Author(s): Nils Reidar B. Olsen; Richard D. Hedger; D. Glen George
Linked Author(s): Nils Reidar B. Olsen
Keywords: Numerical modelling; Computational fluid dynamics; Water reservoir; Algaemodelling; Microcysitis; Blue-green algae; Turbulence modelling; Reservoir circulation
Abstract: A 3D numerical model was used to calculate the wind-induced accumulation of algae in Eglwys Nynydd, a water supply reservoir in Wales. The model solved the NavierStokes equations for the water velocities using the SIMPLE method to calculate the pressure. Two turbulence models were tested: a zero-equation model and the k-e model. An unstructured non-orthogonal 3D grid with hexahedral cells was used. The distribution of the algae Microcystis was calculated by solving the transient convection-diffusion equation for algae concentration, based on the modelled water flow field. The numerical model included algorithms for calculating the growth rate of algae and simulating the response of the algae to changes in underwater light. The model was validated by comparing the horizontal distribution pattern produced by simulation with those recorded during a field survey of surface concentrations. The results demonstrated reasonable agreement, particularly when using the k-e turbulence model.
Year: 1999