Advances in Fluid Mechanics XII最新文献_第3页

RBF-FD BASED DYNAMIC THERMAL RATING OF OVERHEAD POWER LINES 基于Rbf-fd的架空电力线路动态热评定

Advances in Fluid Mechanics XII Pub Date : 2018-07-10 DOI: 10.2495/AFM180261

G. Kosec, J. Slak

{"title":"RBF-FD BASED DYNAMIC THERMAL RATING OF OVERHEAD POWER LINES","authors":"G. Kosec, J. Slak","doi":"10.2495/AFM180261","DOIUrl":"https://doi.org/10.2495/AFM180261","url":null,"abstract":"The essential limiting factor of the power transmission line transfer capabilities is the maximal allowed temperature of the conductor that should not be exceeded to avoid excessive sags. A commonly used conservative approach is to limit transfer capability to the worst case scenarios, i.e. hot, sunny, windless days. Of course, system operators strive to raise the limit with more sophisticated models that take into account actual weather conditions or even weather forecasts. As a consequence, there has been substantial research done on Dynamic Thermal Rating (DTR) models in the last few decades. Based on accumulated knowledge the leading standards in the field published guidelines for thermal rating for operative use. However, the proposed models rely only on empirical relations for determination of the temperature gradient on the surface of the conductor that dictates the heat flux due to the advection. This heat flux is the most intense cooling mechanism in play, and also the most complex to model. In this paper, we extend the discussion about advective cooling with a direct simulation of temperature and velocity fields near the conductor with the focus on the natural convection regime. The introduced model considers joule heat generation and heat transport within the power line and its vicinity, fluid flow driven by buoyancy force, solar heating, and radiation. The solution procedure uses RBF-FD numerical method combined with Poisson disk sampling nodal positioning algorithm. The results of the simulation are presented in terms of temperature and velocity magnitude contour plots, convergence analyses, and comparison of convective heat losses of simulated results to IEC, IEEE and CIGRE standards.","PeriodicalId":261351,"journal":{"name":"Advances in Fluid Mechanics XII","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132794191","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}

引用次数: 5

INTRODUCING NANOTECHNOLOGY THROUGH UNDERGRADUATE THERMAL-FLUID RESEARCH PROJECTS 通过本科生热流体研究项目引入纳米技术

Advances in Fluid Mechanics XII Pub Date : 2018-07-10 DOI: 10.2495/AFM180131

R. Issa

{"title":"INTRODUCING NANOTECHNOLOGY THROUGH UNDERGRADUATE THERMAL-FLUID RESEARCH PROJECTS","authors":"R. Issa","doi":"10.2495/AFM180131","DOIUrl":"https://doi.org/10.2495/AFM180131","url":null,"abstract":"Nanotechnology research has recently been introduced in the mechanical engineering program at West Texas A&M University through undergraduate thermal-fluid science projects. The projects were offered at the junior and senior level in the program as part of either an independent research course or thermal-fluid design course. The projects have been carefully selected to provide the students with an exposure to nanotechnology concepts through experimental studies. Several of those projects were design-oriented in their focus. This paper addresses four of those projects: 1) design of a closed-loop electronics cooling system using nanofluids; 2) performance evaluation of a radiator-type automobile heat exchanger using a circulating nanofluid; 3) evaluation of the energy absorption by alumina nanoparticles in solar vacuumed tubes; and 4) design of a cost effective filter for water purification in developing countries using clay material impregnated with silver nanoparticles for anti-microbial protection capability. The first two projects investigated the effect of using alumina water-based nanofluid compared to distilled water in enhancing the heat transfer performance of the systems. Parametric studies were conducted to investigate the effect flow operating conditions, nanoparticle size and concentration have on the heat exchanger effectiveness. The third project investigated the effect alumina nanoparticles have on the heat gained by an alumina water-based nanofluid in a solar vacuumed tube. In the fourth project, a clay filter was designed for optimal permeability, porosity, filter thickness, daily flow rate, and silver nanoparticles concentration in the clay. An investigation of the effectiveness of the filter was conducted by analyzing certain parameters such as the water turbidity level and presence of bacteria and in the filtered water.","PeriodicalId":261351,"journal":{"name":"Advances in Fluid Mechanics XII","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125310684","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}

