Week 9- Unsteady moving zones Approach
- AIM:
To simulate the motion of blades using Moving Mesh Approach in trainsient. Apply appropriate time step calculations to achieve a single complete cylce.
- Theory:
- MRF: is strictly performed for steady state analysis. In MRF, the entire moving frame moves as a whole where no remeshing is required and the mesh topology remains the same, only the rotation occurs at the interface between moving frame and the stationary frame.
- MMA: is prefered for transient simulations but steady state simulations can also be performed using MMA. In MMA the meshing is moving as the rotation motion occurs and re-meshing is taking place, in MMA only the part which is rotating is being remeshed and not the domain so the entire mesh topology near the rotating part undergoes remshing. This is best suited to understand the physics at the rotating part boundary layers and analyse the pressure differences.
- Fluent setup:
- Transient state simulation
- Cell zones:
- Rotating motion: mesh motion
- Rotatry velocity: 300 RPM
- Boundaries:
- Airfoil: Moving wall : rotational motion
- Solution method:
- Second order upwind
- Uncheck psuedo transient
- Solution control:
- Courant number: 10
- Pressure and momentum: 0.5
- Hybrid initialisation
- Geometry:
- Simulations results:
Residuals:
1. Pressure:
2. Velocity:
- Steady state:
- Transient state:
- Velocity animation:
Drive link: https://drive.google.com/file/d/1dF0ztpYgiGP2id_2M70QUKxWAL7mtqyZ/view?usp=sharing
- Conclusion:
1. Transient simulation was achieved using the mesh motion approach.
2. Time step calculation was done based on the angular velocity formula and the time it takes to complete one revolution and relating that to number of iterations.
- Angular velocity: (2*pi*N)/60
- T = 60/N => T= 60/300 = 0.2 sec to complete one revolution.
Which implies, To achieve one revolution in 1000 iterations. Divide 0.2 by 1000
0.2/1000 = 0.0002 but to achieve good convergence it's best to take lesser value than 0.0002 and I've gone ahead with 0.0001.
3. Therefore, achieved good convergence and got a similar result when compared to steady state.