Showing papers by "Grant P. Steven published in 1974"

Stress diffusion in thick stiffened panels

Abstract: out if higher order basic shapes are used. Surface waviness, apart from the leading edge droop, is small, and the number of surface waves increase with increasing number of basic shapes used in a design. All the designed shapes have a leading edge droop and a washout in incidence in the outboard portion with the tip vicinity showing negative incidences. This should, as in the basic shapes, be helpful in delaying tip stall problems. Numerical calculations also show that combinations of higher order basic shapes or combinations of larger number of basic shapes gradually push the pressure peak outboard, increase the peak intensity, and by acting on the forward facing drooped portion of the leading edge produce a thrust force that alleviates drag, Fig. 4. Table 1 shows that the leading edge thrust lost by prescribing an attachment line at the leading edge is admirably made up by the pressures acting on the droop, and drag values quite close to the plane delta with full suction are attainable. Also, from Table 1, for even combinations, the wing incidence increases as higher order basic shapes are used. For odd combinations, the opposite trend is true. Many of the designed shapes in Fig. 3 appear to be of practical use because of small surface waviness and favourable twist near the leading edge. In practice, the plane delta will never develop full leading edge thrust, which may be almost half the magnitude of the total drag for low aspect ratios, due to flow separation. Hence, the conically cambered delta with its drooped leading edges will provide definite improvements in the lift to drag ratio in a real flow. The designs of this Note do not exhibit pronounced waviness as in Refs. 2 and 4, where the shapes were obtained by superimposing known pressure distributions, and hence our wing shapes are less conducive to produce shocks due to compressions on the wing surface.