bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Splitter Vanes on the Performance and Pressure Pulsation in a Centrifugal Pump
Authors: Li Chao , Gao Bo , Zhang Ning , Ni Dan 
Published: November 2019

Abstract
Two types of arrangement of splitter vanes at the outlet of a centrifugal impeller is proposed in this paper, that is, staggered vanes and splitter vanes. By means of CFD, the effects of different vanes arrangement schemes on the performance and pressure fluctuation characteristics of the centrifugal pump are compared. The influence mechanism of different schemes is explored based on the fluid flow field analysis. The results show that, compared with ordinary impellers, when the short vanes are 10 degree offset to the suction side of the main vanes, staggered vanes impellers cause the pump head and efficiency to decrease, while the amplitude of pressure pulsation at blade passing frequency (BPF) is reduced by 28% compared with that of the ordinary impeller under the design condition. In the splitter vanes scheme, the pump head and efficiency increased, however the efficiency increased more significantly under the large flow rate condition. The amplitude of pressure fluctuation at BPF is decreased by 14% compared with that of the ordinary impeller under the design condition. The existence of short vanes in both schemes changes the wake flow structure downstream the impeller vanes and tends to weaken the pressure pulsation induced by the rotor-stator interaction (RSI) phenomenon. The results can provide a reference for optimized design of the low vibration and less noisy pumps.
Computational Study of the Downpull Force on High-Head Slide Gates
Authors: Arango Escobar Juan C. , Calderon Villegas David , Benavides Moran Aldo , Molina Ochoa Alejandro 
Published: November 2019

Abstract
This paper presents CFD simulations of the flow through a real bottom outlet equipped with high-head slide gates. The operating head of the gates and the maximum flow rate are 70 m and 650 m3/s, respectively. The numerical simulations were performed in ANSYS-FLUENT version 19.2. VOF method was used to model the free surface flow downstream the slide gates. Hydrodynamic forces were calculated at nine gate openings for a standard 45° lip gate; the downpull coefficients obtained from the simulations were compared with estimates from Naudascher’s analytical method. According to the CFD results, the downpull force acting on the 45° lip gate is 5%–10% lower than the one estimated analytically for the analyzed gate positions. Additionally, the flow through an inverted 30° lip gate was simulated to estimate the downpull coefficient at various gate openings. These coefficients cannot be determined analytically. The methodology here described can easily be applied to different gate geometries for which design coefficients are not available.
Effect of Moisture Content on Mixing Air With Water-Liquid Flowing Through Inverted U-Tube for Power Plant Condenser Applications
Authors: Yousef Khaled , Hegazy Ahmed , Engeda Abraham 
Published: November 2019

Abstract
Computational Fluid Dynamics (CFD) for air/water-vapor and water-liquid two-phase flow mixing with condensation in a vertical inverted U-tube is presented in this paper. This study is to investigate the flow behaviors and underlying some physical mechanisms encountered in air/water-vapor and water-liquid mixing flow when condensation is considered. Water-liquid flows upward-downward through the inverted U-tube while the air/water-vapor mixture is extracted from a side-tube just after the flow oriented downward. The CFD simulation is carried out for a side air/water-vapor mixture volume fraction (αm) of 0.2–0.7, water-vapor mass fraction (Xv) of 0.1–0.5 in the side air/water-vapor mixture and water-liquid mass flowrate (mw) of 2,4,6, and 8 kg/s. The present results reveal that, at lower air mass flow rate, no significant effect of Xv on the generated static pressure at the inverted U-tube higher part. However, by increasing the air mass flow rates, ma ≥ 0.001 at mw = 2 kg/s, and ma ≥ 0.00125 at mw = 4 kg/s, we can infer that the lowest static pressure can be attained at Xv = 0.1. This may be attributed to the increased vapor and air mass flow rates from the side tube which results in shifting the condensation from the tube highest part due to air accumulation. This leads to increasing the flow pressure and decelerating the water-liquid flow. Raising mw from 2 to 4 kg/s at the same vapor mass ratio results in a lower static pressure due to more condensation of water vapor. The turbulent intensity and kinetic energy starts to drop approximately at ma = 0.002 kg/s, and αm = 0.55–0.76 at mw = 2 kg/s for all Xv values but no noticeable change at mw = 4 kg/s occurs. These findings estimate the operational values of air and water mass flow rates for stable air entrainment from the side-tube. Increasing the air and vapor mass ratio over these values may block the evacuation process and fails the system continuance. Likewise more air entrainment from the side-tube will decelerate the water flow through the inverted U-tube and hence the flow velocity will decrease thereafter. Moreover, this study reveals that the inverted U-tube is able to generate a vacuum pressure down to 55.104 kPa for the present model when vapor condensation is considered. This generated low-pressure helps to vent an engineering system from the non-condensable gases and water vapor that fail its function if these are accumulated with time. Moreover, the water-liquid mass flow rate in the inverted U-tube can be used to sustain the required operating pressure for this system and extract the non-condensable gases with a less energy consuming system. The present CFD model provides a good physical understanding of the flow behavior for air/water-vapor and water-liquid flow for possible future application in the steam power plant.
Development of High-Efficiency Half-Ducted Propeller Fan for Air-Conditioners by Blade Tip Shape Modification
Authors: Yoshikawa Masashi , Toyoda Hiroyuki , Daisaka Hisashi 
Published: November 2019

