gmgw -1 · 2018. 7. 5. · click to edit master title style program development company © 2017...

GMGW - 1

1st Geometry and Mesh Generation WorkshopDenver, CO June 3-4, 2017

Participants: VimalRaj Anbumani,Samuel Ebenezer James,Peter Robert Eiseman.

Company: Program Development Company

Participant id: 10

Click to edit Master title style

Grid Contributions

Case Code Geometry model Grid type No. of grid

levelsHL-CRM Full Gap

CADfix - Geometry preparationGridPro - Volume Mesh IGES Structured

Multi-Block 3

HL-CRM Partially Sealed

CADfix - Geometry preparationGridPro - Volume Mesh IGES Structured

Multi-Block 3

Geometry Preparation

• Software Used: CADfix• Format: IGES• Export Format: STL (for gridgeneration)

Why?Non matching faces with underlined nurbsRepair components that did not import properlyTo create refined tessellation as a base for Grid

Generation in GridPro

Geometry Preparation

TE split for better tessellation

Grid Generation

• Software Used: GridPro

• Type: Structured Multi-Block

• Algorithm: Dynamic Boundary Conformingtechnology(DBC)

• Topology Approach: Bottom up

Grid Generation Process• Identified the critical regions first

Slat tip and mainelement deflection 2

Slat root and mainelement deflection 1

Gap betweentwo flaps

Flap tip and main element cavity

Grid Generation Process• Guiding surface creation to capture sharp features

Grid Generation Process

Block building

Start with interaction of slat tip and main element deflection 2

Extend to fuselage and main element tip

Start with Cavity and flap 2 tip

Extend to fuselage and main element tip

Step 1

Step 2

Grid Generation ProcessMerged both Upstream and Downstream Topology

Grid Generation Process

Once Merged Extended to farfield

Applied Boundary layer clustering

Merged grid blocks

CGNSExport

Time Expended

Parameter Time (hrs)Geometry Cleanup 5 Block Construction 450

Grid generation 4Quality enhancement 20

Boundary layer clustering 1Block count reduction 4

Export to Solver format 1

Generating other grid resolution levels(for each level) 5

For one grid - Medium grid level

Family of Grids

Input - Medium category Grid

Ratio based density sparsening and refining

Boundary Layer Clustering Merging blocks Export to CGNS

Total of 5 hours is utilized for each of the category

Coarse - 0.75x

Fine - 1.5x

Quality parameters

• Grid convergence based on FOLDS and SKEW

• Avg. Skew = ~0.3 (Range = 0.05-0.99)

• 93.6% cells below 0.5 skew

• 0.02% cells above 0.9 skew

Quality enhancement

• Wake capturing• Grid nodes adjustment manually as a post

processing• Boundary layer clustering - Constant growth

ratio as per guidelines

Grid Summary

Geometry Block Count

Grid Level

Volume cells*

Surface cell faces*

Grid nodes* Folds Skew

HL-CRM Full Gap 1930

Coarse 8 0.16 8.1

0 0.05-0.98Medium 63 0.7 63.3

Fine 311.2 1.95 312.2

HL-CRM Partially Sealed

Coarse 8.6 0.19 8.68

0 0.05-0.98Medium 70 0.78 70.4

Fine 320.7 2.19 321.8

*All values are in Millions

Solver friendly

• Export format: CGNS• Set labels for boundary conditions as per

CGNS Solver• Blocks aligned to right handed orientation

Wing Upper SurfaceFollowing images are from Full gap configuration

Wing Lower Surface

Slat LE at Root

Flap TE at Root

Wing tip LE

Wing tip TE

Flap Gap Upper Surface

Volume Mesh at y = 277.5

Volume Mesh at y = 638

Difficulties

• The pinch-out’s angles are impossible to mesh with good quality.

• Cell size criterion - Unable to achieve due to time limitation

• TE cell count limitation - poses difficulty in capturing the geometry for the curved tip in the coarse mesh.

• Volume to surface cell count ratio was not mentioned

• Limited resources

Improvements• Refine the inlet region of the wing and

fuselage TE• Reduce the no. of singularities• Avoid unnecessary cell size jumps &

stretching

PARTIAL GAP CONFIGURATION

Wing Upper SurfaceFollowing images are from Partially Sealed configuration

Wing Lower Surface

Flap TE at Root

Flap Gap Upper Surface

Volume Mesh at Flap Gap

Flap Wake Refinement

Summary

• Easy to achieve the family of grids• Difficult to attain high grid quality in the

critical regions(pinch outs & cavity)

Expectation:• Mention volume to surface cells ratio• Relax cell size limitation• Mention total cell count for each family

Thank you

Any Questions

Some Advantages of Using GridPro

• No Surface Mesh generation• Smooth transition grid - DBC technology• Grid resolution friendly - only one grid needs

to be generated, rest can be generated in minutes

• Multi-scale analysis• Easy to modify existing mesh to

accommodate new features / components.

gmgw -1 · 2018. 7. 5. · click to edit master title style program development company © 2017...

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