CFD Flocculation Tank Simulation

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.

 
CFD Flocculation Tank Simulation goals and meeting minutes.

Research

Fall 2008 Research Paper

CFD Analysis of Flocculation Tank and Design Recommendations

Fall 2008 Research Paper Sub-Topics

Validate which turbulence model to use. K-e realizable or K-w SST (all cases use air as the material)

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

Calculate Gθ and compare with the theoretical data (all cases used air as the material)

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

Analyze how energy dissipation rate is affected by Reynolds number (all cases used air as the material)

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).

Investigation of Turbulence Boundary Condition (missing data: the material used is unclear; note that the graphs are actually contours of turbulent kinetic energy)

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

Uniform Energy Dissipation Rate Approach in Determining Optimal Geometry (missing data: material used is unclear)

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

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.

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.

   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.*
  

  Spring 2008 Documentations:

Spring 2008 Results

Other Information

• Resources
• CFD Presentations
• Links for other resources