Page History

 Simulation


h2. Overview

Little information is available about the fluid behavior within the flocculation. The flow is turbulent and involves separation, reattachment, and high shear. Our team uses CFD simulation to predict velocity gradients, pressure losses and energy dissipation rate in the flocculation tank. By varying geometric configurations, and analyzing the resulting energy dissipation rates, the design of the flocculation tank can be optimized. Below is the energy dissipation rate for the a five baffle flocculator with a height to baffle spacing ratio of 2, and a clearance height to baffle spacing ratio of 1.

!energy dissipation.png!
 
CFD Flocculation Tank Simulation [goals|CFD FTS Goals] and [meeting minutes|CFD FTS Meeting Minutes].

h2. Research


h3.   Fall 2008 Research Paper

CFD Analysis of Flocculation Tank and Design Recommendation

h3.   Fall 2008 Research Paper Sub-Topics


h6. [Validate which turbulence model to use. K-e realizable or K-w SST | Turbulence model validation]

Examines the back-step example to determine the type of turbulence model to use in FLUENT.

h6. [Calculate Gθ and compare with the theoretical data|Gtheta computation]

Determines the Gθ value for various flocculation height (fh) to baffle spacing (bs) ratios using a UDF in FLUENT.

h6. [Analyze how energy dissipation rate is affected by Reynolds number|Reynolds effects on energy dissipation rate]

Examines the affect of varying the velocity inlet from .1 m/s which corresponds to a Re=10,000 to 1 m/s (Re=100,000) and .01 m/s (Re=1,000).

h6. [Investigation of Turbulence Boundary Condition|Investigation of Turbulence Boundary Condition  ]

Examines the affect of varying the turbulent inlet length scale for the optimal geometry.

h6. [Uniform Energy Dissipation Rate Approach in Determining Optimal Geometry|Uniform Energy Dissipation Rate Approach in Determining Optimal Geometry  ]

Determines the optimal geometry for the flocculation tank by varying the fh/bs, and ch/bs ratios.

h6. [Performance Parameter Approach in Determining Optimal Geometry|Performance Parameter Approach in Determining Optimal Geometry]

Determines the optimal fh/bs ratio for the flocculation tank height by comparing performance parameters which quantify flocculation collision potential.

h6. [Complementary Solution to Analysis of Energy Dissipation Distribution]

Examines the energy dissipation profile for varying fh/bs ratios, and how there is a local maximum for smaller fh/bs flocculation tanks.

h3.    Spring 2008 Research Topics

* Model and validate a simple 180 degree turn over two baffles:\*
* Create fully second order accurate model
* Perform mesh sensitivity analysis (using coarse, medium and fine meshes)
* Model the baffles using alternate Turbulence models (K-e Standard, K-e Realizable, K-w)
* Analyze the effects of changing the baffle clearance height
* Understand and analyze the relationship between Strain Rate, Energy Dissipation and Kinematic Viscosity
* Create a flexible mesh that uses parametrization to easily change geometry dimensions
* Analyze the effect of the Reynolds Number on the results
* Analyze the sensitivity of the model to convergence residuals
* Model flocculation tank and compare Simulation to Experimental results.\*
\\

h3.   Spring 2008 Documentations:

[Spring 2008 Results|CFD results]

[Spring 2008 Minutes|CFD findings]

h2. Other Information

* [Resources|CFD 2008 Resources]
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* [AGUACLARA:Flocculator with multiple baffles]
* [Automation of Mesh Creation|Automation of Mesh Creation  ]
* [Nondimensional Analysis|Nondimensional Analysis  ]
* [Turbulence model validation| Turbulence model validation]
* [Johannes Haarhoff and Jeremia J. van der Walt , J Water SRT - Aqua 50 (2001) 149-160 - - Towards optimal design parameters for around-the-end hydraulic flocculators.|http://www.iwaponline.com/jws/050/jws0500149.htm]
* [Relation of Shear Stresses to Floc Strength]
* [CFD Flocculation Tank Simulation Research]
* [CFD Fall 2008 Midtem Report|CFD Fall 2008 Midtem Report  ]
* [CFD Spring 2008 Midterm Teach-in Presentation|^Spring 2008 Midterm teachin.ppt]
* [CFD Spring 2008 Final Report|CFD Spring 2008 Report]
* [CFD Fall 2008 Midterm Teach-in Presentation|^AguaClara CFD Midterm Presentation.ppt]
* [AGUACLARA:CFD Fall 2008 Midtem Report]
* [CFD Fall 2008 Final Report|^AguaClara CFD Fall 2008 Final Report.pdf]
* [CFD Flocculation Tank Next Semester Quiz]