Volume 7: Fluids Engineering最新文献

{"title":"An Accurate Unstructured Finite Volume Discrete Boltzmann Method","authors":"Leitao Chen, L. Schaefer, Xiaofeng Cai","doi":"10.1115/IMECE2018-87136","DOIUrl":"https://doi.org/10.1115/IMECE2018-87136","url":null,"abstract":"Unlike the conventional lattice Boltzmann method (LBM), the discrete Boltzmann method (DBM) is Eulerian in nature and decouples the discretization of particle velocity space from configuration space and time space, which allows the use of an unstructured grid to exactly capture complex boundary geometries. A discrete Boltzmann model that solves the discrete Boltzmann equation (DBE) with the finite volume method (FVM) on a triangular unstructured grid is developed. The accuracy of the model is improved with the proposed high-order flux schemes and interpolation scheme. The boundary treatment for commonly used boundary conditions is also formulated. A series of problems with both periodic and non-periodic boundaries are simulated. The results show that the new model can significantly reduce numerical viscosity.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117096403","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":"Rheological Characteristics of Surfactant-Based Fluids: A Comprehensive Study","authors":"A. Kamel","doi":"10.1115/IMECE2018-86044","DOIUrl":"https://doi.org/10.1115/IMECE2018-86044","url":null,"abstract":"Surfactant-based fluids, SB fluids exhibit complex rheological behavior due to substantial structural change caused by the molecules self-assembled colloidal aggregation. Various factors affect their rheological properties. Among these factors, surfactant concentration, shear rate, temperature, and salinity are investigated. One of the most popular surfactants, Aromox® APA-T viscoelastic surfactant (VES) is examined. The study focuses on four different concentrations (1.5%, 2%, 3%, and 4%) over a shear rate ranging from 0.0526 sec−1 to 1944 sec−1 using Bohlin rheometer. For salinity effects, two brine solutions are used; 2 and 4% KCl while for temperature effects, a wide range from ambient temperature of 72°F up to 200°F is covered. The results show that SB fluids exhibit a complex rheological behavior due to its unique nature and the various structures form in the solution. In general, SB fluids at all concentrations exhibit a non-Newtonian pseudo-plastic shear thinning behavior. As the surfactant concentration and/or shear increases, a stronger shear thinning behavior can be seen. Increasing solution salinity promotes formation of rod-like micelles and increases its flexibility. Salinity affects micelles’ growth and their rheological behavior is very sensitive to the nature and structure of the added salt. Different molecular structures are formed; spherical micelles occur first and then increased shear rate and/or salinity promotes the formation of rod-like micelles. Later, rod-like micelles are aligned in the flow direction and form a large super ordered structure of micellar bundles or aggregates called shear induced structure (SIS). Different structures implies different rheological properties. Likewise, rheology improves with increasing temperature up to 100°F. Further increase in temperature reverses the effects and viscosity decreases. However, the effects of temperature and salinity diminish at higher shear rates. Furthermore, a rheology master curve is developed to further understand the rheological behavior of SB fluids and correlate rheological properties to its microscopic structure.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"394 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123391666","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":"Mechanistic Modeling of Dynamic Zero-Net Liquid Holdup (ZNLH) in Gas-Liquid Cylindrical Cyclone (GLCC©) Separator","authors":"S. Kolla, Megharaj Praneeth Karpurapu, R. Mohan, O. Shoham","doi":"10.1115/IMECE2018-88481","DOIUrl":"https://doi.org/10.1115/IMECE2018-88481","url":null,"abstract":"Over the past 2 decades, GLCC© compact separators have been replacing the conventional vessel type separators in the Oil & Gas Industry, because of its numerous advantages. Despite these advantages, GLCC separators face two critical problems affecting the performance under extreme operating conditions, namely, Liquid Carry Over (LCO) into the gas leg and Gas Carry Under (GCU) into the liquid leg. This study focuses on the LCO phenomenon. Having a deeper insight into the LCO flow phenomenon helps us to enhance the technical performance of GLCC at these extreme conditions. Several studies were presented in the past on experimental investigations and mechanistic modeling of LCO. In the above cases, mechanistic modeling of LCO was based on Zero Net liquid Holdup (ZNLH) parameter. The liquid holdup in the upper part of the GLCC before it is blown out by gas flow is referred to as ZNLH. ZNLH is an important phenomenon affecting the GLCC pressure behavior