Eulerian Two Phase Flow in a Moving Wall Cylinder, ANSYS Fluent Training

Description

Project Description (Eulerian)

The system consists of two different fluids, including water as the primary fluid and one secondary fluid (with a density of 2610 kg.m-3 and a viscosity of 0.0026 kg.m-1.s-1). Therefore, to define the flow of two fluids in the system, the Eulerian multiphase model has been used. The two-phase flow enters the chamber in the form of a hollow cylinder.

The water fluid enters the cylindrical system with a velocity of 0.629 m.s-1 and a volume fraction of 0.67, the secondary fluid with a velocity of 0.099 m.s-1 and a volumetric fraction of 0.23 and under relative pressure conditions of 1379000 pascals. The outer wall of the cylinder is stationary, while the inner wall is moving wall and has a rotational speed around the central axis of the cylinder of 30 rpm. The aim of this project is to investigate the effect of the rotating wall on Eulerian multi-phase turbulent flow.

Geometry & Mesh

The 3-D geometry of the present model is carried out using Design Modeler software. The geometry of the model consists of two outer and inner cylinders, through which the two-phase fluid flows through the space between the two outer and inner walls. The input and output of the model are in the form of hollow circles. The figure below shows an overview of the model’s geometry.

The meshing of the present model has been done using ANSYS Meshing software. The mesh type is unstructured and the element number is 11,880. The figure below shows an overview of the performed mesh.

CFD Simulation (Eulerian)

To simulate the present model, several assumptions are considered, which are:

• The solver is pressure-based.
• Simulation has only examined fluid behavior; in other words, heat transfer simulation has not been performed.
• The present model is Steady in terms of time; in fact, due to the application of constant rotational speed for the wall, the effect of the term of the time can be separated from the solution process.
• The effect of gravity on the flow is considered to be 9.81 m.s-2 and along with the z-axis in the present model.

The following is a summary of the steps for defining the problem and its solution:

Models (Eulerian)
k-omega	Viscous model
standard	k-omega model
shear flow corrections	k-omega options
dispersed	turbulence multiphase model
Eulerian			Multiphase model
water and secondary phase	phases
implicit	formulation
Boundary conditions
velocity-inlet			Inlet
1379000 pascal	supersonic/initial gauge pressure	mixture
0.629 m.s-1	velocity magnitude	water
0.67	volume fraction
0.099 m.s-1	velocity magnitude	secondary phase
0.23	volume fraction
Pressure outlet			Outlet
1379000 pascal	gauge pressure	mixture
1	backflow volume fraction	water
0	backflow volume fraction	secondary phase
wall			Inner wall
stationary wall (0 rpm)	wall motion
			Outer wall
moving wall (30 rpm)	wall motion
Solution Methods
Phase Coupled SIMPLE			Pressure-velocity coupling
PRESTO	pressure		Spatial discretization
first-order upwind	momentum
first-order upwind	specific dissipation rate
first-order upwind	volume fraction
Initialization
Standard	Initialization method
0 m.s-1	water velocity (x,y,z)
0 pascal	gauge pressure
0 m.s-1	water velocity (x,y,z)
1	the secondary phase volume fraction

Turbulence Model

In the present model, the standard k-omega turbulence model with shear flow correction capability and the dispersed turbulence model for multi-phase flow are considered.

Results (Eulerian)

After the solution process, the two-dimensional and three-dimensional contours related to pressure (for mixing), velocity (for water phase and secondary fluid phase), the volume fraction of water and secondary fluid, as well as path lines (water and secondary fluid), have been obtained. Two-dimensional contours are presented in two sections, YZ, and XY. The YZ section is defined as passing through the central axis of the cylinder and the XY section is defined perpendicular to the central axis of the cylinder at intervals of 4, 9 and 13.716 (output) meters from the input section.

You can obtain Geometry & Mesh file and a comprehensive Training Movie that presents how to solve the problem and extract all desired results.