引用次数: 0

1D ANALYTIC MODEL FOR PV AEROMECHANICAL SYSTEMS pv气动机械系统的一维解析模型

Advances in Fluid Mechanics XII Pub Date : 2018-07-10 DOI: 10.2495/AFM180221

Ronen S. Lautman, Liron Shani, B. Nishri

引用次数: 0

LOCAL THERMAL NON-EQUILIBRIUM MODELLING OF CONVECTIVE HEAT TRANSFER IN HIGH POROSITY METAL FOAMS 高孔隙率金属泡沫对流换热的局部热非平衡模拟

Advances in Fluid Mechanics XII Pub Date : 2018-07-10 DOI: 10.2495/AFM180301

Ubade Kemerli, K. Kahveci

引用次数: 0

NUMERICAL STUDY OF CONVECTIVE HEAT TRANSFER IN AN INCLINED POROUS ENCLOSURE SATURATED WITH NANOFLUID 含纳米流体的倾斜多孔封闭体对流换热数值研究

Advances in Fluid Mechanics XII Pub Date : 2018-07-10 DOI: 10.2495/AFM180031

J. Stajnko, R. Jecl, J. Ravnik

{"title":"NUMERICAL STUDY OF CONVECTIVE HEAT TRANSFER IN AN INCLINED POROUS ENCLOSURE SATURATED WITH NANOFLUID","authors":"J. Stajnko, R. Jecl, J. Ravnik","doi":"10.2495/AFM180031","DOIUrl":"https://doi.org/10.2495/AFM180031","url":null,"abstract":"The addition of nanoscale particles into the fluid is recently a common technology used in several industrial processes, since it has been proved that by introducing particles into the working fluid, the heat transfer characteristics can be improved crucially. However, the understanding of fundamental characteristics of nanofluid saturated porous media domains is still limited. The paper presents a numerical study of free convection in a porous enclosure saturated with a nanofluid. A single-phase mathematical model has been employed assuming that the suspension of nanoparticles in fluid can be modelled as a new fluid with effective properties. Fluid flow in porous media is modelled with the macroscopic Navier–Stokes equations, where the governing parameters are averaged over the representative elementary volume. The obtained set of partial differential equations is solved with use of the numerical code based on the Boundary Element Method, which was primarily developed for pure fluid flow applications and was already proved to be efficient for solving several problems of fluid mechanics. Numerical results for different values of governing parameters are obtained, focusing on the effect of different volume fractions of added nanoparticles and different inclination angles of the porous enclosure on the overall heat transfer through porous domain.","PeriodicalId":261351,"journal":{"name":"Advances in Fluid Mechanics XII","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126978743","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}

引用次数: 0

A STUDY ON CUTTINGS TRANSPORT IN DRILLING FLUIDS WITH INCLINED ANNULUS 倾斜环空钻井液中岩屑运移的研究

