bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat Transfer Enhancement With Delta Winglets Vortex Generator for Different Arrangement in a Circular Tube
Authors: Islam Md. , Nurizki A. , Kareem A. , Baba A.
Published: October 2018

Various technologies have been developed to enhance the heat transfer. Vortex generator (VG) is one of the passive techniques which can change the flow behavior and ultimately enhances the heat transfer performance. Delta winglet (DW) vortex generator can create longitudinal and horseshoe vortices which do not decay until further downstream and consequently increase heat transfer coefficient with comparatively lower pressure drop. With this vortex generator, it is expected to have higher Nusselt number with some increase of friction factor. Therefore, this study is to study the effect of pitch ratio (PR) and attack angle (B) of DW vortex generator to increase the thermal performance of heat exchanger. Four delta winglets are attached into a ring. Those rings attached with VGs will be used to investigate the influence of different parameters to heat transfer performance. In this study VGs were placed inside a circular copper tube and the heating coil was wrapped up around the outer surface of the copper tube to generate a constant heat flux condition. The experimental setup consists of a blower, orifice meter, flow straightener, calm/flow developing section and test section. The results show the friction factor, Nusselt number, and Thermal Performance Enhancement. It increases the thermal performance due to the formation of longitudinal vortex inside the circular tube. Pitch ratio and attack angle seem to have significant impact on the flow and heat transfer. The Pitch ratio of 1.6 have the highest impact on both (f/f0) and (Nu/Nuo) followed by attack angle. Smoke flow visualization technique was used to study flow behavior and flow structures.
Numerical Simulation and Optimization of Electric Field-Based Sorting in Particle Laden Flows in Microchannels
Authors: Davanlou Ashkan , Reddy Venkateswara
Published: October 2018

Advances in nanotechnology allows for electrodeposition and fabrication of micro/nano electrodes between substrates of microfluidic channels which later can be used as electrodes to apply DC or AC voltage. Microchannels taking advantage of this technology have shown promising results in flow cytometry [1,2], and cell sorting applications [3–6].

In this paper, first we study the influence of electric potential on particle sorting in a microchannel. For this purpose, a two dimensional computational fluid dynamics (CFD) model is created, meshed and solved in STAR-CCM+ which is a commercial simulation tool. Two type of spherical solid particles with different diameter are introduced through an injector from particulate flow inlet. These solid particles are treated as Lagrangian phase. The simulations are conducted in transient mode and the particle injection is occurred once the flow regime became steady state. The proposed model is based on finite volume approach and confirms the effectiveness of dielectrophoresis on particle sorting.

In the second part of this work, we focus on optimizing the separation efficiency of microchannel by implementing Siemens exclusive automated design exploration technology named SHERPA. Through this hybrid and adaptive strategy we investigate 4 key parameters including electric potential, flow velocity at two inlets, and particle mass flow rate. The objective is to minimize the electric potential while maximize the efficiency of device, measured by amount of particles separated at the outlet. In total 40 designs are evaluated. The results show that by adjusting the flow rate ratio between inlets, and applying a low voltage such as 5 V, you can increase the mass flow rate of segregated particles by approximately 100 times.

The proposed model not only can help shortening the time to market for new dielectrophoresis based channels, but also be used to optimize the overall device performance to achieve the best separation efficiency at optimal condition.
Study of Transmissivity of a Fracture Under Shearing
Authors: Mofakham Amir A. , Ahmadi Goodarz , Stadelman Matthew , Shanley Kevin , Crandall Dustin
Published: October 2018

A Marcellus shale rock fracture was subjected to four shearing steps and at the end of each shearing step CT (computed tomography) scans with resolution of 26.8 μm were obtained. The CT images were used to generate full aperture maps of the fracture configuration at the end of each shearing phase. The pressure drops along the fracture were also measured for different water flow rates through the fracture. The aperture map of the fracture was used to generate the geometry of the fracture for use in numerical simulations. The water flows and pressure drops in the fracture were simulated with different computational methods that included the full Navier-Stokes simulation, Modified Local Cubic Law (MLCL), and Improved Cubic Law (ICL) methods. Full 3-D Navier-Stokes simulation is the most accurate computational approach which was done with use of the ANSYS-Fluent software for each shear step and different flow rates. The MLCL is a 2-D relatively fast method which is commonly used for prediction of transmissivity of fractures. ICL is a 1-D method proposed in this study in which the effects of surface roughness and tortuosity were included in calculation of the effective aperture height of fractures. To provide an understanding of the accuracy of each of these models their predictions were compared with each other and with the experimental data. Also, to examine the effects of resolution of CT scans and the surface roughness on prediction of fractures transmissivity, similar simulations were performed on average aperture maps. Here the fracture of the full resolution data was averaged over 10 × 10 pixels. Comparing the results of the average aperture maps with those of the full maps showed that the lower resolution of CT scans led to underestimation of the fracture pressure drop due to missing the small features of the fracture surfaces and smoothing out their roughness.
Wake Flow Patterns Behind Rotating Smooth Spheres and Baseballs
Authors: Mortimer Patrick , Vaccaro John C. , Rooney David M.
Published: October 2018

