Volume 7: Fluids Engineering最新文献

{"title":"Numerical Verification of the Thermodynamic Determination of the Hydraulic Efficiency of Radial Fans","authors":"P. Epple, M. Fritsche, Felix Reinker, S. Wiesche","doi":"10.1115/imece2019-11417","DOIUrl":"https://doi.org/10.1115/imece2019-11417","url":null,"abstract":"\u0000 For fans without cooling it is possible to determine the hydraulic efficiency measuring the pressure and the temperature rise through the fan. The shaft work can be determined according applying the first law of thermodynamics for an open system. Without any losses the change of state would be isotropic and the work done equal to the specific heat at constant pressure of the fluid times the isentropic temperature rise in the impeller. Due to the losses, however, the real temperature at the exit of the impeller will be higher than the isentropic temperature since the real process is polytropic. The isentropic temperature at the exit of the impeller can be computed by the isentropic relations with the inlet temperature and the pressure rise. The hydraulic efficiency can be computed as the ratio of the isentropic temperature rise divided by the real temperature rise.\u0000 In order to verify this thermodynamic approach for the determination of the hydraulic efficiency CFD simulations of a radial fan were performed. In the CFD simulation the hydraulic power, the shaft power, the pressure rise and the temperature rise can be read out and computed directly. In such a way the hydraulic efficiency computed by the ratio of the hydraulic power by the shaft power can be compared by the thermodynamically computed efficiency. In this work this comparison has been performed and the results and the precision of the thermodynamically predicted efficiency are presented and discussed in detail.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"44 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":"123182082","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":"Analysis of Labyrinth Seal Flow Patterns to Improve Bulk Flow Code Predictions","authors":"Nathaniel P Gibbons, Cori Watson-Kassa, C. Goyne, H. Wood","doi":"10.1115/imece2019-10972","DOIUrl":"https://doi.org/10.1115/imece2019-10972","url":null,"abstract":"\u0000 Non-contacting annular seals are frequently used in turbomachinery to reduce leakage of a fluid through a section with a large pressure differential. A typical type of non-contacting seal is the labyrinth seal, where circumferential grooves are cut into the rotor, stator or both. Using a tortuous path, labyrinth seals reduce leakage by dissipating the fluid’s kinetic energy through viscous forces caused by the formation of vortices in each seal groove.\u0000 Due to a lower cost when compared to experimental measurements, bulk flow codes are frequently used for predicting seal contributions to rotordynamic performance. Existing seal codes use constant or linear values for the fluid film thickness at different seal sections and display inaccuracies in their prediction of velocity and pressure profiles and rotordynamic coefficients for labyrinth seals when compared to experimental data. The primary objective of this study is to determine the effect of implementing an effective film thickness into the governing bulk flow equations on the code prediction of axial velocity and pressure profiles.\u0000 Simulations were run using ANSYS CFX with cross-sectional models of individual seal grooves. Seal parameters, including inlet circumferential velocity and rotor speed, were varied to better understand the behavior of the film thickness under various operating conditions. Streamlines were used to determine the maximum film thickness and an effective film thickness profile that can be used in the modified bulk flow code. Modified governing equations were developed, and predictions for the axial profiles resulting from the modified code solutions for the zeroth order governing equations are compared to CFD results and previous code predictions for improved accuracy. Preliminary results for a set of cases indicate far higher accuracy when an effective film thickness is used and represent the first results from a seal bulk flow code that implements a nonlinear effective film thickness. Improvement in code prediction of flow behavior across the seal, and subsequently in the seal codes accurate prediction of rotordynamic coefficients, allows for the design of more efficient and effective seals and machine systems.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"11 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":"127201428","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":"Vortex Generator Designs to Improve Flow for a Vehicle Side-View Mirror","authors":"Zulong Dong, B. Jawad, Liping Liu, H. Metwally","doi":"10.1115/imece2019-10669","DOIUrl":"https://doi.org/10.1115/imece2019-10669","url":null,"abstract":"\u0000 The unsteady airflow over automotive side-view mirrors is a typical source of turbulence which creates extra drag force, aerodynamic noise and vibration. A CFD analysis is presented for vortex generators (VGs) application on the vehicle side-view mirrors for the purpose of flow improvement. Vortex generators are used to delay flow separation and increase the control surfaces which affect the drag force and down force of the vehicle. Reduced drag force can potentially increase fuel economy, and an increased downforce will increase vehicle grip force and improve vehicle stability which is essential for racing cars. This paper presents practical solutions for mitigating flow turbulence and adjusting down force for existing side-view mirrors.