1 / 23

Contents

Evaluation of flow resistance in unsteady pipe flow: numerical developments and first experimental results. Contents. Introduction Data Collection and Analysis Quasi-Two Dimensional Model Numerical Results Conclusions and Future Work. Introduction.

melvyn
Download Presentation

Contents

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Evaluation of flow resistance in unsteady pipe flow: numerical developments and first experimental results

  2. Contents • Introduction • Data Collection and Analysis • Quasi-Two Dimensional Model • Numerical Results • Conclusions and Future Work

  3. Introduction

  4. Classic equations of unsteady flow through closed conduits ContinuityEquation Unsteadyfriction DynamicEquation Steady-stadefriction Introduction Assumptions: • Flowisone-dimensional andthevelocitydistributionisuniformoverthe cross section • Formulas for computingthesteady-statefrictionlosses are valid for transientstateconditions.

  5. Classic equations of unsteady flow through closed conduits FlowAssumption: • Flowisone-dimensional andthevelocitydistributionisuniformoverthe cross section. • Formulas for computingthesteady-statefrictionlosses are valid for transientstateconditions. Viscous Forces Inertial Forces Introduction Q=0 Q Real VelocityProfile VelocityProfile – ClassicApproach Theflow reversal close to thepipewallisresponsable for energydissipationthat can notbedescribedbysteadystatefrictionmodels.

  6. Quasi two-dimensional analysis of unsteady flows Discretizationofflowinto a finitenumberofcylinders Compute momentumandcontinuityequations to eachcylinder • axial velocity • lateral velocity Introduction • shear stress Uniforme pressureateachpipe cross-section (Assumption)

  7. Data Collection and Analysis

  8. Data Collection and AnalysisExperimental facility Total lenght 115 m QN= 20 l/s HN= 38 m • Steel pipeline with a 200 mm nominal diameter • (innerdiameter 200 mm) Volume = 1m3 • Centrifugalpump (nominal powerPN= 15 kW) • Hydropneumaticvessel • Reversiblepumpingsystem

  9. Data Collection and AnalysisData Analysis 1stProblem Highelectric noise with a 20 m amplitude in steadystateconditions Pressuresignalatthreelocations for Q = 5 l/sDay 3 (March 2012) 2ndProblem Presenceofair in thesystem Filteredpressuresignalatthedownstreamendofthe pipeline (T3) in consecutivesdays for Q= 5l/s

  10. Data Collection and AnalysisData Analysis Effect due to the installation of air valves Effect due to the installation of a electric filter Filteredpressuresignalatthedownstreamendofthe pipeline for differentflow rates (Day 3 – March 2012) • The calculated wave speed increased from 900 m/s (Day 3 – March 2012) to 1050 m/s (May 2012). • The theoretical wave speed is 1300 m/s.

  11. Quasi-Two Dimensional Model

  12. Quasi-Two-Dimensional ModelContinuity Equation 1D Model Discretizationofflowinto a finitenumberofcylinders Mass flux 2D Model

  13. Quasi-Two-Dimensional ModelMomentum Equation 1D Model 2D Model Forces considered in themomentumequation in 2-D Model

  14. Quasi-Two-Dimensional Model Numerical Solution Shear stress calculation Laminar Flow Five – LayerViscosityDistribution TurbulentFlow

  15. Numerical Results

  16. Numerical Analysis of laminar flow conditions Energydissipationconsideringthe 1D ModelandQuasi - 2D Model (instantaneousvalveclosure) Atmid-lenghtofthe pipeline Thedownstreamendofthe pipeline • Theenergydissipationobtainedwiththe 1D Modelisapproximately 0,36% oftheinitialpressure amplitude. Ontheotherhand, for thesameperiod, theQuasi - 2D Model leads to a 4.8% reductionofpressure amplitude.

  17. Radial distributionof axial velocity Numerical analysis of laminar flow conditions Axisoftheconduit t = ti t = ti+L/c t = ti+0,5L/c t = ti+1,5 L/c t = ti+2 L/c

  18. Numerical Analysis of turbulent flow conditions Energydissipationconsideringthe 1D ModelandQuasi - 2D Model (valveclosure time = 0,2 s) Q = 10,8 l/s Q = 5,5 l/s Q = 2,2 l/s

  19. Numerical analysis of turbulent flow conditions Numerical versus experimental results 1-D Model versus collected data 2-D Model versus collected data • Themaximumpressureisreasonablydescribedbybothmodels. • Noneofthenumericalmodelsdescribesminimumpressuresandpressurewavephaseandshape.

  20. Conclusions and Future Work

  21. Conclusions and Future Work • ResultshaveshownthatQuasi – 2D Models leads to a muchhigherenergydissipation. • Thenext steps in experimental facility: • Instalationofairvalvesalongthe pipeline and a electricfilter in thefrequency converter; • Instalationofstrainsgauges, hot-filmsand a transparant box with PIV measurements; • Thenext steps in thenumericalanalysisare: • Thecomparasionofdifferentturbulentflowmodels; • Theanalysisoftheeffectofgraduallydampedededdyviscositydistribution; • Thecomparisonofthevelocityprofilesusingthe PIV equipmentwiththeresultsobtained for differentturbulentflowmodels; • Theanalysisifthe real energydissipationandthecomparisonwiththemodelresults.

  22. Acknowledgments

  23. Evaluation of flow resistance in unsteady pipe flow: numerical developments and first experimental resultsPedro Leite, Dídia I. C. Covas, Helena M. RamosInstituto Superior Técnico/UniversidadeTécnica de LisboajhjJosé Tentúgal Valente, Manuel Maria Pacheco FigueiredoFaculdade de Engenharia da Universidade do Porto

More Related