An experimental investigation into the flow field behind baseballs at two different seam orientations as well as a smooth sphere of the same diameter was undertaken at Reynolds numbers of 5 × 104 and 1 × 105. The rotational speed of the three spheres varied from 0 to 2400 rpm, with data collected in increments of 400 rpm which correspond to relative spin rates between 0 and 0.94. Mean velocity profiles, turbulence in intensity profiles, and power spectral density of the signals were taken using hot-wire anemometry. The smooth sphere wake was seen to change in orientation over a range of relative rotational speeds. The Strouhal number remained constant around 0.24 for relatively low spin rates. The seams on the baseball suppressed any measurable vortex shedding once rotation began, also eliminating any significant change in wake orientation as evidenced by the mean velocity deficit and turbulence intensity profiles. It was concluded that the so-called inverse Magnus effect recorded by previous investigators at a specific Reynolds number / relative rotational speed of a sphere exists only for a smooth sphere and not for a sphere where the boundary layer separation is governed by raised seams.
Route to Chaos in the Fluidic Pinball
Authors: Deng Nan , Pastur Luc R. , Morzyński Marek , Noack Bernd R.
Published: October 2018

The fluidic pinball has been recently proposed as an attractive and effective flow configuration for exploring machine learning fluid flow control. In this contribution, we focus on the route to chaos in this system without actuation, as the Reynolds number is smoothly increased. It was found to be of the Newhouse-Ruelle-Takens kind, with a secondary pitchfork bifurcation that breaks the symmetry of the mean flow field on the route to quasi-periodicity.
Computer-Aided Design of Valves-Integrated Microfluidic Layouts Using Parameter-Guided Electrical Models
Authors: Feinerman Oron , Sofer Mor , Tsur Elishai Ezra
Published: October 2018

Integrated microfluidic networks are being rapidly deployed in academia and industry for a vast spectrum of applications, ranging from molecular biology to quantum physics. Current design paradigm for microfluidic layouts is typically based on numerical modeling, which is not suitable for rapid prototyping nor parameter driven design. Here, we utilize the hydraulic-electric circuit analogy to propose a circuit analysis methodology and an open-source framework for a parameter-guided design of integrated microfluidic layouts. We provide a method with which a user can intuitively define the circuit’s constraints and an algorithm which optimizes the hydraulic layout according to physical constraints. Our algorithm supports valves-integrated design and provides a simulation framework that describes fluid flow with different valves configuration.
Numerical Simulation of Dielectrophoretic Particle Separation
Authors: Kazemi B. , Darabi J.
Published: October 2018

This study presents the numerical simulation and optimization of a dielectrophoretic bio-separation chip for isolating bioparticles such as circulating tumor cells (CTCs). The chip consists of ten pairs of electrodes placed with an angle of 10° with respect to the direction of the flow on the top and bottom walls of the channel. The spatially non-uniform electric field produced by the slanted electrodes applies a repulsive force on the particles that are flowing through the channel. The repulsive force applied by the top and bottom electrodes are balanced and the particles flow along the centerline of the channel. On the other hand, the magnitude of forces resulted from electric field in the x and z-directions deflects particles depending on their size and guides them towards different outlets. Numerical simulation of the particle-fluid transport was performed using an open-source software named OpenFOAM and the deflection of the particles within the microfluidic channel was predicted. The present computational domain considers the dominant forces such as dielectrophoretic and hydrodynamic forces as well as their effects on the design and operating parameters of the chip. The results show that this device is capable of separating various cells based on their size.
Numerical Analysis of Effects of Surface Tension and Viscosity on 3 Dimensional Pulsating Heat Pipe
Authors: Bastakoti Durga , Zhang Hongna , Cai Weihua , Li Fengchen
Published: October 2018

Since the development of Pulsating Heat Pipe (PHP), it has gained a lot of attention in the field of thermal management. Flow inside multi-turn PHP is dominated by the capillary action mostly driven by the surface tension and drag force. Cetyltrimethyl ammonium chloride (CTAC) surfactant solution has lower surface tension and higher viscosity values compared to water, its base fluid. Experimental results have proven that the thermal resistance of PHP has increased its thermal performance at higher fill ratios and higher heat input, however the operational mechanism is not yet understood. Vapor formation, its movement and flow pattern of phases of working fluid can be well analyzed by the computational approach. In this paper, results of numerical analysis of 3-D PHP with working fluids that has values of surface tension and viscosity equal to that of 2000 ppm of CTAC are presented to validate the experimental results, thereby explain the thermodynamic reason of decreased thermal resistance. Moreover, the reasons for degraded performance of PHP with CTAC solutions at lower fill ratio and lower heat inputs are explained based on the vapor generation and flow of liquid-vapor inside the capillary tube. The numerical investigation was carried out for the case of 35%, 50% and 65% Fill Ratios (FR) at heat supply of 20, 30, 40 and 50 Watts. Lower surface tension promoted the phase change by rapid formation of vapor from liquid phase. Higher viscosity decreased the velocity of the fluid within the pipe. Influence of surface tension and viscosity on the thermal performance of PHP varied with different fill ratios and heat input.
Strength Analysis of Oil Tanker Under Numerical Wave
Authors: Shu Cheng , Hong Li , Dongxu Zhang
Published: October 2018

