Optimization of a Clearwell Design by Using a 3D CFD Model

A practical application of a three-dimensional (3D) computational fluid dynamics (CFD) model to optimize the design of a storage reservoir for its use as a clearwell is presented in this paper. A computational grid of the 20 million gallon (MG) reservoir, incorporating 285 columns supporting the roof, was created from existing design drawings. Initial model simulations indicated poor mixing and contact time, with T₁₀/T ratio of about 0.2, where T₁₀ is the tenth percentile of the hydraulic residence time, T. Therefore, various baffle arrangements were investigated to increase the T₁₀/T ratio to 0.72 and minimize the cost associated with retrofitting the reservoir with baffles. These duel considerations resulted in an unconventional design of the clearwell with an estimated cost saving of 45 percent. The paper analyzes the computed circulation patterns to identify the causes of significantly different hydraulic and mass transport characteristics of the reservoir, with and without columns, and the proposed design incorporating baffles.