Publications
76 results found
Bird J, Santer M, Morrison J, 2018, Compliant kagome lattice structures for generating in-plane waveforms, International Journal of Solids and Structures, Vol: 141-142, Pages: 86-101, ISSN: 0020-7683
This paper details the design, manufacture and testing of an adaptive structure based on the kagome lattice geometry – a pattern with well documented interesting structural characteristics. The structure is used to produce in-plane travelling waves of variable length and speed in a flat surface. The geometry and dimensions, as well as the location and compliance of boundary conditions, were optimized numerically, and a pneumatically-actuated working demonstrator was manufactured. Static and dynamic photogrammetric and force measurements were taken. The structure was found to be capable of producing dynamic planar waveforms of variable wavelength with large strains. The lattice structure was then surfaced with a pre-tensioned membrane skin allowing these waveforms to be produced over a continuous plane.
Jinks E, Bruce P, Santer M, 2018, Optimisation of adaptive shock control bumps with structural constraints, Aerospace Science and Technology, Vol: 77, Pages: 332-343, ISSN: 1270-9638
This paper presents the results from a study to design an optimal adaptiveshock control bump for a transonic aerofoil. An optimisation frameworkcomprising aerodynamic and structural computational tools has been used toassess the performance of candidate adaptive bump geometries based on a novelsurface-pressure-based performance metric. The geometry of the optimal resultantdesign is a unique feature of its adaptivity; being strongly inuencedby the (passive) aerodynamic pressure forces on the exible surface as well asthe (active) displacement constraints. This optimal geometry bifurcates theshock-wave and carefully manages the recovering post-shock ow to maximisepressure-smearing in the shock-region with only a small penalty in L=D for theaerofoil. Short adaptive bumps (with small imposed displacements) generallyperform better than taller ones, and maintain their performance advantage fora wide range of bump positions, suggesting good robustness to variations inshock position, which are an inevitable feature of a real-world ight application.Such devices may o er advantages over conventional ( xed geometry) shockcontrol bumps, where optimal performance is achieved with taller devices, atthe expense of poor robustness to variations in shock position.Keywords: Shock Control Bumps; Aeroelastic Optimisation
Bird J, Santer M, Morrison J, 2018, Experimental control of turbulent boundary layers with in-plane travelling waves, Flow, Turbulence and Combustion, Vol: 100, Pages: 1015-1035, ISSN: 1386-6184
The experimental control of turbulent boundary layers using stream-wise travelling waves of spanwise wall velocity, produced using a novel activesurface, is outlined in this paper. The innovative surface comprises a pneu-matically actuated compliant structure based on the kagome lattice geometry,supporting a pre-tensioned membrane skin. Careful design of the structureenables waves of variable length and speed to be produced in the flat surfacein a robust and repeatable way, at frequencies and amplitudes known to havea favourable influence on the boundary layer. Two surfaces were developed,a preliminary module extending 152 mm in the streamwise direction, and alonger one with a fetch of 2.9 m so that the boundary layer can adjust to thenew surface condition imposed by the forcing. With a shorter, 1.5 m portionof the surface actuated, generating an upstream-travelling wave, a drag re-duction of 21.5% was recorded in the boundary layer withReτ= 1125. Atthe same flow conditions, a downstream-travelling produced a much smallerdrag reduction of 2.6%, agreeing with the observed trends in current simula-tions. The drag reduction was determined with constant temperature hot-wiremeasurements of the mean velocity gradient in the viscous sublayer, while si-multaneous laser Doppler vibrometer measurements of the surface recorded thewall motion. Despite the mechanics of the dynamic surface resulting in someout-of-plane motion (which is small in comparison to the in-plane streamwisemovement), the positive drag reduction results are encouraging for future in-vestigations at higher Reynolds numbers.
