Water Faucet Research Articles

A dual grid method for the compressible two-fluid model which combines robust flux splitting methodology with high-resolution capturing of incompressible dynamics

The speed of sound in two-phase pipe flow systems is often several orders of magnitude greater than the travelling speed of hydraulic information (volume fractions). Dynamically simulating such flows requires resolution of acoustic and hydraulic waves existing at vastly different spatial and temporal scales. If simulated on the same numerical grid, the need for accuracy in hydraulic waves will necessitate an exaggerated resolution of acoustic waves. Likewise, time steps restricted by the speed of sound are small compared to the time scales active in hydraulic waves. This constitutes a waste of computational potential. The method proposed herein decouples the hydraulic and acoustic scales, greatly improving computational efficiency.The proposed dual grid method solves a four-equation compressible two-fluid model on a principal grid which robustly accounts for the pressure evolution and conserves mass and momentum. An incompressible two-equation model is at the same time solved on a finer grid, resolving the details of the hydraulic evolution. Information from both model formulations is coupled through the terms of the governing transport equations, providing consistency between the grids. Accurate and finely resolved schemes can then be employed for the incompressible two-fluid model without suffering from the time and stability restrictions otherwise enforced by acoustic waves. At the same time, the Hybrid Central-Upwind flux splitting scheme of Evje and Flåtten (2005a) allows for an explicit and numerically robust treatment of the acoustic waves without losing hydraulic accuracy.The dual grid method is tested against four dissimilar problems: A shock tube problem, the water faucet problem, a surge wave and pressure wave problem and a roll-wave case. In all problems, the proposed scheme provided significant increases in computational efficiency and accuracy as compared with a single grid arrangement.

Comparison of the effect of hydrodynamic and hydrostatic models for pressure correction term in two-fluid model in gas-liquid two-phase flow modeling

This paper presents a numerical study using two-fluid model in order to compare the effect of hydrodynamic and hydrostatic models for pressure correction term in two-fluid model in gas-liquid two-phase flow modeling to provide a more accurate model. Two-fluid model is solved by Conservative Shock Capturing Method. The two-fluid model is applied using both hydrodynamic pressure correction term and hydrostatic pressure correction term for four test cases including Water Faucet Case, Water-Air Separation Case, Toumi's Shock Tube Case, and Large Relative Velocity Shock Tube Case.Hydrostatic pressure correction term is neglected for vertical geometry, therefore, in this geometry; two-fluid model cannot be hyperbolic. Thus, hydrostatic pressure correction term is not a stabilizing term. Also, in horizontal pipe and for atmospheric conditions, hydrostatic pressure correction term presents better results than hydrodynamic pressure correction term. But, in non-atmospheric conditions, hydrodynamic pressure correction term provides better results. Therefore, we should consider geometry (vertical or horizontal) and flow conditions (atmospheric or under-pressure) in order to select a proper pressure correction term for two-fluid model. Also, hydrodynamic pressure correction term in two-fluid equations system is hyperbolic in a boarder range than hydrostatic pressure correction term.

Extension of staggered-grid-based AUSM-family schemes for use in nuclear safety analysis codes

To overcome the numerical difficulties of the density-based method for low-Mach-number two-phase flow, this paper adopts the AUSM+ and AUSMDV schemes based on a staggered-grid arrangement. The water faucet, air-water shock tube, oscillating manometer and air-water phase separation problems are used as benchmark tests to validate the implementation of the generic four-equation two-fluid model. The present results reveal the advantages of using staggered-grid-based AUSM+ and AUSMDV schemes over the collocated-grid-based counterpart. With a staggered-grid arrangement, odd-even decoupling issues can be avoided. Thus, no sound speed scaling or additional diffusion terms are needed when using AUSM+ and AUSMDV schemes for low-Mach-number two-phase flow. Furthermore, since the pressure and void fraction are already stored at the interface of the velocity control volume, no interpolation of interfacial pressure is needed for momentum equations. Finally, this study will help integrate AUSM+ and AUSMDV schemes into staggered-grid-based thermal hydraulic codes, e.g. CATHENA, used in the nuclear industry. Moreover, to tackle the stiffness issues in relation to phase appearance and disappearance, we propose a new staggered-grid-based scheme referred to as AUSMFVS, which combines the accuracy of AUSM+ and the stability of FVS.

