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COB58 Análise experimental do escoamento ao redor de um perfil de base quadrada em dois diferentes Ângulos de ATAQUE / Experimental analysis of the flow around a square cylinder with two different incidence angles
Cláudio Lindquist, Edson Del Rio Vieira & Sérgio Said Mansur
Departamento de Engenharia Mecânica, Faculdade de Engenharia - UNESP - Ilha Solteira
CEP 15.385-000 Ilha Solteira - SP, Brasil, E-mail: delrio@feis.unesp.br
Flow visualization have been performed to study the flow along a square cylinder placed perpendicularly to the main flow. Two different attack angles have been considered (a = 0 and a = 45 degrees), for Reynolds numbers up to 300. The experimental facilities are composed by a water tunnel of low turbulence intensity and an apparatus for a flow visualization, image capture and processing. A direct dye injection visualization technique has been employed and the images have been captured on two different media, photo-sensible chemical film and video tape with the help of a modern three CCD video camera. Strouhal numbers have been determined by video tape image analysis by frames counting. A sequence of images is shown for a = 0 from which the vortices formation and shedding can be seen.
Keywords: Square cylinder; Strouhal number; flow visualization; water tunnel; image processing; cilindro quadrado; número de Strouhal; visualização de escoamento; túnel hidrodinâmico; processamento de imagem.
COB59 Vortex Velocity Measurement by Hydrodynamic Flow Visualization
Edson D. R. Vieira, Cláudio Lindquist, Emanuel R. Woiski & Sérgio S. Mansur
Departamento de Engenharia Mecânica, Faculdade de Engenharia - UNESP - Ilha Solteira
CEP 15.385-000 Ilha Solteira - SP, Brasil, E-mail: mansur@feis.unesp.br
Since von Kármán’s studies of vortex propagation, vortex streets in wakes of bluff bodies have become a subject of interest to engineers and scientists, producing a great number of experimental vortex velocity measurements. In this work, hydrodynamic flow visualization, by direct dye injection technique, has been employed in order to determine the frequency and propagation speed of vortices shed from circular cylinders in the Reynolds number range up to 600. The experimental procedure consisted on changing the Reynolds number of the flow and evaluating the distance between two vortices on a same row from static images captured on negative film by a SLR camera and determining the Strouhal number from images recorded with a 3 CCD video camera. From the distance and the corresponding Strouhal number, vortex velocity against Reynolds numbers have been calculated and depicted. Results regarding the Strouhal number obtained compared well with literature.
Keywords: Vortex speed; vortex shedding; flow visualization; Strouhal frequency; circular cylinder; velocidade de vórtices; emissão de vórtices; visualização de escoamentos; freqüência de Strouhal; cilindro circular.
COB70 ANÁLISE EXPERIMENTAL DO PROCESSO DE ASPERSÃO DE GOTAS EM UM SISTEMA JATO-PLACA/ EXPERIMENTAL ANALISYS OF THE DROPS ASPERSION PROCES OVER A JET-PLATE SYSTEM
Jorge Luiz Z. Tarqui, Aristeu Silveira-Neto & Thomaz W. Mendoza-Harel
Departamento de Engenharia Mecânica, Centro de Ciências Exatas e Tecnologia - UFU
CEP 38400-206 Uberlândia - MG, Brasil - E-mail: aristeus@ufu.br
This article presents the results obtained with the technique of high-speed photography used to freeze the high frequency dynamic phenomena involved in the problem of drop generation by means of a spray nozzle-plate system. The instabilities that characterize jet transition were initially analyzed to validate the method of experimentation. The physical nature of drop formation was also analyzed and the more important physical phenomena were pointed out: the dynamic instabilities over the liquid sheet; the holes formation and the mass accumulation belongs the borders of the holes and liquid sheet.
Keywords: Experimentation; turbulence; drops ; aspersion; transition.
