Week 9- Unsteady moving zones Approach

Aim: To simulate the motion of blades in a turbomachinery component using an unsteady approach,

Transient simulation:

Transient simulations are performed when the parameters vary with time.

Moving Mesh approach:

• In this approach, the Mesh is moving and the Mesh topology will change that is the mesh shape will vary with the motion of the frame.
• There is a change in the control volume (the region of fluid we need to analyze).
• It is an unsteady Phenomenon. It can be used on unsteady flows when unsteadiness is the main concern of the simulation.
• This method gives good results for unsteady flows but requires inputting complex boundary conditions.
• This approach is used for modeling unsteady phenomena like vortex-induced flows and if there is an interaction of the vortex with the bodies.

Simulation setup:

1. Import the mesh model and select the pressure-based solver and absolute frame of reference.
2. Select the solver as a k-epsilon realizable model as it gives the best results for the turbomachinery components and select standard wall treatment,
3. Select the cell zone conditions.
4. The cell zone conditions for the rotating frame give rotational velocity as 300 rpm and select mesh motion.
5. In solution methods for turbulent kinetic energy and turbulent dissipation rate take a second-order upwind method and coupled, set the courant number to 10.
6. Define required contours

Time Step Calculation :

Time step calculation for 300 rpm:
T= `60/N`

T = 0.2

1. if we want the simulation to be achieved within 1000 time steps then the time period is AT= 0.0002
2. The time step needs to be smaller than this or equal to this to get accurate results.
3. If the time step is larger the solution may be overestimated or underestimated.

Output :

Residual

Velocity Contours

Pressure Contours :

Velocity Vector :

Animations :

Velocity Contours

Pressure Contours :

Conclusion :

• The velocity of the fluid is high at the rotor as the rotor is rotating at a high velocity which makes the fluid have high velocity.
• The velocity at the inlet is low.
• The velocity of the fluid is increased near the outlet
• The velocity near the outer walls is zero following the no-slip condition
• The Pressure on the walls is high
• The pressure at the rotors is low as the pressure energy is converted into kinetic energy
• The mass flow rate at the inlet and outlet is the same according to the newtons law of conservation of mass
• The negative mass flow rate at the outlet is indicating that the flow is leaving the system
• The positive mass flow rate at the inlet indicates that the flow is entering the system