Implementation and Comparison of High-Resolution Spatial Discretization Schemes for Solving Two-Fluid Seven-Equation Two-Pressure Model

As compared to the two-fluid single-pressure model, the two-fluid seven-equation two-pressure model has been proved to be unconditionally well-posed in all situations, thus existing with a wide range of industrial applications. The classical 1st-order upwind scheme is widely used in existing nuclear system analysis codes such as RELAP5, CATHARE, and TRACE. However, the 1st-order upwind scheme possesses issues of serious numerical diffusion and high truncation error, thus giving rise to the challenge of accurately modeling many nuclear thermal-hydraulics problems such as long term transients. In this paper, a semi-implicit algorithm based on the finite volume method with staggered grids is developed to solve such advanced well-posed two-pressure model. To overcome the challenge from 1st-order upwind scheme, eight high-resolution total variation diminishing (TVD) schemes are implemented in such algorithm to improve spatial accuracy. Then the semi-implicit algorithm with high-resolution TVD schemes is validated on the water faucet test. The numerical results show that the high-resolution semi-implicit algorithm is robust in solving the two-pressure two-fluid two-phase flow model; Superbee scheme and Koren scheme give two highest levels of accuracy while Minmod scheme is the worst one among the eight TVD schemes.

Large Time Step Roe scheme for a common 1D two-fluid model

We present the Large Time Step (LTS) extension of the Roe scheme and apply it to a standard two-fluid model. Herein, LTS denotes a class of explicit methods that are not limited by the CFL (Courant–Friedrichs–Lewy) condition, allowing us to use very large time steps compared to standard explicit methods. The LTS method was originally developed in the nineteen eighties (LeVeque, 1985), where the Godunov scheme was extended to the LTS Godunov scheme. In the present work, the relaxation of the CFL condition is achieved by increasing the domain of dependence. This might lead to difficulties when it comes to boundary and source terms treatment. We address and discuss these difficulties and propose different ways to treat them. For a shock tube test case, where there are neither source terms nor difficulties associated with the boundaries, the method increases both accuracy and efficiency. For a water faucet test case that includes a source term, the method increases the efficiency, while the accuracy strongly depends on the appropriate treatment of boundary conditions and source terms.

Development of Transient Mechanistic Three-Phase Flow Model for Wellbores

Summary Multiphase flow models have been widely used for downhole-gauging and production logging analysis in the wellbores. Coexistence of hydrocarbon fluids with water in production wells yields a complex flow system that requires a three-phase flow model for better characterizing the flow and analyzing measured downhole data. In the past few decades, many researchers and commercial developers in the petroleum industry have aggressively expanded development of robust multiphase flow models for the wellbore. However, many of the developed models apply homogeneous-flow models with limited assumptions for slippage between gas and liquid bulks or use purely two-fluid models. In this paper, we propose a new three-phase flow model that consists of a two-fluid model between liquid and gas and a drift-flux model between water and oil in the liquid phase. With our new method, we improve the simplifying assumptions for modeling oil, water, and gas multiphase flow in wells, which can be advantageous for better downhole flow characterization and phase separations in gravity-dominated systems. Furthermore, we developed semi-implicit and nearly implicit numerical algorithms to solve the system of equations. We discuss the stepwise-development procedures for these methods along with the assumptions in our flow model. We verify our model results against analytical solutions for the water faucet problem and phase redistribution, field data, and a commercial simulator. Our model results show very good agreement with benchmarks in the data.

New analytical solutions to the two-phase water faucet problem

The one-dimensional water faucet problem is one of the classical benchmark problems originally proposed by Ransom to study the two-fluid two-phase flow model. With simplifications, such as massless gas phase and no wall and interfacial frictions, analytical solutions had been previously obtained for the transient liquid velocity and void fraction distribution. The water faucet problem and its analytical solutions have been widely used for code assessment, benchmark, and numerical verification. In this work, we present a new set of analytical solutions to the water faucet problem at the steady-state condition, with the gas-phase density’s effect on pressure distribution considered. This new set of analytical solutions is used in a rigorous numerical verification process from which the anticipated second-order spatial accuracy is achieved for a second-order spatial discretization scheme. On the contrary, the same anticipated order of accuracy could not be obtained using the Ransom solutions as the reference. In addition, extended Ransom transient solutions for the gas-phase velocity and pressure are derived with the assumption of decoupled liquid and gas pressures. Numerical benchmark on the extended Ransom solutions is also presented.

