*On Apr.27.13 , In Design Optimization , by barry*

The gas flow in the cyclone separator is turbulent, and this creates a complication when using CFD. With direct numerical simulation (DNS) such CFD simulation were already carried out in small, simple geometries. This field is advancing fast as the computational power increases. However, with currently processing equipment, this is not possible yet. Therefore turbulence models are required. A recent turbulence model technique is Reynolds Stress Model (RSM) Therefore; RSM has been used for CFD Simulation.

In this thesis two cyclone separators with different inlet angles are studied. Predictions of the flow pattern, velocity and pressure drop in the cyclone separator are estimated by using CFD and particularly Reynolds Stress Model (RSM). For that, the specific goals of the work are the following:

• Calculation of the velocity profiles at various axial positions.

• Investigation of particle trajectories

• Calculation of the pressure drop for a given design

*2.1 Particle Dynamics*

Collection of solid or liquid particles in an air pollution control device is based upon the movement of a particle in the gas (fluid) stream. For a particle to be captured, the particle must be subjected to external forces large enough to separate it from the gas stream. Forces acting on a particle include three major forces and other forces. They are Gravitational force, Buoyant force, Drag force, other forces including magnetic, inertial, electrostatic, and thermal forces.

The consequence of acting forces on a particle results in the terminal velocity for a particle to settle. The terminal velocity (also known as the settling velocity) is a constant value of velocity reached when all forces (gravity, drag, buoyancy, etc.) acting on a body is balanced. The sum of all the forces is then equal to zero (no acceleration). To solve for an unknown particle settling velocity, the flow regime of particle motion must be determined. Once the flow regime has been determined, the settling velocity of a particle can be calculated.