A well-formulated design space parametrisation is the key to the success of design optimisation. Most parametrisation methods require manual set-up which typically results in a restricted design space and impedes the generation of superior designs which may be found outside this restricted envelope. In this work, we adopt a NURBS-based automatic and adaptive parametrisation approach where the optimisation begins in a coarser design space and adapts to finer parametrisation during the optimisation. Our approach takes CAD descriptions as input and to alter the shape perturbs the control points of the NURBS patches that form the boundary representation. Driven by adjoint sensitivity information the control net is adaptively enriched using knot insertion. The sensitivity-driven parametrisation method is applied here to reduce the pressure loss of a U-bend passage of a turbine blade serpentine cooling channel.

Numerical shape optimisation with adjoint CFD is applied using the NURBS based Parametrisation method with Continuity Constraints (NSPCC) for aerodynamically optimising three dimensional surfaces. The ONERA M6 wing is re-parametrised with NURBS surfaces including weight adjustments to represent the three dimensional wing accurately, resulting in fewer control points and smoother variation of curvature. The NSPCC CAD kernel is coupled with the inhouse flow and adjoint solver STAMPS and a gradient-based optimiser to minimise the drag of the ONERA M6 wing in transonic Euler flow conditions. Optimisation results are presented for the B-Spline and NURBS parametrisations.

Non-Uniform Rational B-Splines (NURBS) have become the industrial standard to represent and exchange a CAD geometry between CAD/CAE systems. CAD-based shape parameterisation uses parameters of a CAD model to modify the shape which allows to integrate a CAD model into the design loop. However, feature-trees of typical commercial CAD systems are not open and obtaining exact derivatives for gradient-based optimisation methods is not possible. Using the CAD-based NSPCC approach a designer can deform multiple NURBS patches in the design loop without violating geometric and/or thickness constraints. The NSPCC approach takes CAD descriptions as input and perturbs the control points of the NURBS boundary representation to modify the shape.