Imediegwu C, Murphy R, Hewson RW, et al., 2018, The design of a lattice-based periodic microstructure model towards 3D printable optimized structures, 10th European Solid Mechanics Conference
Jones G, Santer M, Debiasi M, et al., 2017, Control of flow separation around an airfoil at low Reynolds numbers using periodic surface morphing, Journal of Fluids and Structures, Vol: 76, Pages: 536-557, ISSN: 0889-9746
The paper investigates experimentally the low Reynolds number flow () around a model that approximates a NACA 4415 airfoil and the control of separation using periodic surface motion. Actuation is implemented by bonding two Macro Fiber Composite patches to the underside of the suction surface. Time-resolved measurements reveal that the peak-to-peak displacement of the surface motion is a function of both the amplitude and frequency of the input voltage signal but the addition of aerodynamic forces does not cause significant changes in the surface behavior. The vibration mode is uniform in the spanwise direction for frequencies below 80 Hz; above this frequency, a secondary vibration mode is observed. The flow around the unactuated airfoil exhibits a large recirculation region as a result of laminar separation without reattachment and consequently produces relatively high drag and low lift forces. Various actuation frequencies were examined. When actuated at , the spectra in the vicinity of the trailing edge and near-wake were found to be dominated by the actuation frequency. Sharp peaks appear in the spectra suggesting the production of Large Coherent Structures at this frequency. The increased momentum entrainment associated with these enabled a significant suppression of the separated region. The result was a simultaneous increase in and decrease in and therefore a large increase in the ratio. In addition, a delay in the onset of stall results in a significant increase in the maximum achievable lift.
Papadakis G, Santer M, Jones G, 2017, Control of low Reynolds number flow around an airfoil using periodic surface morphing: a numerical study, Journal of Fluids and Structures, Vol: 76, Pages: 95-115, ISSN: 0889-9746
The principal aim of this paper is to use Direct Numerical Simulations (DNS) to explain the mechanisms that allow periodic surface morphing to improve the aerodynamic performance of an airfoil. The work focuses on a NACA-4415 airfoil at Reynolds number Rec=5×104 and 0° angle of attack. At these flow conditions, the boundary layer separates at x∕c=0.42, remains laminar until x∕c≈0.8, and then transitions to turbulence. Vortices are formed in the separating shear layer at a characteristic Kelvin–Helmholtz frequency of Sts=4.9, which compares well with corresponding experiments. These are then shed into the wake. Turbulent reattachment does not occur because the region of high turbulent kinetic energy (and therefore mixing) is located too far downstream and too far away from the airfoil surface to influence the near-wall flow. The effect of three actuation frequencies is examined by performing the simulations on a computational domain that deforms periodically. It is found that by amplifying the Kelvin–Helmholtz instability mechanism, Large Spanwise Coherent structures are forced to form and retain their coherence for a large part of the actuation cycle. Following their formation, these structures entrain high momentum fluid into the near-wall flow, leading to almost complete elimination of the recirculation zone. The instantaneous and phase averaged characteristics of these structures are analyzed and the vortex coherence is related to the phase of actuation. In order to further clarify the process of reduction in the size of recirculation zone, simulations start from the fully-developed uncontrolled flow and continue for 25 actuation cycles. The results indicate that the modification of airfoil characteristics is a gradual process. As the number of cycles increases and the coherent vortices are repeatedly formed and propagate downstream, they entrain momentum, thereby modifying the near wall region. During this transient period, the separa
Garland M, Santer M, morrison J, 2017, Optimal aero-structural design of an adaptive surface for boundary layer motivation using an auxetic lattice skin, Journal of Intelligent Material Systems and Structures, Vol: 28, Pages: 2414-2427, ISSN: 1530-8138
The aero-structural design of an adaptive vortex generator for repeatable, elastic, deployment and retraction from anaerodynamically clean surface is presented. A multidisciplinary objective function, containing geometrically nonlinear nite element analysis and large eddy simulation, is used to derive the optimal adaptive geometry for increasing themomentum of the near wall uid. It is found that the rapid increase of in-plane membrane stress with de ection is asigni cant limitation on achievable deformation of a continuous skin with uniform section. Use of a 2D auxetic latticestructure in place of the continuous skin allows signi cantly larger deformations and thus a signi cant improvement inperformance. The optimal deformed geometry is replicated statically and the e ect on the boundary layer is validatedin a wind tunnel experiment. The lattice structure is then manufactured and actuated. The deformed geometry isshown to compare well with the FEA predictions. The surface is re-examined post actuation and shown to return tothe initial position, demonstrating the deformation is elastic and hence repeatable.
