NORTHROP-GRUMMAN EVALUATES WATER TUNNEL

March 1, 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 computational approaches.

The complete RHRC water tunnel system is available in part or whole to universities and research institutions.