Volume 10: Fluids Engineering最新文献

{"title":"Confinement Effects on Molecular Mechanics and Structure of the Liquid Layers at Solid-Liquid Interface","authors":"An Zou, Sajag Poudel, S. Maroo","doi":"10.1115/imece2021-70811","DOIUrl":"https://doi.org/10.1115/imece2021-70811","url":null,"abstract":"\u0000 Liquid layer structuring occurs at the solid-liquid interface. Here we present an investigation of the confinement effects on the first layer adjacent to the solid surface in a nanopore. Compared to a thin film on a surface with free liquid-vapor interface, strong confinement effects were observed in relatively small nanopores, where only structured layers exist and the first layer is affected by both surfaces. The confinement effects are weak in relatively large pores, where bulk liquid exists and the first layer is affected by the adjacent surface only.","PeriodicalId":112698,"journal":{"name":"Volume 10: Fluids Engineering","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128915313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical Investigation and Validation of Jet Temperature Effects on Nozzle-Afterbody Drag","authors":"Berke Haznedaroglu, Omer Ciftci, S. Cadirci, Serhad Aytac","doi":"10.1115/imece2021-69769","DOIUrl":"https://doi.org/10.1115/imece2021-69769","url":null,"abstract":"\u0000 In this study, jet temperature effects on afterbody drag in subsonic, transonic and supersonic flow conditions have been investigated for a wide range of nozzle throat total pressure to free-stream static pressure ratio (NPR) at Mach numbers 0.6, 0.9 and 1.2 using CFD. Preliminary CFD simulations are conducted for cold air flow with constant specific heat. Experimental data available in NASA Technical Paper 1766 is utilized for validation purposes thus, the CFD simulations are carried out for the identical geometry and boundary conditions reported in the technical paper. Depending on the Mach number, either pressure-based solver with coupled algebraic multigrid scheme or implicit density-based flow solver with Roe-FDS are used for the simulation of compressible flows to maintain convergence and obtain accurate solutions. Second order upwind schemes are preferred for all simulations and it is shown that convergence problems could be prevented when density based solvers are used at relatively high Mach numbers. For all simulations SST k-ω turbulence model proposed by Menter is selected. Based on a robust and verified CFD approach for cold jet analysis, the average drag coefficients Cd at various NPR values between 1.5 and 7 have been successfully estimated at all Ma with relative errors ranging from 5 to 15 % compared to experimental data. Then, the same numerical approach is adopted to the hot jet analysis. Further comparisons to empirical relations revealed a satisfactory agreement only at Ma = 1.2, but no acceptable match at Ma = 0.6 and 0.9.","PeriodicalId":112698,"journal":{"name":"Volume 10: Fluids Engineering","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130289424","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Transitional Flow and Heat Transfer on the Pressure Surface of a C-D Compressor Blade","authors":"S. Katiyar, S. Sarkar","doi":"10.1115/imece2021-71171","DOIUrl":"https://doi.org/10.1115/imece2021-71171","url":null,"abstract":"\u0000 A large-eddy simulation (LES) is used here to investigate the laminar-turbulent transition on the pressure surface of a controlled-diffusion (C-D) compressor stator blade at a Reynolds number (Re) of 2.1 × 105. The objective of the present study is focused upon the transition mechanism on the pressure surface and associated heat transfer. Flow features appear laminar at the beginning, followed by the undulation of velocity fluctuations, attributing to the development of elongated streamwise streaks at 27% of the chord. These streaks undergo breakdown at the mid-chord region via a secondary instability. Resolved flow structures also elucidate the formation of abundant small-scale eddies via the appearance of hairpin structures an increase of the turbulent heat flux. The decay of these structures occurs as flow further evolves downstream, attributing to local flow acceleration.","PeriodicalId":112698,"journal":{"name":"Volume 10: Fluids Engineering","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125951789","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A New Approach to Evaluate and Optimize Swirl Tube Demister Efficiency","authors":"K. Anderson, B. Reinhardt, Walead Sultani, Hannah O' Hern, Xiang Zhang, Bahman Abbasi","doi":"10.1115/IMECE2020-23623","DOIUrl":"https://doi.org/10.1115/IMECE2020-23623","url":null,"abstract":"The focus of this report is on a new technique to quantify the air-water separation efficiency of a swirl tube demister that has application in numerous water purification systems. This experimental study adds to the existing literature by quantifying