A modified Rusanov scheme for shallow water equations with topography and two phase flows

In this work, we introduce a finite volume method for numerical simulation of shallow water equations with source terms in one and two space dimensions, and one-pressure model of two-phase flows in one space dimension. The proposed method is composed of two steps. The first, called predictor step, depends on a local parameter allowing to control the numerical diffusion. A strategy based on limiters theory enables to control this parameter. The second step recovers the conservation equation. The scheme can thus be turned to order 1 in the regions where the flow has a strong variation, and order 2 in the regions where the flow is regular. The numerical scheme is applied to several test cases in one and two space dimensions. This scheme demonstrates its well-balanced property, and that it is an efficient and accurate approach for solving shallow water equations with and without source terms, and water faucet problem.

Numerical simulation of terrain-induced severe slugging coupled by hydrodynamic slugs in a pipeline–riser system

A numerical study based on a one-dimensional two-fluid model is carried out to describe the transient hydrodynamic slugging and terrain-induced severe slugging in a pipeline–riser system. The system of equations is rendered well-posed by interfacial pressure model for the riser. The selected flow conditions are restricted in the well-posed region for the horizontal and the downward inclined pipes to ensure the hydrodynamic slug characteristics are predicted correctly. The validity of the model is examined by water faucet problem and horizontal slug flow experiments. Simulations with and without slug capturing are conducted to address the effect of hydrodynamic slugs on severe slugging. It has been found that more accurate predictions are obtained by taking hydrodynamic slugs into account. At low superficial gas velocity, the simulation without slug capturing tends to overestimate the severe slugging period. When hydrodynamic slugs are captured, the upstream gas expansion is suppressed by the hydrodynamic slugs. At relatively high superficial gas velocity, the simulation without slug capturing tends to underestimate the severe slugging period. When hydrodynamic slugs are captured, the upstream compressible volume is greatly enlarged by the blowout of the hydrodynamic slugs. In both situations, the influences of the hydrodynamic slugs can reduce the errors of the predicted severe slugging characteristics.

Applications of high-resolution spatial discretization scheme and Jacobian-free Newton–Krylov method in two-phase flow problems

The majority of the existing reactor system analysis codes were developed using low-order numerical schemes in both space and time. In many nuclear thermal–hydraulics applications, it is desirable to use higher-order numerical schemes to reduce numerical errors. High-resolution spatial discretization schemes provide high order spatial accuracy in smooth regions and capture sharp spatial discontinuity without nonphysical spatial oscillations. In this work, we adapted an existing high-resolution spatial discretization scheme on staggered grids in two-phase flow applications. Fully implicit time integration schemes were also implemented to reduce numerical errors from operator-splitting types of time integration schemes. The resulting nonlinear system has been successfully solved using the Jacobian-free Newton–Krylov (JFNK) method. The high-resolution spatial discretization and high-order fully implicit time integration numerical schemes were tested and numerically verified for several two-phase test problems, including a two-phase advection problem, a two-phase advection with phase appearance/disappearance problem, and the water faucet problem. Numerical results clearly demonstrated the advantages of using such high-resolution spatial and high-order temporal numerical schemes to significantly reduce numerical diffusion and therefore improve accuracy. Our study also demonstrated that the JFNK method is stable and robust in solving two-phase flow problems, even when phase appearance/disappearance exists.

Avaliação da Qualidade da Água em Três Escolas Públicas da Cidade de Macapá, Amapá

The study aimed to analyze the water quality in three public schools in the city of Macapa-AP. The samples were collected at three different points (Water tank, Faucet Kitchen and Trough) from January 2013. The analyzed parameters were: turbidity, color, pH, chlorine, nitrate, total and fecal coliforms. The results showed that not all the samples presented in accordance with current legislation of the ordinance 2914/11 MS. The presence of total and fecal coliforms were detected in the three collection points Irenaeus da Gama Paes school, as well as pH, with values lower than recommended by the concierge. The parameter turbidity in water samples in the point '1' and '3' to the Baron of Rio Branco school and the points '1', '2' and '3' Azevedo Costa school had values above the recommended by the Ministry of Health . The concentration of chlorine was low in most points, only the points '2' and '3' Azevedo school met the values established by ordinance. The concentration of iron in point '1' the Baron of Rio Branco school and at all school Azevedo Costa points was out of certain standard by the Ministry of Health. The color concentrations and nitrate met the standard in all points of the schools . We conclude that the water of the schools do not meet the requisites for drinking water recommended by the Ministry of Health through Regulation no2914 / 11 and therefore require urgent action to adapt the water supplied to these school communities to prevent damage to the health of its members. Keyword : drinking water; water quality parameters; school.

