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By Paolo Conti and Massimiliano Malerba, University of Perugia, Perugia,
Italy
Horizontal pathlines around the scooter
Motorcycle aerodynamics doesn’t usually receive as much attention
as that for automobiles. This is partly because the automobile is more
widely used as a method of transportation, and partly because the aerodynamics
of a motorcycle changes as the rider shifts position. Furthermore, because
the wheels of a motorcycle are only partially shielded, it is difficult
to realize a fully streamlined body for either simulation or testing purposes.
To date, many motorcycle components,
such as the frame and shock absorbers, have
been physically tested and numerically simulated.
These components have a powerful
influence on vehicle handling, safety, and
performance. External aerodynamics, on
the other hand, affects fuel consumption,
vehicle stability and handling, and rider and
passenger comfort. To a lesser degree, the
external airflow affects engine and brake
cooling. Taken together, it is clear that external
aerodynamics plays a significant role
on the overall performance of the bike.
At the University of Perugia in Perugia, Italy, simulations performed
using FLUENT have recently been carried out on a commercial motorscooter.
As a first step in this effort, the motorscooter was studied without a
rider. The FLUENT simulations were focused on identifying, through validation,
the best strategies for grid generation and model selection. The drag
properties of a real motorscooter were measured in a wind tunnel for the
purpose of comparison.
Pressure distribution on the front of the scooter
The motorscooter geometry was written
in the IGES format, and imported into
GAMBIT, where more accurate surfaces were
constructed, and a mesh of tetrahedral elements
was created. Turbulent airflow simulations
in FLUENT were examined closely.
Particular attention was given to the predictions
of pressure field, pitching moment,
drag, and the overall airflow behavior in
the upper areas of the motorcycle, where
aerodynamic phenomena most affect the
rider. Predictions for drag were compared
to the wind tunnel test data, and very good
agreement was found. This has given the
researchers confidence in the other simulation
results, especially the pressure field,
which is usually difficult to characterize experimentally.
It has also encouraged them to
continue their work with more detailed models;
they are currently working on a simulation
of a scooter with a rider.
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