NORTHROP-GRUMMAN EVALUATES WATER TUNNEL
2005 - Rolling Hills Research Corporation
has conducted a set of comprehensive dynamic water tunnel experiments with two research
aircraft configurations for Northrop-Grumman Corporation. The RHRC water
tunnel is capable of measuring aerodynamic forces and moments created on
aircraft during static conditions and during dynamic maneuvers. These
measurements included the generation of damping derivatives.
Until recently, these kind of experiments have only
been possible in wind tunnels with highly specialized hardware. The wind
tunnel models and experiments can be quite expensive, and for that reason are
often not conducted until very late in an aircraft development program.
However, the results of these experiments are of much greater value if they can
be obtained earlier in a program when it is less expensive to modify the
configuration to tailor its characteristics.
RHRC has developed a test facility built around the
Model 2436 Water Tunnel, that
combines a submersible strain gauge
balance and a computer
controlled model support system that is capable of providing
virtually any rotational motion
desired. Testing in the RHRC water tunnel has the distinct advantage of
being far less expensive to use, or provide models for, than a traditional wind
tunnel for dynamic derivatives. For Micro-UAVs, the water tunnel is able
to very closely match the actual flight conditions. For larger aircraft,
the Mach and Reynolds numbers can be quite different than flight. This is
also the case for most existing wind tunnel facilities that are used to measure
aircraft dynamics, which often operate at very low flow velocities.
However, experience has shown that judicious use of sub-scale facilities can
provide important stability and control information, particularly at mid to high
angles-of-attack, that is currently not available with reliable results from
The complete RHRC water tunnel system is available in part
or whole to universities and research institutions.