A Jacobian‐free Newton–Krylov method for thermalhydraulics simulations

SummaryThe current paper is focused on investigating a Jacobian‐free Newton–Krylov (JFNK) method to obtain a fully implicit solution for two‐phase flows. In the JFNK formulation, the Jacobian matrix is not directly evaluated, potentially leading to major computational savings compared with a simple Newton's solver. The objectives of the present paper are as follows: (i) application of the JFNK method to two‐fluid models; (ii) investigation of the advantages and disadvantages of the fully implicit JFNK method compared with commonly used explicit formulations and implicit Newton–Krylov calculations using the determination of the Jacobian matrix; and (iii) comparison of the numerical predictions with those obtained by the Canadian Algorithm for Thermaulhydraulics Network Analysis 4. Two well‐known benchmarks are considered, the water faucet and the oscillating manometer.An isentropic two‐fluid model is selected. Time discretization is performed using a backward Euler scheme. A Crank–Nicolson scheme is also implemented to check the effect of temporal discretization on the predictions. Advection Upstream Splitting Method+ is applied to the convective fluxes. The source terms are discretized using a central differencing scheme. One explicit and two implicit formulations, one with Newton's solver with the Jacobian matrix and one with JFNK, are implemented. A detailed grid and model parameter sensitivity analysis is performed.For both cases, the JFNK predictions are in good agreement with the analytical solutions and explicit profiles. Further, stable results can be achieved using high CFL numbers up to 200 with a suitable choice of JFNK parameters. The computational time is significantly reduced by JFNK compared with the calculations requiring the determination of the Jacobian matrix. Copyright © 2015 John Wiley & Sons, Ltd.

Comparison of implicit and explicit AUSM‐family schemes for compressible multiphase flows

SUMMARYThis paper makes the first attempt of extending implicit AUSM‐family schemes to multiphase flow simulations. Water faucet, air–water shock tube and oscillating manometer problems are used as benchmark tests with the generic four‐equation two‐fluid model. For solving the equations implicitly, Newton's method along with a sparse matrix solver (UMFPACK solver) is employed, and the numerical Jacobian matrix is calculated. Comparison between implicit and explicit AUSM‐family schemes is presented, indicating that similarly accurate results are obtained with both schemes. Furthermore, the water faucet problem is solved using both staggered and collocated grids. This investigation helps integrate high‐resolution schemes into staggered‐grid‐based computational algorithms. The influence of the interface pressure correction on the simulation results is also examined. Results show that the interfacial pressure correction introduces numerical dissipation. However, this dissipation cannot eliminate the overshoots because of the incompatibility of numerical discretization of the conservative and non‐conservative terms in the governing equations. The comparison of CPU time between implicit and explicit schemes is also studied, indicating that the implicit scheme is capable of improving the computational efficiency over its explicit counterpart. Copyright © 2014 John Wiley & Sons, Ltd.

Outbreak of Serratia marcescens bloodstream infections in patients receiving parenteral nutrition prepared by a compounding pharmacy.

Compounding pharmacies often prepare parenteral nutrition (PN) and must adhere to rigorous standards to avoid contamination of the sterile preparation. In March 2011, Serratia marcescens bloodstream infections (BSIs) were identified in 5 patients receiving PN from a single compounding pharmacy. An investigation was conducted to identify potential sources of contamination and prevent further infections. Cases were defined as S. marcescens BSIs in patients receiving PN from the pharmacy between January and March 2011. We reviewed case patients' clinical records, evaluated pharmacy compounding practices, and obtained epidemiologically directed environmental cultures. Molecular relatedness of available Serratia isolates was determined by pulsed-field gel electrophoresis (PFGE). Nineteen case patients were identified; 9 died. The attack rate for patients receiving PN in March was 35%. No case patients were younger than 18 years. In October 2010, the pharmacy began compounding and filter-sterilizing amino acid solution for adult PN using nonsterile amino acids due to a national manufacturer shortage. Review of this process identified breaches in mixing, filtration, and sterility testing practices. S. marcescens was identified from a pharmacy water faucet, mixing container, and opened amino acid powder. These isolates were indistinguishable from the outbreak strain by PFGE. Compounding of nonsterile amino acid components of PN was initiated due to a manufacturer shortage. Failure to follow recommended compounding standards contributed to an outbreak of S. marcescens BSIs. Improved adherence to sterile compounding standards, critical examination of standards for sterile compounding from nonsterile ingredients, and more rigorous oversight of compounding pharmacies is needed to prevent future outbreaks.

