Aerodynamics & Aerospace: Slot Effect on Wing Aerodynamic Performance

Slot Effect on Wing Aerodynamic Performance — ANSYS Fluent CFD Simulation

A slot is a deliberate gap built into a wing that splits the airfoil into two sections, allowing high-pressure air from below to feed energy into the flow over the upper surface. It's a classic aerodynamic device used to delay separation and boost lift — the same principle behind the leading-edge slots and slats on many aircraft wings. This project simulates the steady airflow over a slotted NACA 4421 airfoil in ANSYS Fluent to quantify exactly how that slot changes the wing's lift and drag.

The geometry is built in two dimensions in Design Modeler, with the slot placed near the leading edge so the airfoil is divided into two distinct elements. The domain is meshed in ANSYS Meshing, producing a grid of roughly 260,000 cells resolved around the airfoil surface and through the slot region.

The simulation runs as a steady, incompressible case. Air enters the domain at 10 m/s and the airfoil is held at a zero-degree angle of attack, isolating the effect of the slot itself from any change in incidence. Turbulence is handled with the standard k-ε model, and the solver is run to convergence to extract the aerodynamic force coefficients.

At the end of the solution, you generate 2-D contours of pressure, velocity, and turbulent (eddy) viscosity. The pressure field clearly shows the stagnation point at the leading edge, where pressure rises sharply as the flow is brought to rest. The computed force coefficients for the slotted airfoil are a drag coefficient of 0.0755 and a lift coefficient of 0.3764. Compared with a plain NACA 4421 at the same zero angle of attack — reported at roughly Cd = 0.06 and Cl = 0.1 — both coefficients rise with the slot present. The lift gain is substantial, confirming the slot's intended job, while the modest drag increase shows the trade-off that comes with it. By the end of this project, you'll be able to set up a multi-element airfoil simulation, choose appropriate turbulence and solver settings, and extract and interpret lift and drag coefficients to evaluate an aerodynamic modification.