Dynamic Stall on Airfoils Oscillating in Pitch 



The 4rmy Air Mobility Research and Develop- 

 ment Laboratory investigated the effects of dy- 

 namic stall on airfoils oscillating in pitch by ex- 

 perimentally determining the viscous and inviscid 

 characteristics of the airflow on several airfoils. 

 As a result, a new understanding of the flow envi- 

 ronment on an oscillating airfoil, and, in particu- 

 lar, the relationship between boundary-layer be- 

 havior and normal-force and pitching-moment 

 behavior was obtained. An important result of 

 this study was that a properly scaled cross-plot of 

 normal force versus pitching moment resulted in a 

 single representative curve for each airfoil, pro- 

 vided the vortex had fully developed. This intro- 

 duces the possibility of a method that may allow 

 prediction of engineering parameters without ex- 

 haustive dynamic testing of airfoils. 



References: 



W. J. McCroskey, L. W. Carr, and K. W. McAlister, [:)ynamic 

 Stall Experiments on Oscillating Airfoils, AlAA Journal. Vol. 

 14. No. I. January |y7ft. 



L. W. Carr, K. W. McAlister. W. J. McCroskey. Analysis of 

 the Development of Dynamic Stall Based on f)scillating Airfoil 

 Experiments. NASA TN D-8.^82. January 1977. 



Physical Properties and Processes in Frozen 

 Ground 



Effective Army operations in cold regions are 

 constricted in a significant way by the limitations 

 imposed on mobility and facilities by snow cover, 

 frozen ground, and freeze-thaw conditions. As 

 part of its basic mission, the Army Cold Regions 

 Research and Engineering Laboratory (CRREL) 

 has continuously advanced the state of the art in 

 these areas. In particular, mechanical properties 

 such as strengtfi, deformation, and creep have 

 been examined using modern techniques and 

 equipment. This has led to extremely useful ad- 

 vances in the understanding of unfrozen water and 

 the part it plays in the physics of the microstruc- 

 tures as a function of temperature. The migration 

 of unfrozen water to the advancing or retreating 

 freezing front provides valuable insight into the 

 understanding of the behavior of pavements and 

 foundations in freeze-thaw cycles. 



This technology has been applied to the solu- 

 tion of critical foundation problems such as those 

 on safeguard missile sites and piles used in the 

 Alaska pipeline. The study of thermophysical 

 processes in permafrost has assured successful 

 environmental protection schemes in the retrieval 

 of northern oil resources. Significant advances 

 have been achieved in the subsurface exploration 

 of Arctic and subarctic terrain as a result of 

 CRREL studies of the dielectric behavior of fro- 

 zen ground coupled with a theoretical analysis of 



titled electromagnetic waves traveling along the 

 earth's surface. 



References: 



Haynes. F. D. and Mellor, M.. Measuring the Uniaxial Com- 

 pressive Strength of Ice - International Glaciological Symposi- 

 um. Cambridge. England, September 1976. Proceedings. 



McGaw. R. W. and Tice. A. R., A Single Procedure to Calcu- 

 late the Volume of Water Remaining Unfrozen in A Freezing 

 Soil - Second Conference on Soil - Water Problems in Cold 

 Regions. Edmonton. Canada. 1-2 September 1976. Proceed- 

 ings. 



Tobiasson. W. and Gianotti, J.. Design Data for Construction 

 in Alaska - Second International Symposium on Cold Regions 

 Engineering. University of Alaska. 



Mellor, M., Engineering Properties of Snow - Symposium on 

 Applied Glaciology, Cambridge. England, September 1976. 

 Journal of Glaciology. 



Sellman, P. V., Arcone. S. and Delaney, A.. Preliminary Eval- 

 uation of New LF Radiowave and Magnetic Induction Resis- 

 tivity Units - Over Permafrost Terrain. Vancouver. British 

 Columbia. Canada. October 12. 1976. 



A New Simulation Approach for Combat 

 Training 



REALTRAIN, or realistic training, is a new, 

 successful, and very much accepted approach for 

 training U. S. combat forces. Upon completion of 

 basic and advanced combat training, which is in- 

 tended to impart the necessary combat skills to 

 the individual soldier, it is necessary to embark on 

 team training designed to weld the combat units 

 into effective entities. REALTRAIN represents an 

 innovation replacing current approaches utilizing 

 field training exercises and maneuvers for this 

 purpose. The older methods depend on referee 

 determinations and judgments to assess casualties 

 in the conduct of the combat exercises. These 

 approaches by their very nature are cumbersome 

 and prone to substantial error in casualty assess- 

 ment, thus reducing much of the effectiveness of 

 the training. REALTRAIN permits a soldier 

 definitively to identify his target and provides 

 immediate and reliable feedback concerning the 

 inflicting or sustaining of casualties in simulated 

 two-sided free-play combat engagements. It is a 

 method far superior to those used heretofore. 

 REALTRAIN itself is projected to be augmented 

 by MILES, which relies on weapon-mounted laser 

 devices coupled to highly sophisticated instrumen- 

 tation to permit free-play engagement with minimal 

 interference on the part of referees. Simultaneous- 

 ly it will facilitate the recording of the necessary 

 data and provide immediate casualty assessment 

 feedback to the exercise participants without inter- 

 vention by exercise controllers. 



The evolution of both the REALTRAIN and 

 MILES systems can be traced to considerable 



DEFENSE 63 



