GEM Research in the U.S. 289 
Fig. 8. DTMB GEM Model 448 
and airflow path of Model 448. The four compressor nacelles are powered by calibrated 
electric motors. Several interchangeable sets of nozzle control vanes were employed to 
produce various tangential deflection angles B (see Fig. 3). The model is not equipped 
with an actual propulsion system, but propulsive power was accounted for in the test data 
reduction by arbitrarily assuming it to equal 1.25 DVp (i.e., 7, = 0.8). (It should be noted 
that, as explained in Ref. 3, the assumption P, = 1.25 DV becomes unrealistic at low 
forward speeds. Nevertheless, it provides a convenient and reasonable basis for quick 
examination of the overall performance characteristics.) The performance parameters 
necessary for evaluation of Kgs. (8-8) through (8-11) vary slightly with changing test condi- 
tions, but it will suffice for our purposes to use the fixed set: 
Tint = 0.57 N40 = 0.73 
Wet 1.0.00 Cho = 0.42 
Nr = 0.80 Cor¢ = 0.074. 
