bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of Pathogens Dispersion in an Aircraft Cabin Using Gas Injection Source Versus a Coughing Manikin
Authors: Mahmoud Seif , Bennett James S. , Hosni Mohammad H. , Jones Byron 
Published: October 2020

Abstract
The dispersion characteristics of airborne pathogens were investigated in a Boeing 767 mockup cabin containing 11 rows with 7 seats per row, using two tracer gas source methods: continuous injection at low velocity and a coughing manikin. Both the injection source and the coughing manikin were located on the same seat in the sixth row. The injection source utilized CO2 gas at an injection rate of 5.0 liters per minute mixed with helium at a rate of 3.07 liters per minute to neutralize buoyancy. The manikin coughed approximately once every 75 seconds, with a volume of 4.2 liters of CO2 per cough. To ensure sufficient data were collected at each sampling location, each coughing manikin test was run for 6 coughs and each injection source test for 30 minutes of continuous injection. In both test methods, the tracer gas concentration was measured using CO2 gas analyzers at seated passenger breathing height of 1.2 m and radially up to 3.35 m away from the gas injection location, representing approximately four rows of a standard B767 aircraft. The collected data obtained from each tracer method was then normalized to provide a suitable comparison basis that is independent of tracer gas introduction flowrate. The results showed that both tracer source methods gave similar dispersion trends in diagonal and lateral directions away from the injection location. However, the tracer gas concentration was higher along the longitudinal direction in the coughing manikin tests due to the cough momentum. The results of this work will help researchers analyze different experimental and numerical approaches used to determine contaminant dispersion in various environments and will provide a better understanding of the associated transport phenomena.
Optimal Control Strategy to Distribute Water Through Loop-Like Planar Networks
Authors: Soni Bharat , Mishra Utkarsh A. , Nayak Ameeya Kumar 
Published: October 2020

Abstract
In this article, loop like planar networks formed by circular cross sectioned conduits with possibly different geometric measurements are studied to supply the required amount of isothermal water within the optimal time and through the shortest path. The flow optimization procedure is controlled by time varying pressures at nodes throughout the network for given specifications about pressure value at multiple demanding and single supply nodes. The flow governing equation is solved analytically to correlate transient flow rate and pressure and then studied using analogous electrical circuit. For each possible path between source and demand node, minimum equivalent flow impedance criterion is considered to pick the optimum path. This sets a multi-objective dynamic flow optimization algorithm and the same is executed under the assumption of fully developed and laminar flow. The optimum flow impedance can further be used to measure the pumping power as the cost of flow of a particular path. The algorithm can be extended to reduce the water wastages by controlling pressures efficiently.
Natural Convection Analysis Around Elliptical Shapes With Sinusoidal Heat Flux Using CFD
Authors: Kamstrup Annette G. , Pedersen Anna Marie A. , Elimar Frederik M. , Olsen Lasse , Sørensen Henrik , Hærvig Jakob 
Published: October 2020

Abstract
Heat transfer is important as technology becomes more compact, thereby increasing the heat flux and consequently the need for cooling. This paper will investigate natural convection on an elliptical shape with sinusoidal heat flux input. Natural convection was analysed using CFD simulations on an ellipse, with minor- to major axis ratio b/a = 0.6 and an inclination angle of α = 90°. The sinusoidal heat flux was non-dimensionalised by a modified Grashof number Gr* = g · β · (∂T/∂n) · (Lc)4/v2 with a mean value of 2 × 107, amplitude of up to 2 × 107, and dimensionless angular frequency ω* = ω · Lc2/v = 24, 36, and 72. All simulations were made with a Prandtl number of Pr = 7.0. To ensure reliable results a Grid Convergence Index analysis was carried out. Validation was made by comparing the obtained surface averaged Nusselt numbers to previous studies and results from performed experiments. An experiment using Particle Image Velocimetry, PIV, measured the flow field around an ellipse. The results from the sinusoidal heat flux showed that the difference in accounting for the sinusoidal Grashof function was up to 10% for the time-surface averaged temperature and time-surface averaged Nusselt number. Generally, the amplitude would increase the temperature, while the effect of the dimensionless angular frequency was dependent on the given amplitude.
A DNS Study of the Dispersion and Deposition of Nano- and Micro-Particles in a Turbulent Channel Flow
Authors: Mofakham Amir A. , Ahmadi Goodarz , McLaughlin John B. 
Published: October 2020

