Viscous Damping Characteristics of Dacron Parachute Suspension-Line Cord

The experimental data has been tabulated by Coleman. The measurements of normal force coefficient, CN, for the flat delta and caret wing models are compared with each other and with some theoretical predictions in Fig. 2. The caret wing develops significantly higher values of CN than does the flat delta. Near the caret design incidence (a = 34°) the experimental values agree well with the two-dimensional (wedge) prediction whereas, at the same incidence, CN for the delta wing corresponds more closely to the cone value. Similar comments were found to apply to the measured shock wave angles. Simple Newtonian theory (Cp = 2 sina) also gives a good estimate of CN for the flat delta over the incidence range considered, but tends towards underestimation at low a and overestimation at high a. The agreement of Squire's prediction for the caret wing is striking, but for the flat delta his method is less successful. The lift coefficients (CL) developed by the two models are compared in Fig. 3; the superiority of the caret wing over the entire incidence range is clear. Both shapes develop maximum lift around 50° incidence, corresponding to L/D ~ 0.7.