275 results found
Berte R, Della Picca F, Poblet M, et al., 2018, Acoustic Far-Field Hypersonic Surface Wave Detection with Single Plasmonic Nanoantennas, PHYSICAL REVIEW LETTERS, Vol: 121, ISSN: 0031-9007
Makwana MP, Craster R, 2018, Designing multidirectional energy splitters and topological valley supernetworks, Publisher: AMER PHYSICAL SOC
Makwana MP, Craster R, 2018, Geometrically navigating topological plate modes around gentle and sharp bends, PHYSICAL REVIEW B, Vol: 98, ISSN: 2469-9950
Guenneau S, Brule S, Enoch S, et al., 2018, Some challenges regarding cloaking and earthquake protection, Pages: 158-160
© 2018 IEEE. Building upon analogies with cloaking of elastic waves in plates, a large scale experiment has demonstrated unprecedented control of surface seismic waves in structured soils. Here, we would like to review recent research advances and remaining challenges in the theory and applications of seismic metamaterials for cloaking and earthquake protection. We recall some results on transformation elastodynamics and introduce mathematical theory of near cloaking for elastic equations. The former is a natural framework for scattering problems in unbounded domains, while the latter addresses boundary measurements in bounded domains. These two fields of investigation bring complementary information on cloaking efficiency. Intimate links between cloaking and wave protection will be also discussed.
Bennetts LG, Peter MA, Craster R, 2018, Graded resonator arrays for spatial frequency separation and amplification of water waves, JOURNAL OF FLUID MECHANICS, Vol: 854, ISSN: 0022-1120
Kahouadji L, Nowak E, Kovalchuk N, et al., 2018, Simulation of immiscible liquid-liquid flows in complex microchannel geometries using a front-tracking scheme, MICROFLUIDICS AND NANOFLUIDICS, Vol: 22, ISSN: 1613-4982
Smith ER, Theodorakis PE, Craster R, et al., 2018, Moving Contact Lines: Linking Molecular Dynamics and Continuum-Scale Modeling, LANGMUIR, Vol: 34, Pages: 12501-12518, ISSN: 0743-7463
Craster RV, Sassi R, 2018, Spectral algorithms for reaction-diffusion equations
A collection of codes (in MATLAB & Fortran 77), and examples, for solvingreaction-diffusion equations in one and two space dimensions is presented. Inareas of the mathematical community spectral methods are used to remove thestiffness associated with the diffusive terms in a reaction-diffusion modelallowing explicit high order timestepping to be used. This is particularlyvaluable for two (and higher) space dimension problems. Our aim here is toprovide codes, together with examples, to allow practioners to easily utilize,understand and implement these ideas; we incorporate recent theoreticaladvances such as exponential time differencing methods and provide timings anderror comparisons with other more standard approaches. The examples are chosen from the literature to illustrate points and queriesthat naturally arise.
Choi W, Shi F, Lowe MJS, et al., 2018, Rough surface reconstruction of real surfaces for numerical simulations of ultrasonic wave scattering, NDT & E INTERNATIONAL, Vol: 98, Pages: 27-36, ISSN: 0963-8695
Vanel AL, Craster RV, Schnitzer O, 2018, Asymptotic modelling of phononic box crystals
We introduce phononic box crystals, namely arrays of adjoined perforatedboxes, as a three-dimensional prototype for an unusual class of subwavelengthmetamaterials based on directly coupling resonating elements. In this case,when the holes coupling the boxes are small, we create networks of Helmholtzresonators with nearest-neighbour interactions. We use matched asymptoticexpansions, in the small hole limit, to derive simple, yet asymptoticallyaccurate, discrete wave equations governing the pressure field. These networkequations readily furnish analytical dispersion relations for box arrays, slabsand crystals, that agree favourably with finite-element simulations of thephysical problem. Our results reveal that the entire acoustic branch isuniformly squeezed into a subwavelength regime; consequently, phononic boxcrystals exhibit nonlinear-dispersion effects (such as dynamic anisotropy) in arelatively wide band, as well as a high effective refractive index in thelong-wavelength limit. We also study the sound field produced by sources placedwithin one of the boxes by comparing and contrasting monopole- with dipole-typeforcing; for the former the pressure field is asymptotically enhanced whilstfor the latter there is no asymptotic enhancement and the translation from themicroscale to the discrete description entails evaluating singular limits,using a regularized and efficient scheme, of the Neumann's Green's function fora cube. We conclude with an example of using our asymptotic framework tocalculate localized modes trapped within a defected box array.
