CFD File

Base: A New Definition

Mitochondria: Aerobic Engines

Stripped Down

Project: Rolling Resistance

Stems

Power Meters

Wheels

CFD Study

by: BTR Forum Member: zebragonzo

5/26/08

This model is intended to show the flow of air around a rider and to give armchair aerodynamicists a chance to better understand how air flows.

Because of the complexity of the model and the limited time available to run it, the mesh has had to be simplified such that the accuracy isn't spot on. Additionally, the legs and wheels are not rotating. Finally, there are some areas that did not mesh quite correctly (front of the chainring, some of the rear wheel, top of the down tube). Despite these errors the simulation reports a drag of 2480g for both the rider and bike which is as would be expected for a cyclist in this position thus indicating that the error isn't sufficiently high that the model does not resemble real life.

Some interesting things to note from this model:

- The airflow over the front wheel is far 'cleaner' than for the rear wheel which shows why the rear wheel is said to be only 1/3 as important in terms of aerodynamics as the front

- The region behind the cyclist is terrible in terms of aerodynamics and it is by sitting in this region that the rider behind experiences lower drag

- Flow separation occurs behind most geometries in a fashion similar to a cylinder on the body (arms, legs etc)

In order to view the output file from the analysis, you'll need to download and install the free viewer from CFX here:

DOWNLOAD VIEWER HERE

DOWNLOAD BETA = 0 degrees CFD FILE HERE

DOWNLOAD BETA = 20 degrees CFD FILE HERE

BTR is not affilliated with CFX/ANSYS nor it's viewer software. Contact CFX/ANSYS for software support. BTR would like to hear your feedback - drop us a note.