Mengmeng Zhang

Towards a Unified Framework using CPACS for Geometry Management in Aircraft Design

The performance requirements for the next generations of airliners are stringent and require invention and design of unconventional configurations departing from the classical Cayley functional dec ...

Collaborative Aircraft Design Methodology using ADAS linked to CEASIOM

The aircraft design stages, conceptual and preliminary, are necessarily collaborative bytheir very nature. An example design carried out in this paper brings the collaborativeaspects of design to l ...

Coupling parametric aircraft lofting to CFD a CSM grid generation for conceptual design

The CEASIOM software system for airctaft conceptual design generates tables of forces and moments for the rigid or elastic aircraft with control surfaces using a choice of numerical methods of varying fidelity. In order to obtain this data, the aircraft geometry must be defined and computational meshes for CFD and CSM analyses need to be created. This paper focuses on the generation of computational meshes, for analysis models of different fidelity, from the parameters that define the geometry. As an example to illustrate the procedure, the lofting geometry that was generated by the conceptual design system RDS Professional for a high-speed transport configuration termed Danbus is imported into CEASIOM from which a meshable model is created. Grids for CFD and CSM analyses are created, and results produced in order to study aspects of stability& control characteristics and structural weights along with flutter properties.

Virtual Aircraft Design of TransCruiser - Computing Break Points in Pitch Moment Curve

The SimSAC project has developed the design software CEASIOM, a framework tool that integrates discipline-specific tools like CAD & grid generation, CFD, stability & control analysis etc. for the purpose of aircraft conceptual design. Significant features developed and integrated in CEASIOM are geometry, aerodynamics, flight dynamics and aeroelasticity modules. The design begins with a design specification and uses conventional design methods to prescribe a baseline configuration. Then CEASIOM improves upon this baseline by analyzing its flying and handling qualities. This paper reports on the Transonic cruiser TCR from baseline design to Tier-I design. The baseline T-tail design is based on the design specification, which is a fairly non-complicated one with the exception for the design cruise speed of Mach 0.97. The flight dynamical analysis in CEASIOM of this configuration showed that trimming the aircraft required too large deflections in the design point so a new approach with a canard configuration was designed. A model of this configuration was built and tested in wind tunnel. The paper focuses on the validation of computational tools of different fidelity, from Tier I to Tier II RANS solvers, with test data to get a range of fidelity of the tools. The results showed that Tier I methods fail to reproduce experimental pitch moment already at moderate angles of attack . Euler met hods give reasonably accurate predictions but only RANS offers good overall experimental agreement for all angles attack, in particular at higher angles where the flow starts to separate.

Towards a collaborative and integrated set of open tools for aircraft design

A third generation Multi-Disciplinary Analysis & Optimization setup includes the collaboration of a distributed team of disciplinary experts and their respective anylsis tool to perform aircraf ...

Benchmarking the prediction of dynamic derivatives: Wind tunnel tests, validation, acceleration methods

The dynamic derivatives are widely used in linear aerodynamic models which are considered to determine the flying qualities of an aircraft: the ability to predict them reliably, quickly and sufficiently early in the design process is more and more important, in order to avoid late and costly component redesigns. This paper describes some experimental and computational activities dealing with the determination of dynamic derivatives. The work has been carried out within the FP6 European project SimSAC. Numerical and experimental results are compared for two aircraft configurations: the generic civil transport aircraft, wing-fuselage-tail configuration DLR-F12 and a generic Transonic CRuiser (TCR), which is a canard configuration. Static and dynamic wind tunnel tests have been carried out for both configurations and are briefly described. The data base generated for the DLR-F12 configuration includes force and pressure coefficients obtained during small amplitude pitch, roll and yaw oscillations while the data base for the TCR configuration includes force coefficients for small amplitude oscillations, dedicated to the determination of dynamic derivatives, and large amplitude oscillations, in order to investigate the dynamic effects on nonlinear aerodynamic characteristics. The influence of the canard has been investigated too. Dynamic derivatives have been determined on both configurations with a large panel of tools, from linear aerodynamic (Vortex Lattice Methods) to CFD (unsteady Reynolds-Averaged Navier-Stokes solvers). The study confirms that an increase in fidelity level enables dynamic derivatives to be better calculated. Linear aerodynamics (VLM) tools can give satisfactory results but are very sensitive to the geometry/mesh input data. Although all the quasi-steady CFD approaches give very comparable results (robustness) on steady dynamic derivatives, they do not allow the prediction of unsteady components of the dynamic derivatives (angular derivatives w.r.t. time): this can be done with either a fully unsteady approach (with a time-marching scheme) or with Frequency Domain solvers, both of them giving very comparable results for the DLR-F12 test case. As far as the canard configuration is concerned; strong limitations of linear aerodynamic tools are observed. A specific attention is paid to acceleration techniques in CFD methods, which allow the computational time to be dramatically reduced while keeping a satisfactory accuracy.

