HP
H.C. Prins
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Static Aeroelastic Scaling
Design of a static aeroelastically scaled strut-braced wing wind tunnel test model
Classical aerodynamic wind tunnel tests are performed with stiff or rigid wind tunnel models. Over the years wing structures have become more flexible, and with the rise of non-conventional designs, such as strut-braced wings featuring high aspect ratios, even more flexible designs have risen. To capture the aerodynamic performance of these concepts under varying load conditions, resulting in different flight shapes, a static aeroelastically scaled wind tunnel model is required. The thesis research objective is to structurally design a static-aeroelastically scaled wind tunnel test model using optimization routines to find the optimal scaled aeroelastic characteristics representing the reference wing in wind tunnel test conditions while incorporating the safety constraints. Use cases included in the research are both an unconventional high aspect ratio strut-braced wing as well as a highly flexible cantilever wing.
To obtain aeroelastic and aerodynamic similarity, the aerodynamic similarity parameters should be the same and the elastic properties of the structure should adhere to static-aeroelastic scaling laws, which were found to solely depend on the length and pressure ratios. For finding a structure that has those elastic properties, design optimization is needed. After length scaling for the wind tunnel, little room for structural elements is left, especially in the slender strut-braced wing concept. For this reason, a composite shell with solid foam is used, as composites allow control over the directional stiffness. However, the discrete nature of composites, consisting of various layers with each a variable ply direction, complicates the optimization. To overcome this complication, lamination parameters are used to make the design space continuous, allowing the use of gradient-based solvers. An optimization framework was developed to optimize the lamination parameter space including a finite element solver in combination with scaled aeroelastic loads. The design variables considered in the optimization are the lamination parameters and the thicknesses of the laminate with the root mean square of the difference in deformation as objective. After optimizing in the lamination parameter space, the stacking sequence is retrieved using an open-source tool, OptiBless.
The results showed that the design space of the unconventional strut-braced wing configuration is highly non-convex which results in finding local minimum solutions. For a cantilever wing, the optimization is much more robust, as the optimization yields comparable results for multiple starting points which can be considered as the global optimum. The optimization framework developed was able to design a static aeroelastically scaled wind tunnel model, consistently resulting in a representative match in terms of deformation with the full-scale design for the cantilever wing. For the strut-braced wing, a representative match can also be found but these results were inconsistent. The optimization framework proved to be successful to optimize composite designs for cantilever wings. For non-conventional designs, this method is less powerful as using a great number of starting values is required, diminishing the computational benefit of using a gradient-based solver, and other strategies could be considered that may yield better results. ...
To obtain aeroelastic and aerodynamic similarity, the aerodynamic similarity parameters should be the same and the elastic properties of the structure should adhere to static-aeroelastic scaling laws, which were found to solely depend on the length and pressure ratios. For finding a structure that has those elastic properties, design optimization is needed. After length scaling for the wind tunnel, little room for structural elements is left, especially in the slender strut-braced wing concept. For this reason, a composite shell with solid foam is used, as composites allow control over the directional stiffness. However, the discrete nature of composites, consisting of various layers with each a variable ply direction, complicates the optimization. To overcome this complication, lamination parameters are used to make the design space continuous, allowing the use of gradient-based solvers. An optimization framework was developed to optimize the lamination parameter space including a finite element solver in combination with scaled aeroelastic loads. The design variables considered in the optimization are the lamination parameters and the thicknesses of the laminate with the root mean square of the difference in deformation as objective. After optimizing in the lamination parameter space, the stacking sequence is retrieved using an open-source tool, OptiBless.
The results showed that the design space of the unconventional strut-braced wing configuration is highly non-convex which results in finding local minimum solutions. For a cantilever wing, the optimization is much more robust, as the optimization yields comparable results for multiple starting points which can be considered as the global optimum. The optimization framework developed was able to design a static aeroelastically scaled wind tunnel model, consistently resulting in a representative match in terms of deformation with the full-scale design for the cantilever wing. For the strut-braced wing, a representative match can also be found but these results were inconsistent. The optimization framework proved to be successful to optimize composite designs for cantilever wings. For non-conventional designs, this method is less powerful as using a great number of starting values is required, diminishing the computational benefit of using a gradient-based solver, and other strategies could be considered that may yield better results. ...
Classical aerodynamic wind tunnel tests are performed with stiff or rigid wind tunnel models. Over the years wing structures have become more flexible, and with the rise of non-conventional designs, such as strut-braced wings featuring high aspect ratios, even more flexible designs have risen. To capture the aerodynamic performance of these concepts under varying load conditions, resulting in different flight shapes, a static aeroelastically scaled wind tunnel model is required. The thesis research objective is to structurally design a static-aeroelastically scaled wind tunnel test model using optimization routines to find the optimal scaled aeroelastic characteristics representing the reference wing in wind tunnel test conditions while incorporating the safety constraints. Use cases included in the research are both an unconventional high aspect ratio strut-braced wing as well as a highly flexible cantilever wing.