Johnson M, McCann J, Santer M, et al., 2017, On orbit validation of solar sailing control laws with thin-film spacecraft, The Fourth International Symposium on Solar Sailing, Publisher: Japan Space Forum
Many innovative approaches to solar sail mission and trajectory design have been proposed over the years, but very few ever have the opportunity to be validated on orbit with real spacecraft. Thin-Film Spacecraft/Lander/Rovers (TF-SLRs) are a new class of very low cost, low mass space vehicle which are ideal for inexpensively and quickly testing in flight new approaches to solar sailing. This paper describes using TF-SLR based micro solar sails to implement a generic solar sail test bed on orbit. TF-SLRs are high area-to-mass ratio (A/m) spacecraft developed for very low cost consumer and scientific deep space missions. Typically based on a 5 μm or thinner metalised substrate, they include an integrated avionics and payload system-on-chip (SoC) die bonded to the substrate with passive components and solar cells printed or deposited by Metal Organic Chemical Vapour Deposition (MOCVD). The avionics include UHF/S-band transceivers, processors, storage, sensors and attitude control provided by integrated magnetorquers and reflectivity control devices. Resulting spacecraft have a typical thickness of less than 50 μm, are 80 mm in diameter, and have a mass of less than 100 mg resulting in sail loads of less than 20 g/m2. TF-SLRs are currently designed for direct dispensing in swarms from free flying 0.5U Interplanetary CubeSats or dispensers attached to launch vehicles. Larger 160 mm, 320 mm and 640 mm diameter TF-SLRs utilizing a CubeSat compatible TWIST deployment mechanism that maintains the high A/m ratio are also under development. We are developing a mission to demonstrate the utility of these devices as a test bed for experimenting with a variety of mission designs and control laws. Batches of up to one hundred TF-SLRs will be released on earth escape trajectories, with each batch executing a heterogeneous or homogenous mixture of control laws and experiments. Up to four releases at different points in orbit are currently envisaged with experiments currently
Bird J, Santer M, morrison J, 2016, The determination and enhancement of compliant modes for actuation in structural assemblies, International Journal of Solids and Structures, Vol: 106-107, Pages: 264-273, ISSN: 0020-7683
Linear algebra methods for determining modes of kinematic and static indeter-minacy in jointed frames are extended to reveal modes of compliance in oth-erwise rigid assemblies. These modes are extracted from a structural model,based on nite elements, via a singular value decomposition and yield the waysin which a structure can be most easily deformed. This modal approach alsoallows for the formulation of a reduced-order structural model, whereby relevantmodes are selected and used as the basis for the optimisation of a complaintstructure. The method detailed is shown to be a useful design tool, demon-strated by its application to a structure based on the Kagome lattice geometry.For certain frameworks, rst order e ects produce tightening under actuation.As a result, a scheme to adjust the modes to take nonlinear e ects into accountis also given.