COB268 ANÁLISE DA PROPAGAÇÃO DE PERTURBAÇÕES NO CAMPO DE VELOCIDADES DO ESCOAMENTO EM BANCO DE TUBOS / ANALYSIS ON THE PROPAGATION OF DISTURBANCES IN THE VELOCITY FIELD OF TUBE BANK FLOW
Luiz Augusto Magalhães Endres & Sergio Viçosa Möller
Programa de Pós-Graduação em Engenharia Mecânica, UFRGS
CEP 90.050 - 170 Porto Alegre, Brasil-E - mail: endres@if.ufrgs.br & svmoller@vortex.ufrgs.br
This paper presents the experimental analysis of the propagation of a disturbance with a fixed frequency, generated, by means of an obstacle, in the incidence velocity of the cross flow through a tube bank and its influence on the pressure and velocity fluctuations inside the bank. The tube bank investigated had square arrangement and aspect ratio P/D = 1.60 and air was the working fluid. Measurements were performed with hot wires and pressure transducers. Behavior of fluctuating quantities is described by means of autospectral density functions and the propagation of the disturbance is discussed based on the analysis of cross-correlation functions. The results show that the frequency of the disturbance remains unchanged as it passes through the bank, in spite of the high turbulence intensities and of the fact that flow velocity inside the bank varies with the position. This fact may indicate that external excitations can be transferred to the solid boundaries of the bank.
Keywords: Banco de Tubos, Turbulência, Anemometria de Fio-Quente / Tube Bank, Turbulence, Hot-Wire Anemometry.
COB269 ESCOAMENTO TURBULENTO NA SAÍDA DE UM DUTO CURVO DE SEÇÃO RETANGULAR DIVERGENTE - ESTUDO EXPERIMENTAL / TURBULENT FLOW AT OUTLET OF A CURVED RECTANGULAR DIVERGENT DUCT - EXPERIMENTAL STUDY
Maria Luiza Sperb Indrusiak & Sérgio Viçosa Möller
Programa de Pós Graduação em Engenharia Mecânica, Escola de Engenharia - UFRGS - Porto Alegre
CEP 90.050-170 R. Sarmento Leite, 425,Porto Alegre, RS - Brasil - E-mail: svmoller@vortex.ufrgs.br
This paper presents the experimental study of the turbulent flow in a curved duct which simulates part of a thermal-electrical power plant. Ashes, carried in the power plant by the flow of gases from the furnace, impinge on the pipes of the heat exchanger, which pre-heat water prior of the steam generator, after passing a curved duct, and produce erosion of the pipes of the heat exchanger, leading to failures which stop plant operation. Flow distribution after the curve increase the erosion near the concave wall of the duct. Classical solutions for flow redistribution in curves, like vanes, are not applicable since they could increase operational risks due to the erosion of the vanes. This problem was investigated in a scale model of the curved duct, with, for simplicity, air as the working fluid. Flow visualizations with wool threads on the duct wall, Pitot tube and hot wire measurements were applied. Based on the results, modifications in the test section were made, using boundary-layer control techniques. The results show that flow redistribution after the curve was improved, and the modifications, when implemented in the plant, may lead to safer and economical operation conditions.
Keywords: Escoamento turbulento; Dutos retangulares curvos; Anemometria de fio quente; turbulent flow; curved rectangular ducts; hot wire anemometry
COB276 MEDIÇÃO DE CAMPOS DE VELOCIDADE EM ESCOAMENTOS COM O EMPREGO DA TÉCNICA DE PROCESSAMENTO DE IMAGENS/ FLOW VELOCITY MEASUREMENT USING IMAGE PROCESSING TECHNIQUE
Vilson C. S. Ferreira, Lucas Gutkoski & Flávio V. D. Laan
Departamento de Engenharia Mecânica - UFRGS, Sarmento Leite, 425, Porto Alegre, RS - CEP 90050-170,
e-mail, vferreir@vortex.ufrgs.br
One of the great problem for measuring flow field properties, such as velocity and vorticity, using an intrusive or nonintrusive techniques, is the time consuming. Hot-Wire (HW) and Laser Doppler Velocimetry (LDV), apart from their advantages and disadvantages, demand great effort and care for measuring extensive flow field. Highly unsteady flow is another type of problem not solved when using HW or LDV because both are local velocity techniques, that is, resolving the velocity field at each point at a time. Measuring flow properties having spatial and temporal information is now possible due to new techniques appearing since the great development achieved by the laser technology and the fast digital processors. Particle Image Velocimetry (PIV) is one emerging technology with the proposal of solving part of these measuring flow field problems. The paper describes two developing methodologies for measuring low and fast velocities inside an extensive field flow of a tundish model used in metallurgical process.
