Boundary Layer Thickness Calculator
Estimate laminar and turbulent boundary layer thicknesses over a flat plate for CFD mesh sizing.
Governing Formulas
Laminar (Blasius)
Turbulent (1/7th Power Law)
Boundary Layer Thickness
Results are based on empirical flat-plate correlations and serve as estimates for mesh sizing. Complex geometries and pressure gradients will significantly alter boundary layer development.
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Read the theory behind y+ and First Cell Height →
Example Usage: External Aerodynamics Meshing
Scenario: You are generating a mesh for an airplane wing and need to set the total thickness of the prism layer mesh.
Inputs: Velocity = 100 m/s, Length (Chord) = 2 m. The flow over the wing is mostly turbulent, so choose the "Turbulent" regime.
Outputs: The calculated turbulent boundary layer thickness (e.g., ~0.025 m) should be used as the target total thickness for your prism layer mesh to ensure you capture the entire boundary layer.
Where this fits in the CFD workflow
This estimate is utilized during domain sizing and mesh generation planning. It helps you determine the total thickness required for your boundary layer (prism) mesh to ensure you capture the entire velocity gradient.
Engineering Assumptions
- Assumes a zero pressure gradient flat plate.
- Will underpredict thickness for adverse pressure gradients (e.g., diffusers) and overpredict for favorable gradients.
- Turbulent regime uses the 1/7th power law, assuming fully turbulent flow from the leading edge.
- Auto mode abruptly switches correlations without modeling a transition region.
Documentation
Limitations
- Mixed or composite boundary layers (integrating transition regions) are not explicitly supported.
- Favorable or adverse pressure gradient effects (e.g., Thwaites method or Falkner-Skan) are not accounted for.
- 3D boundary layer effects and crossflows are ignored.