Anaerobic Biogas Digester Modelling

Using OpenFOAM and Fluent

Andrew CoughtrieCivil Engineering

Biogas Digestion?

Problem Definition• Waste Treatment

• Mixing effectiveness

• Failure when scaled up

• Difficult to monitor experimentally

* Karim k. et al. [2007] Gas-lift Digester Configuration Effects on Mixing Effectiveness

Experimental bench scale internal airlift loop biogas digester.*

CFD• Structured square mesh• Ansys Meshing and

BlockMesh• Approximation for inlet

boundaryInlet

Slurry Surface

Outlet

Walls

Problem Setup• Inlet boundary condition based on approximation of flow

velocity• RNG k-epsilon turbulence model

• Zero shear wall at surface

OpenFOAM Control

Function to monitor velocity

Discretisation Schemes

Linear solver

Fluent Wall TreatmentStandard Wall

FunctionsScalable Wall

FunctionsEnhanced Wall

Treatment

Fluent vs. OpenFOAM

OpenFOAM Fluent

*Karim k. et al. [2004] Flow Pattern Visualization of a Simulated Digester

OpenFOAM Fluent Experimental*

Single-phase vs. Multiphase

DPM Single-Phase

Ongoing Work

• Non-Newtonian fluid modelling

• Comparison between single and multiphase for OpenFOAM and Fluent

• Multiphase 3D modelling

• Euler-Euler Multiphase using OpenFOAM

Three-Dimensional

• Full 3D geometry for DPM

• Import mesh to OpenFOAM for use with bubbleFoam

?Questions?