An Artificial Viscosity for the III-Posed One-Dimensional Incompressible Two-Fluid Model

Methods to remedy the ill-posedness of the basic one-dimensional two-fluid model, which is widely used in nuclear reactor safety codes, have been the subject of considerable study. Both of the two prevalent methods have drawbacks. Unconditional hyperbolization uses nonphysical constitutive relations to create a well-posed two-fluid model that is hyperbolic over all flow conditions. However, when the model is hyperbolized, it is also stabilized, which is not a universal property of two-phase flows. The second method, the preferred method of the U.S. Nuclear Regulatory Commission safety codes, is to simply use a first-order upwind numerical method that relies on numerical viscosity to regularize the ill-posedness of the model by damping the short-wavelength instabilities. Unfortunately, the scale of the “short wavelength” is related to a particular numerical grid or discretization. Because of the consistency of the numerical method, in the limit of an infinitely resolved grid, i.e., Δx, Δt→0, the numerical viscosity vanishes, as does its regularization effect. This results in a somewhat heuristic user guideline that suggests a lower limit on the grid size based on a cross-sectional dimension that is a combination of the long-wavelength assumption and experience. However, a cutoff wavelength achieved by numerical viscosity is not set by the grid size alone but also depends on the time step, the material, and the flow properties, as demonstrated with a von Neumann stability analysis. This can create poor resolution in areas where numerical stability may not be a substantial problem, unless the guideline is intentionally violated. Additionally, strict observance of this limit makes verification by convergence difficult or impossible. Therefore, it is proposed that an artificial viscosity be prescribed explicitly, i.e., independently of any particular numerical method or grid. An artificial viscosity model is derived that prescribes exactly a cutoff in the linear stability growth rate at a specified wavelength, e.g., λ0 = 2DH consistent with the aforementioned user guideline. It is shown, using the water faucet problem, that the proposed artificial viscosity model can be used to remove the high-frequency component of the solution without limiting the resolution of the grid. Furthermore, the solution also converges, which was not the case without the artificial viscosity.

Verification of a Higher-Order Finite Difference Scheme for the One-Dimensional Two-Fluid Model

The one-dimensional two-fluid model is widely acknowledged as the most detailed and accurate macroscopic formulation model of the thermo-fluid dynamics in nuclear reactor safety analysis. Currently the prevailing one-dimensional thermal hydraulics codes are only first-order accurate. The benefit of first-order schemes is numerical viscosity, which serves as a regularization mechanism for many otherwise ill-posed two-fluid models. However, excessive diffusion in regions of large gradients leads to poor resolution of phenomena related to void wave propagation. In this work, a higher-order shock capturing method is applied to the basic equations for incompressible and isothermal flow of the one-dimensional two-fluid model. The higher-order accuracy is gained by a strong stability preserving multi-step scheme for the time discretization and a minmod flux limiter scheme for the convection terms. Additionally the use of a staggered grid allows for several second-order centered terms, when available. The continuity equations are first tested by manipulating the two-fluid model into a pair of linear wave equations and tested for smooth and discontinuous initial data. The two-fluid model is benchmarked with the water faucet problem. With the higher-order method, the ill-posed nature of the governing equations presents severe challenges due to a growing void fraction jump in the solution. Therefore the initial and boundary conditions of the problem are modified in order to eliminate a large counter-current flow pattern that develops. With the modified water faucet problem the numerical models behave well and allow a convergence study. Using the L1 norm of the liquid fraction, it is verified that the first and higher-order numerical schemes converge to the quasi-analytical solution at a rate of O(1/2) and O(2/3), respectively. It is also shown that the growing void jump is a contact discontinuity, i.e. it is a linearly degenerate wave. The sub-linear convergence rates are in exact agreement with the theory for a contact discontinuity.