Abstract
We developed a high-efficiency half-ducted propeller fan to reduce the electric power consumption of the outdoor unit of air conditioner by using computational fluid dynamics (CFD). Total pressure loss coefficient on the cylindrical surface of blade tip started increasing at the middle of the blade, and the region of high total pressure loss coefficient was formed after trailing edge. Therefore, we assumed that decreasing this region helped increasing static pressure efficiency. Limiting stream lines on the pressure surface showed that the flow from leading edge leaked at the middle of the blade tip, so it was assumed that the region of the high total pressure loss coefficient arose from the leakage at the middle of the blade tip. We confirmed that static pressure at the middle of blade tip, which was the leakage point, was low. We assumed that low inward force to the flow caused the leakage. On the other hand, static pressure at trailing edge of the blade tip was high. Therefore, it was found that the inward force could be increased by making the static pressure higher at the meddle of the blade tip. In order to make the static pressure higher at the middle of the blade tip, we attempted to move the maximum camber position of the blade tip from trailing edge side to leading edge side. Calculation results showed leakage at the blade tip decreased and the static pressure efficiency increased by 0.5%. Experimental results showed that the static pressure efficiency increased by 1.7 % and sound pressure level was almost the same. For the above reasons, we found leakage of flow from leading edge could be decreased by adjusting the maximum camber position of the blade tip. Decreasing leakage contributed to increasing static pressure efficiency and decreasing electric power consumption.
Pressure Fluctuation Reduction in Side Channel Pumps Using a Modified Impeller Blade
Authors: Wei Xueyuan , Zhang Fan , Appiah Desmond , Chen Ke , Yuan Shouqi , Böhle Martin 
Published: November 2019

Abstract
For the unique performance advantages of side channel pump delivering flows at high heads, it has been applied in many fields such as petrochemical, pharmaceutical, food processing, automobile fuel pumping etc. However, the operation of the pump is strongly affected by the intensity of the pressure fluctuation, thus the pressure fluctuation exiting within the pump cannot be neglected because of its direct influence on the noise and vibration performance. Therefore, reducing the pressure fluctuation intensity is a key point for research. The side channel pump studied in this paper is a prototype with an axial channel and a 24-blade impeller. The pressure fluctuation intensity of the pump is studied using numerical simulations at best efficiency point. The Reynolds-averaged Navier-Stokes equations (URANS) are solved with the Shear Stress Transport (SST) k-ω turbulence model using commercial CFX codes. The time and frequency plots of the pressure fluctuation coefficient, Cp of the original impeller scheme at different monitoring points revealed high pressure fluctuation intensities affecting the pump’s operating reliability. For the purpose of reducing the pressure fluctuation intensity in the pump, the impeller geometry is modified with a small blade at the outer radius. The study showed that the pressure fluctuation within the pump is reduced significantly at the monitoring points. Moreover, it is found out that the pressure fluctuation in both impeller schemes are mainly caused by the flow exchange between the impeller and side channel. The results of this paper can provide reference for pressure fluctuation reduction and Noise-Vibration-Harshness (NVH) study in turbomachinery.
Physicochemical Characterization of Mammalian Mucus and Mucin Solutions in Response to pH and [Ca2+]
Authors: Curnutt Austin , Smith Kaylee , Darrow Emily , Walters Keisha B. , Vasquez Erick S. , Kundu Santanu 
Published: November 2019