the effect of design parameters on both the previously studied water collection efficiency, as well as the air bypass efficiency, defined as the ratio of the air mass flowrate exiting at the desired air outlet, over the inlet air mass flowrate. This parameter is important for the water purification field because air acts as a carrier of contaminants, necessitating that it does not leak into the purified water collection chamber. Results from this study showed there was a clear trend when comparing the air bypass efficiency to the inlet air to water ratio. As the inlet air to water ratio increased, the air bypass efficiency decreased. This trend was consistent among four different experimental apparatuses indicating that either the geometry of the swirl tube had very little effect of the air bypass efficiency, or that the ranges tested for dimensions thought to affect the swirl tube performance were not varied enough.","PeriodicalId":112698,"journal":{"name":"Volume 10: Fluids Engineering","volume":"54 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116075784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deep Learning for Intelligent Bubble Size Detection in the Spallation Neutron Source Visual Target","authors":"F. Rasheed, E. Dominguez-Ontiveros, J. Weinmeister, C. Barbier","doi":"10.1115/IMECE2020-23164","DOIUrl":"https://doi.org/10.1115/IMECE2020-23164","url":null,"abstract":"\u0000 The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) will undergo proton power upgrade (PPU), increasing the proton beam power from 1.4 MW to 2.8 MW. From 2.8 MW, 2.0 MW will go to the current First Target Station and the rest will go to the future Second Target Station (STS). The First Target Station uses a liquid mercury target that is contained in a 316L stainless steel vessel. The proton beam is pulsed at 60 Hz, with a pulse of about 0.7μs. When the proton beam hits the target, the intense energy deposition leads to a rapid rise in temperature in the mercury. This temperature rise creates pressure waves that propagate through the mercury and cause cavitation erosion. The power upgrade will cause stronger pressure waves that will further increase damage because of cavitation. Injecting small helium bubbles in the mercury has been an efficient method of mitigating the pressure wave at 1.4 MW. However, at higher power, additional mitigation is necessary. Therefore, the 2 MW target vessel will be equipped with swirl bubblers and an additional gas injection port near the nose to inject more gas in the target. To develop a gas injection strategy and design, flow visualization in water with a transparent prototypical target (“visual target”) was performed. Bubble sizes and their spatial distribution in the flow loop are crucial to understanding the effectiveness of the bubbles in mitigating pressure waves. Bubbles were generated in the visual target under varied conditions of input pressures with helium and air. Images were captured using a high-speed camera at varied frame rates at different positions away from the swirl bubbler and different depths in the flow loop under varying lighting conditions. Initially, methods such as circular Hough transforms were applied after a series of images processing to obtain a general distribution of bubble sizes. Bubbles smaller than 500 μm are preferred to effectively mitigate the effect of pressure waves, which demands an accurate bubble detection and sizing system. Intelligent detection and identification of bubble sizes alleviate misdetection and improves accuracies. Employing neural networks, intelligent detection of bubble sizes and their distribution was developed and provides a robust alternative to traditional techniques. Human intervention was employed to label in-focus and out-of-focus bubbles in the set of training images. An object detection network using a pretrained convolutional neural network was created that extracted the features from the training images. Data augmentation was used to improve network accuracy through a random transformation of the original data.","PeriodicalId":112698,"journal":{"name":"Volume 10: Fluids Engineering","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114582552","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental Investigation of the Settling of Carbon-Based Nanoparticles in Renewable Jet Fuel","authors":"Nicholas Hentges, Gurjap Singh, A. Ratner","doi":"10.1115/IMECE2020-24157","DOIUrl":"https://doi.org/10.1115/IMECE2020-24157","url":null,"abstract":"\u0000 Recent studies have shown that the addition of nanomaterials to fuels can improve combustion characteristics. A downside, however, is that these mixtures are unstable and prone to phase separation. Finding stable nanomaterial-fuel mixtures are required to make these mixtures viable for practical use. Current research studied the stability of Renewable jet fuel combined with multiple