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  • Journal article
    Milthaler FFM, Gorman GJ, Piggott MD, 2012,

    Reducing spurious drag forces when using mesh adaptivity in CFD

    , ECCOMAS 2012 - European Congress on Computational Methods in Applied Sciences and Engineering, e-Book Full Papers, Pages: 5621-5640

    This work explores the impact of mesh adaptivity methods in combination with fixed as well as adaptive timestepping when modelling fluid dynamical systems that are sensitive to minor changes in the fluid's pressure and velocity. Here the diagnostic of interest for fluidsolid interaction modelling is the drag force. Depending on the solid's properties, even minor unphysical abrupt changes, so-called peaks, in the drag force - due to mesh adaptivity - could lead to a major disturbance in the model. For such systems the need naturally arises to reduce these peaks to a certain degree, until the sudden changes are small enough to be neglected. Hence, in this paper a variety of approaches are described and compared against one another, that aim to reduce these peaks. Moreover, further studies show the relation between the peaks in the drag force to the timestep, and pressure. The 3D-CFD software Fluidity, which uses an arbitrarily unstructured mesh, and a 3D mesh optimization algorithm was used for this case-study.
  • Journal article
    Potts DM, Zdravkovic L, 2012,

    Accounting for partial material factors in numerical analysis

    , Geotechnique
  • Journal article
    Davies DR, Goes S, Davies JH, Schuberth BSA, Bunge H-P, Ritsema Jet al., 2012,

    Reconciling dynamic and seismic models of Earth's lower mantle: The dominant role of thermal heterogeneity

    , EARTH AND PLANETARY SCIENCE LETTERS, Vol: 353, Pages: 253-269, ISSN: 0012-821X
  • Journal article
    van Reeuwijk M, Lari KS, 2012,

    Asymptotic solutions for turbulent mass transfer augmented by a first order chemical reaction

    , INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, Vol: 55, Pages: 6485-6490, ISSN: 0017-9310
  • Journal article
    Viré A, Xiang J, Milthaler F, Farrell P, Piggott MD, Latham JP, Pavlidis D, Pain CCet al., 2012,

    Modelling of fluid–solid interactions using an adaptive mesh fluid model coupled with a combined finite–discrete element model

    , Ocean Dynamics
  • Journal article
    Merchel S, Bremser W, Akhmadaliev S, Arnold M, Aumaître G, Bourlès DL, Braucher R, Caffee M, Christl M, Fifield LK, Finkel RC, Freeman SPHT, Ruiz-Gómez A, Kubik PW, Martschini M, Rood DH, Tims SG, Wallner A, Wilcken KM, Xu Set al., 2012,

    Quality assurance in accelerator mass spectrometry: Results from an international round-robin exercise for <sup>10</sup>Be

    , Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, Vol: 289, Pages: 68-73, ISSN: 0168-583X

    The first international round-robin exercise for the measurement of the long-lived radionuclide 10Be has been conducted. Ten participating accelerator mass spectrometry (AMS) facilities have each measured three samples at the 10 -12 to 10 -1410Be/ 9Be level. All results have been made traceable to the NIST SRM 4325 standard to avoid additional discrepancies that arise when different facilities use different calibration materials. Hence, the data concentrates on pure measurement distinctions. Multivariate statistical investigations have been performed to reveal a bias between facilities, i.e. two distinguished groups could be identified. Maximum discrepancies between two single facilities are in the range of 6-31% depending on the absolute 10Be/ 9Be value. These findings should be considered when comparing 10Be data produced at one AMS facility with that produced at another facility, which is e.g. often the case for in situ 10Be dating studies. Round-robin exercises are a very helpful tool as part of an overall quality assurance scheme to improve the accuracy, and not only the precision, of AMS data. © 2012 Elsevier B.V. All rights reserved.
  • Journal article
    Potter RWK, Kring DA, Collins GS, Kiefer WS, McGovern PJet al., 2012,

    Estimating transient crater size using the crustal annular bulge: Insights from numerical modeling of lunar basin-scale impacts

    , GEOPHYSICAL RESEARCH LETTERS, Vol: 39, ISSN: 0094-8276
  • Conference paper
    Jonker HJJ, Van Reeuwijk M, Sullivan PP, Patton Eet al., 2012,

    Interfacial layers in clear and cloudy atmospheric boundary layers

    , 7th International Symposium on Turbulence, Heat and Mass Transfer, Publisher: International Centre for Heat and Mass Transfer