Colonel Tandja’s Country

Colonel Tandja’s Country Peter Chilson (bio) Not long ago, a man I used to know lost his job and went to prison in the space of a few hours. Months later and just as abruptly he returned home, charges dropped, with little explanation. His name is Mamadou Tandja. He was once a colonel in the army of Niger, a West African country more than twice the size of France and covered mostly by the Sahara. He became, years after I met him, the twice democratically elected civilian leader of an African nation state—an anomaly on a continent of dictators. Tandja’s ten-year reign over Niger ended February 18, 2010, during a cabinet meeting at the gleaming white presidential palace overlooking the Niger River in Niamey, the capital city, when shortly after noon mutinous soldiers blew open the palace gate. This began, The New York Times reported, “a day of gunfire, explosions and nonstop military music on the radio” during which a few soldiers and civilians died. Mutineers burst in on the cabinet and hustled Tandja to a car, unharmed. They kept him a few days at an army base before moving him to house arrest in the servants’ quarters of a palace villa, and accused him of taking more than $100 million in foreign aid and other funds. A year later, in March 2011, Niger’s military rulers demoted Tandja again, this time to Kollo civilian prison outside the capital. There, among thieves, at the age of 73 he awaited trial, complaining of poor health and harsh quarters—until May, when he left Kollo a free man, all sins forgiven for lack of evidence. Yet the criminal stain, the notion that he took the money, haunts me. I feel betrayed by a man I had hoped stood for something. For two years I was a teacher in Niger’s Tahoua region, which Tandja ruled through drought in the 1980s. Governor Tandja owned a spot in the mind of every civil servant, [End Page 89] tangling us in fear, desire, and guilt—fear of being noticed and punished as if we all deserved a stint behind bars; desire to be blessed by his power; and guilt for not working to his standards. Tandja jailed a clerk for losing track of rice stores, an act that made him a man of the people, protector of the food. He locked up others for keeping unclean offices. He jailed a farmer jaywalking on a rural road as his motorcade approached. One man I knew was imprisoned for having a broken water faucet when Tandja visited his home. To my knowledge, no one he sent to prison died, but to this day I cannot decide whether to despise or admire Tandja. He has wandered a Shakespearian path, sometimes Richard III, ruthless and vindictive, or Prince Hal, triumphing over personal vice to lead a country. Tandja-the-devil drank hard and pilfered food aid as his people went without. Tandja-the-last-honest-man tried to be everywhere at once for his people. Under Tandja, half of Niger’s 14 million people starved in a famine he claimed the international press invented. Yet I cannot condemn him. It’s easy to damn a leader for negligence in a land for centuries mired in drought and ethnic conflict. Niger ranks 186, second from last (above the Democratic Republic of the Congo) on the 2011 United Nations Human Development Index—a measure of life expectancy, education, literacy, and standard of living. After a half-century of independence and billions of dollars in aid, Nigeriens barely scratch a living in Saharan heat. They die young in a nation, the borders of which were drawn in 1904 by Frenchmen so frustrated by persistent poverty that they later dubbed Niger a “phantom colony.” Colonel Tandja’s country. I first met Tandja one bright morning in March 1986, when a desert-brown light tank rolled to a stop and cut its engine outside a concrete school building in Bouza, the village where I was a Peace Corps English teacher working with fifth-graders. My students and I watched through the French windows we’d opened to cool the room...

Development of a tri-parameter online monitoring system for UV disinfection reactors

Online monitoring of an ultraviolet (UV) facility not only can ensure disinfection efficiency, but also conserve energy. In this work, a tri-parameter online monitoring system was developed by using three micro-fluorescent silica detectors (MFSDs) installed into a UV disinfection reactor. The detector signals were computed by theoretically derived mathematical equations to determine three key operational parameters: the lamp output attenuation coefficient (N), water UV transmittance (T), and quartz sleeve fouling coefficient (F). Results indicate that the N, T and F parameters could be monitored well by the MFSDs. The monitored lamp output exhibited a significant dependence on water temperature; the monitored water transmittance was verified by a UV–Vis spectrophotometer; and the monitored sleeve fouling coefficient decreased from 1.00 to 0.66 after an 18-day operation with a synthetic hard water. A long-term 30-day experiment, where the UV reactor was directly connected to a tap water faucet to simulate practical conditions, demonstrated the good applicability of the developed monitoring system. This monitoring system in real time can be used to adjust the number of operating lamp modules, alarm any accidental breakdown of the lamps, and trigger auto-cleaning of the quartz sleeves, thus having potential applications to open-channel and enclosed UV disinfection facilities.

