Gust Input Research Articles

Some aspects of calculating subsonic flow over wings of complex planform

The use of wings of complex planform is characteristic of the present stage of development of aviation; with discontinuities along the leading and trailing edges; with curved edges; with variable geometry (by pivoting the wing panels). This article considers some aspects of the calculation of the over-all and distributed aerodynamic characteristics of such wings for low and high subsonic velocities. The methods, based on the lifting surface scheme and the use of discrete vortical singularities, enable quite efficient and reliable digital computation of the flow about these wings at moderate angles of attack. For steady motion of the wing a further development of the method of [1] is obtained, for harmonic oscillations an extension of [2] is obtained, and for aperiodic motions of the wing and gust inputs a modification of the method of [3] is found.

Nature and observation of high-level turbulence especially in clear air

Abstract : This is a ''state-of-the-art'' report on clear air turbulence (CAT) research. Knowledge of micro-structural details of flow patterns in the free atmosphere is of importance to aircraft and missile designers. It also is of interest in considering passenger comfort. There may be at least three different causes for bumpiness experienced by an aircraft flying horizontally: convective currents, gravity waves on interfaces, and temperature discontinuities intercepted by a supersonic aircraft. For vertical take-off vehicles excessive shears of alternating sign in the vertical wind or momentum profiles should be considered as possible sources of vibration. So far, observations of high-level turbulence have been made by aircraft and by balloon-borne gust sondes. Especially aircraft measurements present a problem inasmuch as the response characteristics of the vehicle usually make it difficult to evaluate the actual atmospheric gust input. With our present theoretical modelling capabilities we may be able to study wave perturbations in the free atmosphere from detailed measurements of wind and temperature profiles. Such measurements will have to be orders of magnitude more accurate however, than the ones provided by the synoptic rawinsonde and radiosonde network.