Velocite Aerodynamics Consulting CFD Simulations and Design

Examples of aerodynamic designAero Not aero

Why consider aerodynamics?

Functional benefits● reduced drag● improved handling● improved brake cooling

Business benefits● better marketing story● more OEM wins● unified design language

○ reduced tooling costs○ reduced part count

● create unique products

What do we do?

● Use computational fluid dynamics (CFD) to simulate external airflow over an object ○ Bike, brake, wheel, handlebars, fork, etc.

● Give advice and guidance on aerodynamic design○ Is your design aero? We can make it so.

● Provide aerodynamic designs○ Do you need a new aero product? We can design it.

Computational Fluid Dynamics (CFD)

What is CFD?● in aerodynamics, CFD delivers visual and

numerical analysis of airflow around the object

● Unlike wind tunnel studies, CFD allows visualization of airflow and makes rational aerodynamic design possible

CFD versus wind tunnel

CFD● visualization of airflow● used for design and

development● results not dependant on

external conditions● in Velocite’s case, results also

not dependant on problem or operator

● good for marketing in the bicycle industry

● more expensive

Wind tunnel● used for verification of

assumptions or design, not for development

● results depend on operator, experiment setup, day to day conditions, wind tunnel setup

● faster results● great for marketing in bicycle

industry● cheaper (as used by the bicycle

industry)

Who uses CFD?

Since the 1970’s everyone in aerospace industry relies on CFD for primary design and

development

Velocite CFD versus others

Velocite● Lattice-Boltzmann with

LES turbulence model● transient flow

simulationsComplex, computationally much more demanding. Not possible to run on a workstation.

Other● Navier-Stokes with K-ε

→ DES models● generally steady state

simulationsMuch simpler and computationally less demanding. Workstation level.

ExamplesLattice-Boltzmann LES, transient. Velocite standard

Navier-Stokes K-ε, steady state. Industry standard

Example Airflow detail: front brake location

Front view Rear view

Rotating wheel simulation: 42 km/h @ 12 degrees angle of attack. 132 million cells, 20 thousand time steps.

Example Airflow detail: short conclusion

● Layer of air adheres to the surface of the wheel and has direction vector that follows the rotational vector of the wheel

● Bulk airflow vector is aligned with the apparent wind direction● High air pressure is observed on the front faces of the fork - this is

especially significant at yaw

Conclusion: brake shape and mounting location or integration impacts the overall bicycle

aerodynamics

More examples: Velocite YouTube channel

● Three spoke wheel simulation○ http://youtu.be/Qb9VkYOdCBw

● Airflow around water bottles:○ http://youtu.be/g08s7hR70ok

● Velocite RT50 wheels○ http://youtu.be/mGGm1gEJd8U

● Ahmed body validation example○ http://youtu.be/2I0t5FHKHYc

How accurate or reliable is our CFD?● We use custom made software developed for Velocite by a team of

scientists at The University of Geneva, Switzerland● Velocite CFD expertise was developed through our past and current work

with:○ Acer Computers○ NARL NCHC (National Center for High Performance Computing)

division○ NCKU (National Cheng Kung University) in Tainan

Advantages of Velocite method● Much higher resolution

○ allows better design decisions● More realistic results

○ not idealized, nothing is hidden or smoothed over● Correctly simulates downstream airflow

○ can determine how design changes impact the rest of the bicycle

● Can use actual physical 3D model○ no separate meshing or preparation step

How can our service benefit you?

We can help you design your new world class aero product

If you already have a product, but no data we can help you validate your design

We can make the all-important CFD simulation images, videos and data

Design

Validation

Marketing

Velocite CFD offer● Simulate 3D airflow around any number of parts,

including rotating wheels, or cranks○ variable airspeed, variable angle of attack, variable rotational, or

periodic velocity, as required○ Simulation runs on our in-house compute cluster in Taiwan

● Provide detailed aerodynamics analysis and design recommendations, numerical data, images and videos as required

● Competitive pricing that can suit any design and development budget