The influence of mid-chord battle damage on the aerodynamic charactersticsof two-dimensional wings

This paper briefly considers the method of simulating gunfire damage to a w ing and outlines the key basic assumptions used in modelling. The results o f qualitative and quantitative investigations into the aerodynamic characte ristics of a wing damaged at quarter chord ale then presented. The results are discussed in terms of flow mechanisms, changes to surface pressure dist ributions and increments in lift, drag and pitching moment coefficients. Fo r the damaged wing, the influence on force and moment coefficients was attr ibuted to flow through the damage. This through flow was driven by the pres sure differential between the upper and lower wing surfaces, and took one o f two forms. The first form was a 'weak-jet' which formed an attached wake and resulted in small changes in force and moment coefficients. The second form resulted from either increased incidence, or damage size. This was the 'strong-jet', where through flow penetrated into the freestream flow, resu lting in separation of the oncoming surface flow, and the development of a larger separated wake with reverse flow. The effect on force and moment coe fficients was significant. The paper also compares the structure of the dam age through flow with previously published results for jets in crossflows. Many similarities in the flow features were identified, although there were significant differences in the surface pressure distributions for the two cases.