The strength of an oil carrier is generally checked using static load or equivalent load of wave action in accordance with relevant specifications. In order to accurately calculate the stress and the deformation of an oil carrier under wave action, the fluid-structure interaction system in the platform Workbench is used in this work. And, the pressure-based solver, the two-phase flow model and UDF (User Defined Function) in the software FLUENT are used to compile the three-order Stokes Wave so as to simulate ocean waves. Forces acting on the surface of the oil carrier are obtained by calculating the flow field, and the structural strength of the carrier is then investigated under sagging and hogging conditions. The results show that: the three-order Stokes Wave matches well with the theoretical result, and it is feasible to research the strength of the oil carrier by generating waves using this numerical method. In addition, the method of fluid-structure interaction is applied to investigate the structural strength of the fully-loaded carrier under sagging and hogging conditions.
Improvements in the Dehydration Process of Heavy Crude Oil, Using CFD: Case Study Campo Quifa-Colombia
Authors: Asuaje Tovar Miguel , Benítez Nelson , Quintero Dario , Gaviria Myriam R. , Díaz Eduardo , Chacón Carlos
Published: October 2018

Quifa is one of the largest heavy-oil fields in Colombia with a total fluids production of 1,320 KBPD with a water cut of 96.7% through 272 active wells, approximatively. Facilities to handle such amounts of water, have to deliver crude oil under market specifications and clean up the water prior to its reinjection, require several stages of oil-water separation. The first phase in oil water separation process is Free Water Knock Out vessels (FWKO), which are in charge of extracting to extract most of the water, frequently assisted by heat or chemical products which help gravity to perform the separation. The treated water (which contain still some oil) is then directed to the following stage separation carried out by the big tanks called skimmers, which are designed to clean the water down to a few ppm of oil. Nowadays, even though the advance on computational calculations has increased, these tanks are frequently designed using only the concept of time of residence and considering the internal velocities to be as low as possible, so that improve separation. For these last considerations, FWKOs and Skimmers could have internal components like manifold or baffles.

The present work explains a CFD (Computational Fluids Dynamics) study of different internal manifolds configurations, which aimed to improve the fluid distributions and velocities inside the tanks of Quifa field. Simulations were performed by CFX commercial software under two-phase flow eulerian-eulerian homogeneous model.

The optimum manifold configuration, achieves uniform static pressure and flow distribution across the entire main pipe, reducing secondary internal flows and hydraulic losses.

Then, CFD calculations were carried out in the whole skimmer tank, using the original manifold and the improved one. Results show an increase in the separation process, due to the new internal velocity field.

Supported by the simulations results, these geometrical improvements in the internal manifolds were applied/constructed in one of the skimmer tanks in Quifa Field. Field results show an improvement on separation efficiency, going from 38% average efficiency in the original tanks (Skim-10 and Skim-30), up to 87% in the modified one (Skim-30). The quality of exit-water was reduced from 300 ppm average up to 77 ppm. The flow capacity of the skimmer 30 has been improved and can handle up to 600 KBFPD. This represents 62% more capacity than Skimmer 10, and 42% more than Skimmer 20.
Wind Flow Characteristics of a Model Downburst
Authors: Chowdhury Junayed , Chowdhury Jubayer , Parvu Dan , Karami Mohammad , Hangan Horia
Published: October 2018

Downburst is an anti-tornado system with a slow rotating column of air slowly descending towards the ground which occurs due to the sudden downfall of air and precipitation generated from the cumulonimbus cloud. This natural event produces a strong downdraft which induces an outburst of damaging winds on or near the ground. This radially divergent wind with high velocity transpires when descending air strikes the ground which can cause immense damage to the ground mounted objects and structures.