and performance characteristics. Above mentioned experimental investigations performed to calculate ZNLH were carried out under static conditions where the effects of superficial liquid velocities were neglected. Investigations have been carried out in this study under dynamic conditions to evaluate the effect of superficial liquid velocities on ZNLH. We found that Dynamic ZNLH results are different from static ZNLH data as they show lower liquid holdup for the same gas velocities. A mechanistic model is proposed in this study to predict dynamic ZNLH and this model is validated against the dynamic ZNLH experimental data. It may be noted that a suitable ZNLH model will help in improving the predictions of the LCO mechanistic model considerably.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"112 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124306789","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":"Influence of Blade Shape Geometry on Very Low Specific Speed Centrifugal Pump Performance","authors":"Muhamed Al-badawi, I. Adam, S. Haddara, A. Sherif","doi":"10.1115/IMECE2018-87119","DOIUrl":"https://doi.org/10.1115/IMECE2018-87119","url":null,"abstract":"Direct or inverse design methods for centrifugal pumps play an important role in investigating their performance. In this paper, a very low specific speed centrifugal pump impeller of ns = 9.5 (metric), three blades and 222° wrap angle. This pump was investigated using the direct design method to achieve the blade shape geometry and examine the blade angle distribution. As the blade angle progression affects the pump performance, four models with different blade angle distribution were used to perform the hydrodynamic and suction performance of the pump. The linear and non-linear derived correlation models were designed firstly using ANSYS-BladeGen module then studied numerically using ANSYS-CFX module to solve the three-dimensional Navier-Stokes equations. Validation of the numerical simulation of the investigated centrifugal pump was done using experimental data. Numerical results show that the change in the blade angle distribution has an influence on the blade wrap angle. Consequently, the variation in the blade wrap angle affects the pump head and the relative velocity distribution. The pressure gradient varies in the pump with changing the blade length. Using the velocity streamline and the velocity vector, the eddies existence and distribution in the blade suction side affect the relative velocity distribution and the pump performance. It was found that the blade with the smallest length decreases the pump head and have best velocity distribution.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"89-B 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125275269","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":"The Impact of the Gas Temperature and of the Relative Humidity on the Performance of Fans Operating in Drying Plants","authors":"M. Fritsche, P. Epple, A. Delgado","doi":"10.1115/IMECE2018-88674","DOIUrl":"https://doi.org/10.1115/IMECE2018-88674","url":null,"abstract":"In order to investigate the impact of the gas temperature and its relative humidity on the performance of fans, the similarity laws for fans were extended and verified and numerical computations with the commercial CFD solver ANSYS CFX were performed. First the accuracy of the original fan laws was verified for different operating conditions. In a second step the influence of the temperature on the fan characteristics was investigated. Finally, to include the effect of the relative humidity multiphase simulations with air and water vapor were performed. Therefore, the relative humidity was analyzed for different gas temperatures. In such a way the full influence of the temperature and of the relative humidity on the performance characteristics of radial fans operating in drying plants was obtained. These numerical results have been analyzed in detail and compared with the results predicted by the presented extended similarity laws for turbomachines.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"306 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129343273","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":"The Impact of Adding a Labyrinth Surface to an Optimal Helical Seal Design","authors":"W. Paudel, Cori Watson, H. Wood","doi":"10.1115/IMECE2018-87089","DOIUrl":"https://doi.org/10.1115/IMECE2018-87089","url":null,"abstract":"Non-contacting annular seals are used in rotating machinery to reduce the flow of working fluid across a pressure differential. Helical and labyrinth grooved seals are two types of non-contacting annular seals frequently used between the impeller stages in a pump and at the balance drum. Labyrinth seals have circumferential grooves cut into the surface of the rotor, the stator, or both. They function to reduce leakage by dissipating kinetic energy as fluid expands in the grooves and then is