Keywords: Processamento de Imagens, Video Velocimetria, Velocimetria por Processamento de Imagens.
Image Processing, Video Velocimety, Particle Image Velocimetry
COB497 DESIGN OF AN EIGHT-STAGES CASCADE IMPACTOR FOR THE CLASSIFICATION OF AIRBORNE PARTICLES
Marcos Sebastião de Paula Gomes
Dept. de Eng. Mecânica, Pontifícia Universidade Católica do Rio de Janeiro, DEM/PUC-Rio
CEP 22453-900, Rio de Janeiro, RJ, Brasil - E-mail: mspgomes@mec.puc-rio.br
The work describes the design of a prototype eight-stages cascade impactor, capable of classifying airborne particles with sizes in the range of aerodynamic diameters between 17 and 0.5 microns, while operating with a nominal flow rate of 30 liters/minute. A summary of the theory involved in the project of such devices is also presented. The collection surfaces accommodate 37 mm substrates which may be of different materials (e.g. filter media, aluminum foil), depending on the application of interest. The design is optimized for reducing inter-stage particulate losses, and the instrument may be used in the separation of inhalable PM10 particulate (Particulate Matter 10 microns cut off size). It is also flexible enough for permitting the operation with different sets of nozzle diameters, accepting a diverse selection of cut off sizes.
Keywords: Aerosol Technology, Instrumentation, Air Pollution, Atmospheric Aerosols, Environmental Assessment.
Tecnologia de Partículas, Instrumentação, Poluição do Ar, Aerossóis Atmosféricos, Avaliações Ambientais.
Maurício Dziedzic
CEHPAR - Centro de Hidráulica e Hidrologia Prof. Parigot de Souza, UFPR/COPEL
C.P. 1309, Curitiba -- PR -- 80001-970 --- E-mail: dziedzic@cch.copel.br
Motivated by the role played by vortex rings in the turbulent mixing processes, the present work investigates the stability and evolution of a single vortex ring. A new classification is proposed for vortex rings, which is based on extensive hot-wire measurement of velocities in the vortex core and wake, and on flow visualization. Vortex rings may be classified as laminar, wavy, turbulence-producing, and turbulent.
Kewywords: Vórtice Anelar, Turbulência, Mecânica dos Fluidos, Experimental./ Vortex rings, Turbulence, Fluid Mechanics, Experimental
COB735 EXPERIMENTAL DETERMINATION OF THRUSTER PLUME HEAT LOADS ON SAC-C 753
Adriana Bertoli(1), Carlos José Barrientos(2), Issamu Muraoka(3), José Nivaldo Hinckel(3)
(1) CONAE, Av. Paseo Colón, 751, 1063 - Buenos Aires, Argentina
(2) INVAP, S. E. Moreno 1089, (8400)S.C. de Bariloche, Argentina
Av. dos Astronautas, 1758, Jd. da Granja, 12201-970 - São José dos Campos/SP, Brasil.
In this paper, a theoretical and experimental study of the impact of the exhausted gas produced by a 2N hydrazine thruster is presented, simulating the thermal conditions attained in space during the operation of a spacecraft propulsion system used for orbit control. For this purpose, two different configurations were examined, either in continuous and pulsed firing regimes. The first configuration consisted of a set of small aluminum plates placed perpendicular to the plume flow field, in order to have a direct measurement of the heat load on a surface whose normal is aligned with the incident molecular flow field. The second configuration consisted in a fiberglass-epoxy boom placed near the thruster and parallel to its axis, representing a possible configuration for SAC-C (Satélite Argentino de Aplicaciones Científicas). The boom, when deployed, extends into the area of the flow field of the thrusters used for orbit control and may be subjected to high heat loads during the firing.
