Dr Joseba Murua
Lecturer in Aerospace Engineering
Qualifications: MEng, MSc, PhD, AMRAeS
Email: j.murua@surrey.ac.uk
Phone: Work: 01483 68 2359
Room no: 16A AA 03
Further information
Biography
Joseba Murua graduated in Mechanical Engineering from TECNUN, University of Navarra (2005). After working as structural engineer for IDOM and aerodynamicist for CAF R&D, he decided to merge both disciplines and become an aeroelastician.
Funded by a Fundación Caja Madrid scholarship, he completed an MSc in Advanced Computational Methods for Aeronautics, Flow Management and Fluid-Structure Interaction at Imperial College London (2008). He obtained a PhD in Aeronautics from the same institution (2012), focusing his research on the multidisciplinary modelling of flexible aircraft dynamics.
During his doctoral studies, he was visiting scholar at the Active Aeroelasticity and Structures Research Lab, University of Michigan (2011). Both the PhD and the placement at the University of Michigan were sponsored by the Basque Government.
He joined the University of Surrey as Lecturer in Aerospace Engineering in July 2012.
Research Interests
In the broad sense, my main research goal is to contribute towards more environmentally-friendly forms of flight. I am interested in innovative aerial vehicles, such as solar-powered long-endurance platforms, and also in the aeroelasticity and dynamics of next-generation transport aircraft.
These future aircraft concepts, both manned and unmanned, will most likely consist of light and large-aspect-ratio wings. This minimises weight and maximises aerodynamic efficiency, therefore reducing energy consumption. However, it will also lead to highly flexible structures, prone to exhibit large displacements during normal operation, unconventional dynamic characteristics, and vulnerability against atmospheric disturbances (for some interesting results, see below). As a result, a new design paradigm that integrates aerodynamics, structural dynamics, flight mechanics and control synthesis in a unified nonlinear framework is required in order to model next-generation flexible aircraft.
Large wind turbines also present some of these challenges, and there is a clear knowledge transfer between both fields. Hence, aligned with my concern for sustainability, wind turbine aeroelasticity constitutes my other main area of interest.
In this context, my research focuses on the development of multidisciplinary, multi-fidelity computational tools tailored to these applications, including:
• Unsteady aerodynamic modelling
• Coupled aeroelasticity and flight dynamics
• Control synthesis for gust-load alleviation
• Random atmospheric disturbance modelling
• Numerical schemes for fluid-structure interaction
• Reduced-order modelling techniques
• Multidisciplinary design optimisation
Some interesting results
The following animations illustrate some of the problems we address when modelling the dynamics of very flexible aircraft.
The flexible short-period mode is shown first. This exemplifies the overlap between aeroelastic and flight-dynamic frequencies, whereby pitching and plunging of the aircraft are coupled with the first bending mode of the flexible wing.
Flexible short-period mode
Next, the response of a flexible aircraft under atmospheric disturbances is presented, comparing open- and closed-loop responses. Due to the asymmetric gust loads, the open-loop response departs from the intended straight flight path, but appropriate controllers for ailerons, elevator and rudder successfully steer the vehicle.
Open- and closed-loop gust response
Publications
Journal articles
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(2012) 'Applications of the unsteady vortex-lattice method in aircraft aeroelasticity and flight dynamics'. Progress in Aerospace Sciences, 55, pp. 46-72.Full text is available at: http://epubs.surrey.ac.uk/721937/
Abstract
The Unsteady Vortex-Lattice Method provides a medium-fidelity tool for the prediction of non-stationary aerodynamic loads in low-speed, but high-Reynolds-number, attached flow conditions. Despite a proven track record in applications where free-wake modelling is critical, other less computationally-expensive potential-flow models, such as the Doublet-Lattice Method and strip theory, have long been favoured in fixed-wing aircraft aeroelasticity and flight dynamics. This paper presents how the Unsteady Vortex-Lattice Method can be implemented as an enhanced alternative to those techniques for diverse situations that arise in flexible-aircraft dynamics. A historical review of the methodology is included, with latest developments and practical applications. Different formulations of the aerodynamic equations are outlined, and they are integrated with a nonlinear beam model for the full description of the dynamics of a free-flying flexible vehicle. Nonlinear time-marching solutions capture large wing excursions and wake roll-up, and the linearisation of the equations lends itself to a seamless, monolithic state-space assembly, particularly convenient for stability analysis and flight control system design. The numerical studies emphasise scenarios where the Unsteady Vortex-Lattice Method can provide an advantage over other state-of-the-art approaches. Examples of this include unsteady aerodynamics in vehicles with coupled aeroelasticity and flight dynamics, and in lifting surfaces undergoing complex kinematics, large deformations, or in-plane motions. Geometric nonlinearities are shown to play an instrumental, and often counter-intuitive, role in the aircraft dynamics. The Unsteady Vortex-Lattice Method is unveiled as a remarkable tool that can successfully incorporate all those effects in the unsteady aerodynamics modelling.
