D. Sulsky

University of New Mexico, Albuquerque, New Mexico, United States

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Publications (53)57.63 Total impact

  • Ling Xu, Howard Schreyer, Deborah Sulsky
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    ABSTRACT: Damage in the form of cracks is predicted to assess the susceptibility of a tunnel to failure due to a blast. The material-point method is used in conjunction with a decohesive failure model as the basis for the numerical simulations. The assumption of a cylindrical charge as the source for the blast allows the restriction of plane strain and two-dimensional analyses. In the simulation, a further restriction of a single pressure pulse is used as the source of stress waves that are reflected and refracted after reaching the free surface of the tunnel wall. Three critical zones of significant cracking in the vicinity of a tunnel are identified as potential contributors to tunnel failure. Copyright © 2014 John Wiley & Sons, Ltd.
    International Journal for Numerical and Analytical Methods in Geomechanics 05/2014; · 1.56 Impact Factor
  • Kara Peterson, Howard Schreyer, Deborah Sulsky
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    ABSTRACT: In a previous paper, an elastic-decohesive model was developed for sea ice. Unlike previous models, orientation and displacement discontinuity associated with lead opening are specifically predicted. However, over the course of a season a specific lead may open and close several times with significant implications related to ice production and heat flux. The focus of this paper is to indicate, in a generic manner, how the formation of new ice by freezing within a lead and the recovery of tensile strength by the freezing of ridges can be accommodated easily within the decohesive structure. A sample simulation is provided to show the implications of these additional terms on ice production over several cycles of lead opening and closing.
    Cold Regions Science and Technology - COLD REG SCI TECHNOL. 01/2012;
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    ABSTRACT: Tunnels and other structures are often embedded underground within a media of jointed rock. If the tunnel is subjected to the resulting wave of an explosive blast in proximity, it is of interest to determine the blast properties, as well as the material and geometrical factors which identify a parameter space where the integrity of the structure may be compromised. The constitutive framework within the Material Point Method (MPM) [1,2] is extended to model joints as existing cracks. Results are presented investigating the effect of gap closure, and of impulse and energy transmission around embedded structures such as tunnels.[4pt] [1] Schreyer, H.L., 2007, ``Modelling surface orientation and stress at failure of concrete and geological materials'', J. for Numerical and Analytical Methods in Geomechanics, Vol 31, pp 141-171. [0pt] [2] Sulsky, D., Schreyer, H., Peterson, K., Kwok, R., and Coon, M., 2007, ``Using the material-point method to model sea ice dynamics'', J. Geophys. Res., Vol 112:CO2S90, doi:10.1029/2005JC00329
    06/2011;
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    Kara J Peterson, D. Sulsky
    01/2011: pages 123-140; , ISBN: 978-3-642-16540-5
  • D. Sulsky, K. Peterson
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    ABSTRACT: This paper argues for a new constitutive model, an elastic–decohesive model for sea ice. The model is motivated by examining satellite observations of the Arctic processed to show ice deformation in the form of divergence, shear and vorticity. The model is implemented numerically in the material-point method and used to predict motion and deformation of sea ice by simulating a region of the Beaufort Sea. The model is able to capture the qualitative and statistical behavior of localized deformation seen in the observations.
