Volume 7: Fluids Engineering最新文献

{"title":"Fully Transient Model of a Hydraulic Accumulator","authors":"Filipp Kratschun, Andris Rambaks, K. Schmitz","doi":"10.1115/imece2019-11343","DOIUrl":"https://doi.org/10.1115/imece2019-11343","url":null,"abstract":"\u0000 Hydraulic piston accumulators play a major role especially within the field of stationary hydraulics. The calculation of the amount of hydraulic energy which can be stored in such an accumulator is crucial when it comes to a precise system design. The knowledge of the temperature within the accumulator is required in order to calculate the amount of energy to be stored.\u0000 This paper presents a simulation approach with the goal to simulate the gaseous phase within a piston accumulator and to present results for the polytropic exponent without conducting costly experiments. The temperature, pressure, density and velocity profiles inside of the gaseous phase as well as the temperature profile inside the boundaries are calculated transiently in order to achieve that goal.\u0000 The effects of dissipation, heat transfer and transient wall temperature are added to the simulation routine continuously and their effects on the results are discussed in detail.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115958461","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":"CFD Analysis of Flow Structures in a Mixing Chamber","authors":"S. Cândido, J. Marques, A. Tomé, A. Amorim, Stefan K. Weber","doi":"10.1115/imece2019-11747","DOIUrl":"https://doi.org/10.1115/imece2019-11747","url":null,"abstract":"\u0000 Special mixing chambers are usually used to perform scientific experiments or for routine industrial production processes. This is the case, typically, of fan mixers in a baffled tank. Mixing chambers comprise, among other alternative elements, two counter-rotating fans at the bottom and top. These will eventually allow a mixing effect on the chamber with an adequate level of uniformity. Herein a computational flow simulation is performed for the mixing conditions of air and SO2 inside the chamber used in the CLOUD experiment, by studying in detail the flow structures and uniformity inside the chamber. This Unsteady Navier-Stokes computation is performed using the kω-SST and SAS turbulence models. A first validation step is performed by using an experimental test case, comprising a T-junction geometry, that performs the mixing of air and N2. Following this validation step a detailed analysis of the flow structures inside the 3D chamber is conducted, and specific insights are given regarding the flow uniformity. A detailed analysis of the computed mixing flow structures for the SST and SAS turbulence models is also described. It is shown that the SAS model captures with more detail the macro and meso-mmixing process with an accuracy of, at most, 6%. This value can be further reduced to values around 2% by resorting to high density meshes, with the associated computational burden.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"118 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127974917","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 of the Euler Turbomachinery Equation and Analysis of the Impact of the Impeller Design on the Fan Performance by an Optimization Study","authors":"M. Fritsche, P. Epple, Stefan Gast, A. Delgado","doi":"10.1115/imece2019-11572","DOIUrl":"https://doi.org/10.1115/imece2019-11572","url":null,"abstract":"\u0000 The working machines such as fans, blowers and pumps are often used for transporting fluids in technical systems. The rotating impeller is used for energy conversion of mechanical work into hydraulic work. Leonhard Euler published this relation of energy conversion in 1752–1756 and is still used today for the basic design of turbomachinery.\u0000 In the present work, the Euler-Equation is described and presented in detail. Furthermore, a simplified parameterized blade channel of a centrifugal impeller is investigated with numerical simulation methods. The theoretical Euler-Equation is compared and validated with the numerical CFD-results. Based on an extensive CFD-optimization study, the impact of the impeller design parameters on the fan performance has been investigated. For this purpose, the blade shape and the operating conditions (speed and volume flow rate) were systematically varied.\u0000 After an extensive grid study, the influence of the blade channel contour on the fan performance was investigated. The results of the study are presented in detail.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128811389","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":"Cavitation Number As a Function of Disk Cavitator Radius: A Numerical Analysis of Natural Supercavitation","authors":"R. Prichard, W. Strasser, T. Eldredge","doi":"10.1115/IMECE2019-12492","DOIUrl":"https://doi.org/10.1115/IMECE2019-12492","url":null,"abstract":"\u0000 Due to the greater viscosity and density of water compared to air, the maximum speed of underwater travel is severely limited compared to other methods of transportation. However, a technology called supercavitation — which uses a disk-shaped cavitator to envelop a vehicle in a bubble of steam — promises to greatly decrease skin friction drag. While a large cavitator enables the occurrence of supercavitation at low velocities, it adds substantial drag at higher speeds. Based on CFD results, we propose a new relationship between drag coefficient and disk cavitator radius, and we predict the optimum cavitator radius for a particular torpedo design.