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(2012) 'Assessment of Wake-Tail Interference Effects on the Dynamics of Flexible Aircraft'. AIAA Journal, 50 (7), pp. 1575-1585.doi: 10.2514/1.J051543Full text is available at: http://epubs.surrey.ac.uk/714250/
Abstract
This work investigates the effect of aerodynamic interference in the coupled nonlinear aeroelasticity and flight mechanics of flexible lightweight aircraft at low speeds. For that purpose, a geometrically exact composite-beam formulation is used to model the vehicle flexible-body dynamics by means of an intuitive and easily linearizable representation based on the displacement and Cartesian rotation vectors. The aerodynamics are modeled using the unsteady vortex-lattice method, which captures the instantaneous shape of the lifting surfaces and the free inviscid wake, including large deformations and interference effects. This results in a framework for simulation of high aspect ratio planes that provides a medium-fidelity representation of flexible-aircraft dynamics with a modest computational cost. Previous independent studies on the structural-dynamics and aerodynamics modules are complemented here with the integrated simulation methodology, including vehicle trim, and linear and nonlinear time-domain solutions. A numerical investigation is next presented on a simple wing-fuselage-tail configuration, assessing the interference effects between wing wake and horizontal tail, and the downwash due to the proximity of the wake is shown to play a significant role in the longitudinal dynamics of the vehicle. Finally, a brief discussion of direct wake-tail encounters is included to show the limitations of the approach.
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(2010) 'Structural and Aerodynamic Models in Nonlinear Flight Dynamics of Very Flexible Aircraft'. AIAA Journal, 48 (11), pp. 2648-2659.doi: 10.2514/1.J050513Full text is available at: http://epubs.surrey.ac.uk/714249/
Abstract
An evaluation of computational models is carried out for flight dynamics simulations on low-speed aircraft with very-flexible high-aspect ratio wings. Structural dynamic models include displacement-based, strain-based, and intrinsic (first-order) geometrically-nonlinear composite beams, while thin-strip and vortex lattice methods are considered for the unsteady aerodynamics. It is first shown that all different beam finite element models (previously derived in the literature from different assumptions) can be consistently obtained from a single set of equations. This approach has been used to expand existing strain-based models to include shear effects. Comparisons are made in terms of numerical efficiency and simplicity of integration in flexible aircraft flight dynamics studies. On the structural modeling, it was found that intrinsic solutions can be several times faster than conventional ones for aircraft-type geometries. For the aerodynamic modeling, thin-strip models based on indicial airfoil response are found to perform well in situations dominated by small amplitude dynamics around large quasi-static wing deflections, while large-amplitude wing dynamics require three-dimensional descriptions (e.g. vortex lattice).
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(2010) 'Camber effects in the dynamic aeroelasticity of compliant airfoils'. Journal of Fluids and Structures, 26 (4), pp. 527-543.Full text is available at: http://epubs.surrey.ac.uk/714248/
Abstract
This paper numerically investigates the effect of chordwise flexibility on the dynamic stability of compliant airfoils. A classical two-dimensional aeroelastic model is expanded with an additional degree of freedom to capture time-varying camber deformations, defined by a parabolic bending profile of the mean aerodynamic chord. Aerodynamic forces are obtained from unsteady thin airfoil theory and the corresponding compliant-airfoil inertia and stiffness from finite-element analysis. V- g and state-space stability methods have been implemented in order to compute flutter speeds. The study looks at physical realizations with an increasing number of degrees of freedom, starting with a camber-alone system. It is shown that single camber leads to flutter, which occurs at a constant reduced frequency and is due to the lock in between the shed wake and the camber motion. The different combinations of camber deformations with pitch and plunge motions are also studied, including parametric analyses of their aeroelastic stability characteristics. A number of situations are identified in which the flutter boundary of the compliant airfoil exhibits a significant dip with respect to the rigid airfoil models. These results can be used as a first estimation of the aeroelastic stability boundaries of membrane-wing micro air vehicles. © 2010 Elsevier Ltd.