Skelton EA, Craster RV, Colombi A, et al., 2018, The multi-physics metawedge: graded arrays on fluid-loaded elastic plates and the mechanical analogues of rainbow trapping and mode conversion, NEW JOURNAL OF PHYSICS, Vol: 20, ISSN: 1367-2630
Shin S, Chergui J, Juric D, et al., 2018, A hybrid interface tracking - level set technique for multiphase flow with soluble surfactant, JOURNAL OF COMPUTATIONAL PHYSICS, Vol: 359, Pages: 409-435, ISSN: 0021-9991
Shi F, Lowe MJS, Skelton EA, et al., 2018, A time-domain finite element boundary integral approach for elastic wave scattering, COMPUTATIONAL MECHANICS, Vol: 61, Pages: 471-483, ISSN: 0178-7675
Puvirajesinghe TM, Zhi ZL, Craster RV, et al., 2018, Tailoring drug release rates in hydrogel-based therapeutic delivery applications using graphene oxide, JOURNAL OF THE ROYAL SOCIETY INTERFACE, Vol: 15, ISSN: 1742-5689
Berte R, Picca FD, Poblet M, et al., 2018, Generation and detection of surface acoustic waves using single plasmonic nanoresonators
© 2018 The Author (s). We show in this work that coherent phonons generated after the decay of optically-excited plasmons in isolated metallic nanoantennas, are transmitted through the substrate as surface acoustic waves (SAWs) which can be detected by other nanoantennas used as receptors and positioned at distances up to 3μm away from the source. Two color sub-ps pump-probe technique and numerical methods suggest wave speed and amplitude decay characteristic of Rayleigh waves, the former within 3.2% of the predicted for fused silica. It is also shown that the mechanical excitation of the receptors via SAW modulates the optical response of the probe transmission and that its spectral content shows that the detection is feasible, even when the vibrational modes of the receptor are detuned from those of the source.
Craster RV, 2018, Platonic localisation: one ring to bind them, Archive of Applied Mechanics, ISSN: 0939-1533
© 2018, The Author(s). In this paper, we present an asymptotic model describing localised flexural vibrations along a structured ring containing point masses or spring–mass resonators in an elastic plate. The values for the required masses and stiffnesses of resonators are derived in a closed analytical form. It is shown that spring–mass resonators can be tuned to produce a “negative inertia” input, which is used to enhance localisation of waveforms around the structured ring. Theoretical findings are accompanied by numerical simulations, which show exponentially localised and leaky modes for different frequency regimes.
Vanel AL, Schnitzer O, Craster RV, 2017, Asymptotic network models of subwavelength metamaterials formed by closely packed photonic and phononic crystals, EPL, Vol: 119, ISSN: 0295-5075
Haslinger SG, Movchan NV, Movchan AB, et al., 2017, CONTROLLING FLEXURAL WAVES IN SEMI-INFINITE PLATONIC CRYSTALS WITH RESONATOR-TYPE SCATTERERS, QUARTERLY JOURNAL OF MECHANICS AND APPLIED MATHEMATICS, Vol: 70, Pages: 215-247, ISSN: 0033-5614
Colombi A, Ageeva V, Smith RJ, et al., 2017, Enhanced sensing and conversion of ultrasonic Rayleigh waves by elastic metasurfaces, SCIENTIFIC REPORTS, Vol: 7, ISSN: 2045-2322
O'Neill J, Selsil O, Haslinger SG, et al., 2017, ACTIVE CLOAKING FOR FINITE CLUSTERS OF PINS IN KIRCHHOFF PLATES, SIAM Journal on Applied Mathematics, Vol: 77, Pages: 1115-1135, ISSN: 0036-1399
This paper considers active cloaking of a square array of evenly spaced pins in a Kirchhoff plate in the presence of flexural waves. Active sources, modeled as ideal point sources, are represented by the nonsingular Green's function for the two-dimensional biharmonic operator and have an arbitrary complex amplitude. These sources are distributed exterior to the cluster, and their complex amplitudes are found by solving an algebraic system of equations. This procedure ensures that selected multipole orders of the scattered field are successfully annulled. For frequencies in the zero-frequency stop band, we find that a small number of active sources located on a grid is sufficient for cloaking. For higher frequencies, we achieve efficient cloaking with the active sources positioned on a circle surrounding the cluster. We demonstrate the cloaking efficiency with several numerical illustrations, considering key frequencies from band diagrams and dispersion surfaces for a Kirchhoff plate pinned in a doubly periodic fashion.
