1. Azipod ® propulsor in oblique flow at full scale:
STAR Global Conference 2017 Berlin, march 2017
Azipod ® propulsor in oblique flow at full scale:
comparison between traditional approach and fully coupled FSI for propeller stress analysis
Dr Pasi Miettinen, Senior CFD Analyst, ABB Marine, Helsinki, Finland

2. Agenda Earlier presentations and background
Azipod ® propulsor in oblique flow at full scale
propeller stress analysis
Comparison between simulation approaches
Conclusions
November 21, 2018

3. Earlier presentations and background
Dr Pasi Miettinen and Andrei Korsström, Full scale CFD simulation of Azipod unit performance at varied steering angles, STAR Global Conference 2014, Vienna, March 2014
Dr Pasi Miettinen, Use of STAR-CCM+ for Marine applications at ABB Marine, Oil, Gas and Chemical CFD Conference 2014, Houston, November 2014
Dr Pasi Miettinen, Use of STAR-CCM+ for Propeller simulations at ABB Marine, CD-adapco Marine Workshop, Helsinki, January 2016
Statements in 2014
November 21, 2018

4. Azipod ® propulsor in oblique flow at full scale
Propeller stress analysis
Method 1
Method 2
Method 3
Transient CFD analysis
Static FEM analysis
Third party software
Import data, map imported data on FE mesh and check mapping quality (visual, thrust and torque)
Run analysis
Need for rerun?
Transient CFD analysis
Static FEM analysis
STAR-CCM
Import data, map imported data on FE mesh and check mapping quality (visual, thrust and torque)
Run analysis
Need for rerun?
Fully coupled transient Fluid Structure (FSI) analysis
No need for data transfer
Only one sim file
CFD and FE meshes and solvers
One-way coupling
(CFD -> FEA)
Two-way coupling
(CFD <-> FEA)
Export pressure and wall shear stresses on propeller surfaces based on thrust or torque
Export pressure and wall shear stresses on propeller surfaces based on thrust or torque
November 21, 2018

5. Azipod ® propulsor in oblique flow at full scale
Propeller stress analysis
Method 1
Transient CFD analysis
Static FEM analysis
Third party software
Import data, map imported data on FE mesh and check mapping quality (visual, thrust and torque)
Run analysis
Need for rerun?
Export pressure and wall shear stresses on propeller surfaces based on thrust variation
Static pressure on CFD mesh Mapped pressure on FE mesh
Propeller thrust is equal on both meshes
Minimum principal stress
Amplitude and mean at 0.6 R are used in a semi empirical formula for estimating propeller fatigue strength by high cycle stress criterion
November 21, 2018

6. Azipod ® propulsor in oblique flow at full scale
Propeller stress analysis
Method 1
Method 2
Method 3
Transient CFD analysis
Static FEM analysis
Third party software
Import data, map imported data on FE mesh and check mapping quality (visual, thrust and torque)
Run analysis
Need for rerun?
Transient CFD analysis
Static FEM analysis
STAR-CCM
Import data, map imported data on FE mesh and check mapping quality (visual, thrust and torque)
Run analysis
Need for rerun?
Fully coupled transient Fluid Structure (FSI) analysis
No need for data transfer
Only one sim file
CFD and FE meshes and solvers
One-way coupling
(CFD -> FEA)
Two-way coupling
(CFD <-> FEA)
Export pressure and wall shear stresses on propeller surfaces based on thrust or torque
Export pressure and wall shear stresses on propeller surfaces based on thrust or torque
November 21, 2018

7. Azipod ® propulsor in oblique flow at full scale
Propeller stress analysis
Method 3
Fully coupled transient Fluid Structure (FSI) analysis
No need for data transfer
Only one sim file
CFD and FE meshes and solvers
One-way coupling
(CFD -> FEA)
Two-way coupling
(CFD <-> FEA)
November 21, 2018

8. Azipod ® propulsor in oblique flow at full scale
Propeller stress analysis
Red line
Method 3
Fully coupled transient Fluid Structure (FSI) analysis
No need for data transfer
Only one sim file
CFD and FE meshes and solvers
One-way coupling
(CFD -> FEA)
Two-way coupling
(CFD <-> FEA)
Blue line
Green line
November 21, 2018

9. Azipod ® propulsor in oblique flow at full scale
Propeller stress analysis
Method 1
Method 3
Transient CFD analysis
Static FEM analysis
Third party software
Import data, map imported data on FE mesh and check mapping quality (visual, thrust and torque)
Run analysis
Need for rerun?
Fully coupled transient Fluid Structure (FSI) analysis
No need for data transfer
Only one sim file
CFD and FE meshes and solvers
One-way coupling
(CFD -> FEA)
Two-way coupling
(CFD <-> FEA)
Export pressure and wall shear stresses on propeller surfaces based on thrust or torque
November 21, 2018

10. Comparison between simulation approaches
Propeller stress analysis
Method 3 (Fully coupled transient Fluid Structure analysis)
Method 1 (Transient CFD + external FEA)
Pros
Very clear work flow
First CFD and then FEA
Analysis are decoupled
CFD expert for CFD work
FEA expert for FEA work
Cons
Possibly large amount of data from CFD
Exported CFD data correct for FEA?
Data collection frequency
Might miss extreme values
Data transfer and mapping
Pros
Full control of both analysis
No data transfer, only one sim file
Need expert who knows both CFD and FEA
This approach works very well even for the very first time
Cons
If you want modify something
Mesh settings or run CFD first then you need to update reports etc…
Room for improvement if all the settings are not correct first time or you want to add some features during simulation steps
November 21, 2018

11. Conclusions
High Performance Computing (HPC) combined with automated meshing operations and java macros has accelerated the design cycle significantly
Parts-based meshing is one of the best improvements I have seen within STAR-CCM+
Next year inclusion of the stress solver with FEA approach will further speed up the the design cycle
In 2015 the inclusion of the stress solver with FEA approach has further sped up the the design cycle
Now only 3D solid elements, waiting for shell elements
November 21, 2018