    This paper reports on some recent advances in the understanding of the behaviour of atmosphericinterfacial layers. We focus on those interfaces where a turbulent layer is separated from a quiescentlayer by a relatively strong density gradient and study in particlar the entrainment rate, i.e. the rate withwhich the mixed layer penetrates into the quiescent layer by entraining fluid across the density interface.Making use of massively parallelized supercomputers, we conduct a large number of Direct NumericalSimulations (DNS) for a wide range of conditions and study the impact exerted on the entrainment rate bythe Reynolds number, the Prandtl/(Schmidt) number, and the strength of the density jump represented bythe Richardson number. We study two cases that are relevant for the atmosphere (/ocean), i.e. I] whereturbulence is generated by a surface buoyancy flux, and II] where turbulence is generated by shear (surfacemomentum flux). Of course with DNS one cannot simulate the high Reynolds numbers encountered in atmosphericcontexts, but present computer resources do allow us to faithfully simulate the classical laboratoryexperiments on these situations and even achieve Reynolds numbers more than ten times larger.
  • Journal article
    Young NE, Briner JP, Rood DH, Finkel RCet al., 2012,

    Glacier extent during the Younger Dryas and 8.2-ka event on Baffin Island, Arctic Canada

    , Science, Vol: 337, Pages: 1330-1333, ISSN: 0036-8075

    Greenland ice cores reveal that mean annual temperatures during the Younger Dryas (YD) cold interval - about 12.9 to 11.7 thousand years ago (ka) - and the ∼150-year-long cold reversal that occurred 8.2 thousand years ago were ∼15° and 3° to 4°C colder than today, respectively. Reconstructing ice-sheet response to these climate perturbations can help evaluate ice-sheet sensitivity to climate change. Here, we report the widespread advance of Laurentide Ice Sheet outlet glaciers and independent mountain glaciers on Baffin Island, Arctic Canada, in response to the 8.2-ka event and show that mountain glaciers during the 8.2-ka event were larger than their YD predecessors. In contrast to the wintertime bias of YD cooling, we suggest that cooling during the 8.2-ka event was more evenly distributed across the seasons.
  • Journal article
    Solano JMS, Jackson MD, Sparks RSJ, Blundy JD, Annen Cet al., 2012,

    Melt Segregation in Deep Crustal Hot Zones: a Mechanism for Chemical Differentiation, Crustal Assimilation and the Formation of Evolved Magmas

    , Journal of Petrology, Vol: 53, Pages: 1999-2026, ISSN: 1460-2415

    Mantle-derived basaltic sills emplaced in the lower crust provide amechanism for the generation of evolved magmas in deep crustal hotzones (DCHZ).This study uses numerical modelling to characterizethe time required for evolved magma formation, the depth and temperatureat which magma formation occurs, and the composition ofthe magma.The lower crust is assumed to comprise amphibolite. Inan extension of previous DCHZ models, the new model couples heattransfer during the repetitive emplacement of sills with mass transfervia buoyancy-driven melt segregation along grain boundaries.The resultsshed light on the dynamics of DCHZ development and evolution.TheDCHZ comprises a mush of crystals plus interstitial melt,except when a new influx of basaltic magma yields a short-lived(20^200 years) reservoir of melt plus suspended crystals (magma).Melt segregation and accumulation within the mush yields two contrastingmodes of evolved magma formation, which operate over timescalesof c. 10 kyr-1 Myr, depending upon emplacement rate andstyle. In one, favoured by emplacement via over-accretion, or emplacementat high rates, evolved magma forms in the crust overlying theintruded basalt sills, and is composed of crustal partial melt, and residualmelt that has migrated upwards out of the crystallizingbasalt. In the other, favoured by emplacement via under- orintra-accretion, or by emplacement at lower rates, evolved magmaforms in the intruded basalt, and the resulting magma is composedprimarily of residual melt. In all cases, the upward migration ofbuoyant melt yields cooler and more evolved magmas, which arebroadly granitic in composition. Chemical differentiation is thereforedriven by melt migration, because the melt migrates through, andchemically equilibrates with, partially molten rock at progressivelylower temperatures. Crustal assimilation occurs during partial melting,and mixing of crustal and residual melt occurs when residualmelt migrates into the partially molten crust, yielding
  • Journal article
    Jurecic N, Zdravkovic L, Jovicic V, 2012,

    Predicting ground movements in London Clay

    , Proceedings of the Institution of Civil Engineers - Geotechnical Engineering, Vol: 166, Pages: 466-482, ISSN: 1353-2618

    The necessity of accounting for small-strain behaviour of soils in numerical analyses of the serviceability limit states of geotechnical structures is well established both nationally and internationally. This has led to further development of appropriate soil constitutive models, as well as to further advances in accurate laboratory measurements of small-strain stiffness. The current paper considers recent laboratory research into the behaviour of London Clay, performed at Imperial College in conjunction with the major ground works for Heathrow Terminal 5 in London, UK. This research has shown the small-strain response of London Clay to be different to that assumed previously and in particular to that determined from good-quality commercial experiments. Both sets of small-strain stiffness data are applied in this paper in finite-element analyses of a deep excavation and a tunnel construction in London Clay, with the objective of investigating their effect on predicted ground movements.
  • Journal article
    Bacon AR, Richter DDB, Bierman PR, Rood DHet al., 2012,

