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Domain Configuration

The computational domain defines the 3D space where your CFD simulation will be performed. The Navier AI Platform provides intelligent domain sizing that automatically adapts to your geometry.

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Domain Sizing Philosophy

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Why Domain Size Matters

  • Boundary Effects: Domain boundaries can artificially influence your results
  • Accuracy: Insufficient domain size leads to incorrect pressure and velocity fields
  • Efficiency: Oversized domains waste computational resources
  • Convergence: Proper sizing ensures stable, converged solutions

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Platform Approach

The platform automatically calculates optimal domain dimensions based on:
  • Geometry bounding box analysis
  • Flow physics requirements
  • Industry best practices
  • Computational efficiency

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Preset Configurations

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Small Domain

Use Cases: Initial testing, simple geometries, quick results 
Multipliers (based on characteristic length):
- Upstream: 8× 
- Downstream: 15×
- Lateral: 6×
- Vertical: 4×

Typical Applications:
- Basic validation studies
- Preliminary design analysis
- Simple external flow

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Medium Domain

Use Cases: Standard simulations, most engineering applications 
Multipliers (based on characteristic length):
- Upstream: 10×
- Downstream: 20×
- Lateral: 8×
- Vertical: 6×

Typical Applications:
- Production vehicle analysis
- Drone performance studies
- Building aerodynamics
- General external flow

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Large Domain

Use Cases: Wake studies, high-accuracy requirements, research 
Multipliers (based on characteristic length):
- Upstream: 15×
- Downstream: 30×
- Lateral: 12×
- Vertical: 8×

Typical Applications:
- Detailed wake analysis
- Academic research
- Validation against experiments
- High-precision simulations

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Custom Domain Configuration

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Manual Sizing

For specialized applications, specify custom multipliers:
Guideline: 5-15× characteristic length
  • 5×: Minimum for attached flow
  • 10×: Standard for most applications
  • 15×: High accuracy or complex inlet conditions
Considerations:
  • Allows flow development before reaching geometry
  • Prevents inlet boundary condition artifacts
  • Required for realistic approach flow
Guideline: 10-30× characteristic length
  • 10×: Minimum for basic pressure recovery
  • 20×: Standard for complete wake capture
  • 30×: Detailed wake analysis and far-field effects
Considerations:
  • Captures pressure recovery region
  • Prevents outlet boundary effects
  • Essential for accurate drag calculation
Guideline: 5-15× characteristic width
  • 5×: Minimum for symmetric flows
  • 8×: Standard for external aerodynamics
  • 15×: Crosswind studies or asymmetric effects
Considerations:
  • Prevents side boundary interference
  • Allows for flow expansion around geometry
  • Critical for lift-generating bodies
Guideline: 3-10× characteristic height
  • 3×: Ground effect studies (wind tunnel)
  • 6×: Standard atmospheric boundary layer
  • 10×: High-altitude or unconstrained flow
Considerations:
  • Ground plane simulation requirements
  • Atmospheric boundary layer development
  • Vertical flow structures (updrafts, downdrafts)

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Flow Direction Setup

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Coordinate System

  • X-axis: Primary flow direction (streamwise)
  • Y-axis: Lateral/crosswind direction (spanwise)
  • Z-axis: Vertical direction (normal to ground)

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Direction Selection

X-Direction Flow

Most Common
  • Standard for vehicles, aircraft
  • Streamwise flow analysis
  • Typical wind tunnel setup

Y-Direction Flow

Crosswind Analysis
  • Vehicle stability studies
  • Building wind loading
  • Lateral flow effects

Z-Direction Flow

Vertical Flow
  • Helicopter rotor analysis
  • Vertical take-off aircraft
  • Stack emissions

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Characteristic Length Calculation

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Automatic Calculation

The platform automatically determines characteristic length from:
  • Vehicles: Overall length
  • Aircraft: Wingspan or chord length
  • Buildings: Maximum dimension
  • General: Largest bounding box dimension

