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Falkner-Skan Wedge Flow Boundary Layer Calculator

The Falkner-Skan family of similarity solutions generalizes boundary layer theory to flows with external pressure gradients along wedges.

Hartree parameter β: 0 for flat plate, >0 for accelerated wedge flow (up to 2.0 stagnation), -0.1988 for boundary layer separation.

Freestream velocity outside the boundary layer at distance x.

Fluid kinematic viscosity (e.g. 1.5×10⁻⁵ m²/s for ambient air).

Streamwise distance from the wedge leading edge or stagnation point.

Calculated Result
1.054 mm

Boundary Layer Displacement Thickness (δ*)

Momentum Thickness (θ)

0.407 mm

Shape Factor (H = δ*/θ)

2.592

Skin Friction Coeff (Cf)

1.150e-3

Local Reynolds Number (Rex)

6.67e+5

Velocity Exponent (m)

0.000

Calculation Breakdown

  1. Velocity Potential Exponentm = β / (2 - β) = 0 / (2 - 0) = 0.000
  2. Local Reynolds NumberRex = (Ue · x) / ν = (20 · 0.5) / 1.50e-5 = 6.67e+5
  3. Falkner-Skan Wall Shear & Thicknessf''(0) = 0.4696, H = 2.59, δ* = 1.054 mm

What Is the Falkner-Skan Wedge Flow Boundary Layer Calculator?

The Falkner-Skan solution describes laminar boundary layers in flows where the external velocity varies as U(x) = C·x^m.

The Hartree parameter β = 2m / (m + 1) directly quantifies the imposed pressure gradient.

How Does the Falkner-Skan Wedge Flow Boundary Layer Calculator Work?

Positive β corresponds to favorable pressure gradients (dp/dx < 0), thinning the boundary layer and stabilizing against separation.

Negative β corresponds to adverse pressure gradients; at β = -0.1988, the wall shear stress f"(0) vanishes, signifying separation onset.

Falkner-Skan Wedge Flow Boundary Layer Calculator Formula & Variables

The core mathematical equation utilized by this calculator is expressed as:

m = \frac{\beta}{2 - \beta}, \quad \delta^* = \frac{x}{\sqrt{Re_x}} \eta^*, \quad C_f = \frac{2 f''(0)}{\sqrt{Re_x}}

Relates wedge half-angle to external velocity exponent m = beta / (2 - beta) and evaluates boundary layer thickness parameters.

How to Use the Falkner-Skan Wedge Flow Boundary Layer Calculator

  1. Specify the Hartree pressure gradient parameter β.
  2. Input the edge freestream velocity, kinematic viscosity, and streamwise station x.
  3. Inspect displacement thickness, momentum thickness, and skin friction coefficient.

Step-by-Step Example Calculation

Zero-Gradient Flat Plate Airflow (Blasius)

Input Values:

wedgeAngleParameterBeta:0
freestreamVelocityMPerS:25
kinematicViscosityM2PerS:0.000015
distanceFromLeadingEdgeM:0.5
Worked Steps: Generates standard Blasius displacement and momentum thickness metrics.

Understanding Your Result

Displacement thickness δ* measures mass flow deflection away from the surface.

The shape factor H = δ*/θ indicates transition susceptibility and proximity to separation.

Factors That Affect the Result

  • Accelerating flows (β > 0) reduce boundary layer thickness and increase skin friction.
  • Decelerating flows (β < 0) thicken the boundary layer and drive wall shear toward zero.

When Should You Use This Calculator?

  • Aerodynamic wing leading-edge wedge design and turbine airfoil boundary layer analysis.
  • Estimating separation margins on diffusing aerodynamic surfaces.

Assumptions & Limitations

  • Valid for 2D, laminar, incompressible boundary layer flow under similarity conditions.

Frequently Asked Questions

Calculation Accuracy & Reference Note

Semi-analytical approximation matching Runge-Kutta numerical integration within 1%.

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