    Physica D Nonlinear Phenomena 01/2011; 240(20):1674-1683. · 1.67 Impact Factor
  • D. Sulsky, G. Levy
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    ABSTRACT: Ideally, a verification and validation scheme should be able to evaluate and incorporate lower dimensional features (e.g., discontinuities) contained within a bulk simulation even when not directly observed or represented by model variables. Nonetheless, lower dimensional features are often ignored. Conversely, models that resolve such features and the associated physics well, yet imprecisely are penalized by traditional validation schemes. This can lead to (perceived or real) poor model performance and predictability and can become deleterious in model improvements when observations are sparse, fuzzy, or irregular. We present novel algorithms and a general framework for using information from available satellite data through fuzzy verification that efficiently and effectively remedy the known problems mentioned above. As a proof of concept, we use a sea-ice model with remotely sensed observations of leads in a one-step initialization cycle. Using the new scheme in a sixteen day simulation experiment introduces model skill (against persistence) several days earlier than in the control run, improves the overall model skill and delays its drop off at later stages of the simulation. Although sea-ice models are currently a weak link in climate models, the appropriate choice of data to use, and the fuzzy verification and evaluation of a system’s skill in reproducing lower dimensional features are important beyond the initial application to sea ice. Our strategy and framework for fuzzy verification, selective use of information, and feature extraction could be extended globally and to other disciplines. It can be incorporated in and complement existing verification and validation schemes, increasing their computational efficiency and the information they use. It can be used for model development and improvements, upscaling/downscaling models, and for modeling processes not directly represented by model variables or direct observations. Finally, if successful, it can also be used for scale selection in models and for selecting models for specific applications, e.g., component models of ensemble forecasting. The potential and requirements to extend this scheme to different applications, and to both empirical and statistical multivariate and full cycle model validation schemes are discussed.
    AGU Fall Meeting Abstracts. 12/2010;
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    Levy G, Coon M, Nguyen G, Sulsky D
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    ABSTRACT: Ideally, a validation and assimilation scheme should maintain the physical principles embodied in the model and be able to evaluate and assimilate lower dimensional features (e.g., discontinuities) contained within a bulk simulation, even when these features are not directly observed or represented by model variables. We present such a scheme and suggest its potential to resolve or alleviate some outstanding problems that stem from making and applying required, yet often non-physical, assumptions and procedures in common operational data assimilation. As proof of concept, we use a sea-ice model with remotely sensed observations of leads in a one-step assimilation cycle. Using the new scheme in a sixteen day simulation experiment introduces model skill (against persistence) several days earlier than in the control run, improves the overall model skill and delays its drop off at later stages of the simulation. The potential and requirements to extend this scheme to different applications, and to both empirical and statistical multivariate and full cycle data assimilation schemes, are discussed.
    Geoscientific Model Development. 01/2010;
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    Jason J Sanchez, Howard L Schreyer, Deborah L Sulsky
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    ABSTRACT: Recently, a decohesive model [1] has been developed with special attributes appropriate for modeling the initiation of failure for quasibrittle materials such as concrete and ice. In particular, the model provides a prediction for the orientation of the plane of failure that varies smoothly with the state of stress at failure and is in agreement with experimental data including splitting under uniaxial compression. This model has been used successfully with a smeared-crack algorithm in the material point method (MPM) with one recent application being that of large-scale lead (crack) formation in Arctic ice [2,3]. A limitation of the method is that cracks are represented only weakly in the sense that neither the crack path nor displacement discontinuity is continuous. However, in addition to computational simplicity, there are other important advantages of the model and the computational scheme. These advantages include: (1) a method involving rotation for choosing one orientation over another when the model predicts two orientations for planes of material failure, and (2) the capability to handle simultaneously two or more cracks with different orientations at a single material point.
    European Congress on Computational Methods in Applied Sciences and Engineering. 07/2008;
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    Gad Levy, Max Coon, Giang Nguyen, Deborah Sulsky
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    ABSTRACT: Novel metrics designed to evaluate the skill of geophysical models in simulating discontinuities and linear features are introduced and tested using a sea-ice model and remotely sensed observations of leads. The metrics are formulated as frequency-based indices of agreement, thus maintaining the simplicity desired in model development and operational applications, while remedying known shortcomings of common existing skill metrics. User-selectable spatial scales and features of significance allow for the general use of the metrics in variable applications, scales, and observation types.