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"300 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134324884","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 Characterization of a Novel Piezoelectric Fan","authors":"Jingru Benner, Eric Shilyuk, Jarrod A. Coletta, M. Mortazavi, Anthony D. Santamaria, Shun Su, Tony Nguyen","doi":"10.1115/imece2019-11039","DOIUrl":"https://doi.org/10.1115/imece2019-11039","url":null,"abstract":"\u0000 Piezoelectric fans have attracted attentions in the past decades because of their low energy consumption, low noise level, light weight and reliability. A novel form of piezoelectric flapping fan is characterized experimentally and numerically. An experimental setup was built to measure the pressure and flow rate of piezoelectric fans with low static pressure at various frequencies. The fan performance curve was established. A high speed camera system was used to analyze the oscillation motion of the fan wings. The displacement of the leading edge and trailing edge of the piezoelectric fan wings are used as inputs to describe the deflection of the fan in the numerical model. The flow field obtained from the model is analyzed. The vortex shedding is observed and discussed. The pressure and flow rate obtained from the 2D numerical model are compared with the experimental results. The results provide a fundamental understanding of a piezoelectric fan with opposing oscillating wings.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117045512","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":"CFD Modeling of the Hydrogen Fast Filling Process for Type 3 Cylinders and Cylinders Lined With Phase Change Material","authors":"M. Liszka, A. Fridlyand, A. Jayaraman, Michael Bonnema, C. Sishtla","doi":"10.1115/imece2019-11449","DOIUrl":"https://doi.org/10.1115/imece2019-11449","url":null,"abstract":"\u0000 A simulation of the fast filling of a 195-liter type 3 tank with hydrogen was completed with ANSYS Fluent as a baseline case for developing a CFD model capable of accurately modeling the hydrogen cylinder filling process. 141-second profiles of mass flow and temperature of the incoming hydrogen flow into the cylinder were prescribed from experimental data previously collected at the Gas Technology Institute (GTI) in Des Plaines, IL. All the simulations were completed with the coupled pressure based algorithm with the K-Omega SST turbulence model and real gas NIST properties (REFPROP) to capture the effects of compressibility of hydrogen during the filling process. Gravity was enabled in the axial direction of the cylinder. The initial pressure and temperature in the cylinder were 124 bar and 292.3 K, respectively, with a target, experimental pressure of 383 bar at the end of the filling.\u0000 For the initial case, the walls of the cylinder were modelled as adiabatic to reduce the computational effort. The final pressure and temperature of the adiabatic wall case matched the experimental pressure and temperature within approximately 30 bar and 6 degrees, respectively. The overall pressure and temperature profiles over the course of the filling process also provided a good match between the simulation results and experimental data. A conjugate heat transfer case with the aluminum liner as part of the domain and an adiabatic outer wall was attempted in order to capture the heat transfer to the liner. The conjugate heat transfer case provided promising results but was taxing in the computational time needed to simulate the entire filling process.\u0000 A User Defined Function (UDF) for a simple lumped heat capacitance model was applied at the wall to model the wall temperature and capture the heat transfer occurring to the wall while reducing the time needed to complete the simulation. The final pressure prediction for this case was excellent, within 3 bar of the experimental value, and matched it accurately for the duration of the fill process. The final temperature prediction worsened and exceeded the experimental value by 16 degrees Celsius. The UDF model also allowed the ability to easily explore more exotic liners such as Phase Change Materials (PCM) which were also simulated in this work.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115393970","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":"Verification of CFD Prediction Accuracy of Flow Turbulence Induced Vibration Loadings Around a Pipe Bend","authors":"Xidong Hu, Shaoxiang Qian, Kota Matsuura, S. Kataoka","doi":"10.1115/imece2019-10200","DOIUrl":"https://doi.org/10.1115/imece2019-10200","url":null,"abstract":"\u0000 Bends widely used in process piping systems can cause strong pressure fluctuations on pipe wall for a high-velocity flow, and hence, flow induced vibration (FIV) of piping occurs. Currently, the FIV assessment is made primarily based on the guideline published by Energy Institute. However, it is based on very conservative assumptions, and thus, results in excessive design of piping systems. The coupling analysis of CFD/FEA (Computational Fluid Dynamics/Finite Element Analysis) is expected to be a useful approach for more proper FIV assessment. The present study mainly aims at verifying CFD prediction accuracy of wall pressure fluctuations or FIV loadings around a pipe bend.\u0000 In CFD benchmark study, large eddy simulations (LES) with dynamic Smagorinsky model (DSM) were performed for a 90° mitred bend used in the experiments in literature, under two different flow velocity conditions. The benchmark simulation results show that the power spectral density (PSD) of the LES-predicted wall pressure fluctuations at the sampling locations is near to the experimental results with moderate conservativeness desirable for engineering applications. Also, the LES-predicted peak frequencies are close to the experimental data. Therefore, it is suggested that the applied numerical approaches be applicable to predict the FIV loadings with moderately high accuracy for engineering applications.