Aerodynamic characteristics and flow round cross parachutes in steady motion

Because of their simplicity of manufacture as well as the excellence of their drag and stability characteristics, cross-parachute canopies are widely applied, particularly where their propensity to rotate is not an important design feature. Making extensive force measurement and flow visualization tests in a wind tunnel and also conducting blockage effect experiments under water in a large cross-sectional area ship tank using the same cross-shaped canopy models, the authors considered the physical reasons for these aerodynamic characteristics. It was already known that the arm ratio of the canopy is a significant aerodynamic parameter in the determination of its drag and stability characteristics, and their tests showed that the porosity of the canopy fabric is equally important. Physical reasons are advanced for the importance of these two parameters and recommendations are made as to their best choice in a given application.