Flutter

About: Flutter is a research topic. Over the lifetime, 10344 publications have been published within this topic receiving 137120 citations.

General Theory of Aerodynamic Instability and the Mechanism of Flutter

Abstract: The aerodynamic forces on an oscillating airfoil or airfoil-aileron combination of three independent degrees of freedom were determined. The problem resolves itself into the solution of certain definite integrals, which were identified as Bessel functions of the first and second kind, and of zero and first order. The theory, based on potential flow and the Kutta condition, is fundamentally equivalent to the conventional wing section theory relating to the steady case. The air forces being known, the mechanism of aerodynamic instability was analyzed. An exact solution, involving potential flow and the adoption of the Kutta condition, was derived. The solution is of a simple form and is expressed by means of an auxiliary parameter k. The flutter velocity, treated as the unknown quantity, was determined as a function of a certain ratio of the frequencies in the separate degrees of freedom for any magnitudes and combinations of the airfoil-aileron parameters.

The sense of flutter-vibration: comparison of the human capacity with response patterns of mechanoreceptive afferents from the monkey hand.

Abstract: IT WAS OUR PURPOSE in the studies described in the intact, behaving organism are therefore this paper to combine two experimental of the first importance for sensory neurophysdesigns which differ remarkably in method, iology, for they establish: 7) the dynamic and in their historical and conceptual derange required of the input on the afferent side of the system to account for the output-the measured sensory capacities; 2) the information about the stimulus which must be preserved in the initial encoding to account for the over-all information transmitting capacity of the nervous system in a particular sensory sphere; and 3) a basis for determining which of the many codes available to the pulse-operated input sys tern may be of functional significance in the sensory performance measured. It is thought that a continued correlation of the results of these two types of studies will set the limits and establish some of the parameters to be expected of that higher order neural mechanism intervening between initial cortical display and sensory experience, referred to above. mechanisms (30). Electrophysiological studies, particularly with the method of singleunit analysis, can now provide precise measures of the neural encoding in first-order nerve fibers of the parameters of peripheral stimuli, and of the successive relay and transformation of that neural replication from periphery to cerebral cortex. They have so far provided little understanding of those cerebral mechanisms which, operating upon the transformed replication of the peripheral event in the primary receiving areas of the cerebral cortex, are thought to lead to subjective sensory experience and its overt behavioral counterparts. Psychophysical studies, on the other hand, seek to establish Ideally, the two types of observation should be made in the same organism at the same lawful relations between those experiences time. Given the demands of the single-unit and certain physical aspects of the stimuli method when applied in its quantitative which evoke them. The results of these quantiform, and particularly the desired level of tative measures of the sensory performance of control of stimulus parameters, this is not vet possible for somesthesis. For the present Received for publication August 24, 1967. l This study was supported by Public Health &e Ahave made the assumption thai what Service Grants NB-1045 and NB-06828, Air Force monkeys and humans feel with their hands Contract no. 49 (638) 1305. is in principle the same, and that neuro2 Visiting Lecturer in Physiology, 1966, from the physiological observations made in the one School of Physiology, University of New South Wales, New South Wales, Australia. may with some validity be correlated with 3 Foreign Fellow of the Public Health Service, psychophysical measures in the other, given 1965-1966, from the University of Freiburg im Breisa precise identity of experimental design in gau, Germany. the two cases.

Airfoil and Bridge Deck Flutter Derivatives

Abstract: The writers compare the flutter phenomena of the suspension bridge and the airfoil and employ a free-oscillation experimental method to measure model bridge flutter coefficients analogous to airfoil flutter coefficients. They employ the airfoil as a check on the experimental method, both as a theoretical backdrop and to test out the nature of aerodynamic oscillatory forces under exponentially modified motion. A short catalogue of bridge deck flutter coefficients is then experimentally obtained and presented covering a range of bridge deck forms. Detailed results are described to account for a number of phenomena observed in the wind tunnel and in the field.

Piston Theory-A New Aerodynamic Tool for the Aeroelastician

Abstract: Representative applications are described which illustrate the extent to which simplifications in the solutions of high-speed unsteady aeroelastic problems can be achieved through the use of certain aerodynamic techniques known collectively as "piston theory." Based on a physical model originally proposed by Hayes and Lighthill, piston theor}^ for airfoils and finite wings has been systematically developed by Landahl, utilizing expansions in powers of the thickness ratio 8 and the inverse of the flight Mach Number M. When contributions of orders 8/M and 8/M are negligible, the theory predicts a point-function relationship between the local pressure on the surface of a wing and the normal component of fluid velocity produced by the wing's motion. The computation of generalized forces in aeroelastic equations, such as the flutter determinant, is then always reduced to elementary integrations of the assumed modes of motion.