Abstract
Nano- and micro-particles dispersion and deposition in a dilute gas-solid turbulent flow in a channel were studied. A pseudo-spectral DNS code was used to solve the Navier-Stokes equations, and to generate the instantaneous turbulent velocity fluctuation field for the gas flow. Under the one-way coupling assumption, the gas flow carries the particles, but the influence of particles on the flow can be neglected. To provide an understanding of the transport behavior of particles of different sizes, 200,000 monodisperse point particles with Stokes numbers of 0.1, 1, 5, 25, and 125 were introduced with a random distribution in the channel. The corresponding Lagrangian particle equation of motion, including the Stokes drag, the gravity, and the lift forces, were solved, and the trajectories of the particles for the duration of 10,000 wall units were evaluated for dilute suspension. The trap boundary condition on the lower and upper walls of the channel was assumed, and the deposition rates of particles with different sizes were evaluated and recorded as a function of time. Ensemble and time averaging of the simulation results were performed, and the corresponding concentration profiles and the deposition velocities of particles were evaluated for various conditions. A series of simulations were performed, and the effects of wall roughness, lift force, and the gravity direction on the deposition rate were carefully examined. It was found that the surface roughness and the direction of gravity in conjunction with the lift force significantly affect the fine particle deposition rate and could improve the agreement of the DNS simulation with the available experimental data.
CFD Modeling of Multi-Fuel Suspension Co-Combustion and Calcination Processes Within a DDF Precalciner of Cement Kiln
Authors: Cristea Eugen-Dan , Conti Pierangelo 
Published: October 2020

Abstract
The paper reports a CFD engineering application for modeling the thermal-fluid dynamics and thermochemical conversion processes, which govern the conventional air-fossil fuel firing or multi-fuel co-processing, responsible for thermal sustain of raw material calcination process, within a dry process cement kiln. We simulate a Dual-Combustion and Denitration Furnace (DDF) precalciner, which co-combusts in suspension the petroleum coke (primary fuel) with alternative fuels (e.g., the pre-dried sewage sludge and/or the animal meat and bonemeal). CFD software package ANSYS Fluent R18.2 is used to build CFD reactive model and to perform the numerical simulations. The Eulerian–Lagrangian approach is usually employed for modeling turbulent multiphase reacting flows. Few turbulence and radiation heat transfer models are compared, to identify pros and cons of each model applicability and to determine which model is most suitable. The Discrete Phase Model (DPM), in Lagrangian framework, is employed for tracking petcoke/alternative fuels and limestone particle clouds. CFD analysis provides valuable insights into the DDF precalciner performance e.g., combustion and calcination characteristics, in-furnace NOx control strategy by combustion aerodynamics optimization (particularly the effect of Tertiary Air tangential inlet, which creates swirl and induces several local flow recirculation zones). The major predicted results e.g., exit degree of calcination, fuel burnout, gas species concentration fields etc., are quite well captured and validated against control system continuously logged operation data and the measurements collected by newly installed instrumentation.
Hamiltonian Modeling and Energy Analysis of a Hydro Electric Generating Set in the Sudden Load Decreasing Transient
Authors: Wang Pengfei , Chen Diyi , Li Huanhuan 
Published: October 2020

Abstract
Hydroelectric generation system is mainly composed of penstock, hydro-turbine, generator, servicing facility and power load, its stability is directly related to the dynamic characteristics of each subsystem, but not completely dependent on the behavior of the subsystems. To better study the transient energy characteristics and stabilization mechanism of the hydroelectric generating set in the sudden load decreasing transient. And make full use of strengths of generalized Hamiltonian system in describing energy flow, the Hamiltonian model of a hydroelectric generating set including the turbine, water diversion system and generator is established by the method of orthogonal decomposition. Firstly, the energy flow of the hydroelectric generating set in the framework of generalized Hamiltonian theory is proved theoretically to be consistent with the real system, and the transient process of sudden load decreasing can be described effectively. Moreover, the variation laws of the flow, the rotating speed and the power angle of the set in the sudden load decreasing transient are studied respectively. The results indicate that the constructed Hamilton function can effectively describe the energy change of the system. It provides theoretical support for the stable operation of the hydroelectric generating set in the sudden load decreasing transient, and a new research idea for the stable operation of the set in other transient processes.
Motility Response to Hydrodynamic Stress During the Growth Cycle in Active Fluid Suspensions
Authors: Fadlallah Hadi , Peerhossaini Hassan , De Groot Christopher , Jarrahi Mojtaba 
Published: October 2020