This paper discusses the wind flow characteristics of downbursts produced in the Wind Engineering, Energy and Environment (WindEEE) Dome at Western University, Canada. Downdraft diameter and speed were varied to produce several downbursts like flow. Point measurements using Cobra probes and surface measurements using Particle Image Velocimetry (PIV) were performed to analyze the wind flow field in detail. Instantaneous downburst wind speeds were decomposed into slowly varying mean and residual fluctuations for different averaging time. Velocity profile with height from WindEEE was compared with previous experiments and full scale data.
Flow Separation Control and Drag Reduction for a Two-Dimensional Boat-Tailed Bluff Body Through Transverse Grooves
Authors: Mariotti Alessandro , Buresti Guido , Salvetti Maria Vittoria
Published: October 2018

The present work focuses on a passive strategy consisting in the introduction of properly contoured transverse grooves to delay the flow separation occurring on a boat-tailed bluff body before its sharp-edged base. We consider a two-dimensional body having a cross-section with a 3:1 elliptical forebody and a rectangular main part followed by a circular-arc boat tail. We carry out Variational Multiscale Large Eddy Simulations at Re = Du∞/v = 9.6 × 104. A boat-tail drag reduction of the order of 9.7% is produced by the significant delay of the flow separation caused by the groove and by the consequent increase of the base pressure. This effect is mainly due to the relaxation of the no-slip condition over the small and steady recirculation region inside the groove, which reduces the momentum losses near the wall and thus delays boundary layer separation. The flow control device is also robust to small variations of the groove location and depth.
Comparison of Two Active Flow Control Mechanisms of Pure Blowing and Pure Suction on a Pitching NACA0012 Airfoil at Reynolds Number of 1 × 106
Authors: Asgari Ehsan , Tadjfar Mehran
Published: October 2018

In this study, we have applied and compared two active flow control (AFC) mechanisms on a pitching NACA0012 airfoil at Reynolds number of 1 × 106 using 2-D computational fluid dynamics (CFD). These mechanisms are continuous blowing and suction which are applied separately on the airfoil which pitches around its quarter-chord in a sinusoidal motion. The location for suction and blowing was determined in our previous study based on the formation of a counter clock-wise vortex near the leading-edge. In our current study, we have compared the effectiveness of pure blowing and pure suction in suppressing the dynamic stall vortex (DSV) which is the main contributor to the drag increase, particularly near the maximum angle of attack (AOA) and in early downstroke motion. The blowing/suction slot is considered as a dent on the airfoil surface which enables the AFC to perform in a tangential manner. This configuration would allow blowing jet to penetrate further downstream and was shown to be more effective compared to a cross-flow orientation. We have compared the two aforementioned mechanisms in terms of hysteresis loops of lift and drag coefficients and have demonstrated the dynamics of flow in controlled and uncontrolled situations.
Quantifying the Spatial-Temporal Evolution of Rim/Ligament in Drop Breakup via Digital In-Line Holography
Authors: Yao Longchao , Chen Jun , Sojka Paul E. , Wu Xuecheng
Published: October 2018

A liquid drop undergoes aerodynamic deformation and breakup when it is exposed into a gas stream. Many techniques were used to measure the size and velocity of the secondary droplets while quantifying the rim/ligament still remains a challenge. An automatic method to extract the 3D properties of the toroidal rim in the bag breakup was recently developed based on digital in-line holography (DIH). To reduce the uncertainty caused by the out-of-focus overlap, a DIH configuration with a slightly rotated view is adopted here. The entire rim is reconstructed by stitching all the sections together. Holograms are recorded with a high-speed camera operated at 20 kHz to study the dynamic evolution of the rim in the bag breakup of an ethanol drop. Both the 3D visualization and z–y view reflect the rim’s structure development within 5.2 ms. The rim expands followed with disintegration into ligaments and relatively larger droplets. The volume of the rim is measured ∼ 95 % and that of the secondary droplets is ∼ 5 % of the initial drop volume before rim breakup. Then the volume of rim/ligament decreases after rim breakup which on the other hand increases the volume fraction of secondary droplets. The total volume of the rim/ligament and fragments is very close to the initial drop volume in most measurements except when the instant swelling happens in local atomization. Then the total measured volume decreases rapidly as the relatively large fragments move out of the field of view.
Clogging Mechanisms of Vortex Pumps: Fibrous Material Motion Capture and Simulation With a CFD and DEM Coupling Method
Authors: Imasaka Yamato , Kanno Hitoshi , Saito Sumio , Miyagawa Kazuyoshi , Nohmi Motohiko , Isono Miho , Kawai Masahito
Published: October 2018

Since wastewater pumps used in sewage systems have a trade-off relationship between non-clogging ability and efficiency, many internal flow and performance estimation studies so far have focused on optimizing both parameters. Here we focus on vortex pumps with a large space that allows foreign matters to pass through inside the casing that are used as sewage pumps.

In this paper, using experimental and numerical methods, we clarified clogging mechanism in the pumps using CFD (Computational Fluid Dynamics), Motion Capture and PIV (Particle Image Velocimetry) method.

Firstly, since it was difficult to observe the motion of foreign matter in the pumps, a simple experimental apparatus was built to quantify it. Five cylindrical rods were set in a rectangular water passage made of acrylic that has an 80mm*80mm cross section. The motion of strings in the passage was studied with experiments and computations. Strings were chosen as foreign matter because they are comparatively easy to compute and experiment with compared to fabric for example. In the experiments, the motion of strings could be recorded with a high-speed video camera and their motions were quantified with two-dimensional motion capture system.