Advances in Fluid Mechanics XII Pub Date : 2018-07-10 DOI: 10.2495/afm180101

Sangmok Han, N. Woo, Young-Ju Kim

引用次数: 0

DNS INVESTIGATION INTO THE EFFECT OF FREE-STREAM TURBULENCE ON HAIRPIN-VORTEX EVOLUTION 自由流湍流对发夹涡演化影响的DNS研究

Advances in Fluid Mechanics XII Pub Date : 2018-07-10 DOI: 10.2495/AFM180151

K. Matsuura

{"title":"DNS INVESTIGATION INTO THE EFFECT OF FREE-STREAM TURBULENCE ON HAIRPIN-VORTEX EVOLUTION","authors":"K. Matsuura","doi":"10.2495/AFM180151","DOIUrl":"https://doi.org/10.2495/AFM180151","url":null,"abstract":"The effects of free-stream turbulence (FST) on the evolution of hairpin vortices during the process of laminar-turbulent transition are investigated by direct numerical simulation. The simulations are conducted for FST intensities of 0–6% and a free-stream Mach number of 0.5. FST changes the symmetry of the hairpin vortex, the arrangement of vortices inside the boundary layer, the location of high friction at the wall, and the scales of the vortices. The relationship between high-friction regions at the wall and hairpin vortices convected downstream is investigated by analyzing the computed flow fields. When FST is introduced along with inlet sinuous disturbances, asymmetric hairpin vortices and numerous secondary hairpin vortices, which are different from the case of no FST, are generated. The boundary-layer transition is characterized by an increase in skin-friction. As a result of vortex creation very close to the wall, high-friction regions are generated. To detect the vortex parts responsible for generating the high-friction regions, a new judgement algorithm for interior points is derived based on the Euler angle. The interior points of the near-wall vortices responsible for generating such highfriction regions are successfully visualized as a group of points in R3. The high-friction regions are the tips of hairpin legs and the regions of near-wall vortices induced beneath a hairpin packet. These regions often correspond to the periphery of the hairpin packets.","PeriodicalId":261351,"journal":{"name":"Advances in Fluid Mechanics XII","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126455466","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}

引用次数: 2

COMPARATIVE STUDY OF THE AERODYNAMIC PERFORMANCES OF MOTORCYCLE RACING WHEELS USING NUMERICAL CFD SIMULATIONS 摩托车赛车车轮气动性能的数值模拟比较研究

Advances in Fluid Mechanics XII Pub Date : 2018-07-10 DOI: 10.2495/AFM180181

F. Concli, M. Gobbi, C. Gorla

{"title":"COMPARATIVE STUDY OF THE AERODYNAMIC PERFORMANCES OF MOTORCYCLE RACING WHEELS USING NUMERICAL CFD SIMULATIONS","authors":"F. Concli, M. Gobbi, C. Gorla","doi":"10.2495/AFM180181","DOIUrl":"https://doi.org/10.2495/AFM180181","url":null,"abstract":"In motorcycle competitions, aerodynamics play a fundamental role. In order to improve the performance of racing motorbikes, different front-wheel geometries have been studied by means of numerical CFD simulations. Different lean angles were analysed for each geometry and the air motionfield were calculated. The considered geometries range from standard spoked design to solid wheels. . ® source free software OpenFOAM state and dynamic simulations were run using the open steady Both This open-source code was selected because, like all the computer programs of this type, it allows a higher flexibility with respect to any close-source commercial software, allowing a customization of the code by implementing specific models for the analysis of the physical problem of interest and also, at the same time, a higher parallelization of the computations. Steady-state simulations were performed using a rotating reference frame (MRF) while, for the transients, a partially-rotating mesh was adopted, thus taking advantage of the internal sliding interfaces (AMI). Drag, lift and force-moments have been calculated with the aim of examining the stability and manoeuvrability of the different configurations.","PeriodicalId":261351,"journal":{"name":"Advances in Fluid Mechanics XII","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116258514","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}

引用次数: 2

STUDY OF A STATIC AND VERTICALLY FREE-TO-OSCILLATE 4:1 RECTANGULAR CYLINDER BY MEANS OF 2D URANS SIMULATIONS 静态和垂直自由振荡4:1矩形圆柱的二维数值模拟研究