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"269 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116066685","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 DNS Study on Roughness-Induced Transition in Oscillating Pipe Flow by Employing Overset Methodology","authors":"Ali A. Abdulrasool, Yongho Lee","doi":"10.1115/imece2019-12300","DOIUrl":"https://doi.org/10.1115/imece2019-12300","url":null,"abstract":"\u0000 In this paper, we model a circular pipe with wavy inner wall, for the purpose of studying the role of surface roughness in a purely oscillating flow. Overset-grid technique is utilized for two combined flow domains, and the interpolation process within the shared zone is validated with the exact laminar flow solution for long-time oscillation. Direct numerical simulations are performed at different flow conditions, taking advantage of the overlapping capability of the spectral element method. All simulations begin with zero initial conditions, and periodic boundary conditions are applied at the two ends of the pipe with different roughness heights. The internal pipe roughness modeled by the overset meshes operates as a triggering mechanism for transition to turbulence, and the critical Reynolds number based on the Stokes thickness and the centerline velocity amplitude is determined to be 223.5 at the Stokes number of 10. The results confirm that the periodic turbulence bursts react to the presence of the roughness with different levels of turbulence intensity among the four Stokes numbers presented herein. Additionally, friction losses are calculated and compared with three cases of the existing experimental results for smooth and rough walls.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129637965","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":"Detailed Three-Dimensional Velocity Field Measurements of a Complex Internal Cooling Flow Within a Gas Turbine Vane","authors":"M. Benson, D. Helmer, B. V. Poppel, Benjamin Duhaime, David Bindon, Mattias Cooper, R. Woodings, C. Elkins","doi":"10.1115/IMECE2019-11764","DOIUrl":"https://doi.org/10.1115/IMECE2019-11764","url":null,"abstract":"\u0000 A 6.67 scale model of the Advanced Recirculation Total Impingement Cooling (ARTIC) gas turbine vane insert’s leading edge was designed, built using stereolithography (SLA) fabrication methods, and tested using Magnetic Resonance Velocimetry (MRV), a non-invasive data acquisition technique that captures three-dimensional, three-component velocity fields of a copper sulfate solution over the course of several hours. The experimental apparatus supplied constant flow rates through a test section placed within a 3.0 Tesla MRI magnet. Tests were run at two fully turbulent flow rates corresponding to Reynolds numbers based on hydraulic diameter of 10,000 and 20,000 with the higher flow rate case achieving dynamic similarity with the full-scale ARTIC device. The experimental results elucidated key details and intricacies of the complex flow within the insert. Analysis of flow distribution between each of the three independent impingement zones revealed a degree of measurable jet to jet variability. Stagnation and recirculation zones were detected, informing design modifications and enabling assessment of inlet effects on impingement. Measurement uncertainty was assessed and estimated to be approximately 7.5% of the peak velocity at the inlet to the central feed cavity.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129895276","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 Natural Evolution Based Numerical Optimisation Framework to Develop and Enhance Airfoil-Slat Arrangement","authors":"Sushrut Kumar, Priyam Gupta, R. Singh","doi":"10.1115/imece2019-10846","DOIUrl":"https://doi.org/10.1115/imece2019-10846","url":null,"abstract":"\u0000 Leading Edge Slats are popularly being put into practice due to their capability to provide a significant increase in the lift generated by the wing airfoil and decrease in the stall. Consequently, their optimum design is critical for increased fuel efficiency and minimized environmental impact. This paper attempts to develop and optimize the Leading-Edge Slat geometry and its orientation with respect to airfoil using Genetic Algorithm. The class of Genetic Algorithm implemented was Invasive Weed Optimization as it showed significant potential in converging design to an optimal solution. For the study, Clark Y was taken as test airfoil. Slats being aerodynamic devices require smooth contoured surfaces without any sharp deformities and accordingly Bézier airfoil parameterization method was used. The design process was initiated by producing an initial population of various profiles (chromosomes). These chromosomes are composed of genes which define and control the shape and orientation of the slat. Control points, Airfoil-Slat offset and relative chord angle were taken as genes for the framework and different profiles were acquired by randomly modifying the genes within a decided design space. To compare individual chromosomes and to evaluate their feasibility, the fitness function was determined using Computational Fluid Dynamics simulations conducted on OpenFOAM. The lift force at a constant angle of attack (AOA) was taken as fitness value. It was assigned to each chromosome and the process was then repeated in a loop for different profiles and the fittest wing slat arrangement was obtained which had an increase in CL by 78% and the stall angle improved to 22°. The framework was found capable of optimizing multi-element airfoil arrangements.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132684526","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}