Aerodynamics and aero-acoustics of rectangular planform cavities.
Part IIID: Alleviation of unsteady flow effects - Store deployment
ESDU 09002 deals with the problems of store deployment from weapons bays and their alleviation. Such problems are principally related to the type of flow in and around the bay; deep bays commonly experiencing open or transitional flow, whereas shallow bays typically experience closed flow. The problems relating to deep bays are considered in some detail, using evidence from wind-tunnel drop tests at low and supersonic speeds, wind-tunnel force and moment tests on stores translating from cavities, together with computational studies. Particular attention is paid to the effects of release time on the subsequent trajectories of stores using the substantial body of available data from wind-tunnel drop tests and computational simulations. The problems associated with shallow bays are similarly discussed in terms of data from wind-tunnel force and moment tests, including the important effects of bay doors, together with the limited computational evidence.
The various methods used to alleviate store deployment problems are considered. The use of an ejection system, which is a necessity for other than the deployment of heavy stores at low airspeeds, can help in overcoming many of the separation problems, but it is not always successful without the use of other aids, especially for light-weight or marginally stable stores. Aids, such as trapeze mechanisms, bay geometry modifications, spoilers and mass injection, are discussed using mainly wind-tunnel tests and computational studies. A considerable amount of information concerns the use of mass injection, where flight tests using slot blowing are available to compare with trajectory data from wind-tunnel captive trajectory tests at subsonic and low supersonic speeds. Similar data are available from supersonic wind-tunnel drop tests with micro-jet control.
The overriding conclusion from the available data on the alleviation of store separation problems due to internal carriage is that the most severe of such problems are mainly related to the use of light-weight stores, especially those with marginal stability. In terms of the assessment of the effectiveness of the various devices, it is concluded that each have their uses in specific situations. Trapeze mechanisms are widely used for the deployment of air-to-air missiles from shallow bays. Bay ceiling porosity has also been found to be beneficial for shallow bays. For other types of store, the use of spoilers, the traditional device used, is effective for deeper bays at subsonic speeds but less so - even detrimental - at supersonic speeds. For that reason, recent work has concentrated on the use of mass injection, which was found to be effective for acoustic suppression at both subsonic and supersonic speeds, with corresponding benefits to store deployment. Steady mass injection via slots at sonic speed has been shown to be effective for light-weight store deployment in flight tests at subsonic speeds, but poor at low supersonic speeds. Subsequent development led to the use of a mass injection system using a tandem pair of micro-jets, which enabled a successful release of a JDAM from a full-scale cavity on a rocket-powered sled at Mach 2.
|Data Item ESDU 09002|
- Aircraft Noise
- Fatigue - Endurance Data
- Fatigue - Fracture Mechanics
- Fluid Mechanics, Internal Flow
- Fluid Mechanics, Internal Flow (Aerospace)
- Heat Transfer
- Physical Data, Chemical Engineering
- Stress and Strength
- Transonic Aerodynamics
- Vibration and Acoustic Fatigue
- Wind Engineering