CFD-based Evaporation Estimation Approach

• 1. Introduction The Proposed Approach Case Study: Lake Binaba Simulation Process Results ConclusionShort-term Evaporation Estimating fromComplex Small Lakes in (Semi-)Arid RegionsAli AbbasiNick van de GiesenDelft University of TechnologyWater Resources ManagementAugust 20, 20141 / 37

2. Introduction The Proposed Approach Case Study: Lake Binaba Simulation Process Results ConclusionOutline1 IntroductionEvaporationEstimating Evaporation2 The Proposed ApproachAdvantagesApproach TheoryApplication of CFDCFD ScenariosFramework3 Case Study: Lake BinabaDescription4 Simulation ProcessCFDEvapModel-ToolBox5 ResultsResults6 ConclusionConclusion2 / 37 3. Introduction The Proposed Approach Case Study: Lake Binaba Simulation Process Results ConclusionEvaporationEvaporationWhy do we need to estimate Evaporation?As a major component of the hydrologic cycle.The largest one of water loss from lakes, especially in arid andsemi-arid regions.Approximately one half of the stored water in shallow lakes maybe lost due to evaporationAects the storage eciency of small lakes,EvaporationFood SecurityDetermining the evaporation precisely is critically important toassessing the reliability of small reservoir in arid regions.3 / 37 4. Introduction The Proposed Approach Case Study: Lake Binaba Simulation Process Results ConclusionEstimating EvaporationEstimating EvaporationAccurately estimate evaporation from water bodies:The key element to make improvements in water storage(reservoir) managementEstimating or measuring evaporation over a lake or reservoir is avery dicult taskThe required meteorological parameters rarely measured over thewater surface.The thermal lag between the water body and land surfacesrendersThe land-based measurements inecient in parameterization ofopen water evaporationEvaporation: from Lake vs. from LandLake evaporation is largely uncoupled from the landevapotranspiration4 / 37 5. Introduction The Proposed Approach Case Study: Lake Binaba Simulation Process Results ConclusionEstimating EvaporationMethodsA wide range of methods are available to estimate evaporation:Measurements: evaporation pan,eddy correlation technique.Mass balance(budget)method.Energy budget methods.Mass transfer method.Combination methods.Temperature and radiation base methodsCFD-based approach.5 / 37 6. Introduction The Proposed Approach Case Study: Lake Binaba Simulation Process Results ConclusionEstimating EvaporationComplexityEstimating evaporation from water surface is ...!! :Perhaps the most dicult component of all the hydrological cyclecomponentsComplex interactions between the components of thelake-atmosphere systemBeing a function of:meteorological and climatological factors(temperature, relativehumidity, wind speed, etc.)geology and physiography of water bodies(size, depth, shape,advective, location, etc.)Evaporation: a unique feature of each lakeDue to dependency of evaporation on these parameters, it is a uniquefeature of each lake and developing a clearly an unique theoreticalmethod for its estimation could be inhibited6 / 37 7. Introduction The Proposed Approach Case Study: Lake Binaba Simulation Process Results ConclusionEstimating EvaporationComplexityWith respect to evaporation, lake and reservoirs quite dierent fromland surfaces:The penetrating of suns energy into the waterMixing the water column by surface motionThe large heat storage capacity of waterThe density of water (approximately 1000 times dense moredense than air)Nearly constant evaporation rate for night and day7 / 37 8. Introduction The Proposed Approach Case Study: Lake Binaba Simulation Process Results ConclusionEstimating EvaporationComplexityEvaporation from water surface8 / 37 9. Introduction The Proposed Approach Case Study: Lake Binaba Simulation Process Results ConclusionOutline1 IntroductionEvaporationEstimating Evaporation2 The Proposed ApproachAdvantagesApproach TheoryApplication of CFDCFD ScenariosFramework3 Case Study: Lake BinabaDescription4 Simulation ProcessCFDEvapModel-ToolBox5 ResultsResults6 ConclusionConclusion9 / 37 10. Introduction The Proposed Approach Case Study: Lake Binaba Simulation Process Results ConclusionAdvantagesAdvantagesThe propose approach is:Based on mass-transfer(aerodynamic) method.Moderate input data demandsA generalisable and cost eective approachUsing Computational Fluid Dynamics(CFD)as a very powerfultool.Assuming heat and mass transfer analogyDrive convective heat transfer coecient and mass-transfercoecients for a given water bodyThe spatial variation of the evaporation rate over the watersurfaceConsider the advection eects under arid climate conditionsCFDEvapModel: CFD-based Evaporation ApproachDierent Climate conditions, the Spatial Distribution of Evaporationover the Water Surface and the eects of advection(oasis) over thewater surface10 / 37 11. Introduction The Proposed Approach Case Study: Lake Binaba Simulation Process Results ConclusionApproach TheoryApproach TheoryBased on the mass-transfer(aerodynamic) methodE = f(u)(es