The test measurements were analysed in order to find some general
relationships useful for parametric design analyses.
No correlation is found between mean values
and wind speed on the mirror.
The reason is that we have in many cases large differences in
mean pressure on the four pressure taps and also in some instances
a reversed flow on the mirror, whereby the mirror upper surface
is actually under a mean negative pressure.
On the contrary a correlation between and wind speed
is well established and is independent of the wind direction.
Recalling that
is referred to the external reference
speed
:
we introduce a similar coefficient referred to the wind speed U measured on the mirror:
obtaining the relationship
Fig. is a scatter plot of this relationship.
The correlation is independent of the azimuth angle and of the
venting configuration of the enclosure. The coefficient
depends only on the zenith angle:
, for zenith angle
, for zenith angle
Although it cannot be generalized to other types of
enclosures, this result
suggests that simple parameterisations between speed measurements and
pressure fluctuations should be looked for in the
study of a new enclosure.
Since the ratio is a parameter that can be adjusted by
acting on the ventilation devices of the enclosure (louvers,
windscreen), a relationship of the type (
) will be
particularly useful for parametric design analyses as well as for
operational simulations of the use of the enclosure venting devices.