GMGW -1 · 2018. 7. 5. · Click to edit Master title style Program Development Company © 2017 GMGW-1, Denver CO, June 2017 Difficulties •The pinch-out’s angles are impossible

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

Program Development Company © 2017GMGW-1, Denver CO, June 2017

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

2086

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.

Documents

GMGW -1 · 2018. 7. 5. · Click to edit Master title style Program Development Company © 2017 GMGW-1, Denver CO, June 2017 Difficulties •The pinch-out’s angles are impossible