Abstract
In this work, we focus on the motility behavior of two model microorganisms widely used in the study of active fluids: Chlamydomonas reinhardtii microalga and Synechocystis sp. Cyanobacterium. Understanding the physiological responses of microorganisms under variable environmental conditions is essential for bioreactor engineering. Yet, most of the previous studies focused on the observation of cellular motility regardless of the growth process. Here, we measure the motility of Chlamydomonas reinhardtii and Synechocystis sp. during their growth when subjected to different intensities of hydrodynamic shear stress. The results demonstrate a significant difference in the motility response of the two species against the applied hydrodynamic shear stress.
Mechanical agitation appears to affect the motility of Chlamydomonas reinhardtii microalgae by stimulating the growth process and increasing the magnitude of the cellular swimming velocity. The motility varies following 3 different phases: the rising phase starting almost at the middle of the exponential growth phase, and the decay and damped phases during the stationary phase. This behavior is described using a linear model for the rising phase and a damped oscillatory model for the decay and damped phases.
The motility of Synechocystis does not follow a well-defined pattern in time. However, it seems that the peak of the swimming velocity occurs always in the middle of exponential phase of growth. Synechocystis cells show a high endurance to the applied shear such that the global effect of agitation intensity on their motility is insignificant.
Numerical Simulations of Flows in Cerebral Aneurysms Using the Lattice Boltzmann Method
Authors: Osaki Susumu , Hayashi Kosuke , Kimura Hidehito , Kohmura Eiji , Tomiyama Akio 
Published: October 2020

Abstract
The lattice Boltzmann method (LBM) is used to simulate blood flows in cerebral aneurysms and the effects of the outflow boundary condition on predictions are studied. The LBM utilizes the D3Q19 discrete velocity model, the multiple-relaxation time collision operator (MRT), and the interpolated bounce-back rule to treat complex aneurysm shapes. Flow characteristics in regions of a large fluctuation in the wall shear stress (WSS) were then investigated using the LBM to understand the relation between the flow structure and the aneurysm wall remodeling. As a result the following conclusions were obtained under the present range of the numerical condition: (1) even with significant changes in the flow rate distributions at outflow boundaries, the WSS in an aneurysm is not much affected if the boundaries are far from the aneurysm, and (2) the geometry of an aneurysm and the main artery largely affects the formation of large WSS fluctuation regions, which may thickens the aneurysm wall due to inflammation-induced wall remodeling.
A Simple Method for the Design of Supersonic Nozzles of Arbitrary Cross Section Shape
Authors: Boughazi N. , Haddad A. 
Published: October 2020

Abstract
A simple approach for the design of supersonic nozzles of complex 3D shapes is presented. The Method of characteristics is primarily applied to compute the axisymmetric flow field of the supersonic section of the de-Laval nozzle. Two-dimensional simulations are performed for the axisymmetric flow fields.
The 3D configuration is then generated from the desired exit axisymmetric cross-sectional shape chosen through tracing its geometrical parameters back.to the throat. Elliptical, corrugated and two-dimensional wedge nozzles were designed using this approach. Preliminary results show a smooth geometrical transition from the throat to the exit cross section. Further three-dimensional analyses of the obtained geometries along with cold flow testing constitute the next steps to be performed.
Optimization of the Aerodynamic and Aeroacoustic Characteristics of a Small Centrifugal Fan by Means of Inverse Design and Evolutionary Algorithms
Authors: Eisenmenger Chris , Frank Stefan , Thamsen Paul Uwe 
Published: October 2020

Abstract
In this work, the inverse design code TURBOdesign 1 has been used in a direct approach to optimize both the aerodynamic and aeroacoustic properties of a small centrifugal fan with backward-curved blades. Two promising fan designs along with a reference fan have been investigated numerically using CFD and the results have been validated experimentally using a chamber test rig for the aerodynamics and the in-duct method for acoustics. A design aiming for good aerodynamic performance showed an increased efficiency in a wide operating range of about 5 to 10%. Another design aiming for low noise showed a numerically determined reduction in the overall sound radiation of 1 dB on average. This trend could not be reproduced in the experiments, instead the high efficiency design showed the best acoustic characteristics in a wide frequency range, which is why this is a subject of ongoing research.
Analyses of Turbulent Characteristics of the Air-Core Vortex Formation
Authors: Zi Dan , Wang Fujun 
Published: October 2020

Abstract
Air-core vortex often appears at the hydraulic intakes, it not only degrades hydraulic performance but also causes vibrations of the pump or turbine, resulting in efficiency reduction and operation instability. In this paper, large eddy simulation using an in-house code with the coupled level-set and volume-of-fluid method for capturing the air-water interface is performed. Vortices motions and turbulent characteristics are investigated. The fully-developed air-core vortex is well reproduced in the simulation. The distribution of the turbulent kinetic energy of the flow field is relevant to the evolution of vortices during the air-core vortex formation. At the early stage of the air-core vortex formation, the turbulent kinetic energy is high near the intake and the two side of the intake along the streamwise direction, and the streamwise component of the Reynolds normal stress is dominant, which indicates that vortices on the two sides move towards the intake along the streamwise direction and gather near intake. The turbulent kinetic energy increases rapidly as it approaches to the intake, and it has two peaks near the intake with the development of the flow field, which indicates that the gathered vortices evolve into two strong vortices. The turbulent kinetic energy only has one peak at the late stage, which indicates that there only exists one dominant vortex, and air is entrained in the intake, forming a fully-connected air-core vortex.
Performance Evaluation for SCO2 Compressor With Loss Models Consideration
Authors: Huang Yiting , Wang Tong 
Published: October 2020