forced to contract in the jet stream region. Helical groove seals have continuously cut grooves on either or both the rotor and stator surfaces. Like labyrinth seals, they reduce leakage through dissipation of kinetic energy, but have the added mechanism of functioning as a pump to push the fluid back towards the high-pressure region. Previous work has shown that mixed helical-labyrinth seals with labyrinth grooves on stator and helical grooves on rotor or labyrinth grooves on rotor and helical grooves on stator have an approximately 45% lower leakage than an optimized helical groove seal with grooves just on the stator in a high pressure application. The primary objective of this study is to determine whether the same performance gains can also be achieved in a low pressure application. Simulations were run in ANSYS CFX for seal designs with a helical stator and labyrinth rotor. Several labyrinth design parameters including the number of grooves and the groove width and depth are varied while the helical variables such as the groove width and depth as well as helix angle are kept constant. The data obtained are analyzed using backward regression methods and various response plots to determine the relationship between the design parameters and mass flow and power loss. The optimized helical design was simulated and the axial pressure profiles of the designs were compared to analyze the mechanism of the mixed helical-labyrinth seal. Then, the same labyrinth seal designs were simulated for a labyrinth rotor and a smooth stator to determine whether the optimal number of grooves, groove width and groove depth change due to the helical stator. The findings of this study show the effectiveness of mixed helical labyrinth grooved seals for both low and high pressure cases, and thus their efficiency and reliability for numerous industrial applications.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128497296","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":"The Reynolds Stress in Turbulence From an Alternate Perspective","authors":"Taewoo Lee","doi":"10.1115/IMECE2018-86870","DOIUrl":"https://doi.org/10.1115/IMECE2018-86870","url":null,"abstract":"We present a unique method for solving for the Reynolds stress in turbulent canonical flows, based on the momentum balance for a control volume moving at the local mean velocity. A differential transform converts this momentum balance to a closed form, with the longitudinal component, u’2 and the mean velocity, U as its constituents. Validations with experimental and computational data in simple geometries show quite good results. Using this perspective, determination of the Reynolds stress in terms of computable turbulence parameters is rendered possible.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122244511","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":"Analyzing the Shear Heating Effects in Modeling the Hydrodynamic Lubrication of High Torque Low Speed Diesel Engine by Considering Different Viscosity-Grade Lubricants","authors":"S. Naseer, S. A. Qasim, R. A. Azim, Kishwat Ijaz Malik","doi":"10.1115/IMECE2018-88238","DOIUrl":"https://doi.org/10.1115/IMECE2018-88238","url":null,"abstract":"Journal bearings of high torque diesel engines are used to cater for high combustion loads which are applied intermittently. A lubrication layer is provided between journal (crankshaft) and bearing to avoid contact between them. The relative velocity between crankshaft and journal bearing results in viscous shear heating among the different layers of lubricating oil. The shear heating reduces the viscosity of the lubricant that ultimately reduces the load carrying ability of the journal bearing. It offers a physical contact and reduces the designed life of crankshaft. In this study the 2-D transient numerical lubrication model is developed by employing the Reynolds equation to calculate the pressure and film thickness profiles as a function of crankshaft speed. The shear heating effects are determined by coupling the energy equation with lubrication model. The finite difference method is used and an appropriate numerical scheme is employed to simulate the conduction and convection based thermal energy transfer in transient and steady state journal bearing lubrication model. The lateral displacement of crankshaft is incorporated in the thermal model to analyze the effect of secondary dynamics of crankshaft. The viscosity and temperature relationship are used to ascertain its variation with temperature. The characteristic of three different viscosity-grade lubricates are incorporated separately in the model to carry out the comprehensive comparative analysis. The results are simulated for particular application where low operating speed and length to width ratio of journal bearing is fixed and analyzed the results for complete 720 degrees of crankshaft in its two revolutions. The results show that the oil with high viscosity produces high hydrodynamic pressures as compared to the oil that have low viscosity. The viscous shearing temperature reduces the hydrodynamic pressures but still the high viscosity lubricating oil have enough pressures to uplift the shaft after incorporating the shear heating effects. This study determines the hydrodynamic pressure, and variation of density, viscosity and thermal-conductivity with temperature for three different lubricating oils. These analyses will facilities towards the selection of appropriate lubricant for high torque low speed diesel engine in order to enhance the life of crankshaft.