In the computations, the motion of strings was simulated using DEM (Discrete Element Method) in the CFD software STAR-CCM+ by connecting particles with straight lines and coupling CFD with DEM. It is a numerical value method in which the motion and interaction of a large number of disintegrating objects is simulated. Its characteristic is that the point of contact between the particles is included in the equation of motion. Particles are connected by massless rods. These rods transmit force and momentum to each particle. Furthermore, the force between each particle is computed of the interaction between soft-particles and their bonding strength. In order to formulate the contact force between the particles, the spring-dashpot system is used. In addition, the optimal parameters of the DEM particles were obtained by conducting a parameter study.

We confirmed that the motion of the strings in the flow direction coincided with at a high precision in the passage. Furthermore, by applying the computational method with the above results, we were able to simulate the motion of strings in a vortex pump. We found that strings were pulled back into the pump by the backflow in the tongue of the pump. This backflow was observed using PIV results, providing experimental confirmation of this mechanism. Moreover, we were able to simulate the motions of fibrous materials in the passage and vortex pump.
Experimental and Numerical Study on Hydraulic Performances of a Turbopump With and Without an Inducer
Authors: Fu Yanxia , Fan Meng , Pace Giovanni , Valentini Dario , Pasini Angelo , d’Agostino Luca
Published: October 2018

The hydraulic performance of a centrifugal turbopump with and without a 3-bladed axial inducer has been studied both experimentally and numerically. A 3D numerical model has been used to simulate the flow through from the inlet to the outlet ducts of the turbopump with and without an inducer using the ANSYS CFX code. The sensitivity of the numerical results has been analyzed with reference to the adopted turbulent flow models, to the length of the input and output ducts included in the simulations, to the reference positions used for the evaluation of the total pressure rise and to the temperature of the operating fluid. The measured and predicted hydraulic performances of the turbopump with and without the inducer have been compared under different operating conditions. As expected, the predicted hydraulic performance of the turbopump is significantly influenced by the lengths of the inlet and outlet ducts, the turbulence models and, at low flow rates, the reference positions of the total pressure rise measurements. The pressure rise coefficients obtained from the simulations using an inlet duct with length of 3 rTi and 10 rTi were significantly lower than the experimental results, while at low flow rates those referring to the inlet duct with length greater than 10 rTi were significantly higher than those obtained for the shorter inlet duct. With reference to the effect of the pressure measurement locations, the difference between the numerical results of the pressure rise coefficient and the experimental values was much higher when the data were obtained at the locations where the transducers was mounted in the experimental tests at lower flow rates. Moreover, the hydraulic performance of the turbopump at lower flow rates can be significantly influenced by the use of the upstream inducer, with a pressure drop of 20% in particular at 60% of the design flow rate.
Performance Analysis of Nek5000 for Single-Assembly Calculations
Authors: Merzari Elia , Rahaman Ronald , Min Misun , Fischer Paul
Published: October 2018

The ExasSMR project focuses on the exascale application of single and coupled Monte Carlo (MC) and computational fluid dynamics (CFD) physics. Work is based on the Shift MC depletion, OpenMC temperature-dependent MC, and Nek5000 CFD codes. The application development objective is to optimize these applications for exascale execution of full-core simulations and to modularize and integrate them into a common framework for coupled and individual execution. Given the sheer scale of nuclear systems, the main algorithmic driver on the CFD side is weak scaling. The focus for the first four years of the project is on demonstrating scaling up to a full reactor core for high-fidelity simulations of turbulence. Full-core fluid calculations aimed at better predicting the steady-state performance will be conducted with a hybrid approach in which large eddy simulation is used to simulate a portion of a core and unsteady Reynolds-averaged Navier-Stokes handles the rest. This zonal hybrid approach provides an additional scaling dimension besides the number of assemblies. The present manuscript focuses on performance assessment using assembly-level simulations with Nek5000. We discuss the development of two benchmark problems: a subchannel (single-rod) problem to assess internode performance and a larger full-assembly problem representative of a small modular reactor (SMR). We note that current SMR assemblies are considerably simpler than pressurized water reactor assemblies since they contain no mixing vanes. This feature allows for considerable reduction in the degrees of freedom required to simulate the full core. We discuss profiling and scaling results with Nek5000, describe current bottlenecks and potential limitations of the approach, and suggest optimizations for future investigation.
Experimental Study of Large-Scale Flow Structures in an Aneurysm
Authors: Yu Paulo , Durgesh Vibhav
Published: October 2018