Abstract
Mucus is a complex fluid that maintains moisture and simultaneously acts as a barrier and facilitates transport of select materials between the body and adjacent fluids. While mucus is comprised primarily of water, it is highly heterogeneous containing the biopolymer mucin along with lipids, salts, DNA, proteins, and cells. Complex mechanisms control the reversible network formation observed in mucus and mucin solutions. Some isolated relationships between biopolymer network structure, pH and ionic strength, and rheology have been identified; however, a complete understanding of the interplay in these mechanisms is lacking. In this effort, rheology of native mucus and mucin solutions was examined as a function of pH and salt concentration. Bulk rheology of native and artificial lung mucus confirmed that native mucus displays a solid-like behavior at low strain values. Mucus displays this solid-like gel behavior at pH values ca. 4 and below, and displays solution behavior at higher pH values. Ion concentration also plays an important role with divalent cations (Ca2+) reducing the viscosity of gelled mucin and increasing the viscosity of solution-state mucin. In addition to rheological characterization, mucin-mucin and mucin-solute interactions and resultant changes in microstructure were also studied. Morphological and chemical changes at the nano-scale were correlated to the micro-structural changes observed with rheology. Dynamic light scattering showed mucin polymer particle size heterogeneity as well as a significant increase in particle size at pH values ca. 4 and below — where the solutions display a gel behavior. Using zeta potential a decrease in dispersive forces was observed that allows for polymer-polymer interaction and particle aggregation at low pH values. Atomic force micrography showed spheroid-like aggregates between adjacent mucin particles under acidic conditions. The ability to understand and control the reversible association of network structures in polymer and biopolymer systems, such as mucin, through supramolecular interactions has fundamental impacts in the field of polymer science and engineering. There is also significant potential to advance applications involving novel hydrogel materials, such as disease treatments and drug delivery.
Flow Past Two Cylinders Arranged in Tandem Within a Microbubble Plume
Authors: Uchiyama Tomomi , Kano Ryota , Degawa Tomohiro , Takamure Kotaro 
Published: November 2019

Abstract
This study investigates the flow past two cylinders arranged in tandem within a microbubble plume inside a tank. Microbubbles with a mean diameter of 0.055 mm are released by water electrolysis from electrodes placed at the bottom of the tank. Upon rising, these microbubbles induce an upward water flow around them due to buoyancy. Orthogonally to the axis of this microbubble plume, two cylinders with a diameter D of 30 mm are arranged in tandem. The distance between the cylinders, L, ranges between 1.5D and 3D. The bubbles and the water flow around the cylinders are visualized, and the bubble velocity distribution is measured. The experiments reveal the water and bubble shear layers originating at the sides of the lower cylinder, and allow the elucidation of their behavior around the upper cylinder. Furthermore, this study makes clear the effects of L on the flow around the two cylinders, such as the stagnant bubbly flow and the bubbly wake.
Design and Development of a Small Multistage Flash Desalination System Using Aspen HYSYS
Authors: Islam Md. , Banat F. , Baba A. , Abuyahya S. 
Published: November 2019

