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 examines 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 Recommendation

  Fall 2008 Research Paper Sub-TopicsTurbulence model validation

Validate which turbulence model to use. K-e realizable or K-w SST

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

Calculate Gθ and compare with the theoretical data

Determines the Gθ value for various flocculation height (fh) to baffle spacing (bs) ratios using a UDF in FLUENT.Reynolds effects on energy dissipation rateReynolds effects on energy dissipation rate

Analyze how energy dissipation rate is affected by Reynolds number

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 ConditionInvestigation of Turbulence Boundary Condition

Investigation of Turbulence Boundary Condition

Examines the affect of varying the turbulent inlet length scale for the optimal geometry.Uniform Energy Dissipation Rate Approach in Determining Optimal GeometryUniform 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.Performance Parameter Approach in Determining Optimal GeometryPerformance 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

• Complementary Solution to Analysis of Energy Dissipation Distribution

  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

Spring 2008 Minutes

Other Information

• Flocculator with multiple baffles
• Automation of Mesh Creation
• Nondimensional Analysis
• 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.
• Relation of Shear Stresses to Floc Strength
• CFD Flocculation Tank Simulation Research
• CFD Fall 2008 Midtem Report
• CFD Spring 2008 Midterm Teach-in Presentation
• CFD Spring 2008 Final Report
• CFD Fall 2008 Midterm Teach-in Presentation
• CFD Fall 2008 Midtem Report
• CFD Fall 2008 Final Report
• CFD Flocculation Tank Next Semester Quiz