Half models are used for objects with a symmetrical structure and
are especially suitable for focusing on particular aspects of the
object, for instance the interaction between an engine and the wing of
an aircraft, or the acoustic conditions near a wing.
Half models enable a more detailed model representation than full
models because larger scales can be used. Moreover, testing can be
performed at higher Reynolds numbers. These conditions are favorable
for wing design studies aimed at investigating Reynolds number effects
or the influence of design changes, but also for studies on power plant
installation effects of control surface effectiveness.
Because the models used for the tests are mounted to a wall of the
test section of a tunnel, aerodynamic data is influenced by the
proximity of tunnel walls and the related boundary layer effects. As a
consequence, the absolute levels of the measurements performed with the
half model technique are unreliable, and the tests need to be performed
on a relative basis by means of comparison of the results due to model
changes with a reference configuration. Despite this need for
additional comparison with a reference situation, half models are
frequently used because of the more detailed model representation.