An engineering method for modeling the interaction of circular bodies and very low aspect ratio cruciform wings at supersonic speeds

• Main Author: Tuling, S.
• Published: University of the West of England, Bristol 2013
• Subjects: 629.132305
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.589106

An engineering method using a 2D unsteady potential formulation (called the free vortex model or FVM) has been developed to predict the normal force, centre-of-pressure and vortex position for cruciform wing-body combinations in the “plus” orientation, at supersonic speeds and cross flow Mach numbers less than or equal to 0.55 up to angles of attack 20◦. The wings are of very low aspect ratio ( ≤ 0.1), have taper ratios greater than 0.85 (or significant side edges) and have low span to body diameter ratios ( ≤ 1.5). The method predicts the position and subsequent loads imposed by the vortex along the length on the wing-body combination by determining the shed vorticity using Jorgensen’s modified Newtonian impact method. The vortex position is well predicted for angles of attack from 4◦ until symmetric vortex shedding occurs, whilst the normal force is well predicted from 0◦. The centre-of-pressure is predicted further aft at the low angles and further forward at the high angles of attack. If this method is used in combination with the single concentrated vortex of Bryson applied to cruciform wing-body combinations the vortex positions prediction limitations at angles of attack less than 4◦ can be overcome. An investigation of the lee side flow field of cruciform wing-body configurations was also performed, and revealed that the vortex position is dependent upon the lee side secondary vortex separation characteristics. Other features revealed that symmetric vortex shedding occurs when both the region of flow outside the shed vortex sheet and reverse flow region are supersonic and a termination shock exists. The thesis also investigated the applica- tion of the discrete vortex model (DVM) method to cruciform wing-body combinations and found that the potential only formulation overpredicts the normal force, whilst the inclusion of boundary layer separation (and therefore modeling the secondary separation vortex) predicted the normal force very well. The application of the concentrated vortex method of Bryson was also investigated and found to be only applicable at low angles of attack (< 4◦).