Flutter Experiments Research Articles

Measurement of transonic dips in the flutter boundaries of a supercritical wing in a wind tunnel

Flutter experiments were performed on a supercritical transport type wing to investigate the transonic dip in the flutter boundaries and to obtain data for verification of a calculation method for unsteady aerodynamic loads Complete transonic dips were measured at three wing angles of attack At the highest wing angle of at tack, a second dip was found Simultaneously, the mean pressure distribution was measured in one chordwise section which could explain the flutter characteristics. Using a flutter damper device, flutter onset could be measured accurately and rapidly This paper deals with the experimental test setup, describes the on line data reduction, and presents the results.

EMERGING NAPPE SUBJECT TO FLUCTUATING UNDERPRESSURES

The effects of small sinusoidal pressure fluctuations on a nappe springing clear of a broadcrested weir are analyzed, with particular reference to fluctuations in local and average velocity of the emerging nappe. Reference is made to the effects of pressure fluctuations measured during flutter experiments on a full-scale dam, and numerical values are given for this case.

Some Tunnel-Wall Effects on Transonic Flutter

Significant effects of wind-tunnel walls were observed on the transonic flutter boundaries of wall-mounted models during two flutter model research studies, a joint ONERA-NASA-Boeing program and a follow-on NASA exploratory study. In these studies, flutter experiments with cantilevered SST-type wing models were conducted in three different wind tunnels: the ONERA S2 tunnel at Modane, France; the NASA Langley transonic dynamics tunnel; and the NASA Ames 6-ft by 6-ft supersonic tunnel. The experimental results are compared to flutter boundaries calculated for the models in free air. The results indicate that transonic flutter boundaries can be affected by tunnel-wall interference, tunnel resonances, and shock-wave reflections, and that flutter model data accuracy is a function of model/tunnel size and tunnel wall porosity. However, models within the recommended size limits should give accurate results in transonic tunnels with normal ventilation. A flutter trend analysis for a two-dimensional wing demonstrating tunnel wall and resonance effects on flutter is also presented.