    Coupling meteoric <sup>10</sup>be with pedogenic losses of <sup>9</sup>be to improve soil residence time estimates on an ancient North American interfluve

    , Geology, Vol: 40, Pages: 847-850, ISSN: 0091-7613

    We couple meteoric 10Be measurements with mass balance analysis of 9Be to estimate the soil residence time (SRT) of a biogeomorphically stable Ultisol in the Southern Piedmont physiographic region of the southeastern United States. We estimate SRT after correcting the meteoric 10Be inventory to account for observed 9Be losses, which indicate that more than half of the 9Be weathered from primary minerals has been leached from the upper 18.3 m of the Ultisol. Our estimates of minimum SRT range between 1.3-1.4 Ma and between 2.6-3.1 Ma under high and low (2.0 and 1.3 × 106 atoms cm -2 yr -1, respectively), estimates of 10Be delivery. Denudation rates of the physiographic region corroborate our estimates. We redefine pedogenic time constraints in the Southern Piedmont, and demonstrate that the assumption of complete meteoric 10Be retention in acidic soil systems cannot always be made; the latter has far-reaching consequences for soil, sediment, river, and ocean research using meteoric 10Be. © 2012 Geological Society of America.
  • Conference paper
    Merritt A, Schroeder F, Jardine RJ, Stuyts B, Cathie D, Cleverly Wet al., 2012,

    Development of pile design methodology for an offshore wind farm in the North Sea

    , London, 7th International Conference on Offshore Site Investigations and Geotechnics, Publisher: Society for Underwater Technology, Pages: 439-448
  • Conference paper
    Carneiro A, Jardine RJ, 2012,

    A model study of how pre-drilling affects displacement pile capacity in stiff clays

    , London, 7th International Conference on Offshore Site Investigations and Geotechnics, Publisher: Society for Underwater Technology, Pages: 473-480
  • Conference paper
    Papaspiliou MI, Kontoe S, 2012,

    Ground Motion Selection for the Integration of Site Response in Probabilistic Seismic Hazard Analyses

    , 15th World Conference on Earthquake Engineering

    This paper examines issues related to ground-motion selection for the performance of site response analysis and the integration of the site-specific amplification function within probabilistic seismic hazard calculations. The, typically, deterministic modification of the probabilistically estimated rock ground motions to consider site effects often leads to nonconservative ground motions at the soil surface. In this paper a methodology proposed by Bazzurro and Cornell (2004b), which allows the transformation of a rock ground-motion prediction equation into a site-specific one by modifying both the median and standard deviation terms of the equation, is used and its sensitivity to different suites of ground-motion records is explored. Suites of 10, 15 and 20 records are used for the performance of the site response analysis in order to examine their impact on capturing the median site amplification and its standard deviation. Subsequently, their impact on the results of a probabilistic seismic hazard assessment is explored.
  • Conference paper
    Lessi-Cheimarios A, Kontoe S, Stafford PJ, 2012,

    Comparison of the Total Uncertainty Associated With Alternative Approaches to Site Response Analysis

    , 15th World Conference on Earthquake Engineering

    Within PSHA, the effects of site response can be treated in a variety of different manners. Typically, there is an assumed hierarchy of accuracy for the alternatives, but the validity of this hierarchy has not been formally assessed. Site response can be modelled directly using empirical Ground Motion Prediction Equations (GMPEs) and the precision of the analysis is related to the published variance components of the model. An alternative approach is to conduct site-specific site response analyses, and this approach is commonly assumed to be the most accurate. Using equivalent linear (EQL) and non-linear (NL) site response analysis for two magnitude-distance (M-R) scenarios this study focuses on the total uncertainty associated with this computational demanding route. The spectral ordinates and the variability of the site response methods are further compared to the predictions of the Campbell and Bozorgnia (2008) GMPE for these two M-R combinations.
  • Journal article
    Jackson CA-L, Lewis MM, 2012,

    Origin of an anhydrite sheath encircling a salt diapir and implications for the seismic imaging of steep-sided salt structures, Egersund Basin, Northern North Sea

    , JOURNAL OF THE GEOLOGICAL SOCIETY, Vol: 169, Pages: 593-599, ISSN: 0016-7649
  • Journal article
    Jackson CA-L, 2012,

    Seismic reflection imaging and controls on the preservation of ancient sill-fed magmatic vents

    , JOURNAL OF THE GEOLOGICAL SOCIETY, Vol: 169, Pages: 503-506, ISSN: 0016-7649
  • Journal article
    Liu JG, Yan H, Morgan G, 2012,

    PCIAS Subpixel Technology

    , MEASUREMENT & CONTROL, Vol: 45, Pages: 207-211, ISSN: 0020-2940
  • Conference paper
    Jardine RJ, Andersen K, Puech A, 2012,

    Keynote Paper. Cyclic loading of offshore piles: potential effects and practical design.

    , London, 7th International Conference on Offshore Site Investigations and Geotechnics, Publisher: Society for Underwater Technology, Pages: 59-100

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