Institute for Flight Propulsion Technische Universität München

Implementation of a DomainScaling Approach for

Turbomachinery Computationsin OpenFOAM

Oliver Borm, Fethi Tekin, Hans-Peter Kau

Institute for Flight PropulsionTechnische Universität München

2010-06-23

Introduction Implementation Results Conclusion and Outlook

O. Borm, F. Tekin, H.-P. Kau, Institute for Flight Propulsion Implementation of a Domain Scaling Approach for Turbomachinery Computations in OpenFOAM – 1/22

Institute for Flight Propulsion Technische Universität München

Outline

Introduction

Implementation

Results

Conclusion and Outlook

Introduction Implementation Results Conclusion and Outlook

O. Borm, F. Tekin, H.-P. Kau, Institute for Flight Propulsion Implementation of a Domain Scaling Approach for Turbomachinery Computations in OpenFOAM – 2/22

Institute for Flight Propulsion Technische Universität München

Outline

Introduction

Implementation

Results

Conclusion and Outlook

Introduction Implementation Results Conclusion and Outlook

O. Borm, F. Tekin, H.-P. Kau, Institute for Flight Propulsion Implementation of a Domain Scaling Approach for Turbomachinery Computations in OpenFOAM – 3/22

Institute for Flight Propulsion Technische Universität München

Domain Scaling Method

TR

T'S 2 T'x S = TR

TR

2 T'x S = TR

Domain Scaling

Frozen Rotor

Rotor Stator Interfaces

• Domain Scaling– Identical pitch for each blade row– Least common denominator

simulated– Pitch-wise periodicity– Time varying position of rotor and

stator blade is resolved(unsteady)

• Frozen Rotor– Solution is position dependent

(steady)

Introduction Implementation Results Conclusion and Outlook

O. Borm, F. Tekin, H.-P. Kau, Institute for Flight Propulsion Implementation of a Domain Scaling Approach for Turbomachinery Computations in OpenFOAM – 4/22

Institute for Flight Propulsion Technische Universität München

Periodicity

overlapGgi Interface

Inlet

Walls

Outlet

• Periodicity ensures physicalcorrectness and numericalstability

• Duplicated velocity profile ofslave (dashed blue line)conflicts with profile of master(red line) at overlapGgiinterface

• Jump in profile at uncoveredpart of interface

• Even if numerics allow thatsetup, it crashes at run time!

Introduction Implementation Results Conclusion and Outlook

O. Borm, F. Tekin, H.-P. Kau, Institute for Flight Propulsion Implementation of a Domain Scaling Approach for Turbomachinery Computations in OpenFOAM – 5/22

Institute for Flight Propulsion Technische Universität München

Outline

Introduction

Implementation

Results

Conclusion and Outlook

Introduction Implementation Results Conclusion and Outlook

O. Borm, F. Tekin, H.-P. Kau, Institute for Flight Propulsion Implementation of a Domain Scaling Approach for Turbomachinery Computations in OpenFOAM – 6/22

Institute for Flight Propulsion Technische Universität München

Main Problem - Partial Uncovered Patches

A A

BB

1 2

1 2

z

A1 ⇐⇒ A2 and B1 ⇐⇒ B2

• Implementation based onoriginal overlapGgi interface

• Two partially uncoveredcoupled patches

• Expansion of both patches tocover 360° full circumferentialsurface

• No face left uncovered• Ggi interpolation between these

two surfaces

Introduction Implementation Results Conclusion and Outlook

O. Borm, F. Tekin, H.-P. Kau, Institute for Flight Propulsion Implementation of a Domain Scaling Approach for Turbomachinery Computations in OpenFOAM – 7/22

Institute for Flight Propulsion Technische Universität München

New overlapGgi Boundary File Definition

interface1{

type overlapGgi;nFaces 200;startFace 50400;shadowPatch interface2;rotationAxis (0 0 1);n 12; // number of passages in this blade row

}

Introduction Implementation Results Conclusion and Outlook

O. Borm, F. Tekin, H.-P. Kau, Institute for Flight Propulsion Implementation of a Domain Scaling Approach for Turbomachinery Computations in OpenFOAM – 8/22

Institute for Flight Propulsion Technische Universität München

Finite Volume Dynamic Mesh Handling

turboFvMesh

1. Dynamic mesh handling required for unsteady cases

2. No change in mesh topology during simulation⇒ no mesh motion3. Arbitrary number of blade rows treated as separate cell zones

4. Possibility to extract each blade row from internal mesh duringpost-processing

Introduction Implementation Results Conclusion and Outlook

O. Borm, F. Tekin, H.-P. Kau, Institute for Flight Propulsion Implementation of a Domain Scaling Approach for Turbomachinery Computations in OpenFOAM – 9/22

Institute for Flight Propulsion Technische Universität München

turboFvMesh Setup

turboFvMesh

1. Splitting mesh into cell sets for every blade row using regionCellSets

2. Cell sets⇒ cell zones3. Individual definition of rpm for each cell zone

4. Counter rotating multistage turbomachinery simulations possible

Caution!