Lefebvre G, Antonakakis T, Achaoui Y, et al., 2017, Unveiling extreme anisotropy in elastic structured media, Physical Review Letters, Vol: 118, ISSN: 0031-9007
Periodic structures can be engineered to exhibit unique properties observed at symmetry points, such as zero group velocity, Dirac cones, and saddle points; identifying these and the nature of the associated modes from a direct reading of the dispersion surfaces is not straightforward, especially in three dimensions or at high frequencies when several dispersion surfaces fold back in the Brillouin zone. A recently proposed asymptotic high-frequency homogenization theory is applied to a challenging time-domain experiment with elastic waves in a pinned metallic plate. The prediction of a narrow high-frequency spectral region where the effective medium tensor dramatically switches from positive definite to indefinite is confirmed experimentally; a small frequency shift of the pulse carrier results in two distinct types of highly anisotropic modes. The underlying effective equation mirrors this behavior with a change in form from elliptic to hyperbolic exemplifying the high degree of wave control available and the importance of a simple and effective predictive model.
Achaoui Y, Antonakakis T, Brule S, et al., 2017, Clamped seismic metamaterials: ultra-low frequency stop bands, NEW JOURNAL OF PHYSICS, Vol: 19, ISSN: 1367-2630
Shi F, Lowe M, Craster R, 2017, Diffusely scattered and transmitted elastic waves by random rough solid-solid interfaces using an elastodynamic Kirchhoff approximation, PHYSICAL REVIEW B, Vol: 95, ISSN: 2469-9950
Theodorakis PE, Muller EA, Craster RV, et al., 2017, Physical insights into the blood-brain barrier translocation mechanisms, Physical Biology, Vol: 14, ISSN: 1478-3975
The number of individuals suffering from diseases of the central nervous system (CNS) is growing with an aging population. While candidate drugs for many of these diseases are available, most of these pharmaceutical agents cannot reach the brain rendering most of the drug therapies that target the CNS inefficient. The reason is the blood–brain barrier (BBB), a complex and dynamic interface that controls the influx and efflux of substances through a number of different translocation mechanisms. Here, we present these mechanisms providing, also, the necessary background related to the morphology and various characteristics of the BBB. Moreover, we discuss various numerical and simulation approaches used to study the BBB, and possible future directions based on multi-scale methods. We anticipate that this review will motivate multi-disciplinary research on the BBB aiming at the design of effective drug therapies.
Dubrovina E, Craster RV, Papageorgiou DT, 2017, Two-layer electrified pressure-driven flow in topographically structured channels, JOURNAL OF FLUID MECHANICS, Vol: 814, Pages: 222-248, ISSN: 0022-1120
Maling B, Colquitt DJ, Craster RV, 2017, Dynamic homogenisation of Maxwell's equations with applications to photonic crystals and localised waveforms on gratings, WAVE MOTION, Vol: 69, Pages: 35-49, ISSN: 0165-2125
Uppal AS, Craster RV, Matar OK, 2017, Dynamics of spreading thixotropic droplets, JOURNAL OF NON-NEWTONIAN FLUID MECHANICS, Vol: 240, Pages: 1-14, ISSN: 0377-0257
Colquitt DJ, Colombi A, Craster RV, et al., 2017, Seismic metasurfaces: Sub-wavelength resonators and Rayleigh wave interaction, JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS, Vol: 99, Pages: 379-393, ISSN: 0022-5096
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.