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Manual Override

You can specify custom characteristic length for:
  • Non-standard reference dimensions
  • Industry-specific conventions
  • Validation against specific test cases

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Common Reference Lengths

Application Examples:
- Automotive: Vehicle length (4-5m)
- Aircraft: Wing chord (1-10m)  
- Drones: Rotor diameter (0.2-2m)
- Buildings: Height or width (10-100m)

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Domain Positioning

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Automatic Centering

  • Geometry automatically centered in lateral (Y) and vertical (Z) directions
  • Upstream/downstream positioning based on flow direction
  • Ground plane handling for surface vehicles

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Manual Positioning

Available adjustments:
  • Translation: Move geometry within domain
  • Ground Clearance: Adjust height above ground plane
  • Flow Alignment: Rotate geometry relative to flow direction

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Boundary Identification

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Automatic Patch Creation

The platform creates six domain boundary patches:
  • Inlet: Upstream boundary (flow enters)
  • Outlet: Downstream boundary (flow exits)
  • Sides: Left and right lateral boundaries
  • Top: Upper vertical boundary
  • Bottom: Lower boundary (often ground plane)

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Naming Convention

Boundary Patch Names:
- inlet (upstream face)
- outlet (downstream face)
- side_left (negative Y face)
- side_right (positive Y face)
- top (positive Z face)  
- bottom (negative Z face, ground)

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Validation and Quality Checks

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Automatic Validation

The platform checks for:
  • Minimum Distances: Ensures adequate spacing
  • Aspect Ratios: Prevents extreme domain shapes
  • Boundary Clearance: Verifies geometry doesn’t touch boundaries
  • Physical Realism: Checks for reasonable dimensions

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Warning Indicators

Common Warnings:
  • Domain too small: Boundary effects likely
  • Extreme aspect ratio: Poor mesh quality possible
  • Geometry near boundary: Artificial flow constraint
  • Unrealistic dimensions: Check geometry scale

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Advanced Domain Features

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Ground Plane Modeling

  • Automatic Detection: Platform identifies ground-based vehicles
  • Clearance Setting: Specify ride height or ground gap
  • Boundary Conditions: Appropriate wall/symmetry conditions

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Multi-Body Domains

  • Component Spacing: Automatic domain sizing for assemblies
  • Interference Effects: Domain sized to capture interactions
  • Individual Analysis: Option to analyze components separately

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Wind Tunnel Simulation

  • Tunnel Walls: Constrained domain boundaries
  • Blockage Effects: Account for tunnel cross-section
  • Test Section: Realistic wind tunnel geometry

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Best Practices

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Domain Size Guidelines

Conservative Approach

When to use larger domains:
  • High-accuracy requirements
  • Research applications
  • Validation studies
  • Unknown flow characteristics

Efficient Approach

When smaller domains are acceptable:
  • Preliminary analysis
  • Parametric studies
  • Known flow patterns
  • Resource constraints

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Performance Optimization

  • Start Small: Begin with medium domain, increase if needed
  • Mesh Density: Balance domain size with mesh resolution
  • Convergence: Monitor for boundary effects in results
  • Validation: Compare different domain sizes for key metrics

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Common Domain Setups

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Automotive Analysis

Typical Setup:
- Upstream: 3-5× vehicle length
- Downstream: 10-15× vehicle length
- Width: 3-5× vehicle width
- Height: 3-4× vehicle height
- Ground clearance: 0.05-0.1m

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Aircraft Analysis

Typical Setup:
- Upstream: 5-10× chord length
- Downstream: 15-25× chord length
- Span: 5-8× wingspan
- Height: 5-10× chord length
- Symmetry plane option available

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Building Analysis

Typical Setup:
- Upstream: 5-10× building height
- Downstream: 15-20× building height
- Width: 5-8× building width
- Height: 6-10× building height
- Atmospheric boundary layer
Next Step: With your domain configured, proceed to Mesh Configuration to set up your computational mesh with intelligent refinement zones.