An aneurysm is an abnormal growth in the wall of a weakened blood vessel, and can often be fatal upon rupture. Studies have shown that aneurysm shape and hemodynamics, in conjunction with other parameters, play an important role in growth and rupture. The objective of this study was to investigate the impact of varying inflow conditions on flow structures in an aneurysm. An idealized rigid sidewall aneurysm model was prepared and the Womersley number (α) and Reynolds number (Re) values were varied from 2 to 5 and 50 to 250, respectively. A ViVitro Labs pump system was used for inflow control and Particle Image Velocimetry was used for conducting velocity measurements. The results showed that the primary vortex path varied with an increase in α, while an increase in Re was correlated to the vortex strength and formation of secondary vortical structures. The evolution and decay of vortical structures were also observed to be dependent on α and Re.
Generation IV International Forum Education and Training Webinars: Education Tools for the Next Generation Workforce
Authors: Paviet Patricia
Published: October 2018

The Gen IV International Forum (GIF) Education and Training Task Force was created to respond to the challenge of not only forming, training and/or retaining qualified Gen IV workforce but also educating and informing a more general public, policy makers on topics related to Gen IV reactor systems and cross-cutting subjects. The task force serves as a platform to enhance open education and training as well as communication and networking in support of GIF, and its objectives are to maintain the know-how in this field, to increase the knowledge of new advanced concepts, and to avoid the loss of the knowledge and competences that could seriously and adversely affect the future of nuclear energy.

While many countries are either ramping up or developing nuclear power production as an important step towards economic development and environmental protection, a decrease or uncertainty of the fiscal year budgets have left organizations and agencies looking for new avenues for training and educating a qualified workforce. This has led to an increase in those looking for readily available education and training resources.

Using modern internet technologies, the GIF Education and Training Task Force has launched a webinar series on Gen IV systems in September 2016, which is accessible to a broad audience and is educating and strengthening the knowledge of participants in applications to advanced reactors. This achievement is the direct result of partnering with university professors and subject matter experts who conduct live webinars on a monthly basis. The live webinars are recorded and archived as an online educational resource to the public from the GIF website (www.gen-4.org). In addition, the webinars offer unprecedented opportunities for interdisciplinary crosslinking and collaboration in education and research. The GIF webinars, with their expansion of topics, targets a large spectrum of those that do not know but are desiring to learn about the many aspects of advanced reactor systems. The details and examples of the GIF webinar modules will be presented in our paper.
Countercurrent Flow Limitation at Sharp-Edged Upper End in Vertical Pipes
Authors: Murase Michio , Nishida Koji , Tomiyama Akio
Published: October 2018

In our previous study, we derived a correlation for countercurrent flow limitation (CCFL) at the sharp-edged upper end in vertical pipes, where the dimensionless velocity was the Kutateladze parameter with the characteristic length of the Laplace capillary length, by using air-water experimental data reported by Richter (1981) with the diameters of D = 19–140 mm and Doi et al. (2012) with D = 30, 45, and 60 mm. In this study, we reevaluated effects of the diameter on CCFL in detail for small diameters by using those data by Richter and Doi et al. The dimensionless velocity for CCFL data by Richter was the Kutateladze parameter for D = 44–140 mm but was the Wallis parameter (where the characteristic length is the diameter) for D = 19–51 mm (data for D = 44 and 51 mm could be expressed by both of the Wallis and Kutateladze parameters). The difference of the CCFL constants in the Wallis CCFL correlation for D = 30 mm by Doi et al. and D = 32 mm by Richter was a little larger than the uncertainty bands. This means that it is needed to measure reliable CCFL data in the small diameters of D < 30 mm in order to make effects of the diameter clear.
Statistical Burnup Distribution of Moving Pebbles in HTR-PM Reactor
Authors: Vitullo Fanny , Krepel Jiri , Kalilainen Jarmo , Prasser Horst-Michael , Pautz Andreas
Published: October 2018

In the pebble-bed high temperature reactor under construction in China, called HTR-PM, the spherical fuel elements continuously flow downward in the cylindrical core. After the discharge, the burnup of each pebble is checked at the core outlet and, according to the achieved burnup level, the pebble might be disposed or reinserted into the upper section of the core, distributing randomly in the radial direction and defining a variable number of passes necessary to achieve the average maximum burnup of 90 MWd/kgU. Discrete Element Method (DEM) simulations have been carried out to achieve a clear understanding of the movement of 420,000 fuel pebbles in the HTR-PM core. At the same time, neutronic properties have been investigated for a single pebble and for the full core with Serpent 2 Monte Carlo code in order to perform a parametrization of the one-group microscopic cross sections at the core-level. The pebble movement has been coupled with the neutronic behavior of a single pebble in a dedicated burnup script called Moving Pebble Burnup (MPB), developed in Matlab. 3,000 single pebble burnup histories were simulated to obtain sufficient statistics and insight on the burnup process in the HTR-PM. The decrease of the average burnup gained per single pass implies that a miss-handling of recirculated fuel elements is unlikely to lead to exceedance of the maximum allowed burnup of 100 MWd/kgU. Furthermore, the core demonstrates a self-compensation effect of burnup, meaning that it always compensates burnup under- or over-runs in the successive passes. Finally, it is possible to conclude that the fuel cycle of the HTR-PM, as it has been laid out, is well-designed and feasible.
Nonlinear Analysis in Pressure Vessel Design Codes: Recommendations for Codified Rules Improvements
Authors: Faidy Claude
Published: October 2018

During the past 30 years the main rules to design pressure vessels were based on elastic analyses. Many conservatisms associated to these different elastic approaches are discussed in this paper, like: stress criteria linearization for 3-D components, stress classification in nozzle areas, plastic shake down analysis, fatigue analysis, Ke evaluation, and pipe stress criteria for elastic follow-up due to thermal expansion or seismic loads...