Human emotional response to energy visualisations

Past research has found that frequent energy usage feedback is an important factor in reducing home energy consumption, and that the sensory appeal and cognitive relevance of the feedback are key components of user engagement with energy systems. The visual design of the information interface is important not just due to its role in communicating data of cognitive relevance, but also because the choice of information type and format is important towards achieving interactive Hebbian learning. The objective of the current research study was to investigate the possible effect of image format on the human emotional response to scenes of energy systems, and to evaluate whether any gender related differences in emotional response occurred. An automated PC-based test was developed which utilised five visual image formats (Optical Gray-Scale, Optical Coloured, Optical Augmented, Infrared Gray-Scale and Infrared Blue-Red) and nine home energy scenes (hot water boiler, radiator, water faucet, kitchen oven, tea kettle, toaster, electrical connector, laptop computer and tea mug). The emotional response of the participant was measured in the automated test by means of a Self-Assessment Manikin (SAM) which provided symbolic graphical representations of the human body under various degrees of emotional response, and associated Likert format rating scales for the valence and activation level of the emotional response. Comparison of the results obtained for the different visual scenes suggests that the greatest level of human emotional activation was achieved by the Infrared Blue-Red (thermal image) format, and that, generally, coloured images provided higher levels of emotional activation than gray-scale images. The increased activation achieved by the infrared images suggests attention capturing potential due to novelty, or due to the direct link to heat and energy, or both. Significant differences in emotional response (both activation and valence) were found to occur as a function of gender. The current results provide first guidance which a designer can use when choosing image spectrum and colours to represent energy systems on the displays of thermostats, smart meters and the energy devices. Relevance to industryThe current results provide first guidance which a designer can use when choosing image spectrum and colours to represent energy systems on the displays of thermostats, smart meters and the energy devices. Such design guidance is currently lacking internationally but is of increasing importance due to the expansion of digital devices, internet services and the upcoming internet-of-things.

Slug type hydrodynamic instability analysis using a five equations hyperbolic two-pressure, two-fluid model

This paper presents a new and accurate method for modeling dynamic and transient behaviors of slug initiation and growth in horizontal ducts. In this analysis, a hyperbolic, two-pressure, five-equation, two-fluid model predicted the dynamic behavior of a complicated slug flow regime. The model was modified by including friction with the wall and at the interfaces between phases. In this paper, highly accurate shock capturing numerical methods were applied to slug modeling for the first time. The applied method is low cost, simple and does not exhibit the problems of previous numerical methods, such as the high computational time associated with the finite volume of two-fluid models. The new method does not use experimental correlations and assumptions to simplify the model like unit cell and slug tracking methods. In the present work, the numerical method of AUSMDV was used for a one-dimensional, two-pressure, five-equation, hyperbolic, two-fluid model. The calculation is conducted by applying second order time and space accuracy. The AUSMDV numerical method does not identify a complicated matrix solution; therefore, it renders the flow field solution using minimal computational resources. Discretization of non-conservative products that appear in the momentum equations was performed using a conservative linear path scheme (based on path conservative schemes by Pares), and accurate discretization of non-conservative terms based on AUSM fluxes have been conducted. Numerical solutions are presented for well-defined problems of two-phase, gas–liquid flows. The well-defined test cases that were considered for verification and validation are the Reiman Shock Tube and the Ransom Water Faucet. Numerical estimates of slug flows in horizontal ducts were compared with two sets of experimental results. Good agreement between modeled and experimental results, as well as a grid independency study, suggests that the presented model is capable of slug tracking and slug capturing. In addition, the numerical method that is used here can predict flows with sufficient accuracy. Finally, several facts related to the physics of slug behavior were outlined. These facts could be useful for scientists who wish to model the flow regime correctly, and they may be important for system designers who must predict slug behavior physically.