To obtain aeroelastic and aerodynamic similarity, the aerodynamic similarity parameters should be the same and the elastic properties of the structure should adhere to static-aeroelastic scaling laws, which were found to solely depend on the length and pressure ratios. For finding a structure that has those elastic properties, design optimization is needed. After length scaling for the wind tunnel, little room for structural elements is left, especially in the slender strut-braced wing concept. For this reason, a composite shell with solid foam is used, as composites allow control over the directional stiffness. However, the discrete nature of composites, consisting of various layers with each a variable ply direction, complicates the optimization. To overcome this complication, lamination parameters are used to make the design space continuous, allowing the use of gradient-based solvers. An optimization framework was developed to optimize the lamination parameter space including a finite element solver in combination with scaled aeroelastic loads. The design variables considered in the optimization are the lamination parameters and the thicknesses of the laminate with the root mean square of the difference in deformation as objective. After optimizing in the lamination parameter space, the stacking sequence is retrieved using an open-source tool, OptiBless.
The results showed that the design space of the unconventional strut-braced wing configuration is highly non-convex which results in finding local minimum solutions. For a cantilever wing, the optimization is much more robust, as the optimization yields comparable results for multiple starting points which can be considered as the global optimum. The optimization framework developed was able to design a static aeroelastically scaled wind tunnel model, consistently resulting in a representative match in terms of deformation with the full-scale design for the cantilever wing. For the strut-braced wing, a representative match can also be found but these results were inconsistent. The optimization framework proved to be successful to optimize composite designs for cantilever wings. For non-conventional designs, this method is less powerful as using a great number of starting values is required, diminishing the computational benefit of using a gradient-based solver, and other strategies could be considered that may yield better results.
To obtain aeroelastic and aerodynamic similarity, the aerodynamic similarity parameters should be the same and the elastic properties of the structure should adhere to static-aeroelastic scaling laws, which were found to solely depend on the length and pressure ratios. For finding a structure that has those elastic properties, design optimization is needed. After length scaling for the wind tunnel, little room for structural elements is left, especially in the slender strut-braced wing concept. For this reason, a composite shell with solid foam is used, as composites allow control over the directional stiffness. However, the discrete nature of composites, consisting of various layers with each a variable ply direction, complicates the optimization. To overcome this complication, lamination parameters are used to make the design space continuous, allowing the use of gradient-based solvers. An optimization framework was developed to optimize the lamination parameter space including a finite element solver in combination with scaled aeroelastic loads. The design variables considered in the optimization are the lamination parameters and the thicknesses of the laminate with the root mean square of the difference in deformation as objective. After optimizing in the lamination parameter space, the stacking sequence is retrieved using an open-source tool, OptiBless.
The results showed that the design space of the unconventional strut-braced wing configuration is highly non-convex which results in finding local minimum solutions. For a cantilever wing, the optimization is much more robust, as the optimization yields comparable results for multiple starting points which can be considered as the global optimum. The optimization framework developed was able to design a static aeroelastically scaled wind tunnel model, consistently resulting in a representative match in terms of deformation with the full-scale design for the cantilever wing. For the strut-braced wing, a representative match can also be found but these results were inconsistent. The optimization framework proved to be successful to optimize composite designs for cantilever wings. For non-conventional designs, this method is less powerful as using a great number of starting values is required, diminishing the computational benefit of using a gradient-based solver, and other strategies could be considered that may yield better results.
E-SPARC: Electrically, Sustainably Propelled Aerobatic Racing Aircraft
Make Aerobatic Racing Innovative and Eco-friendly for the Future
Bachelor thesis
(2015)
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J. Hoogendoorn, Paul Hulsman, D.A.J. Peschier, O.F. Pfeifle, W. Plaetinck, H.C. Prins, B. Röell, L.N. de Ruiter, E.T.B. Smeets, N. Weber, S. Shroff, A.C. in 't Veld, M.F.M. Hoogreef, H.J. van Overvest
Following in the footsteps of the automotive industry with the successful implementation of Formula E, the E-SPARC design is the world’s first all-electric racing aircraft. E-SPARC’s mission is to proof the feasibility of a sustainable and high performance alternative for the current state-of-the-art in aerobatic racing. Thereby, the aim is to present a design worthy of competing in the popular Red Bull Air Races. Given the combination of being the world’s fastest growing international motorsport with the commitment towards reducing the carbon footprint [1], Red Bull Air Races provide the optimal platformfor the E-SPARC design. The leading design question is therefore whether an all-electric racing aircraft can be designed with performance characteristics equal to or exceeding the performance characteristics of the current competition. This report describes the design decisions and outcomes taken during the preliminary design phase, continuing upon the pusher canard configuration that was selected during the conceptual design phase...
...
Following in the footsteps of the automotive industry with the successful implementation of Formula E, the E-SPARC design is the world’s first all-electric racing aircraft. E-SPARC’s mission is to proof the feasibility of a sustainable and high performance alternative for the current state-of-the-art in aerobatic racing. Thereby, the aim is to present a design worthy of competing in the popular Red Bull Air Races. Given the combination of being the world’s fastest growing international motorsport with the commitment towards reducing the carbon footprint [1], Red Bull Air Races provide the optimal platformfor the E-SPARC design. The leading design question is therefore whether an all-electric racing aircraft can be designed with performance characteristics equal to or exceeding the performance characteristics of the current competition. This report describes the design decisions and outcomes taken during the preliminary design phase, continuing upon the pusher canard configuration that was selected during the conceptual design phase...