Advances in Fluid Mechanics XII Pub Date : 2018-07-10 DOI: 10.2495/AFM180051

A. J. Álvarez, F. Nieto, S. Hernández

{"title":"STUDY OF A STATIC AND VERTICALLY FREE-TO-OSCILLATE 4:1 RECTANGULAR CYLINDER BY MEANS OF 2D URANS SIMULATIONS","authors":"A. J. Álvarez, F. Nieto, S. Hernández","doi":"10.2495/AFM180051","DOIUrl":"https://doi.org/10.2495/AFM180051","url":null,"abstract":"Flexible structures, such as cable-supported bridges, are prone to suffer from vortex-induced vibrations (VIV) under wind ﬂow, as their span lengths are steadily growing in the last decades. VIV is a phenomenon that takes place at reduced wind speeds. The movements of the structure at VIV are self-limited and their frequency corresponds with the natural frequency of the structure (lock in). Therefore, VIV affects the structure’s serviceability and can cause fatigue related damage. Hence, the need for identifying and avoiding this phenomenon at the early design stages is a key issue in long-span bridges design. In the present study a rectangular cylinder of width to depth ratio 4:1, which is a common simpliﬁcation of a bridge deck cross section, is analysed for the static case as well as undergoing free vibration in the vertical direction under wind ﬂow. These analyses have been carried out by 2D URANS CFD simulations, adopting two different turbulence models: the k − ω SST, which is based upon the Boussinesq eddy-viscosity approximation, and the Reynolds Stress Model, which directly calculates the components of the speciﬁc Reynolds stresses. For the static case the force coefﬁcients, Strouhal number and the pressure coefﬁcient distributions were calculated and compared with the available experimental data. In the case of the free-to-oscillate 4:1 rectangular cylinder, the oscillation amplitudes are compared with wind tunnel data reported in the literature. In addition, the frequencies and phase-lags between the time-dependent lift coefﬁcient and the vertical oscillations are studied.","PeriodicalId":261351,"journal":{"name":"Advances in Fluid Mechanics XII","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124335983","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}

引用次数: 0

WIND TUNNEL STUDY ON THE EFFECT OF THE GAP WIDTH IN THE AERODYNAMIC AND AEROELASTIC RESPONSES OF TWIN-BOX DECKS 间隙宽度对双箱式甲板气动和气动弹性响应影响的风洞研究

Advances in Fluid Mechanics XII Pub Date : 2018-07-10 DOI: 10.2495/AFM180071

F. Nieto, M. C. Montoya, A. Fontán, S. Hernández, C. Rapela, A. J. Álvarez, J. Á. Jurado, Alejandro Casteleiro, V. Garcia

{"title":"WIND TUNNEL STUDY ON THE EFFECT OF THE GAP WIDTH IN THE AERODYNAMIC AND AEROELASTIC RESPONSES OF TWIN-BOX DECKS","authors":"F. Nieto, M. C. Montoya, A. Fontán, S. Hernández, C. Rapela, A. J. Álvarez, J. Á. Jurado, Alejandro Casteleiro, V. Garcia","doi":"10.2495/AFM180071","DOIUrl":"https://doi.org/10.2495/AFM180071","url":null,"abstract":"Twin-box decks have recently been introduced in long-span bridges because this type of slotted crosssection provides flutter critical wind speeds higher than mono-box streamlined decks for flexible structures. The two parallel girders are linked together by means of transverse beams with a central gap between them. Experimental and CFD studies have shown that the length of this central gap plays a key role in the aerodynamic and aeroelastic responses of the deck. In this work, the geometry of the Stonecutters Bridge in Hong Kong (China) has been chosen as an application case to conduct a series of parametric studies based on wind tunnel tests. The tests have been conducted under smooth flow, for a 1:80 geometric scale sectional model able to modify its slot length. For an ample range of gap lengths, the force coefficients and the flutter derivatives have been obtained. It has been found that the slopes of the lift and moment coefficients suffer important changes with the gap length. In the same manner, it has also been found that the gap distance modifies the values of flutter derivatives. Finally, for a longspan bridge example, the critical flutter speeds for different gaps are obtained, aiming to identify the gap length that provides a safer threshold for the flutter phenomenon. The results reported herein permit the assessment of the impact caused by the gap length in the aerodynamic and aeroelastic responses of twin-box decks.","PeriodicalId":261351,"journal":{"name":"Advances in Fluid Mechanics XII","volume":"298 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134286679","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}

引用次数: 3