Computational Fluid Dynamics Flocculation Tank Simulation, Fall 2009

Abstract:

Computational Fluid Dynamics (CFD) is a tool used by AguaClara to obtain a description of the flow through a portion of the plant where particle formation and growth (flocculation) occurs. This part of the plant is referred to as the flocculator. In this section, dirty (turbid) water flows through a series of baffles that enhances turbulent mixing. Essentially, for particles (flocs) to grow and eventually settle out in the sedimentation tank, they first must collide. By increasing the level of turbulence, the flocculator is increasing the collision potential of flocs. However, if there is too much turbulence, the flocs will break up and not settle out. By running CFD simulations of the flocculator, AguaClara can analyze the parameters important to flocculation and use the resulting data when making design decisions.

Computational Fluid Dynamics Flocculation Tank 3D Simulation, Spring 2009

Abstract:

The flocculation tank simulation team works on building a stable and reliable numerical model to simulate the flow inside the hydraulic flocculation tank, and providing well-studied guidelines for design, construction and operation of the flocculation tank.

Gravity powered hydraulic flocculators are used by AguaClara small-scale water treatment plants due to their low cost, inherent simplicity and robust operation. However, their inflexibility of energy input into the water relative to mechanical flocculators requires well studied design based on the understanding of the flow field and relevant performance parameters.

An appropriate CFD simulation can provide detailed numerical solutions for all the variables in the flow field, and by varying parameters such as tank geometry and flow conditions, we could obtain predictions of each of the flow variables and thus optimize the design towards lower cost and better performance.

Currently, our effort is focused on depicting an accurate energy dissipation map inside the flocculator, describing the size and the shape of the region where most of the energy is dissipated and the formation and collisions of flocs happen, thus providing basis for more efficient and economical design utilizing geometries that dissipate energy as uniformly as possible.

Validation CFD in ANSYS Fluent, Spring 2010

Validation Studies of Fluent Turbulence Models for Fluent Simulations of AguaClara Flocculators

Travis Stanislaus

Introduction:

The AguaClara water treatment project uses ANSYS Fluent computational fluid dynamics (CFD) software to simulate and analyze turbulent fluid flow in idealized models of flocculators in AguaClara water treatment plants. The flocculator simulations in Fluent are used to obtain turbulent kinetic energy dissipation rate, ε, and energy loss coefficient, K, between baffle in the flocculator for AguaClara design equations that determine the height of the flocculator, H, the spacing between baffles, S, the quantity of baffles in the flocculator, and flocculation performance, Ѳε^(1/3) , Ѳ is the residence time between two baffles. The results from Fluent are used in the design of AguaClara facilities, so verification and validation of the Fluent flocculator model and simulation has been conducted continuously since the time AguaClara began using Fluent simulations. Verification is determination of the degree the model being simulated is an accurate representation of the developer’s description and solution to the model. Validation is determining if the model is an accurate representation of the real world physics and intended uses of the model.