This paper summarizes the status of ongoing NASA research supported over the past eight years to advance computational capabilities for modeling civil aircraft loss of control due to airframe damage or wing stall The research is motivated by a desire to exploit the capabilities of computational methods to create augmented flight simulation models that improve pilot training for such loss-of-control scenarios Flight of aircraft with either airframe damage or operating near and beyond the stall boundary encounters additional nonlinear aerodynamic influences on stability and control from dynamic motions that, if not included in flight simulation models, may lead to incorrect pilot responses In the present work, both low- and high-fidelity computational methods are explored for analyzing such nonlinearities The challenge of creating nonlinear reduced-order models from high-fidelity computational data is also addressed At the beginning, few guidelines were available for computing or modeling the dynamic s

Computational Aerodynamic Modeling Tools for Aircraft Loss of Control

Efficient radial basis function mesh deformation methods for aircraft icing

Numerical simulation of icing has become a standard. Once the iced shape is known, however, the analyst needs to update the computational fluid dynamics (CFD) grid. This paper aims to propose a method to update the numerical mesh with ice profiles.,The present paper concerns a novel and fast radial basis functions (RBF) mesh morphing technique to efficiently and accurately perform ice accretion simulations on industrial models in the aviation sector. This method can be linked to CFD analyses to dynamically reproduce the ice growth.,To verify the consistency of the proposed approach, one of the most challenging ice profile selected in the LEWICE manual was replicated and simulated through CFD. To showcase the effectiveness of this technique, predefined ice profiles were automatically applied on two-dimensional (2D) and three-dimensional (3D) cases using both commercial and open-source CFD solvers.,If ice accreted shapes are available, the meshless characteristic of the proposed approach enables its coupling with the CFD solvers currently supported by the RBF4AERO platform including OpenFOAM, SU2 and ANSYS Fluent. The advantages provided by the use of RBF are the high performance and reliability, due to the fast application of mesh smoothing and the accuracy in controlling surface mesh nodes.,As far as authors’ knowledge is concerned, this is the first time in scientific literature that RBF are proposed to handle icing simulations. Due to the meshless characteristic of the RBF mesh morphing, the proposed approach is cross solver and can be used for both 2D and 3D geometries.

RBF-based mesh morphing approach to perform icing simulations in the aviation sector

The paper presents unique blast experiments in reference to scientific literature and official standards. Experimental scenarios reflect a hypothetical realistic combat situation of a human being covered from a blast wave behind a rigid building corner. In the scenario assumed, the overpressure loads affect the lungs while the person is standing or the eardrums while the person is kneeling at the aiming position. The paper presents 27 free-field experiments measuring the overpressure loads. All the measurements were taken behind the right angle of the rigid wall. Two masses of TNT were considered: 200 g and 400 g. In the selected cases, a low test-to-test variability of the measured data was observed. Detailed plots of overpressure versus time are presented for various distances behind the building corner and TNT charge masses. Peak overpressure versus positive impulse plots are also demonstrated. Furthermore, the safety thresholds regarding different locations behind the building corner are defined for the considered explosive masses.

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Experimental study of blast loading behind a building corner

This paper presents a mesh generation strategy that facilitates the numerical simulation of ice accretion on realistic aircraft configurations by automating the deformation of surface and volume meshes in response to the evolving ice shape. The discrete surface evolution algorithm is based on a face-offsetting strategy that uses an eigenvalue decomposition to determine 1) the nodal offset direction and 2) a null space in which the quality of the surface mesh is improved via point redistribution. A fast algebraic technique is then used to propagate the computed surface deformations into the surrounding volume mesh. Due to inherent limitations in the icing model employed here, there is no intent to present a tool to predict three-dimensional ice accretions but, instead, to demonstrate a meshing strategy for surface evolution and mesh deformation that is appropriate for aircraft icing applications. In this context, sample results are presented for a complex glaze-ice accretion on a rectangular-planform wing ...

Three-Dimensional Surface Evolution and Mesh Deformation for Aircraft Icing Applications

Robust, automated mesh generation for problems with deforming geometries, such as ice accreting on aerodynamic surfaces, remains a challenging problem. Here we describe a technique to deform a discrete surface as it evolves due to the accretion of ice. The surface evolution algorithm is based on a smoothed, face-offsetting approach. We also describe a fast algebraic technique to propagate the computed surface deformations into the surrounding volume mesh while maintaining geometric mesh quality. Preliminary results presented here demonstrate the ecacy of the approach for a sphere with a prescribed accretion rate, a rime ice accretion, and a more complex glaze ice accretion.

/pdf/discrete-surface-evolution-and-mesh-deformation-for-aircraft-3103plsbi4.pdf

Discrete Surface Evolution and Mesh Deformation for Aircraft Icing Applications

Detailed blast propagation and evolution through multiple structures representing an urban environment were simulated using the code Loci/BLAST, which employs an overset meshing strategy. The use of overset meshes simplifies mesh generation by allowing meshes for individual component geometries to be generated independently. Detailed blast propagation and evolution through multiple structures, wave reflection and interaction between structures, and blast loadings on structures were simulated and analyzed. Predicted results showed good agreement with experimental data generated by the US Army Engineer Research and Development Center. Loci/BLAST results were also found to compare favorably to simulations obtained using the Second-Order Hydrodynamic Automatic Mesh Refinement Code (SHAMRC). The results obtained demonstrated that blast reflections in an urban setting significantly increased the blast loads on adjacent buildings. Correlations of computational results with experimental data yielded valuable insights into the physics of blast propagation, reflection, and interaction under an urban setting and verified the use of Loci/BLAST as a viable tool for urban blast analysis.

High-fidelity simulations of blast loadings in urban environments using an overset meshing strategy

This paper presents the application of a mesh generation strategy for problems involving deforming geometries produced by three-dimensional ice accretion simulations, which are more challenging than corresponding two-dimensional problems. A technique to deform a discrete surface as it evolves due to the accretion of ice is described. The surface evolution algorithm is based on a face-offseting approach. A fast algebraic technique to propagate the computed surface deformations into the surrounding volume mesh while maintaining geometric mesh quality is also presented. Results are presented for a complex glaze ice on a rectangular planform wing with a constant GLC-305 airfoil section and rime ice and glaze shapes on a swept, tapered GLC-305 wing also with a GLC-305 cross section.

Qiuhan Arnoldus

Papers

Three-Dimensional Surface Evolution and Mesh Deformation for Aircraft Icing Applications

Discrete Surface Evolution and Mesh Deformation for Aircraft Icing Applications

High-fidelity simulations of blast loadings in urban environments using an overset meshing strategy

Robust Surface Evolution and Mesh Deformation for Three Dimensional Aircraft Icing Applications on a Swept GLC-305 Airfoil