Windcatcher

Windcatcher — ANSYS Fluent CFD Simulation

Description

This project simulates airflow and natural ventilation in an octagonal windcatcher using ANSYS Fluent. Windcatchers are tall rooftop towers that capture ambient wind to flush out warm, polluted indoor air and drive fresh air into the building. Their internal walls and channels trap and guide the flow downward from the upper intake panels into the occupied space below. The windcatcher sits in a large open-domain environment with a horizontal wind of 10 m/s at atmospheric pressure. As part of the HVAC Engineering: Beginner CFD Training Package, this project introduces a traditional passive-ventilation device, showing how building form alone — with no fan or heat source — can capture and direct outdoor air into a space.

Methodology

The geometry is created in ANSYS DesignModeler and meshed in ANSYS Meshing with an unstructured grid of 2,332,185 cells. This is a fluid-only analysis with no heat transfer. The internal layout above the windcatcher includes barrier surfaces so that some upper inlets face the wind directly while others are shielded. This arrangement establishes a pressure differential: the windward openings promote inflow and traction, while the leeward sides promote suction, together driving circulation through the windcatcher shaft and the room beneath.

Analysis

Post-processing provides velocity and pressure contours, along with velocity vectors and pathlines. The windward side of the windcatcher shows higher pressure than the leeward side, confirming the pressure-driven mechanism behind its operation. The flow visualizations show that air enters through the top panels, is guided and trapped by the interior walls, then descends and discharges through the lower panels into the interior — indicating that the windcatcher operates as intended. From these results you can evaluate how effectively the tower captures and directs the incoming wind and assess the ventilation it delivers to the space below.