Conference papers
- . (2012) 'Open-Loop Stability and Closed-Loop Gust Alleviation on Flexible Aircraft Including Wake Modeling'. Honolulu, HI, USA: AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials.
- . (2012) 'Consistent Structural Linearization in Flexible Aircraft Dynamics with Large Rigid-Body Motion'. Honolulu, HI, USA: AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials.
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(2011) 'A discrete-time state-space model with wake interference for stability analysis of flexible aircraft'. Paris, France: International Forum of Aeroelasticity and Structural Dynamics.Full text is available at: http://epubs.surrey.ac.uk/714256/
Abstract
This paper investigates the coupled aeroelastic and flight dynamics stability of flexible lightweight aircraft. The aerodynamics are modelled by the discrete-time unsteady vortex lattice method, which can capture the large deformations of the lifting surfaces, and includes 3-D effects and in-plane motions. A geometrically-exact composite beam formulation is used to model the nonlinear flexible-body dynamics, including rigid-body motions, and the equations are accommodated to discrete-time formulation. The governing equations are linearised around an equilibrium configuration, which can be highly deformed, performing a small perturbation analysis and assuming a frozen aerodynamic geometry. The resulting framework is a monolithic discrete-time state-space formulation, which provides a powerful tool for the stability boundary prediction of a flexible vehicle through a direct generalized eigenvalue analysis. It offers increased fidelity as compared to traditional tools, and at very low computational cost. As a suitable test case to illustrate the capabilities of this approach, the flutter of a T-tail is examined. In addition, previous open-loop results are extended in order to asses wake interference effects on flexible aircraft dynamics.
- . (2011) 'Stability and Open-Loop Dynamics of Very Flexible Aircraft Including Free-Wake Effects'. Denver, CO, USA: AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials.
- . (2010) 'Modeling of Nonlinear Flexible Aircraft Dynamics Including Free-Wake Effects'. Toronto, ON, Canada: AIAA Atmospheric Flight Mechanics.
- . (2009) 'Camber effects in the dynamic aeroelasticity of compliant airfoils'. Seattle, WA, USA: International Forum of Aeroelasticity and Structural Dynamics.
- . (2009) 'Application of heat pipe based refrigeration system for an electric train traction converter. An experimental study case'. 2009 13th European Conference on Power Electronics and Applications, EPE '09,
Other publications
- . (2011) 'Stability analysis of coupled aeroelastic/flight dynamics equations using unsteady vortex-lattice aerodynamics'. Bristol, UK : Airbus Flight Physics Distributed R&T Partnership, Loads and Aeroelastics (workshop presentation).
- . (2011) 'Aeroelastic modelling of highly-efficient flexible aircraft'. Imperial College London, UK : Green Aviation Symposium (rolling poster).
- . (2010) 'Coupled aeroelasticity and flight mechanics with large wing deformations'. Bristol, UK : Airbus Flight Physics Distributed R&T Partnership, Loads and Aeroelastics (workshop presentation).
- . (2009) 'On why human snoring is more likely than flying carpets'. Imperial College London, UK : GSEPS Research Symposium (poster).
- . (2008) 'Dynamic aeroelasticity of wings with compliant aerofoils'. Royal Geographical Society, London, UK : Department of Aeronautics Research Colloquium (paper, presentation and poster).
Theses and dissertations
- . (2012) 'Flexible aircraft dynamics with a geometrically-nonlinear description of the unsteady aerodynamics'. PhD thesis (Imperial College London, UK).
- . (2008) 'Camber and flap effects in the dynamic aeroelastic analysis of the typical aerofoil section'. MSc dissertation (Imperial College London, UK).
Teaching
- ENG1066 - Solid Mechanics 1
- ENG2096 - Aircraft Structures & Materials
- ENG3162 - Group Design Project (Aircraft Design)
- ENG3163 - BEng Individual Project
- ENGM247 - MEng Individual Project
Affiliations
- Associate Member of the Royal Aeronautical Society
- Member of the American Institute of Aeronautics and Astronautics