Keywords: Plume Impingement, Heat Estimations
COB778 LIQUID FILM THICKNESS MEASUREMENT BY ULTRASONIC TRANSMISSION TECHNIQUE
Marcelo L. Morandim1, Marcelo Albuquerque L. Gonçalves2,
Fernando A. França1, Geraldo S. Ribeiro2 & Eugenio S. Rosa1
1- Depto. de Energia, Fac. de Eng. Mecânica - UNICAMP - CEP 13081-970 - Campinas, SP - BRASIL
(morandim@ fem.unicamp.br , ffranca@fem.unicamp.br e erosa@ fem.unicamp.br)
2- PETROBRAS - CENPES - DIPLOT - Ilha do Fundão - 21949-900 - Rio de Janeiro, RJ - BRASIL (marcelog@cenpes.petrobras.com.br e spin@cenpes.petrobras.com.br)
In this paper is proposed and tested the use of a non-intrusive ultrasonic transmission technique for the measurement of the thickness of a liquid film flowing along a solid wall. The physical principles, as well as the experimental procedures for the method are presented. The tests were performed measuring film thickness inside a cylindrical chamber in which a liquid was tangentially injected, causing a film of liquid containing certain quantities of dissolved gas bubbles to rotate along the wall. The technique was tested using water, and the results were compared with values measured with an electric impedance sensor. In general, there was a good agreement between the values obtained from both methods, though there is a systematic difference due to the fact that the electric sensor is able to measure film thickness almost locally, while the ultrasonic technique averages the values over a larger region. The ultrasonic technique was also tested with a higher viscosity liquid, obtained by adding corn syrup to the water, for which the electric sensor was unable to measure. In this case, the results were compared to an analytical model, which was verified for the previous measurements with water. The results also showed good agreement.
Keywords: Liquid films, ultrasonic sensors, measurement techniques
COB799 DETERMINAÇÃO DO COEFICIENTE GLOBAL DE TRANSFERÊNCIA DE CALOR EM RODAS FERROVIÁRIAS / DETERMINATION OF THE OVERALL HEAT TRANSFER COEFFICIENT IN RAILROAD WHEELS.
Auteliano Antunes dos Santos Júnior & Fausto Rodrigues Filho
Laboratório Ferroviário - Departamento de Projeto Mecânico
Faculdade de Engenharia Mecânica - UNICAMP, CEP. 13100-970 - Campinas (SP) - Brasil - E.mail: aute@fem.unicamp.br
The objective of this work is to present a determination of a value for the overall heat transfer coefficient to be able to simulate the heating during the braking process in 33 inch ( 838 mm) railroad wheels. To achieve this objective it was necessary to design and construct a full scale dynamometer to reproduce the most commom braking conditions found in railway operation. The variations in brake power and temperature were measured during standardized tests and were compared to the results obtained from a finite element numerical simulation. Many trial simulations were realized in orde to achieve better agreement betwen the numerical predictions and the experimental results. A value of 25 W/m 2 o C was found for the overall heat transfer coefficient when used with 80% of the total generated friction power. The results of this work are important to determine the thermal stresses in railway wheels during braking and this represents the major aim of the Railway Laboratory of the State University of Campinas.
