NACA 4421 Slotted Airfoil Analysis - Advanced Flow Control Techniques

Learning Objective

In this comprehensive episode, you’ll explore advanced airfoil design by analyzing a NACA 4421 airfoil with a leading-edge slot using ANSYS Fluent. This tutorial introduces you to passive flow control techniques commonly used in aerospace applications to enhance aerodynamic performance.

Project Overview

This simulation investigates how leading-edge slots affect airfoil performance by comparing flow characteristics and aerodynamic coefficients. You’ll analyze steady airflow over a modified NACA 4421 airfoil at zero angle of attack, providing insights into lift enhancement mechanisms used in modern aircraft design.

Problem Definition

The study examines airflow behavior over a slotted NACA 4421 airfoil to understand how geometric modifications influence aerodynamic performance. The slot creates flow separation, dividing the airfoil into two distinct sections for enhanced flow control.

Geometric Configuration

Using ANSYS Design Modeler, we’ll create a two-dimensional computational setup featuring:

• Airfoil Type: NACA 4421 with leading-edge slot
• Angle of Attack: 0 degrees
• Inlet Velocity: 10 m/s
• Slot Configuration: Leading-edge deformation for flow optimization

Simulation Methodology

The analysis employs steady-state simulation with turbulence modeling to capture complex flow phenomena around the slotted airfoil configuration.

Turbulence Modeling

• Model Selection: Standard k-epsilon turbulence model
• Application: Accurate prediction of separated flows and wake regions
• Benefits: Reliable results for external aerodynamic flows

Mesh Generation Strategy

The computational grid uses ANSYS Meshing with 260,000 cells, providing:

• Adequate resolution near airfoil surfaces
• Proper boundary layer capture
• Efficient computational resource utilization

Boundary Conditions Setup

• Inlet: Velocity inlet at 10 m/s
• Outlet: Pressure outlet
• Airfoil Surfaces: No-slip wall conditions
• Domain Boundaries: Appropriate far-field conditions

Performance Analysis Results

Aerodynamic Coefficients Comparison

The simulation reveals significant performance improvements due to slot implementation:

Slotted NACA 4421 Performance

• Drag Coefficient (CD): 0.0755
• Lift Coefficient (CL): 0.3764

Standard NACA 4421 Performance (Reference)

• Drag Coefficient (CD): 0.06
• Lift Coefficient (CL): 0.1

Flow Visualization Insights

Pressure Distribution Analysis

• Clear stagnation point identification at the leading edge
• Pressure increase at flow impingement locations
• Modified pressure gradients due to slot presence

Velocity Field Characteristics

• Flow acceleration through the slot opening
• Velocity redistribution over airfoil surfaces
• Wake region modifications behind the airfoil

Turbulence Effects

• Eddy viscosity contours reveal turbulent mixing regions
• Enhanced momentum transfer due to slot-induced turbulence
• Improved boundary layer energization

Key Learning Outcomes

This episode demonstrates how geometric modifications can significantly impact aerodynamic performance:

• 276% increase in lift coefficient due to slot implementation
• 25.8% increase in drag coefficient as trade-off
• Understanding of passive flow control mechanisms
• Practical application of CFD for airfoil optimization

This advanced tutorial prepares you for complex aerospace applications involving high-lift devices, flow control systems, and aerodynamic optimization techniques commonly used in modern aircraft design.