Author(s): A. I. Stamou
Linked Author(s):
Keywords: CFD models; Mathematical models; Model validation protocol; Secondary settling tanks
Abstract: CFD models are not used widely in the design and the operation of Secondary Settling Tanks (SSTs), because they are considered by engineers as too sophisticated, too complicated and not necessarily-reliable. The formulation of a protocol for the validation of CFD models for SSTs is required to change these characterizations and to assist the engineers in (a) choosing the required CFD model for their specific task and (b) ensuring the reliability of the results with the performance of the required QA/QC procedures. In the present paper, the main points of the procedure of CFD modeling for SSTs, which are relevant to the formulation of such a protocol, are presented. The modeling procedure is presented as comprising of the following 3-stages: (1) synthesis (construction of the model), (2) analysis (calibration-validation and sensitivity analysis) and (3) application of the model. The improvement and the increase of the validity of the existing CFD models require the performance of research in certain areas. These areas include: (1) The development of equations for the description of turbulence in regions of SSTs with strong density effects, flocculation (and break-up), re-suspension of Suspended Solids (SS) and viscous flow in the sludge blanket, (2) the generation of numerical grids for the accurate representation of the complicated 3-D geometries of SSTs, (3) the formulation of robust and fast algorithms for the solution of the equations of the models, (4) the development of analytical solutions for “simple cases” of SSTs for code verification, (5) the performance of experiments to obtain data for model calibration and validation, (6) the development of new techniques and instruments for the measurement of very low flow velocities and SS concentrations without disturbing the flow and (7) the application of CFD models in transient problems, which will form the basis of the application of CFD models in the operation of SSTs in combination with biological units.
Year: 2003