Keywords: Railroad wheels, railroad braking, wheels failures, brake heating, frenagem ferroviária
COB906 ANÁLISE EXPERIMENTAL DO PROCESSO DE ASPERSÃO DE GOTAS EM UM SISTEMA JATO-PLACA/ EXPERIMENTAL ANALISYS OF THE DROPS ASPERSION PROCES OVER A JET-PLATE SYSTEM
Jorge Luiz Z. Tarqui, Aristeu Silveira-Neto & Thomaz W. Mendoza-Harel
Departamento de Engenharia Mecânica, Centro de Ciências Exatas e Tecnologia - UFU
CEP 38400-206 Uberlândia - MG, Brasil - E-mail: aristeus@ufu.br
This article presents the results obtained with the technique of high-speed photography used to freeze the high frequency dynamic phenomena involved in the problem of drop generation by means of a spray nozzle-plate system. The instabilities that characterize jet transition were initially analyzed to validate the method of experimentation. The physical nature of drop formation was also analyzed and the more important physical phenomena were pointed out: the dynamic instabilities over the liquid sheet; the holes formation and the mass accumulation belongs the borders of the holes and liquid sheet.
Keywords: Experimentation; turbulence; drops ; aspersion; transition.
COB1211 UM EXPERIMENTO DIDÁTICO EM CONVECÇÃO NATURAL / A Didactic Experiment on Free Convection
Saulo Güths & Vicente de Paulo Nicolau
Laboratório de Meios Porosos e Propriedades Termofísicas de Materiais (LMPT), Departamento de Engenharia Mecânica, Universidade Federal de Santa Catarina, CEP 88040-900 Florianópolis/SC, Brasil - E-mail: saulo@lmpt.ufsc.br
This paper describes a didactical experiment on natural convection along a vertical flat plate at constant temperature. It describes a methodology to determine the heat transfer coefficient based on the use of heat fluxmeters. The effect of radiant exchanges on the heat transfer coefficient is presented. A new type of heat fluxmeter, the "tangential heat fluxmeter", is presented as well the calibration technique.The experiment is very useful to ilustrate heat transfer concepts.
Keywords: convecção, convecção natural, fluxo de calor, fluxímetro / convection, free convection, heat flux, heat fluxmeter
COB1233 Coeficientes Hidrodinâmicos em Seções Semi-Circulares em Escoamento Turbulento / hydrodYnamic coefficients in a semi-circular ducts in turbulent flow
Philemon Melo Cunha, Francisco Eduardo Mourão Saboya
Dep. Eng. Mecânica CEFET-RJ, Dep. Eng. Mecânica UFF-RJ, CEP: 22 451-070 Rua Rubens Berardo 175/3/408 Rio de Janeiro - RJ
Pressure drop coefficients have been experimentally determined for turbulent flow in smooth semi-circular ducts. The experiments were performed by measuring the pressure distribution along the flow. The flowing fluid was air and the pressure drop coefficients are presented as function of the flow Reynolds number. Results for circular ducts are also presented and compared with Blasius. The agreement was very good.
Keywords: Perda de Carga - Métodos Experimentais - Mecânica dos fluidos - Trocadores de Calor
Pressure Drop - Experimental Methods - Fluid Mechanics - Heat Transfer
COB1273 DIESEL PARTICULATE MATTER EMISSIONS MEASUREMENT BY MEANS OF A PARTIAL DILUTION MINITUNNEL
A. F. Romero López, D. E. Arroyo Amaro, H. Cabadas Estrella, J. A. Canuto Carranco, O. Hernández Romero, L. López Godínez, J. Saavedra Badillo, V.A. Trejo Chávez.
Departamento de Mecánica, Térmica y Fluidos, Instituto de Ingeniería, UNAM 04510 México,
D. F., Tel. (5) 622-8138 Fax (5) 622-8091 e-mail: afrl@servidor.unam.mx
A minitunnel is proposed in lieu of a full dilution tunnel, that will allow determination of carbon monoxide (CO, CO2), unburned hydrocarbons (HC), oxides of nitrogen (NOx)and particulate matter (PM). The design will permit independent evaluation of emissions from Diesel engines.
Keywords: Sample, Control, Filters, Particulate Matter, Mesurement, Sign, Acquisition.
