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Mesh Generation

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Meshing Workflow Overview

1. Block Mesh Setup: Define computational domain and base mesh resolution
2. Refinement Zones: Add local mesh density control where needed
3. Mesh Settings: Configure parallel processing and quality parameters
4. Generation: Create mesh with real-time monitoring and validation
5. Quality Check: Verify mesh metrics and visual inspection

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Block Mesh Configuration

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External Flow Setup

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Access and Configuration

• Search Box: Ctrl+K → “External Flow”
• Toolbar: Click the domain icon
• Presets: Choose from Small, Medium, or Large domain presets

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Domain Sizing Guidelines

Recommended Domain Factors (relative to geometry size):
- Upstream: 5-10× geometry length (flow development)
- Downstream: 15-25× geometry length (wake capture)
- Lateral: 5-8× geometry width (side effects)
- Vertical: 5-8× geometry height (boundary effects)

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Core Parameters

• Cell Size: Base mesh resolution (start coarse, refine locally)
• Exterior Point: Location inside flow domain but outside geometry
• Domain Bounds: Manual adjustment for custom requirements

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Automatic Boundary Conditions

• Inlet (X-min): Velocity inlet
• Outlet (X-max): Pressure outlet
• Sides (Y±, Z±): Slip walls or symmetry

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Internal Flow Setup

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When to Use

• Pipe flows, ducts, and enclosed volumes
• Flow through components with defined inlet/outlet

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Configuration

• Interior Point: Location inside the flow domain
• Geometry Boundaries: Platform automatically detects surface patches
• Boundary Assignment: Manual assignment of inlet/outlet/wall conditions

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Mesh Settings

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Parallel Processing

• Number of Cores: 3-8 cores recommended for parallel mesh generation
• Access: Gear icon in toolbar → “Mesh Settings”
• Performance: More cores = faster generation (diminishing returns beyond 8)

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Cell Size Guidelines

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Refinement Zones

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Available Zone Types

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Box Refinement Zone

• Access: Search → “Box Refinement Zone” or hotkey R1
• Best for: Wake regions, general flow areas
• Configuration: Min/max coordinates, refinement level
• Modes: Inside, outside, or distance-based refinement

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Sphere Refinement Zone

• Access: Search → “Sphere Refinement Zone” or hotkey R2
• Best for: Point sources, localized features
• Configuration: Center point, radius, refinement level

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Cylinder Refinement Zone

• Access: Search → “Cylinder Refinement Zone” or hotkey R3
• Best for: Rotating machinery, cylindrical wakes
• Configuration: Two axis points, radius, refinement level

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Plane Refinement Zone

• Access: Search → “Plane Refinement Zone” or hotkey R4
• Best for: Symmetry planes, ground effects
• Configuration: Base point, normal vector, refinement level

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Geometry Refinement Zone

• Access: Search → “Geometry Refinement Zone” or hotkey R6
• Best for: Surface refinement and boundary layers
• Configuration: Surface levels, feature angles, boundary layers

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Refinement Strategy

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Hierarchical Approach

1. Background Mesh: Coarse base mesh (Level 0)
2. Flow Region: Medium refinement around geometry (Level 1-2)
3. Critical Areas: High refinement near surfaces (Level 2-4)
4. Boundary Layers: Surface layers for viscous effects

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Refinement Level Guidelines

Level 0 (Base): Cell size = base_size
Level 1: Cell size = base_size / 2
Level 2: Cell size = base_size / 4
Level 3: Cell size = base_size / 8
Level 4: Cell size = base_size / 16

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Surface Layers (Boundary Layers)

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Key Parameters

• Number of Layers: 3-5 layers typically sufficient
• Expansion Ratio: 1.1-1.3 (gradual growth from surface)
• Final Layer Thickness: Target y+ values for flow regime
• Minimum Thickness: Prevent layer collapse

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Y+ Guidelines

• y+ < 1: Direct viscous sublayer resolution (most accurate)
• 30 < y+ < 300: Wall function region (efficient)
• y+ > 300: Avoid this range (inaccurate)

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Mesh Generation Process

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Pre-Generation Validation

• Geometry Upload: STL files properly uploaded and oriented
• Domain Size: Adequate clearance from boundaries
• Refinement Setup: Zones configured appropriately
• Settings Check: Core count and quality parameters set

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Generation Workflow

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Starting Generation

1. Access: Search (Ctrl+K) → “Generate Mesh” or hotkey G
2. Validation: Platform automatically checks configuration
3. Resource Allocation: Cores assigned for parallel processing

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Real-Time Monitoring

• Progress Bar: Completion percentage and time estimates
• Log Output: Detailed meshing progress and warnings
• Quality Metrics: Ongoing validation during generation

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Typical Runtime Expectations

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Mesh Quality Assessment

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Automatic Quality Checks

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Key Metrics

• Orthogonality: Should be > 0.1 (higher is better)
• Aspect Ratio: Typically < 100 for most cells
• Volume Ratio: Smooth transitions between adjacent cells
• Skewness: Measure of cell distortion

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Visual Inspection

• Surface Resolution: Geometry features properly captured
• Boundary Layers: Smooth inflation from surfaces
• Transitions: Gradual refinement level changes
• Coverage: Complete domain discretization

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Quality Optimization Tips

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For Better Accuracy

• Increase surface refinement around critical flow features
• Add boundary layers for viscous flow effects
• Extend refinement zones to capture flow phenomena
• Smooth transitions between refinement levels

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For Computational Efficiency

• Optimize base cell size for problem scale
• Limit refinement levels to essential regions
• Use distance refinement when appropriate
• Balance accuracy vs. cost based on objectives

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Troubleshooting Common Issues

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Mesh Generation Failures

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Quality Issues

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Low Orthogonality

• Cause: Poor geometry or aggressive refinement
• Solution: Smooth geometry transitions, adjust refinement zones

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High Aspect Ratio

• Cause: Boundary layer settings or domain shape
• Solution: Adjust layer parameters, modify domain proportions

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Volume Ratio Problems

• Cause: Abrupt refinement transitions
• Solution: Add intermediate refinement levels

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Advanced Meshing Techniques

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Mesh Independence Studies

1. Coarse Mesh: Baseline case for quick iteration
2. Medium Mesh: Production mesh with balanced accuracy/cost
3. Fine Mesh: Validation mesh for critical results

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Adaptive Refinement Strategies

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Error-Based Refinement

• Identify high-gradient regions automatically
• Focus computational resources where needed
• Iterative improvement of solution quality

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Feature-Based Refinement

• Target geometric features (edges, corners)
• Capture flow physics (shocks, boundary layers)
• Application-specific refinement patterns

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Optimization Workflows

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Template Creation

• Save successful mesh configurations
• Reuse for similar geometries
• Standardize team practices

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Batch Processing

• Automate mesh generation for parameter studies
• Queue multiple configurations
• Unattended operation for overnight runs

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Best Practices Summary

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Planning Phase

1. Understand Flow Physics: Know what features need resolution
2. Start Simple: Begin with coarse meshes, add complexity gradually
3. Plan Refinement: Identify critical regions before mesh generation

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Execution Phase

1. Validate Geometry: Ensure clean, properly oriented STL files
2. Size Domain Appropriately: Balance accuracy with computational cost
3. Use Hierarchical Refinement: Multiple levels for optimal efficiency

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Validation Phase

1. Check Quality Metrics: Review orthogonality, aspect ratio, skewness
2. Visual Inspection: Verify surface resolution and layer quality
3. Mesh Independence: Test solution sensitivity to mesh density