Rotating Disk Airflow Analysis - Understanding Moving Wall Boundary Conditions

Learning Objective

In this episode, you’ll master the simulation of rotating disk effects on surrounding airflow using ANSYS Fluent’s moving wall boundary condition. This fundamental technique is essential for analyzing propellers, turbomachinery, and rotating equipment in aerospace applications.

Project Overview

This hands-on tutorial demonstrates how a rotating disk influences nearby airflow patterns. You’ll learn to model a 0.1-meter diameter disk (0.02m thick) rotating at 5 rad/s within a confined space (0.5m × 0.5m × 1m room), providing practical experience with rotational aerodynamics.

Problem Definition

The simulation investigates airflow behavior under the influence of rotational motion within a computational domain. A rotating disk with specific rotational speed is positioned centrally to analyze flow patterns and velocity distributions.

Geometric Configuration

Using ANSYS Design Modeler, we’ll create a three-dimensional computational domain featuring:

• Room dimensions: 0.5m × 0.5m × 1m
• Disk diameter: 0.1m
• Disk thickness: 0.02m
• Central positioning for optimal flow analysis

Simulation Methodology

You’ll implement the moving wall boundary condition to define the disk’s rotational motion, while utilizing the laminar flow model for solving the governing fluid equations. This approach provides clear visualization of flow physics without turbulence complexity.

Boundary Conditions Setup

• Moving Wall: 5 rad/s rotational speed for disk surface
• Laminar Model: Enabled for fluid equation solving
• Room Walls: Stationary no-slip conditions

Meshing Strategy

The mesh generation process using ANSYS Meshing will produce approximately 716,870 cells, ensuring adequate resolution for capturing flow details near the rotating surface.

Key Learning Outcomes

Through velocity and pressure contour analysis, you’ll observe how:

Flow Velocity Characteristics

• Maximum velocities occur at the disk’s outer edge
• Velocity decreases with distance from the rotating boundary
• Room air velocity increases near the rotating disk region

Pressure Distribution Patterns

• Pressure reduction occurs near the disk surface
• Symmetric pressure patterns develop around the disk
• Flow separation occurs from the disk surface due to rotational effects

Flow Visualization Insights

• Velocity vectors demonstrate flow separation behavior
• Three-dimensional contours reveal complex flow structures
• Symmetric results appear on both disk faces

This episode builds essential skills for aerospace CFD applications involving rotating components and prepares you for more complex propeller and rotor simulations.