• Same rotational origin and axis for all zones• Cylindrical coordinate system in dictionary file• Rotational direction determined by sign of rpm

Introduction Implementation Results Conclusion and Outlook

O. Borm, F. Tekin, H.-P. Kau, Institute for Flight Propulsion Implementation of a Domain Scaling Approach for Turbomachinery Computations in OpenFOAM – 10/22

Institute for Flight Propulsion Technische Universität München

turboFvMesh dynamicMeshDict DefinitiondynamicFvMesh turboFvMesh;turboFvMeshCoeffs{

coordinateSystem{

type cylindrical;origin (0 0 0);axis (0 0 1);direction (1 0 0);

}rpm{

rotor_1 60;stator_1 0;rotor_2 -120;stator_2 0;

}}

Introduction Implementation Results Conclusion and Outlook

O. Borm, F. Tekin, H.-P. Kau, Institute for Flight Propulsion Implementation of a Domain Scaling Approach for Turbomachinery Computations in OpenFOAM – 11/22

Institute for Flight Propulsion Technische Universität München

Compressible Dynamic Mesh Solver without Mesh Motion

sonicTurbDyMFoam

• Required due to lack of suitable solver• Based on sonicTurbFoam and sonicFoamAutoMotion• Replaced motionSolver library with dynamicFvMesh library, more

suitable as internal mesh topology does not change

• Adjustable global time step based on CFL Number

Introduction Implementation Results Conclusion and Outlook

O. Borm, F. Tekin, H.-P. Kau, Institute for Flight Propulsion Implementation of a Domain Scaling Approach for Turbomachinery Computations in OpenFOAM – 12/22

Institute for Flight Propulsion Technische Universität München

Outline

Introduction

Implementation

Results

Conclusion and Outlook

Introduction Implementation Results Conclusion and Outlook

O. Borm, F. Tekin, H.-P. Kau, Institute for Flight Propulsion Implementation of a Domain Scaling Approach for Turbomachinery Computations in OpenFOAM – 13/22

Institute for Flight Propulsion Technische Universität München

Incompressible Generic Test Case

Description

• Radial inlet velocity of 10 ms• Constant pressure at outlet• Gap between rotor and

stator with cyclicGgi atsides

• Remaining boundariesconsist of solid walls

• Solver: icoFoam andicoDyMFoam

Introduction Implementation Results Conclusion and Outlook

O. Borm, F. Tekin, H.-P. Kau, Institute for Flight Propulsion Implementation of a Domain Scaling Approach for Turbomachinery Computations in OpenFOAM – 14/22

Institute for Flight Propulsion Technische Universität München

Incompressible Steady Case

Introduction Implementation Results Conclusion and Outlook

O. Borm, F. Tekin, H.-P. Kau, Institute for Flight Propulsion Implementation of a Domain Scaling Approach for Turbomachinery Computations in OpenFOAM – 15/22

Institute for Flight Propulsion Technische Universität München

Incompressible Steady Case - Transformed

Introduction Implementation Results Conclusion and Outlook

O. Borm, F. Tekin, H.-P. Kau, Institute for Flight Propulsion Implementation of a Domain Scaling Approach for Turbomachinery Computations in OpenFOAM – 16/22

Institute for Flight Propulsion Technische Universität München

Incompressible Unsteady Cases

Single Rotating Rotor Counter Rotating Rotors

Introduction Implementation Results Conclusion and Outlook

O. Borm, F. Tekin, H.-P. Kau, Institute for Flight Propulsion Implementation of a Domain Scaling Approach for Turbomachinery Computations in OpenFOAM – 17/22

icoDymFoam.aviMedia File (video/avi)

counter.aviMedia File (video/avi)

./animations/icoDymFoam.avi./animations/counter.avi

Institute for Flight Propulsion Technische Universität München

Axial Compressor Test Case

Rotor Stator

Outlet

Inlet

overlapGgiInterface

• Rescaled axial compressor stage for domain scaling interface

• Pitch angle ∼= 15.6522° (conform to 23 rotor and stator passages)

• Constant static pressure at outlet: 95000Pa

• Inlet: U/|U | = (0 0 1); pt = 101325Pa; Tt = 293KIntroduction Implementation Results Conclusion and Outlook

O. Borm, F. Tekin, H.-P. Kau, Institute for Flight Propulsion Implementation of a Domain Scaling Approach for Turbomachinery Computations in OpenFOAM – 18/22

Institute for Flight Propulsion Technische Universität München

Unsteady Domain Scaling

Unsteady Domain Scaling

• Aforementioned sonicTurbDyMFoam

• Operating point near stall

• S1 surface at approx. 70% span

Introduction Implementation Results Conclusion and Outlook

O. Borm, F. Tekin, H.-P. Kau, Institute for Flight Propulsion Implementation of a Domain Scaling Approach for Turbomachinery Computations in OpenFOAM – 19/22

ds_omega_full.aviMedia File (video/avi)

./animations/ds_omega_full.avi

Institute for Flight Propulsion Technische Universität München

Steady Frozen Rotor

• sonicTurbFoam due to problems with MRF solver

• Stage acts like a tandem stator

• Huge deflection⇒ bad efficiencyIntroduction Implementation Results Conclusion and Outlook

O. Borm, F. Tekin, H.-P. Kau, Institute for Flight Propulsion Implementation of a Domain Scaling Approach for Turbomachinery Computations in OpenFOAM – 20/22

Institute for Flight Propulsion Technische Universität München

Outline

Introduction

Implementation

Results

Conclusion and Outlook

Introduction Implementation Results Conclusion and Outlook

O. Borm, F. Tekin, H.-P. Kau, Institute for Flight Propulsion Implementation of a Domain Scaling Approach for Turbomachinery Computations in OpenFOAM – 21/22

Institute for Flight Propulsion Technische Universität München

Conclusion and Outlook

Current Status

• Domain Scaling and Frozen Rotor approaches applicable with newoverlapGgi interface

• Parallelization works rarely

Outlook

• Full parallelization• GAMG solver for overlapGgi interface• Phaselag rotor-stator interface based on modified cyclicGgi and

overlapGgi

Introduction Implementation Results Conclusion and Outlook

O. Borm, F. Tekin, H.-P. Kau, Institute for Flight Propulsion Implementation of a Domain Scaling Approach for Turbomachinery Computations in OpenFOAM – 22/22

IntroductionImplementationResultsConclusion and Outlook