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116554849","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 Modeling of Phan-Thien-Tanner Viscoelastic Fluid Flow Through a Square Cross-Section Duct: Heat Transfer Enhancement due to Shear-Thinning Effects","authors":"Fouad Hagani, M. Boutaous, R. Knikker, S. Xin, D. Siginer","doi":"10.1115/IMECE2018-87568","DOIUrl":"https://doi.org/10.1115/IMECE2018-87568","url":null,"abstract":"Non-isothermal laminar flow of a viscoelastic fluid through a square cross-section duct is analyzed. Viscoelastic stresses are described by the Phan-Thien – Tanner model and the solvent shear stress is given by the linear Newtonian constitutive relationship. The solution of the set of governing equations spawns coupling between equations of elliptic-hyperbolic type. Our numerical approach is based on the finite-differences method. To treat the hyperbolic part, the system of equations are rewritten in a quasilinear form. The resulting pure advection terms are discretized using high-order upwind schemes when the hyper bolicity condition is satisfied. The incompressibility condition is obtained by the semi-implicit projection method. Finally we investigate the evolution of velocity, shear stress, viscosity and heat transfer over a wide range of Weissenberg numbers.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"384 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131723589","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":"New Design Method for Spiral Casings Considering the Properties of the Impeller and Spiral Casing at Design and Off-Design Conditions and Numerical Verification With CFD","authors":"P. Epple, M. Fritsche, M. Steppert, Michael Steber","doi":"10.1115/IMECE2018-88673","DOIUrl":"https://doi.org/10.1115/IMECE2018-88673","url":null,"abstract":"Radial fans for industrial applications are very commonly operated with a spiral casing, also called volute. The function of the volute is to collect the air from the impellers outlet and to transport it to the fans outlet. In the volute the tangential velocity component of the impeller is transformed in a straight velocity component at the volute’s outlet. In the volute the static pressure is increased according to the cross sectional area of the volute. When the flow exits the impeller the flow rate is given basically by the radial velocity component times the outlet area of the impeller. In the volute, however, the flow rate is basically given by the tangential velocity component at the impeller exit and in the volute considering the conservation of angular momentum. Hence, there is only one operating point, i.e. the design point of the volute, where the flow rate in the impeller matches the flow rate in the volute. In the literature the design of the volute is performed at the design point only and the cross sectional area of the volute is usually computed distributing the flow rate linearly from the tongue to the exit of the volute.\u0000 In this work an extended theoretical approach was developed considering the design point flow rate and off design flow rates. At the design point, the properties of the specific impeller, i.e. it’s radial and its tangential velocity components at the impeller’s exit are considered to design the volute. Furthermore, also the off-design characteristics of the impeller, i.e. its radial and tangential velocity components are considered in the design process of the volute. The flow rates in the impeller and in the volute match only at the design point, at off-design points the flow rates in the impeller and in the volute are different. This has an important impact on the design process of impeller – volute units. Each volute has also to be matched to the specific impeller.\u0000 In the numerical part a usual volute was designed considering the properties of a particular impeller. The performance of the volute and of complete fan was investigated with the commercial Navier–Stokes Solver ANSYS CFX. A detailed analysis of the results and the flow conditions in volute as well as in the impeller-volute unit and a comparison with the results predicted by the new volute theory is given.","PeriodicalId":229616,"journal":{"name":"Volume 7: Fluids Engineering","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133075605","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}