Vortex Separator, Hydrodynamic Eulerian CFD Simulation, ANSYS Fluent Training

Description

Hydrodynamic Vortex Separator Project Description

The present problem simulates two-phase flow inside a hydrodynamic vortex separator using ANSYS Fluent software. These hydrodynamic vortex separators (HDVS), can separate soluble particles in a fluid from the base fluid. The structure of these devices is such that the flow of the solution entering the system is significantly rotated. This high rotation of the flow causes the fluid movement path inside the system to be significantly longer. This lengthening of the solvent flow path provides an opportunity to separate the suspended particles in the fluid and settle them in the system. Therefore, the Eulerian multiphase model has been used.

The Eulerian multiphase model is considered the most complex model for defining multiphase flows because it solves a set of momentum and conservation equations for each phase independently. From the Eulerian model in applications such as bubble columns, droplet flows, particle-laden flows with a volume fraction of more than 10%, pneumatic transitions for granular, liquid flows, Fluidized beds are used for solid-gas flows, the slurry flows, particle suspension, and sedimentation phenomena as solid-liquid flows. In the present simulation, water flow is defined as a base fluid with a density of 1000 kg.m-3 and a viscosity of 0.001 kg.m-1.s-.

Hydrodynamic Vortex Separator Project Description

The secondary phase in the form of particles with a density of 1060 kg.m-3 and a viscosity of 0.0046 kg.m-1.s-1 is defined. The particle dispersion in the base liquid is defined as granular, and the particle diameter is defined as 0.000006 m. The flow of water and its soluble particles enter the device at a rate of 0.36 m.s-1 through an intermediate duct; While the volume fraction of water flow is equal to 0.4 and the volume fraction of soluble particles is equal to 0.6. Finally, after the separation process, this solution leaves the outlet ducts at the top of the device (for water passage) and the bottom of the device (for particle settling).

Hydrodynamic Vortex Separator Geometry & Mesh

The present model is designed in three dimensions using Design Modeler software. The current model is related to a vertical hydrodynamic vortex separator. The cylindrical part of this vertical device’s body is 0.3 m in diameter and 0.63 m high. In this model, a pipe for inlet current is located on the middle part of the body, and two outlet pipes are located in the lower part of the model and on the upper part of the model body.

We carry out the meshing of the model using ANSYS Meshing software, and the mesh type is unstructured. The element number is 472707. The following figure shows the mesh.

CFD Simulation

We consider several assumptions to simulate the present model:

• We perform a pressure-based solver.
• The simulation is unsteady (Transient Solver).
• The gravity effect on the fluid is equal to -9.81 m.s-2 along the Z-axis.

The following table represents a summary of the defining steps of the problem and its solution:

Models (Hydrodynamic Vortex Separator)
Viscous		Reynolds Stress
	Reynolds stress model (RSM)	linear pressure-strain
	near-wall treatment	standard wall function
Multiphase Model		Eulerian
	number of eulerian phases	2
	formulation	implicit
Boundary conditions (Hydrodynamic Vortex Separator)
Inlet		Velocity Inlet
	gauge pressure	0 pascal
	velocity magnitude for the primary phase	0.36 m.s-1
	velocity magnitude for the secondary phase	0.36 m.s-1
	volume fraction for particle	0.6
Overflow		Pressure Outlet
	gauge pressure	0 pascal
Underflow		Pressure Outlet
	gauge pressure	0 pascal
Walls		Wall
	wall motion	stationary wall
Methods (Hydrodynamic Vortex Separator)
Pressure-Velocity Coupling		Phase Coupled SIMPLE
	Pressure	PRESTO
	momentum	second order upwind
	volume fraction	first order upwind
	turbulent kinetic energy	second order upwind
	turbulent dissipation rate	second order upwind
	Reynolds stresses	first order upwind
Initialization (Hydrodynamic Vortex Separator)
Initialization methods		Hybrid

Results

At the end of the solution process, two-dimensional and three-dimensional contours related to the mixture pressure, base fluid velocity, soluble particle velocity, and the volume fraction of the base fluid and soluble particles are obtained. As can be seen from the pictures, it can be said that the flow of water is directed to the upper outlet of the device, and the flow of settled particles is directed to the lower outlet of the device. This shows that the system’s performance is good and exhibits its primary task of separating soluble particles from the base fluid.