Jinks E, Santer M, bruce P, 2016, Aero-Structural Design Optimization of Adaptive Shock Control Bumps, 54th AIAA Aerospace Sciences Meeting, Publisher: American Institute of Aeronautics and Astronautics
Shock control bumps (SCB) are a transonic flow control device that aim to reduce theoverall drag due to a normal shock on a typical passenger jet at cruise. The concept of adaptiveSCB which can be deployed for best use are investigated through an aero-structuraldesign tool that produces optimal geometries. The optimizer uses a surface based performancemetric to highlight the importance of the flow quality around the SCB as wellas including a structural element that is required to provide the necessary flexibility todeform. The performance metric produces the target pressure distribution and successfullysmears the shock. It is found that the structural constraint does not inhibit bumpheight and global airfoil performance is not significantly a↵ected, L/D varies < 0.6%. Theaerodynamic pressure loading can be utilised to produce a new family of SCB geometriesthat are unachievable with mechanical actuation alone. The study shows that adaptiveSCB that exploit the naturally occurring pressure field around an airfoil in a passive wayare a feasible technology to mitigate the poor o↵-design performance of static SCB.
Jinks E, bruce P, Santer M, 2016, Wind Tunnel Experiments with Flexible Plates in Transonic Flows, 54th AIAA Aerospace Sciences Meeting, Publisher: AIAA
The evolution of adaptive shock control bump (SCB) design has seen the system flexibilityincrease to a point where the aerodynamic loading can affect the deformation of theplate. By studying the effects of a flexible plate subject to transonic flow the fluid structureinteraction can be investigated. In this study an array of thin plates (0.4 and 0.6 mm)with different aspect ratios (1 and 1.33) are exposed to a Mach 1.4 normal shockwave.PIV is used in combination with Schlieren imaging to provide a detailed view of the flowcurvature surrounding the plate as well as the global shock structure. A technique thatextracts the plate deformation from the PIV images is also presented which provides fluidand structural information for each test. The relationship between plate and flow angleis discussed as well as the effect of plate stiffness and free stream influence of each plateconfiguration.
Jones G, Santer M, Papadakis G, et al., 2016, Active Flow Control at Low Reynolds Numbers by Periodic Airfoil Morphing, 54th AIAA Aerospace Sciences Meeting, Publisher: American Institute of Aeronautics and Astronautics
This paper investigates the application of a periodically deforming airfoil surface for thepurpose of flow control at low Reynolds numbers. A physical model has been fabricatedby bonding Macro Fiber Composite (MFC) actuators to the underside of a NACA 4415’ssuction surface. The results presented build on work by Jones et al.1 First, the behavior ofthe surface when actuated at a range frequencies is investigated through a combination ofphotogrammetric and laser sensor measurements. Second, the aerodynamic performanceof this novel flow control technique is presented. It is shown that when the actuationfrequency ‘locks-in’ to the surface motion significant improvements in performance areobserved in a flight regime notorious for poor airfoil behavior.
Yasin R, Cui Y, Santer M, 2016, Reconfigurable Deployable CubeSat Solar Arrays Usin Thin Composite Flexures, 3rd AIAA Spacecraft Structures Conference
Cui Y, Santer M, 2015, Characterisation of tessellated bistable composite laminates, Composite Structures, Vol: 137, Pages: 93-104, ISSN: 0263-8223
Tessellated surfaces consisting of both unsymmetric composite elements with opposite layups, and unsymmetric composite elements in combination with symmetric composite elements, are investigated. It is shown that in simple cases these continuous surfaces only exhibit bistability due to the strong interaction between the connected elements. Strategies to mitigate against this interaction are proposed and implemented to achieve surfaces with high degrees of multistability up to the theoretical maximum.
Johnson M, 2015, TWIST: High performance thin film small satellite subsystems with a twist, Centre for Earth Observation Instrumentation Final Report, JA - PS - 7.7.2.13.5.1R1
The core goal of TWIST is to demonstrate that a multifunctional thin-filmdeployable small satellite subsystem can be stowed in the same volume as a traditional nanosatellite solar array, yet achieve 2-32x increase in likefor like available surface area when deployed, enabling novel spaceapplications hitherto impossible or non-viable due to power, communications or orbit constraints.
