NASA Technical Note


Book Description




An Integral Equation Method for Boundary Interference in a Perforated-wall Wind Tunnel at Transonic Speeds


Book Description

The wind tunnel boundary interference at transonic speeds on a thin airfoil in a two-dimensional perforated-wall wind tunnel was determined. The interference was found by applying an integral equation method to the nonlinear transonic small disturbance equation including embedded supersonic regions with shock waves. The kernels of the ensuing integral equation were replaced by series approximations, and the integrals were evaluated in closed form. The iterative technique used to calculate the interference from the integral equation method is shown to converge rapidly, and the computing time for the integral equation method is typically an order of magnitude less than present numerical methods. As a special case, the integral equation method for a thin airfoil in free air was also examined. It was found that the introduction of a novel influence function yields, for the first time, a self-contained integral equation for a lifting airfoil. In addition, a systematic study of the classical assumption used to simplify the integral equation shows that the integral method can provide solutions in good agreement with results from the numerical methods.
















Flow at Ultra-High Reynolds and Rayleigh Numbers


Book Description

Scientists have learned to use liquid and gaseous helium to overcome the limitations imposed by the usual wind and water tunnels for testing the performance of aircraft or the behavior of the atmosphere. This book covers fundamental studies of the turbulence problem, practical applications of turbulence, superfluid turbulence, cryogenic turbulence research, and new types of miniature flow instrumentation, all which are crucial for high Reynolds number research. This state-of-the-art presentation will interest physicists in fluid dynamics, engineers working with turbulent flows, and naval and aerospace engineers testing realistic parameter ranges.




Partners in Freedom


Book Description

Established in 1917 as the nation#s first civil aeronautics research laboratory under the National Advisory Commit-tee for Aeronautics (NACA), Langley was a small laboratory that solved the problems of flight for military and civil aviation. Throughout history, Langley has maintained a working partnership with the Department of Defense, U.S. industry, universities, and other government agencies to support the defense of the nation with research. During World War II, Langley directed virtually all of its workforce and facilities to research for military aircraft. Following the war, a balanced program of military and civil projects was undertaken. In some instances Langley research from one aircraft program helped solve a problem in another. At the conclusion of some programs, Langley obtained the research models for additional tests to learn more about previously unknown phenomena. The data also proved useful in later developmental programs. Many of the military aircraft in the U.S. inventory as of late 1999 were over 20 years old. Langley activities that contributed to the development of some of these aircraft began over 50 years prior. This publication documents the role, from early concept stages to problem solving for fleet aircraft, that Langley played in the military aircraft fleet of the United States for the 1990's.