Variable Fidelity Methods and Surrogate Modeling of Critical Loads on X-31 Aircraft

The thesis develops computational tools for early stages of the aircraft design process. The work focuses on a framework which allows several design teams concurrently to develop a baseline concept into a configuration which meets requirements and whose aerodynamics has been assessed by flight simulation. To this end, a data base format suggested by the German Aerospace Center DLR was adopted in the CEASIOM system, developed in the EU 6th Framework Program, enabling more accurate transonic analysis and tabulation of forces and moments as well as control surface authority assessment. Results from simple, fast models are combined with computationally expensive full CFD results by co-Kriging to speed up productionof the aero-data for flight simulation.Non-linear optimization methods in wing design play an increasingly important role together with computational aerodynamics. High performance computing enables the use of high-fidelity non-linear flow predictions in optimization loops. It is argued that the optimization tools should allow the engineer to influence the process by setting up suitable target pressure distributions for the shape to approach, combined with steps to minimize drag under suitable constraints on geometry, forces, and moments. The simulation framework incorporated into CEASIOM was applied to a number of configurations, conventional as well as un-conventional, such as an a-symmetric twin prop, a canard-configured transonic cruiser, and a novel chinrudder concept for transonic airliners. Aerodynamic shape design by the developed methods was applied to the standard M6 benchmark wing, a joined-wing concept, a wing-tip, and a blended wing-body.

Aerodynamic Design Considerations and Shape Optimization of Flying Wings in Transonic Flight

This paper provides a technique that minimize the cruise drag (or maximize L/D) for a blended wing body transport with a number of constraints. The wing shape design is done by splitting the problem into 2D airfoil design and 3D twist optimization with a frozen planform. A 45% to 50% reduction of inviscid drag is nally obtained, with desired pitching moment. The results indicate that further improvement can be obtained by modifying the planform and varying the camber more aggressively.

Hybrid feedback design for subsonic and transonic airfoils and wings

The thesis develops computational tools for early stages of the aircraft design process. The work focuses on a framework which allows several design teams concurrently to develop a baseline concept into a configuration which meets requirements and whose aerodynamics has been assessed by flight simulation. To this end, a data base format suggested by the German Aerospace Center DLR was adopted in the CEASIOM system, developed in the EU 6th Framework Program, enabling more accurate transonic analysis and tabulation of forces and moments as well as control surface authority assessment. Results from simple, fast models are combined with computationally expensive full CFD results by co-Kriging to speed up productionof the aero-data for flight simulation.Non-linear optimization methods in wing design play an increasingly important role together with computational aerodynamics. High performance computing enables the use of high-fidelity non-linear flow predictions in optimization loops. It is argued that the optimization tools should allow the engineer to influence the process by setting up suitable target pressure distributions for the shape to approach, combined with steps to minimize drag under suitable constraints on geometry, forces, and moments. The simulation framework incorporated into CEASIOM was applied to a number of configurations, conventional as well as un-conventional, such as an a-symmetric twin prop, a canard-configured transonic cruiser, and a novel chinrudder concept for transonic airliners. Aerodynamic shape design by the developed methods was applied to the standard M6 benchmark wing, a joined-wing concept, a wing-tip, and a blended wing-body.

RDS‐SUMO: from lofting to physics‐based grids

Purpose – The goal for this paper is to bring the easy‐to‐use geometry drawing software RDS to a “solid” mesh, which could be analyzed and simulated in CEASIOM, to enhance both CEASIOM and RDSs capabilities.Design/methodology/approach – The RDS‐SUMO interface is developed based on the feature that both RDS and SUMO define their geometric model using cross‐sectional information, i.e. their “universe” shapes are close to each other.Findings – The translation is automated and allows the engineer to easily modify and augment the geometry in the process. Two test cases are shown, with their high quality Euler mesh and CFD computations. The A321‐look‐alike test case tests the mesh quality for transonic aerodynamics, such as high‐speed trim and drag divergence; the twin‐prop asymmetric aircraft is a “diffi+cult” non‐conventional configuration analyzed for yaw stability in one‐engine out mode.Practical implications – This paper shows that the CFD solutions based on solid grids could be obtained once the design i...