\u0000 Four VG configurations were designed and numerically analyzed in combination with the baseline model at air speeds ranged from 15 to 80 miles per hour. This research investigated the effect of each VG configuration on the side-view mirror’s aerodynamic performance. The turbulent flow through the side-view mirror were analyzed by using standard K-epsilon (K-ε) Reynolds-averaged Navier-Stokes method. The drag and down forces results were obtained and compared with the baseline model. The CFD analysis concluded the following: (1) Setting the VGs with a 5 degree attack angle on the upwind face of the mirror slightly reduced the drag force. (2) Setting the VGs at the top of the mirror surface greatly increased the downforce with a large drag force increase.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"36 6 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":"123354277","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":"Direct Pressure Measurement and Flow Visualization of Cavitation in a Converging-Diverging Nozzle","authors":"B. Gallman, B. T. Beck, M. Hosni","doi":"10.1115/imece2019-12236","DOIUrl":"https://doi.org/10.1115/imece2019-12236","url":null,"abstract":"\u0000 While normally certain unwanted phenomena are to be avoided, cavitation has useful engineering applications. Specifically, it can be used as to create cooling potential in a novel non-vapor compression refrigeration process. Cavitation occurs when the pressure of the working fluid (compressed liquid) drops below the saturation pressure. Since the cavitation (flash) results in an abrupt reduction in temperature, the working fluid can take in energy as heat from the surroundings during cavitation, which results in a cooling potential (refrigeration). In a converging-diverging nozzle, as the fluid passes through the throat the pressure decreases. If the pressure drops below the saturation pressure, cavitation can occur. The current research focuses on measuring the pressure nearby the cavitation front, and the associated pressure distribution within the two-phase region, in a converging diverging nozzle. A blow-down flow system was used to conduct measurements with water as the working fluid. The flow rate was measured with a rotameter and a Coriolis flow meter. The nozzle is a transparent 3D printed nozzle with an inlet diameter of 9.3 mm, throat diameter of 1.71 mm, and an outlet diameter of 9.3 mm. The upstream reservoir was kept at atmospheric pressure and was elevated above the level of the nozzle inlet. The downstream reservoir was evacuated to create a pressure difference that would drive fluid through the nozzle. The pressure distribution within the nozzle was measured using eight pressure transducers connected to the nozzle with 0.006” diameter taps, and a high-speed camera was used to capture flow visualization. The pressure distribution was measured for steady cavitating flow at several back pressures, and during an increasing flow rate to capture pressure changes during cavitation initiation. These results give direct pressure measurements during cavitating flow, along with the accompanying flow visualization. They should prove useful for furthering the understanding of the metastable fluid mechanics behavior of cavitating flows, and thereby contribute to the ability to ultimately maximize the cooling potential of the cavitation phenomena.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"11 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":"123470452","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":"Computational Evaluation of a Novel Aerodynamic Road Vehicle Design and Drag Reduction Using Vortex Generators","authors":"B. B. Arora, Ujjwal Suri, Utkarsh Garg, Shraman Das, Sushrut Kumar","doi":"10.1115/imece2019-11319","DOIUrl":"https://doi.org/10.1115/imece2019-11319","url":null,"abstract":"Vehicle aerodynamics is a prime domain of research and development. Multiple active and passive aerodynamic systems have been applied for its enhancement. The reduction of drag plays a pivotal role in the improvement of vehicle aerodynamic performance. The present paper studies the innovative design of a road vehicle for a fuel efficiency challenge, implemented for optimal drag reduction. Vortex generators are utilized as a passive aerodynamic feature for further minimization of the wake region size and reduction of pressure drag. High fidelity computational fluid dynamics simulations were applied for the evaluation of this design. Data was collated from simulations for both the cases, with and without the usage of vortex generators and compared objectively. The results of the study establish that the vehicle design has an exceptionally low drag coefficient. It also exhibits a strong reduction in drag when the vortex generators are fitted. These results reveal that the design can be deployed for production as a worthy competition vehicle.