Airship shape optimization with NURBS and gradient based algorithms

The present work attempts to conduct shape optimization of stratospheric airships with a method based on a combination of NURBS (non-uniform rational B-spline) and a gradient-based optimization algorithm.Drag coefficient was chosen as the objective function and airship volume as the constraint.NURBS based geometric parameterization was used because of its more efficient representation of the discrete geometric data than other methods (e .g. B?zier curve).Drag coefficient was obtained during the optimization iteration by solving two dimensional incompressible viscous flow field.Both form and viscous drags were considered when drag coefficient was calculated.Using LOTTE airship shape as initial shape,an improved shape with the above algorithm was obtained.Airship with the new shape obviously had better aerodynamic performance.It is eventually proved that the optimization method above can be effectively applied to airship optimization.