numerical modelling

We will apply an existing Computational Fluid Dynamics (CFD) model to predict the three dimensional velocity and turbulence over the dune fields. The modelling approach will apply a methodology previously developed by the project team to incorporate the different scales of bed topography into the model. The experimental and field data will provide the necessary information to construct the model and then used to assess the model predictions. The successfully validated model will then be used to answer:

  1. whether the flume experiments are replicating the morphodynamic processes observed within the field and;
  2. how different scale of topography influence the local flow. This will be achieved by removing identified scales of topography from the measured bed topography. Such information will allow us to determine how that scale of topography determines the hydraulics forces driving the morphological change.

Once we have a full understanding of the hydraulics we will focus upon the morphology. A key challenge for modelling fluvial dynamics is capturing fully the dynamics of dune migration including the process-based feedbacks between sediment transport, dune morphology and flow. Here we will develop a new morphodynamic model to consider form-flow interactions where the erosion or deposition will be scaled upon the flow forcing. Once fully developed, the model will be applied to the field data. Initially we will consider morphological change under constant flow conditions and then extended to short-term (daily/weekly) epochs. The results will be compared and contrasted to the results from the field survey.