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"31 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":"126503821","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":"2D and 3D Stability of Cavity Flows in High Mach Number Regimes","authors":"Parshwanath S. Doshi, R. Ranjan, D. Gaitonde","doi":"10.1115/imece2019-10828","DOIUrl":"https://doi.org/10.1115/imece2019-10828","url":null,"abstract":"\u0000 The stability characteristics of an open cavity flow at very high Mach number are examined with BiGlobal stability analysis based on the eigenvalues of the linearized Navier-Stokes equations. During linearization, all possible first-order terms are retained without any approximation, with particular emphasis on extracting the effects of compressibility on the flowfield. The method leverages sparse linear algebra and the implicitly restarted shift-invert Arnoldi algorithm to extract eigenvalues of practical physical consequence. The stability dynamics of cavity flows at four Mach numbers between 1.4 and 4 are considered at a Reynolds number of 502. The basic states are obtained through Large Eddy Simulation (LES). Frequency results from the stability analysis show good agreement when compared to the theoretical values using Rossiter’s formula. An examination of the stability modes reveals that the shear layer is increasingly decoupled from the cavity as the Mach number is increased. Additionally, the outer lobes of the Rossiter modes are observed to get stretched and tilted in the direction of the freestream. Future efforts will extend the present analysis to examine current and potential cavity flame holder configurations, which often have downstream walls inclined to the vertical.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"20 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":"125692668","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":"Investigating the Flowfield Physics Within Compressible Turbulent Boundary Layers","authors":"F. Ferguson, Dehua Feng, Yang Gao","doi":"10.1115/imece2019-10079","DOIUrl":"https://doi.org/10.1115/imece2019-10079","url":null,"abstract":"\u0000 Predicting the velocity, the temperature and the heat transfer rates within compressible boundary layers remains a challenging problem. Under compressibility and high Reynolds conditions, the density variations become very significant, resulting in high heat transfer rates. The net result is an altering of the dynamics within the boundary layer that is significantly different from its laminar counterpart. Physical properties, such as the specific heat capacities, the viscosity and the thermal conductivity, which are often considered constant, now vary with respect to temperature, creating a strong coupling between the velocity and the temperature fields. Despite the progress made in this field of research, a common issue frequently expressed in the literature is the difficulty in acquiring high quality time-resolved velocity and temperature data in compressible flows, especially near the wall. The major objective of this study is to demonstrate the capabilities of the Integral-Differential Scheme (IDS) by solving the flow field challenges within compressible boundary layers. It was demonstrated that IDS have the capability of accurately solving the full Navier-Stokes equations under realistic conditions. In the case of the compressible boundary layer, the IDS capture the flow field physics. However, it was demonstrated that the IDS is highly sensitive to grid resolution as well as the prescribed boundary conditions.","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":"125701450","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":"Natural Convection in Yield Stress Fluids From a Confined Horizontal Plate","authors":"S. Patel, A. Raja, R. Chhabra","doi":"10.1115/imece2019-11258","DOIUrl":"https://doi.org/10.1115/imece2019-11258","url":null,"abstract":"\u0000 The heat transfer characteristics from an isothermal heated plate in a quiescent yield stress fluid in a cavity was investigated over a wide range of parameters (Rayleigh number, 102 ≤ Ra ≤ 105, Prandtl number, 10 ≤ Pr ≤ 100, and Bingham number, Bn ≥ 0) where the flow is known to be laminar and steady. The coupled momentum and energy equations have solved here numerically within the framework of Boussinesq approximation to capture the temperature-dependent fluid density. The results demonstrate that for a given value of the Rayleigh number, there exists a critical value of the Bingham number, above which the fluid is completely unyielded and heat transfer occurs solely by conduction. In order to delineate the effect of domain geometry on the conduction limit, the study was extended over a range of geometrical aspects by varying the aspect ratio (λ = diameter of the cavity/ a length of the plate), 2 ≤ λ ≤ 5. This work shows that the critical value of the Bingham number can be described as a function of geometry of domain, Ra and Pr. The value of critical Bingham number increases with the increasing aspect ratio and Rayleigh number in order to approach the conduction limit. The yield surfaces show that the increasing values of Rayleigh number induce fluid-like behaviour whereas Bingham number opposes this propensity. The average Nusselt number decreases with the increasing Bingham number due to the suppression of the advective component of heat transfer.