Determination of synthetic wind functions for estimating open water evaporation with Computational Fluid Dynamics

A computational fluid dynamics (CFD)-based methodology is proposed to derive convective mass-transfer coefficients (wind functions) that are required for estimating evaporation of water bodies with the mass-transfer method. Three-dimensional CFD was applied to model heat transfer in two water bodies: a Class-A tank evaporimeter and an on-farm artificial pond. The standard k-e{open} model assuming isotropic turbulence was adopted to describe turbulent heat transport, whereas the heat and mass transfer analogy was assumed to derive the wind functions. The CFD-derived wind functions were very similar to those empirically derived from the experimental water bodies. The evaporation rates calculated with the synthetic wind functions were in good agreement with hourly and daily evaporation measurements for the tank and pond, respectively. The proposed CFD-approach is generalisable and cost effective, because it has low input data requirements. Besides, it provides additional capability of modelling the spatial distribution of the evaporation rate over the water surface. Although the application of CFD to water bodies evaporation modelling is still in development, it looks very promising. © 2012 John Wiley & Sons, Ltd.