Abstract
Fresh water demands are increasing day by day because of growing population, industrialization, and increased living standards. Desalination technology has become a significant solution of fresh drinking water for many parts of the world. Lack of fresh water resources in dry environments has encouraged the establishment of desalination processes and developed technology to compensate for water scarcity. The MSF (multistage flash) desalination technique has received wide spread acceptance due to low temperature heat source (waste heat/inexpensive energy), simple construction high process reliability and simple maintenance. MSF typically has the highest water production cost among available desalination technologies, which can be reduced with using solar energy/co-generation. Since Abu Dhabi is in the solar belt region and is blessed with huge solar energy, MSF desalination can be powered by solar power in addition to industrial waste/fossil fuel energy, which will significantly reduce the cost as well as carbon, footprint. In this research, multistage flash desalination is modelled using ASPEN HYSYS package V8. We have designed each components of the system, mostly heating source, vacuum/flash chambers, heat exchangers and developed the whole system. Some parametric study, i.e. feed rate, top brine temperature, heat input, pressure, productivity etc. of multistage flash desalination system has been conducted in this research. Two case studies have been conducted and found a relation between feed flow rate and water production rate as well as chamber pressure with vapor formation. This design will help to build the pilot plant, do experimental test and validate the model.
Experimental, Numerical and Analytical Evaluation of a Helical-Turbine Performance
Authors: Kang Donghyuk , Tsutsumi Hiromasa , Hirahara Hiroyuki 
Published: November 2019

Abstract
A helical wind turbine has been analyzed experimentally and numerically and a novel design protocol has been proposed by means of blade element and momentum theory. The subject of the present analysis is to discuss the effect of low tip speed ratio and high one, respectively. In the low tip speed ratio, the turbine is driven by the torque generated from the flow turning radially after colliding with the runner. On the other hand, in the high tip speed ratio, the turbine is operated by the torque generated from the flow passing through axially the turbine.
Experimental Investigation on the Electrokinetic Motions of Colloidal Particles at an Interfacial Boundary Between Solid and Liquid
Authors: Shirai Katsuaki , Kaji Shoichiro , Hosokawa Shigeo , Kawanami Tsuyoshi , Hirasawa Shigeki 
Published: November 2019

Abstract
We investigate electrokinetic behavior of colloidal particles in the vicinity of a solid-liquid interface. Colloidal liquids are expected to be used as thermal transport media for heat transfer applications such as nanofluids and phase change emulsions. They contain submicrometer-sized particles in liquid, and electrokinetic behavior of the solute particles should play an important role in the heat transfer between solid-liquid interfacing boundaries. However, experimental investigation of the behavior remains difficult due to the required spatial resolution beyond diffraction limit. We developed a measurement system based on laser Doppler principle using an interference of evanescent waves generated at total internal reflections of incident lasers at a solid wall. The system was developed for the measurement of velocities of colloidal particles at an interfacing boundary of colloidal liquid and a solid wall. The system has a unique advantage of a high spatial resolution in the direction perpendicular to the boundary due to the short penetration depth of an evanescent wave in the range of a few hundred nanometers. The principle and performance of the measurement system were investigated using a scanning probe in the measurement volume. We experimentally confirmed the validity of the measurement and characterized the uncertainty of velocity measurement. The system was further applied in a series of measurements of alumina particles dispersed in water in a square-shaped cell under induced electric fields. The measured velocities are proportional to the field strengths at different particle concentrations. The linear relationship is consistent with theoretical predictions, which demonstrates the feasibility of the system for the measurement of velocities of colloidal particles in the near wall region.
A Multi-Relaxation-Time Finite Volume Discrete Boltzmann Method for Viscous Flows
Authors: Chen Leitao , Sadat Hamid , Schaefer Laura 
Published: November 2019

