Imperial College London

ProfessorRichardCraster

Faculty of Natural SciencesDepartment of Mathematics

Professor of Applied Mathematics
 
 
 
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Contact

 

+44 (0)20 7594 8554r.craster Website

 
 
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Location

 

6M24Huxley BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

275 results found

Berte R, Della Picca F, Poblet M, Li Y, Cortes E, Craster RV, Maier SA, Bragas AVet al., 2018, Acoustic Far-Field Hypersonic Surface Wave Detection with Single Plasmonic Nanoantennas, PHYSICAL REVIEW LETTERS, Vol: 121, ISSN: 0031-9007

JOURNAL ARTICLE

Makwana MP, Craster R, 2018, Designing multidirectional energy splitters and topological valley supernetworks, Publisher: AMER PHYSICAL SOC

WORKING PAPER

Makwana MP, Craster R, 2018, Geometrically navigating topological plate modes around gentle and sharp bends, PHYSICAL REVIEW B, Vol: 98, ISSN: 2469-9950

JOURNAL ARTICLE

Guenneau S, Brule S, Enoch S, Diatta A, Achaoui Y, Ungureanu B, Hutridurga H, Craster RVet 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.

CONFERENCE PAPER

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

JOURNAL ARTICLE

Kahouadji L, Nowak E, Kovalchuk N, Chergui J, Juric D, Shin S, Simmons MJH, Craster RV, Matar OKet 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

JOURNAL ARTICLE

Smith ER, Theodorakis PE, Craster R, Matar OKet al., 2018, Moving Contact Lines: Linking Molecular Dynamics and Continuum-Scale Modeling, LANGMUIR, Vol: 34, Pages: 12501-12518, ISSN: 0743-7463

JOURNAL ARTICLE

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.

WORKING PAPER

Choi W, Shi F, Lowe MJS, Skelton EA, Craster RV, Daniels WLet 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

JOURNAL ARTICLE

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.

WORKING PAPER

Skelton EA, Craster RV, Colombi A, Colquitt DJet 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

JOURNAL ARTICLE

Shin S, Chergui J, Juric D, Kahouadji L, Matar OK, Craster RVet 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

JOURNAL ARTICLE

Shi F, Lowe MJS, Skelton EA, Craster RVet al., 2018, A time-domain finite element boundary integral approach for elastic wave scattering, COMPUTATIONAL MECHANICS, Vol: 61, Pages: 471-483, ISSN: 0178-7675

JOURNAL ARTICLE

Puvirajesinghe TM, Zhi ZL, Craster RV, Guenneau Set 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

JOURNAL ARTICLE

Craster RV, Guenneau SRL, Hutridurga HR, Pavliotis GAet al., 2018, CLOAKING VIA MAPPING FOR THE HEAT EQUATION, MULTISCALE MODELING & SIMULATION, Vol: 16, Pages: 1146-1174, ISSN: 1540-3459

JOURNAL ARTICLE

Berte R, Picca FD, Poblet M, Li Y, Cortés E, Craster RV, Maier SA, Bragas AVet 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.

CONFERENCE PAPER

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.

JOURNAL ARTICLE

Brule S, Ungureanu B, Achaoui Y, Diatta A, Aznavourian R, Antonakakis T, Craster R, Enoch S, Guenneau Set al., 2017, Metamaterial-like transformed urbanism, INNOVATIVE INFRASTRUCTURE SOLUTIONS, Vol: 2, ISSN: 2364-4176

JOURNAL ARTICLE

Haslinger SG, Movchan NV, Movchan AB, Jones IS, Craster RVet 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

JOURNAL ARTICLE

Colombi A, Ageeva V, Smith RJ, Clare A, Patel R, Clark M, Colquitt D, Roux P, Guenneau S, Craster RVet al., 2017, Enhanced sensing and conversion of ultrasonic Rayleigh waves by elastic metasurfaces, SCIENTIFIC REPORTS, Vol: 7, ISSN: 2045-2322

JOURNAL ARTICLE

O'Neill J, Selsil O, Haslinger SG, Movchan NV, Craster RVet 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.

JOURNAL ARTICLE

Lefebvre G, Antonakakis T, Achaoui Y, Craster RV, Guenneau S, Sebbah Pet 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.

JOURNAL ARTICLE

Achaoui Y, Antonakakis T, Brule S, Craster RV, Enoch S, Guenneau Set al., 2017, Clamped seismic metamaterials: ultra-low frequency stop bands, NEW JOURNAL OF PHYSICS, Vol: 19, ISSN: 1367-2630

JOURNAL ARTICLE

Theodorakis PE, Muller EA, Craster RV, Matar OKet 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.

JOURNAL ARTICLE

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

JOURNAL ARTICLE

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

JOURNAL ARTICLE

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

JOURNAL ARTICLE

Colquitt DJ, Colombi A, Craster RV, Roux P, Guenneau SRLet 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

JOURNAL ARTICLE

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