This paper will improve existing codified rules in nuclear and non-nuclear Codes that are proposed as alternatives to elastic evaluation for different failure modes and degradation mechanisms: plastic collapse, plastic instability, tri-axial local failure, rupture of cracked component, fatigue and Ke, plastic shakedown. These methods are based on limit loads, monotonic or cyclic elastic-plastic analyses.

Concerned components are mainly vessels and piping systems.

No existing Code is sufficiently detailed to be easily applied; the needs are stress analysis methods through finite elements, material properties including material constitutive equations and criteria associated to each methods and each failure modes.

A first set of recommendation to perform these inelastic analysis will be presented to improve existing codes on an international harmonized way, associated to all material properties and criteria needed to apply these modern methods. An international draft Code Case is in preparation.
RCIC Turbo-Pump Scaling Through CFD and Model Testing for the Texas A&M University NHTS Facility
Authors: Hawila Mohammad A. , Kirkland Karen Vierow
Published: October 2018

One of the requirements for licensing a nuclear power plant in the U.S is the capability to survive and recover from a station blackout according to the U.S Nuclear Regulatory Commission (USNRC). Station blackout is the loss of all off-site and onsite power simultaneously. Therefore, experimental test facilities are being constructed and operated to test the performance of the related safety systems in a nuclear power plant. Design and construction of a test facility creates the need to perform scaling analysis to ensure proper representation of key components and phenomena of interest. One of the main outcomes of the scaling analysis is the quantitative estimation of the Similarity Level (SL), which requires derivation of dimensionless scaling parameters and prediction of appropriate input values for the scaling parameters.

To study the performance of the Reactor Core Isolation Cooling (RCIC) system, the Nuclear Heat Transfer Systems (NHTS) Laboratory at Texas A&M University has constructed and is operating a RCIC test facility. This paper presents the scaling analysis with reference to a full-size RCIC system and the RCIC system turbine was used as the main component for scaling. The input parameters for dimensionless scaling parameters were obtained through experimental measurements and CFD analysis. The CFD analysis is for the ZS-1 RCIC system turbine model. The STAR-CCM+ CFD code was used in this study to create and run simulations for steady state normal and abnormal operating conditions for the NHTS-developed CAD models.

The input for the dimensionless scaling parameters was estimated. Input parameters were collected both experimentally and from CFD simulations and inserted into these equations. As a result, a high degree of similarity was confirmed, with a minimum of 82% between the NHTS and full-size RCIC systems. The 82% represents the amount of transfer properties conserved between the two systems. Consequently, this high similarity level allows the NHTS RCIC system to be used to study the behavior of the full-size RCIC system under Beyond Design Bases Accident (BDBA) conditions.

Future work is to study and model other components of the RCIC system such as the suppression chamber to estimate similarity levels and study their effects on behavior of the system under BDBA.
Research on Steam Generator False Water Level Calculation Improvement for PWR NPP Simulation Program
Authors: Hong Junying , Xu Zhao
Published: October 2018

A U tube PWR NPP Steam Generator (SG) false water level phenomenon is researched in this paper. Lumped parameter method was employed to establish the SG thermo-hydraulic model. To simulate the false level phenomenon of SG, a fossil electricity generation plant boiler steam pocket model technique was applied by adding a non-linear equation into the original model. Furthermore, a set of static calculation and dynamic calculation in typical plant transient condition were done. And related preliminary validation was also carried out. It is indicated that the model established in this paper is able to simulate the false level phenomenon of SG with proper accuracy. And it will be helpful for future design and related analysis work.
The Influence of Thermal Deformation on the Dynamic Characteristics of AMB Rotor of HTR-PM Helium Blower
Authors: Du Guowei , Yu Jinpeng , Wang Hong , Zhao Lei
Published: October 2018

