This paper briefly considers the method of simulating gunfire damage to a wing and outlines the key basic assumptions used in modelling. The results of qualitative and quantitative investigations into the aerodynamic characteristics of a wing damaged at quarter chord are then presented. The results are discussed in terms of flow mechanisms, changes to surface pressure distributions and increments in lift, drag and pitching moment coefficients. For the damaged wing, the influence on force and moment coefficients was attributed to flow through the damage. This through flow was driven by the pressure differential between the upper and lower wing surfaces, and took one of 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, resulting in separation of the oncoming surface flow, and the development of a larger separated wake with reverse flow. The effect on force and moment coefficients was significant. The paper also compares the structure of the damage 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.

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

This investigation looks into the induced surface pressure field and flow field of a 2-D
flat plate aerofoil with simulated battle damage. Enhancing survivability is a major
design criteria for military aircraft designers, and the aerodynamic effects of battle
damage has recently come to the fore as an area that warrants further attention. The
current investigation is in effect a continuation of the battle damage research initiated at
Loughborough University by Irwin, with the ultimate aim of enabling quick and accurate
CFD studies to assess the aerodynamic impact of battle damage on a lifting surface. [Continues.]

The flow field induced by a flat plate aerofoil with simulated battle damage

Rapid reanalysis by the force method

Mechanical Engineering) The Effect of Wing Damage on Aeroelastic Behavior by Howard J. Conyers Department of Mechanical Engineering and Materials Science Duke University

/pdf/the-effect-of-wing-damage-on-aeroelastic-behavior-2lje6cebnn.pdf

The Effect of Wing Damage on Aeroelastic Behavior

: Tests were made using a 2-D insert in a subsonic wind tunnel to examine the effects of simulated ballistic damage on the aerodynamic characteristics of ten helicopter rotor blade sections. Two undamaged baseline blade sections, comprised of SC1095 and SC1095R8 airfoils, were tested and then modified with different simulated ballistic damage configurations. These comprised of a circular hole with the surrounding skin removed, fore and aft circular holes, and an aft wedge-shaped hole. One blade section was subjected to actual ballistic damage near the trailing edge. The sectional lift, drag and pitching moment were measured at positive and negative angles of attack at Reynolds numbers of one, two, and three million. Pressure measurements were also made for two configurations fitted with pressure taps. Additional tests were conducted over a full 360 degree range in angle of attack for a Reynolds number of one million. The measurements were complemented by oil flow visualization on the blade sections. The simulated damage caused large disturbances in the flowfield near and downwind of the damaged regions. Generally, flow separation was initiated at the upstream leading edge of the damage, followed by a growth in separation, both in span and intensity, with increasing angle of attack. The aerodynamic characteristics were significantly degraded, with up to a 60 percent reduction in lift-curve-slope, a loss of maximum lift capability of nearly 30 percent, and a significant decrease in the lift-to-drag ratio due to drag increases of up to nearly 340 percent at low angles of attack.

Aerodynamic Characteristics of Rotor Airfoils as Affected by Simulated Ballistic Damage.

: An investigation is carried out to determine whether ballistic damage can seriously degrade the aeroelastic integrity of lifting surfaces on aircraft A promising aeroelastic failure mechanism is identified that results from the localized drag generated when a lifting surface encounters severe damage to its aerodynamic shape This damage induced drag is shown to significantly decrease the divergence speed of a generic or statistical fighter wing for certain damage site locations while increasing the flutter speed of the wing Consequently, a critical damage level exits where divergence becomes the critical aeroelastic instability for a wing which may still have adequate strength and flutter integrity In view of the very limited information existing on the aerodynamic modeling of damaged lifting surfaces, a combined analytical and experimental modeling study was initiated to investigate the flow field in the vicinity of thru hole type damages on lifting surfaces (Author)

A Sigal

Papers

The Influence of Ballistic Damage on the Aeroelastic Characteristics of Lifting Surfaces.