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The
Fluid Dynamics Laboratory
 Subsonic Wind Tunnel
The main facility used for experimental aerodynamic research is the subsonic wind tunnel, located in
the Engineering Faculty Building (Via Diotisalvi, 2). It is a closed return oettingen type wind tunnel
with open round test section, 1.1 m in diameter and 1.5 m in length, and a velocity range from 10
m/s to 35 m/s. The tunnel is equipped with a computer-controlled traversing rig for the accurate
positioning of measurement probes. Experiments carried out in the tunnel mainly regard the
measurement of mean and unsteady loads and pressure distributions on models, as well as the
characterization of the connected mean and fluctuating velocity fields. The measuring equipment
includes four channels of hot-wire anemometry, various pressure transducers and strain gage
balances; the latter are designed and in-house manufactured to comply with the specific
requirements of the various research activities. The acquisition system can receive up to 16
simultaneous signals at 100kHz with high-velocity multiplexing, with a 16 bit resolution. The tunnel
has its own dedicated computer and data acquisition system, while different PCs are available for
data processing.
The construction of a new, more modern subsonic wind tunnel adjacent to the Department building
is planned in the near future.
 Coaxial Jet Facility
A new high-quality coaxial jet facility, designed for basic and applied research on the development
of turbulent jet, has recently been installed in the Fluid Dynamics Laboratory. It is basically a
precision manufactured small wind tunnel, with double coaxial still chambers and converging
nozzles. The geometry of the outlets, the turbulence level and characteristics of the two main flows
and of the wall boundary layers can easily be varied, allowing the study of a considerable number of
different conditions. The flow is produced by two independent blowers placed sufficiently upstream
of the facility, and the outlet velocities of the two streams may be set with an accuracy of 0.1 m/s.
To ensure a satisfactory axisymmetry of the two streams, great care was devoted to the design of
the air inlets. In particular, an original and effective geometry was devised for the outer annular jet,
in order to avoid undesired azimuthal velocity components: air is conveyed through four radial ducts
into a first still chamber, and then in the main external duct through a faired inlet. Various screens
and honeycombs are also present in the two ducts. This ensures less than 0.5% deviation from
axisymmetry in the mean and fluctuating flow quantities both in the coaxial jet and in the annular jet
configurations. Measurements are taken by hot-wire anemometry, using a computer-controlled
traversing equipment for the accurate positioning of the probes. Several computers are available for
data acquisition and processing. The facility will soon be equipped with a laser flow visualization
system.
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