Abstract
Conventional constitutive law-based fluid dynamic models solve the conservation equations of mass and momentum, while kinetic models, such as the well-known lattice Boltzmann method (LBM), solve the propagation and collision processes of the Boltzmann equation-governed particle distribution function (PDF). Such models can provide an a priori modeling platform on a more fundamental level while easily reconstructing macroscopic variables such as velocity and pressure from the PDF. While the LBM requires a rigid and uniform grid for spatial discretization, another similar unique kinetic model known as the finite volume discrete Boltzmann method (FVDBM) has the ability to solve the discrete Boltzmann equation (DBE) on unstructured grids. The FVDBM can easily and accurately capture curved and more complicated fluid flow boundaries (usually solid boundaries), which cannot be satisfactorily realized in the LBM framework. As a result, the FVDBM preserves the physical advantages of the LBM over the constitutive law-based model approach, but also incorporates a better boundary treatment. However, the FVDBM suffers larger diffusion errors compared to the LBM approach. Building on our previous work, the FVDBM is further developed by integrating the multi-relaxation-time (MRT) collision model into the existing framework. Compared to the existing FVDBM approach that uses the Bhatnagar–Gross–Krook (BGK) collision model, which is also known as the single-relaxation-time (SRT) model, the new model can significantly reduce diffusion error or numerical viscosity, which is essential in the simulation of viscous flows. After testing the new model, the MRT-FVDBM, and the old model, the BGK-FVDBM, on Taylor-Green vortex flow, which can quantify the diffusion error of the applied model, it is found that the MRT-FVDBM can reduce the diffusion error at a faster rate as the mesh resolution increases, which renders the MRT-FVDBM a higher-order model than the BGK-FVDBM. At the highest mesh resolution tested in this paper, the reduction of the diffusion error by the MRT-FVDBM can be up to 30%.
Dissipation of Injected Slug in Enlarged Impacting Tee in Single Branch Blocking Configuration
Authors: Cole Tanner , Dabirian Ramin , Mohammadikharkeshi Mobina , Mohan Ram , Shoham Ovadia 
Published: November 2019

Abstract
A novel Enlarged Impacting Tee-Junction (EIT), which introduces longer slugs to be dissipated utilizing “Single-Branch-Blocking” is studied experimentally and theoretically under stationary slug-injection conditions to further understand the dissipation mechanism through observation of longer slugs.
The EIT test section is designed and constructed, which consists of one inlet pipe connected to a larger, perpendicular pipe allowing flow in both directions. The inlet is 4.6 m of 0.05 m diameter pipe, while the perpendicular “manifold” is 0.074 m in diameter and 5.5 m in length. In order to observe the dissipation of longer slugs, a modification is made to the Normal EIT configuration. The longer slugs in the EIT are generated by blocking one of the EIT branches, allowing flow in only the unblocked branch of the EIT. Thus, the entire injected slug (rather than half in the case of no blocking configuration) dissipates in the branch. For this configuration, stationary slugs are injected into the EIT with lengths of 40d, 50d, 60d, and 70d (with d being the inlet diameter). A total of 64 slug injection tests are conducted utilizing both air-water and air-oil flow.
The experimental data show that slug dissipation has a nonlinear increasing relationship with mixture velocity. Furthermore, the data show that higher dissipation length is observed with air-water flow as compared to air-oil flow in the slug injection experiments due to higher shed slug volume of oil. Also, the acquired data are used to validate the EIT slug dissipation model developed by Mohammadikharkeshi (2018). For the Single-Branch-Blocking investigation, comparison between the acquired experimental data and the modified Mohammadikharkeshi (2018) Normal EIT model predictions reveals excellent comparison, with an average discrepancy of 12%.
Numerical Investigation of an Intake Duct for a Waterjet Propulsion System Using Modified Partially Averaged Navier-Stokes Method
Authors: Huang Renfang , Luo Xianwu 
Published: November 2019

Abstract
When the marine vessels exceed the speed of 30 knots, it is preferred to adopt the waterjet propulsion method due to its high propulsive efficiency, good maneuverability, less vibration and good anti-cavitation performance. The efficiency of the waterjet pump is up to 90% with advanced modern design methods while 7∼9% of total power is lost in the intake duct. In this paper, the flow simulation in an intake duct has been conducted using the modified partially averaged Navier-Stokes method for better understanding of flow features inside the intake duct and instructing how to reduce the power loss at various ship speeds and inlet velocity ratio (IVR) with considering the hull boundary layer. The nonuniformity and perpendicularity at the impeller plane is applied to analyze the flow quality at the outlet plane of intake duct. The results indicate that the nonuniformity decreases while the perpendicularity increases with increasing IVR. Thus a large IVR together with a high ship speed would cause better outflows. Further analyses of the pressure along the ramp and cutwater depict that cavitation easily occurs at the upper side of the cutwater with a larger IVR. The hydraulic efficiency is seen to firstly increase and then decrease with an increase in IVR. The hydraulic efficiency of the intake duct is over 80% during IVR = 0.4∼1.2 with the maximum value of 92.19% at IVR = 0.6.