Abstract
Centrifugal compressor is one of the key components in the Super-critical carbon dioxide (SCO2) Brayton cycle process, its performance prediction under variable operating conditions are concerned a lot with consideration of the unique of SCO2 properties. At the same time, the general techniques, including numerical simulation, test, and theoretical analysis with the loss models, are applied to evaluate the compressor performance. In addition with numerical analysis on the performance of the compressor, the flow loss models from air compressor were studied and extended the application to the SCO2 compressors, including incidence loss, blade loading loss, passage flow loss, tip clearance loss, mixing loss, disk friction loss, vaneless diffuser loss. All of these models were investigated to get the performance of a SCO2 compressor. The CO2 quality was got from the multipurpose NIST REFPROP 9.0 (NiST) which is based on Span and Wagner equation of state. The quality was added in the numerical simulation process. Besides, the passage flow loss factor has been modified to get more accurate theoretical performance prediction method for SCO2 compressor. The predicted performance map was compared to the numerical results, and the comparison results proved that, the combination of the loss models provided the similar results as those from the numerical simulation. For the SCO2 centrifugal compressor, the passage flow loss covers the most part among all the compressor flow losses. The value of the passage flow loss factor applied in the theoretical performance prediction method ranges between 0.008∼0.025, which is higher than that for air. Finally, the performance evaluation by improved loss models at different compression starting points were compared with that by the numerical results, it was found that, closer to the critical point would make the passage flow loss increase a lot, which may even exceed its rational range and the produced loss would be beyond expectation. This might be the reason for the low efficiency of SCO2 compressor in the practical working conditions.
Parametrisation of the Pressure and the Momentum Integral for Inclined Sluicegates Flows
Authors: Steppert Michael , Epple Philipp , Malcherek Andreas 
Published: October 2020

Abstract
The flow under sluice gates is nowadays frequently still determined by empirical approaches, based on the Bernoulli equation and a specific discharge coefficient which depends on the geometry of the sluice gate. This discharge coefficient is determined from a selection of tables and charts, which are based on a variety of experimental series. In 2016 Malcherek developed a fundamentally new approach to describe hydraulic structures based on integral momentum balance instead of Bernoulli’s energy conservation principle. In this approach a flow is described as the result of the integral momentum balance including pressure forces on open boundaries as well as closed walls, momentum fluxes through open boundaries and gravitational and frictional forces. In this theoretical approach, the discharge under inclined sluice gates can be described as a result of the acting pressure forces and momentum fluxes. To apply the theory, the pressure integral at the sluicegate and under the sluice gate and also the momentum integral of the flow under the sluice gate have to be known. For the determination of these values, multiphase CFD simulations for different angles of inclination and waters levels upstream of the sluicegate were done by the authors in the paper “Theoretical and numerical analysis of the pressure distribution and discharge velocity in flows under inclined sluice gates” (AJKFLUIDS2019 5020).
Using the values determined in this previous paper, parametrized model equations for the pressure and momentum integrals in dependency of the angle of inclination and upstream water levels were derived in this work. These polynomial approaches have been used to determine the three unknown physical quantities in the integral momentum balance: the pressure integral at the sluice gate, the pressure integral under the sluice gate and the momentum integral of the flow under the sluicegate. The polynomial approaches are shown in detail in this work.
A Combined CFD-Mechanistic Approach for Predicting Solid Particle Erosion in Annular Flow in Pipe Fittings and Elbows
Authors: Darihaki Farzin , Fallah Shojaie Elham , Zhang Jun , Shirazi Siamack A. 
Published: October 2020

Abstract
In internal flows, solid particles carried by the fluid could damage pipelines and fittings. Particles that are entrained in the fluid can cross streamlines and transfer a part of their momentum to the internal surface by impacts and cause local wall material degradation. Over the past decades, a wide range of models is introduced to predict particle erosion which includes empirical models, mechanistic models, and CFD which is currently the state-of-art numerical approach to simulate the erosion process. Multiphase flow under annular flow conditions adds to the complexity of the model. Although with the current computational capabilities transient CFD models are effectively applicable, this type of transient multiphase approach is not practical yet for engineering prediction of erosion especially for the large diameter applications with huge computational domains. Therefore, the presented combined approach could be utilized to obtain erosion rates for large diameter cases. Thus, an approach combining CFD and mechanistic multiphase models characterizing annular flow is developed to predict solid particle erosion. Different factors including film thickness in pipes and fittings which are affecting erosion under gas-dominated multiphase flow conditions are investigated. The results from the current approach are compared to experimental data and transient CFD simulations for annular flow in elbows showing a very good agreement with both.