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"96 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":"131596013","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":"Effects of Spraying Parameters on the Paint Transfer Efficiency in Air Spray","authors":"Simin Zhang, Guolei Wang, Xingjie Liu, Xiaotong Hua, Zhiliang Chen, Ken Chen","doi":"10.1115/imece2019-11896","DOIUrl":"https://doi.org/10.1115/imece2019-11896","url":null,"abstract":"\u0000 Automation is widely used for automotive paint application because of the repeatability of the resulting surface finish, as well as the benefit of removing humans from a hazardous environment. So the improvement of automobile coatings is significant. One compelling aspect of improvement is the paint transfer efficiency (TE), which is defined as the amount of paint that remains on a surface relative to the amount supplied to the paint applicator during coating operations. The effects of spray parameters namely shaping air pressure, atomizing air pressure, paint flow rate, spraying distance and spray velocity on paint transfer efficiency. A orthogonal experiment is designed to analysis the effects of spraying parameters on paint transfer efficiency. After the acquisition and analysis of all experiments, the relationship between spraying parameters and paint transfer efficiency is performed. Through variance analysis and regression analysis of experiment data, a conclusion following had been drawn: shaping air pressure has the strongest influence on TE, shaping air pressure and spray distance are inversely proportional to TE, atomizing air pressure is proportional to TE, paint flow rate and spray velocity nearly have no influence on TE.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"261 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":"133040656","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":"Improving the Performance of Centrifugal Pumps in Serial and Parallel Configurations Using Digital Twins","authors":"Andrés L. Carrillo Peña, Jeffer S. Eugenio Barroso, Alberto A. Martínez Vesga, S. R. Prada, Victor A. Ardila Acuña","doi":"10.1115/imece2019-12038","DOIUrl":"https://doi.org/10.1115/imece2019-12038","url":null,"abstract":"\u0000 Centrifugal pumps are devices commonly used in countless industrial and residential applications, from water supply systems to oil and gas processing plants. These rotatory hydraulic machines have a strong impact on the energy consumption of industry worldwide, not only because of their vast amount but also because of their continuous operation. Therefore, developing techniques to improve the efficiency of pumping systems is of great help to make communities and industrial activity more sustainable. The overall performance of these pieces of machinery cannot be fully predicted by means of analytical procedures due to the complexity of the fluid flow phenomena that occurs in their interior, so it is common practice to resort to alternate modeling techniques, such as computer aided numerical analysis, which can predict the performance of a pump, given its CAD computer model. However, the performance of an actual centrifugal pump may deviate from its ideal behavior due to multiple causing factors which may alter the performance curves given by the manufacturers in the corresponding data sheets. The discrepancies between the real and the simulated responses of centrifugal pumps demand for better modeling and simulation techniques to improve the design of more efficient pumping systems. Digital twins have the ability to bring the simulation environment closer to reality, by replicating the behavior of the physical system in a simulation environment with the support of experimental data. The digital twin of a multiple pumps system with serial and parallel configurations was developed, based on two identical industrial centrifugal pumps available in the laboratory. Experimental data was collected to calibrate the digital twin system so that the simulated system can predict the response under changing operating conditions. The simulation environment was developed with the assistance of a commercial Computational Fluid Dynamics computer program. After validating the behavior of the virtual components, with respect to the behavior of their actual counterparts, tests were carried out to predict the behavior of the pumping system in case of downstream disturbances which can affect the operating point of the overall pumping system and its corresponding efficiency. The development of the digital twin for the pumping system allowed visualizing how the pumps connected in series or in parallel can be maneuvered to adjust its operating conditions to achieve higher efficiency operating conditions in response to changes in the conditions downstream in the pipeline.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"33 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":"133045166","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}