nanomaterial additives being acetylene black, graphene nanoparticles, and multiwalled carbon nanotubes, at 1.0% w/w ratio. Results were compared with prior research and it was shown that renewable jet fuel had a similar effect on settling as soy biodiesel and the results indicated that the fuel’s bulk viscosity was not a major factor determining the stability of the nanofuel.","PeriodicalId":112698,"journal":{"name":"Volume 10: Fluids Engineering","volume":"107 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124703994","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydrogen Fast Fill Modeling and Optimization of Cylinders Lined With Phase Change Material","authors":"M. Liszka, A. Fridlyand, A. Jayaraman, Michael Bonnema, C. Sishtla","doi":"10.1115/IMECE2020-24154","DOIUrl":"https://doi.org/10.1115/IMECE2020-24154","url":null,"abstract":"This work is a continuation of a previous study (IMECE2019-11449) which sought to explore the feasibility and means of successfully modeling the hydrogen fast filling process of cylinders lined with phase change material (PCM) entirely in CFD software. The first focus of this work was to address the simplistic approach of how the liner temperature was modelled in the previous study. Previously, the entire liner was assigned a single temperature which was obtained and updated through the lumped heat capacity method. This meant that the hotter gas at the end of the cylinder opposite the inlet was in contact with a liner at a temperature lower than could realistically be expected. This was remedied by splitting the liner into four sections. Two sections were used for the curved portions at each end of the cylinder, and the straight wall section was split into two. Each section had its temperature independently calculated through the lumped heat capacity method. A temperature difference on the order of a ten degrees Celsius was observed between the different sections of the liner prior to latent heating beginning. The mass averaged temperature of the hydrogen inside the cylinder obtained with the sectioned wall case matched that obtained with the single wall temperature almost exactly, less than a degree difference. Despite the unexpected findings of the average hydrogen temperature not changing much when the wall is split into sections, this approach was still taken with all the cases completed in this study. The liner could be split into a greater amount of sections than four, but this was considered unnecessary due to the findings regarding the overall hydrogen temperature. Four sections were considered adequate and used to model the temperature gradient along the wall or liner. The effect of gravity on the filling process was also explored based on the orientation of the cylinder. This required completing three-dimensional simulations to accurately simulate buoyancy driven flow in horizontally mounted cylinders. All the simulations were completed with ANSYS Fluent 2019 R1 without the use of additional software to handle the heat transfer involving the PCM. All simulations were completed with the coupled pressure-based solver and K-Omega SST turbulence model. The gas properties were obtained from tables generated from NIST properties (REFPROP) available within ANSYS Fluent to limit the amount of error in the accumulated mass within the cylinder due to inaccurate gas properties. The initial conditions for the gas and liner temperatures were 25°C and 100 bar for the gas pressure. A constant mass flow rate of 0.02174 kg/s at a temperature 0°C were used as the initial conditions for the inlet hydrogen gas.","PeriodicalId":112698,"journal":{"name":"Volume 10: Fluids Engineering","volume":"85 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126237254","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Strain Response and Aerodynamic Damping of a Swirl Distortion Generator Using Computational Fluid Dynamics","authors":"A. Hayden, A. Untăroiu","doi":"10.1115/IMECE2020-24599","DOIUrl":"https://doi.org/10.1115/IMECE2020-24599","url":null,"abstract":"\u0000 Boundary layer ingestion (BLI) concepts have become a prominent topic in research and development due to their increase in fuel efficiency for aircraft. Virginia Tech has developed the StreamVane™, a secondary flow distortion generator, which can be used to efficiently test BLI and its aeromechanical effects on turbomachinery. To ensure the safety of this system, the complex vanes within StreamVanes must be further analyzed structurally and aerodynamically. In this paper, the induced strain of two common vane shapes at three different operating conditions is computationally determined. Along with these observations, the aerodynamic damping of these vanes are calculated to predict flutter conditions at the same three operating points. Steady CFD calculations are done to acquire the aerodynamic pressure loading on the vanes. Finite element analysis (FEA) is performed to obtain the strain and modal response of the StreamVane structure. The mode shapes and steady CFD are used to initialize an unsteady CFD analysis which determines the aerodynamic damping of the vanes. The testcase used for this evaluation was specifically designed to overstep the structural limits of a StreamVane, and the results provide an efficient computational method to observe flutter conditions of stationary systems.","PeriodicalId":112698,"journal":{"name":"Volume 10: Fluids Engineering","volume":"23 10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125782721","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quantifying the Dynamics of Water-CO2 Multiphase Flow in Microfluidic Porous Media Using High-Speed Micro-PIV","authors":"Yaofa Li, G. Blois, F. Kazemifar, K. Christensen","doi":"10.1115/IMECE2020-24545","DOIUrl":"https://doi.org/10.1115/IMECE2020-24545","url":null,"abstract":"\u0000 Multiphase flow in porous media is central to a large range of applications in the energy and environmental sectors, such as enhanced oil recovery, groundwater remediation, and geologic CO2 storage and sequestration (CCS). Herein we present an experimental study of pore-scale flow dynamics of liquid CO2 and water in two-dimensional (2D) heterogeneous porous micromodels employing high-speed microscopic particle image velocimetry (micro-PIV). This novel technique allowed us to spatially and temporally resolve the dynamics of multiphase flow of CO2 and water under reservoir-relevant conditions for varying wettabilities and thus to evaluate the impact of wettability on the observed physics and dynamics. The preliminary results show that multiphase flow of liquid CO2 and water in hydrophilic micromodels is strongly dominated by successive pore-scale burst events, resulting in velocities of two orders of magnitude larger than the bulk velocity. When the surface wettability was altered such that imbibtion takes place, capillarity and instability are significantly suppressed, leading to more compact and axi-symmetric displacement of water by liquid CO2 with generally low flow velocities. To our knowledge, this work represents the first of its kind, and will be useful for advancing our fundamental understanding and facilitating pore-scale model development and validation.","PeriodicalId":112698,"journal":{"name":"Volume 10: Fluids Engineering","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129491692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Inlet Box Structure Optimization of a Large Axial-Flow Fan Using Response Surface Methodology","authors":"Jin Xiong, Yin Zhang, Penghua Guo, Jingyin Li","doi":"10.1115/IMECE2020-23566","DOIUrl":"https://doi.org/10.1115/IMECE2020-23566","url":null,"abstract":"\u0000 Large axial-flow fans are widely used in many fields. The inlet box is an integral part of large axial-flow fans, and a well-designed inlet box could effectively improve fan efficiency. However, the inlet box structure is complicated, and the existing inlet box design method severely depends on the design experience. In this study, we propose a structure optimization design system based on a surrogate model technique for researching the critical structure parameters of the inlet box and accomplishing aerodynamic performance optimization. As for this expensive optimization problem, the design system contains twice optimization procedures by using the Response Surface Methodology (RSM) with the orthogonal design method. The optimization object is an existing large axial-flow fan. The optimization objective is the total pressure efficiency of the fan, and the total pressure rise is the restriction condition. We generate eighteen different inlet boxes connect with the same impeller and outlet pipe by the orthogonal design method and calculated fan aerodynamic performance by CFX software. After the first optimization, we find the key structural parameters by the sensitivity analysis and the reselect variables total of 25 cases are adopted in a further RSM optimal process. The ultimate surrogate model estimates the fan with the optimal inlet box has a better aerodynamic characteristic and a 6.7% total pressure efficiency rise. Finally, we compare the aerodynamic characteristics of the ultimate design fan and the initial fan by CFD simulation. The numerical results show that: the total pressure efficiency is 6.5% higher than that of the initial impeller, and the pressure rise is 3% higher than that of the initial impeller. The result demonstrates that some most critical parameters of the inlet box structure decide the aerodynamic performance, and the inlet box optimization effectively increases the fan efficiency in the meanwhile.","PeriodicalId":112698,"journal":{"name":"Volume 10: Fluids Engineering","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126812779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}