Cui Y, Santer M, 2015, Highly multistable composite surfaces, Composite Structures, Vol: 124, Pages: 44-54, ISSN: 0263-8223
Novel continuous composite surfaces are presented which possess a high degree of multistability. Inspired by the illustrative behaviour of a multistable analog model, we first show how two identical bistable composite shells with tailored asymmetric bistability may be connected to form a continuous quadstable surface. The concept is then extended to surfaces composed of three and by extension more identical bistable shells connected in series in order to achieve additional stable states. The multistable behaviour of these surfaces is investigated by finite element analysis and verified by experimental work.
Garland M, Santer M, Morrison J, 2015, Adaptive Vortex Generator Structures for the Reduction of Turbulent Separation, AIAA SciTech: 23rd AIAA/AHS Adaptive Structures Conference, Publisher: American Institute of Aeronautics and Astronautics
The stereotypical separation control method is the vortex generator which, as a passivedevice, produces an influence on the flow at all times. We investigate the production ofa deployable compliant separation control system that can be formed from the continuoussurface of an aerofoil when and where required, and return to normal conditions whennot required. The limitations in the development of a 3D finite geometry change froma surface are investigated and a systematic search of the design space is conducted toidentify the ideal material parameters. Based on these results a novel method of producinga spatially finite morph is proposed through the use of a 2D lattice structure. Deficienciesare identified with the use of an objective function which reduces geometric error, basedon prior knowledge of a suitable geometry, for flow within the boundary layer and analternative objective is proposed.
Jinks E, Bruce P, Santer M, 2015, The use of actuated flexible plates for adaptive shock control bumps, 53rd AIAA Aerospace Sciences Meeting, Publisher: American Institute of Aeronautics and Astronautics
Jones G, Debiasi M, Bouremel Y, et al., 2015, Open-loop flow control at low Reynolds numbers using periodic airfoil Morphing, 53rd AIAA Aerospace Sciences Meeting, Publisher: American Institute of Aeronautics and Astronautics
Bird J, Santer M, Morrison J, 2015, Adaptive Kagome Lattices for Near Wall Turbulence Suppression, AIAA SciTech: 23rd AIAA/AHS Adaptive Structures Conference
Murphey T, Francis W, Davis B, et al., 2015, High Strain Composites, AIAA SciTech: 2nd AIAA Spacecraft Structures Conference
Jinks E, Bruce P, Santer M, 2014, Adaptive Shock Control Bumps, 52nd Aerospace Sciences Meeting, Publisher: American Institute of Aeronautics and Astronautics
Cui Y, Santer M, 2014, Adaptive Multistable Flexible Composite Surfaces, AIAA SciTech: Spacecraft Structures Conference
Brinkmeyer A, Pellegrino S, Weaver P, et al., 2013, EFFECTS OF VISCOELASTICITY ON THE DEPLOYMENT OF BISTABLE TAPE SPRINGS, International Conference; 19th, Composite materials; 2013; Montreal, Canada
Santer M, 2013, Deployable CubeSat Truss Structures with Compliant Shape Memory Hinges, 54th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference
Brinkmeyer A, Pirrera A, Santer M, et al., 2013, Pseudo-bistable pre-stressed morphing composite panels, INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, Vol: 50, Pages: 1033-1043, ISSN: 0020-7683
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- Citations: 28
Rhodes O, Santer M, 2012, Optimal Problem Definition for Optimization of Morphing Structures, 51st AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference
Sim A, Santer M, 2012, Analysis of a Segmented Compliant Deployable Boom for CubeSat Magnetometer Missions, 51st AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference
Santer M, Pellegrino S, 2012, An Asymmetrically-Bistable Monolithic Energy-Storing Structure, 45TH AIAA/ASME/ASCE/AHS/ASC STRUCTURES, STRUCTURAL DYNAMICS & MATERIALS CONFERENCE
Brinkmeyer A, Pirrera A, Weaver P, et al., 2012, Pseudo-Bistable Morphing Composites, 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference
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