On the role of shocks in the 'sub-transonic' flutter phenomenon

A semi-quantitative investigation is reported on the influence of partial-chord transonic shocks on flutter of 'typical-section' wing models. Unsteady airloads are assumed as the sum of linearized theory and a 'shock-force doublet' centered at the measured steady shock location. The shock is shown usually to destabilize single-degree pitching motion; it may affect flexure-torsion flutter either way - often profoundly. Various typical-section parameters are studied, along with the important phase lag known to be present in the shock oscillation. Energy transfer during flutter is examined. Simplified calculations are presented that are believed relevant to the transonic tests by Farmer and Hanson.