On the Application of the Double-Averaging Methodology in Modelling Vegetated Open-Channel Flows

The double-averaging methodology (DAM) arose to respond to a need to provide mathematically rigorous tool for describing spatially heterogeneous turbulent . Initial developments originate from micrometeorologists who revealed discrepancies between measured and simulated temperature and fields above trees when using only Reynolds-averaged Navier-Stokes (RANS) equations with various turbulence model closures. The discrepancies were to the spatial inhomogeneity of the flow field caused by vegetation. , additional spatial averaging of RANS equations over horizontal planes large to provide statistical averaging of all differences caused by an distribution of plants and the influence of the biggest vortices responsible the transfer of momentum was suggested. The advantages of using the DAM open-channel hydraulics of gravel-bed rivers were recognised in the early 2000s DAM was first applied and consequently improved. Open-channel vegetated are another example of spatially heterogene¬ous turbulent flows to which DAM can be applied. The paper presents the results of the DoubleVeg project by the author, in which a new set of equations was derived. After introducing basic DAM concepts, the procedure of deriving Depth-Integrated Double Navier-Stokes equations is presented. Consequently, the main in solving these equations are discussed, and the results of initial testing systems of homogeneous and non-homogeneous equations are shown.