COB1296 ANÁLISE EXPERIMENTAL DO AQUECIMENTO DE ÁGUA ATRAVÉS DE MICROONDAS / EXPERIMENTAL ANALYSIS OF WATER HEATING BY MICROWAVE ENERGY
Maria Helena Farias & Carlos Valois Maciel Braga
Departamento de Engenharia Mecânica - PUC-Rio, Rua Marquês de São Vicente, 225 - Gávea, CEP 22453-900 - Rio de Janeiro - RJ - Brasil - E-mail: mhfarias@mec.puc-rio.br, cvalois@rio.faperj.br
In the present paper is showed an experimental study. The main object of this study is to improve the microwave power absorption by the water in a resonant cavity. This cavity has a cylindrical geometry and contains a glass (Pyrex) tube in its longitudinal position. Distilled water flows through this tube. The following parameters were varied: water flow mass, glass tubes diameters and the screws position (disturbances) inside the cavity. The results show a strong influence of those parameters about the absorbed power by the water. In this way, it is possible to obtain a situation for the maximum microwave power transferred to the water.
Keywords: Microwave, resonant cavity, water heating by microwave, thermal optimization: geometry.
Microondas, cavidade ressonante, aquecimento de água por microondas, otimização térmica: geometria.
COB1419 A THEORETICAL AND EXPERIMENTAL STUDY OF THE VORTEX TUBE
Luiz Alberto Oliveira Rocha1, George Stanescu2 & Jose Viriato Coelho Vargas3
1Departamento de Física, Fundação Universidade do Rio Grande, 96201-900, Rio Grande, RS, E-mail: dfsrocha@super.furg.br
2Departamento de Matemática, Fundação Universidade do Rio Grande, 96201-900, Rio Grande, RS, E-mail: dmtgs@super.furg.br
3Departamento de Engenharia Mecanica, Universidade Federal do Parana, 81531-990, Curitiba, PR, E-mail: jvargas@demec.ufpr.br
This paper presents a theoretical and experimental study and introduces a mathematical model for a Vortex tube on steady state operation. The internal swirling flow is modeled by a set of ordinary differential equations that are integrated along the radial direction. Experimental temperature measurements from a Vortex tube built in the laboratory are compared to numerical results obtained with the theoretical model, with good qualitative agreement. The temperature variation with respect to the inlet fluid temperature along the radial direction is understood as a result of the distribution of the kinetic energy through the swirling flow, i.e., temperature increase in the periphery and decrease in the core. The theoretical estimation of the flow reversal at the Vortex tube axis agrees well with the internal swirling flow results of Armfield and Fletcher (1991).
Keywords: Refrigeration, swirling flow, irreversible model, experimental measurements
COB1491 OPTIMIZACION EN EL DISEÑO Y CALIBRACION DE REDES DE DISTRIBUCION HIDRAULICA
*Lisandro Curia, *Alejandra Perini, **Ariel Marchegiani, *Sergio Cabezas, *Griselda Itovich
*Departamento de Matematica, Facultad de Economia, **Depto. de Mecanica Aplicada, Facultad de Ingenieria, UNIVERSIDAD NACIONAL DEL COMAHUE, Buenos Aires 1400 - (8300) Neuquen - ARGENTINA - E-mail: lcuria@uncoma.edu.ar
In this Work an algorithm that allow design and calibrate water distribution network is developed. The network topology is analised by graph teory. The conservation equations that establish the state of network equilibrium allow the analytic formulation of the problem as boundary value problem, and the proposed method is applicable for open, closed and combinated networks.
Since that in regime state, a network is put to quick changes: pumps starter and stoped, flow rate variations, etc., during design and calibration of this is necesary to know the effect that caused over the variables group, the modification that try out one of this, denominated resolution parameter, so that satisficy the new regime conditions.
The correction of quasilineal equations system that shown the network equilibrium state allow obtain the analytic solution of new problem.
The operation range and the algorithm ductility are shown by mean of aplication example, the solution obtained is optimal since satify exactly the especificated state parameters.
Keywords: water distribution, calibration, networks analysis, graph teory, optimization.