値的及び実験的研究(2)(GS-1-2 様々な流動現象,GS-1 様々な流動現象,一般セッション)

G108 水流ジェットによって誘起されるサイフォン現象の数値的及び実験的研究(2)(GS-1-2 様々な流動現象,GS-1 様々な流動現象,一般セッション)