Helium blower is the core component of high temperature gas cooled reactor, which rotor is supported by active magnetic bearings (AMBs). The special advantage of AMB is that there is no contact between bearing and rotor, and this permits operation with small friction, long service life, no lubrication system, and no pollution to the helium environment. [1–3] Helium blower rotor is mainly composed of rotating shaft, impeller, motor, cooling blower and so on, which runs in an uneven temperature field that the impeller runs in a helium chamber of 250 degrees centigrade, and the motor housing’s outer surface temperature is 65 degrees centigrade. The temperature rises from standstill to stable operation will cause the thermal deformation of rotor and bearing, leading to the change of gap between rotor and bearing, which will lead to the change of electromagnetic force of AMB. The electromagnetic force determines the bearing stiffness and bearing damping of the AMB, so the change of temperature is the most important to the stiffness and damping of the AMB, which can affect the dynamic characteristics of the rotor. Through finite element method (FEM) to calculate the temperature field and displacement field of helium blower, the change of the gap of AMB and rotor is calculated. The rotor radial displacement orbits are obtained through numerical simulation, which are affected by thermal deformation. Finally, the results of numerical simulation are verified by experiments. The simulation and experiments both show that temperature rise can increase the vibration amplitude of rotor, so the influence of thermal deformation should be considered when designing the active magnetic bearings.
A Scaling Analysis for a General Passive Heat Removal System
Authors: Wei Li , Zhenfeng Qi , Qiang Guo , Yidan Yuan
Published: October 2018

Passive cooling technology has been adopted by more and more designs of advanced PWRs, because of its benefits to simplifying the design of safety systems, to reducing mis-operations performed by operators during accidents, and to cutting the cost of operation and maintenance. This paper presents a dimensional analysis by means of the Hierarchical two-tiered scaling (H2TS) method for the heat transfer process in a general passive heat removal system (PHRS) based on the research in which the most important phenomenon was conducted by a code module. The comparison of calculation results of the prototype and the experimental facility designed by the dimensional analysis shows that a scaled-down experimental facility could not simulate the flashing phenomenon which is the most important phenomenon in this process perfectly. But we could introduce a dimensionless parameter related to the flashing and choose an appropriate experiment condition to reproduction the flashing in the scaled-down facility. Our work in this paper made a well foundation for future design and experimental research of the PHRS.
Coordinated Control of a Small Pressurized Water Reactor
Authors: Sun Peiwei , Wang Chong
Published: October 2018

Small Pressurized Water Reactors (SPWR) are different from those of the commercial large Pressurized Water Reactors (PWRs). There are no hot legs and cold legs between the reactor core and the steam generators like in the PWR. The coolant inventory is in a large amount. The inertia of the coolant is large and it takes a long time for the primary system to respond to disturbances. Once-through steam generator is adopted and its water inventory is small. It is very sensitive to disturbances. These unique characteristics challenge the control system design of an SPWR. Relap5 is used to model an SPWR. In the reactor power control system, both the reactor power and the coolant average temperature are regulated by the control rod reactivity. In the feedwater flow control system, the coordination between the reactor and the turbine is considered and coolant average temperature is adopted as one measurable disturbance to balance them. The coolant pressure is adjusted based on the heaters and spray in the pressurizer. The water level in the pressurizer is controlled by the charging flow. Transient simulations are carried out to evaluate the control system performance. When the reactor is perturbed, the reactor can be stabilized under the control system.
A Structural Integrity Assessment of a Nuclear Boiler Superheater Bifurcation at High Temperature
Authors: Nadri Brahim , Wang Robert X.
Published: October 2018

Steam generating boilers in gas cooled nuclear reactors in the UK operate at high temperatures and some of them have been in service for more than 30 years and are now facing the challenges from long term operation extension demand. The tubular components experience surface metal losses due to exposure to oxidation and corrosive environment and as a result, some tubes suffer from restricted flow which may lead to an increased creep-fatigue crack initiation damage. To maintain or recover boiler heat transfer efficiency, internal chemical cleaning of selected boiler tubes is carried out, which introduces additional metal loss in the tube wall, weakening its load bearing capacity.

Some boiler components are subject to high temperature, pressure and mechanical loadings in large number of operating cycles through life, introducing creep in addition to cyclic fatigue damage.

In support of an operational safety case and plant long term operation extension requirements, structural integrity assessments have been carried out on a critical boiler component — bifurcation, taking into account tube wall metal loss for extended long term services, including the effects of possible future chemical cleaning operations.

This paper presents the finite element analyses and R5 Volume 2/3 assessment work carried out for the structural integrity substantiation of a stainless steel boiler tube bifurcation. The bifurcation is a tubular component subject to significant applied displacement due to long range thermal expansion of the neighbouring components. The initial study following normal industry practice using a decoupled analysis approach showed that the strain ranges obtained would exceed the creep-fatigue crack initiation capacity and plastic ratchetting would occur which would lead to short term, incremental plastic collapse, hence a safety case could not be made.

To meet the challenge, the analysis and assessment processes have been examined. A coupled FE analysis approach was used to remove the pessimism associated with the decoupled analysis approach. This approach captures the displacement-controlled nature of the system loads and allows a more realistic assessment. In addition, the plant life has been divided into a number of assessment periods such that the more realistic metal loss appropriate for each period could be used. Furthermore, segregated temperature zones have been considered in the assessment, leading to a significant reduction in the creep-fatigue crack initiation damage and a satisfactory extended long term operation safety case.