    Geophysical Research Letters 01/2008; 35(21). · 3.98 Impact Factor
  • M. Coon, D. Sulsky, R. Kwok, M. Pruis
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    ABSTRACT: Our team has developed a new sea ice model which accounts for lead formation and deformation explicitly. This model will account directly for the evolution of that part of the mass balance resulting from the mechanical redistribution of ice in leads. We show results from our first simulation of the Beaufort Sea for 28 days 52-70 (February/March) in 2004. The numerical simulation was done using the material-point method with an elastic- decohesive constitutive model for sea ice. In the simulation, land is represented by material points that are treated as rigid and a no slip boundary condition is used between land and ice. Observed displacements from the RGPS data are used to prescribe the motion along the portion of the computational region that intersects the ocean, also. The simulation was forced with 6 hour NCEP winds on a 10 km grid. Earlier simulations on a smaller region of the Beaufort Sea showed that for these 16-day simulations some initialization of the ice conditions is required to reproduce the observed deformations in detail. Not surprisingly, the ice is too strong and does not deform appropriately in 16 days if we start from a homogeneous state of intact ice. Thus, we use RGPS observations from day 53.6-54.7 to determine the location and extent of some of the larger existing leads and use these observations to initialize a simulation that begins on day 54 and runs through day 70. The leads in the simulation can be compared visually with the leads from RGPS. Observations and simulations are not exactly the same. Nevertheless, we can see that reasonable looking lead patterns are produced in the simulation. This first simulation with the elastic-decohesive model shows great potential for reproducing observed pack ice dynamics.
    AGU Fall Meeting Abstracts. 11/2007; -1:07.
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    ABSTRACT: 1] The material-point method (MPM) is a numerical method for continuum mechanics that combines the best aspects of Lagrangian and Eulerian discretizations. The material points provide a Lagrangian description of the ice that models convection naturally. Thus properties such as ice thickness and compactness are computed in a Lagrangian frame and do not suffer from errors associated with Eulerian advection schemes, such as artificial diffusion, dispersion, or oscillations near discontinuities. This desirable property is illustrated by solving transport of ice in uniform, rotational and convergent velocity fields. Moreover, the ice geometry is represented by unconnected material points rather than a grid. This representation facilitates modeling the large deformations observed in the Arctic, as well as localized deformation along leads, and admits a sharp representation of the ice edge. MPM also easily allows the use of any ice constitutive model. The versatility of MPM is demonstrated by using two constitutive models for simulations of wind-driven ice. The first model is a standard viscous-plastic model with two thickness categories. The MPM solution to the viscous-plastic model agrees with previously published results using finite elements. The second model is a new elastic-decohesive model that explicitly represents leads. The model includes a mechanism to initiate leads, and to predict their orientation and width. The elastic-decohesion model can provide similar overall deformation as the viscous-plastic model; however, explicit regions of opening and shear are predicted. Furthermore, the efficiency of MPM with the elastic-decohesive model is competitive with the current best methods for sea ice dynamics.
    J. Geophys. Res. 01/2007; 112.
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    ABSTRACT: 1] This paper revisits the Arctic Ice Dynamics Joint Experiment (AIDJEX) assumptions about pack ice behavior with an eye to modeling sea ice dynamics. The AIDJEX assumptions were that (1) enough leads were present in a 100 km by 100 km region to make the ice isotropic on that scale; (2) the ice had no tensile strength; and (3) the ice behavior could be approximated by an isotropic yield surface. These assumptions were made during the development of the AIDJEX model in the 1970s, and are now found inadequate. The assumptions were made in part because of insufficient large-scale (10 km) deformation and stress data, and in part because of computer capability limitations. Upon reviewing deformation and stress data, it is clear that a model including deformation on discontinuities and an anisotropic failure surface with tension would better describe the behavior of pack ice. A model based on these assumptions is needed to represent the deformation and stress in pack ice on scales from 10 to 100 km, and would need to explicitly resolve discontinuities. Such a model would require a different class of metrics to validate discontinuities against observations.
    J. Geophys. Res. 01/2007; 112.
  • G. Levy, M. Coon, D. Sulsky
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    ABSTRACT: The treatment of leads as cracks or discontinuities (see Coon et al. presentation) requires some shift in the procedure of evaluation and comparison of lead-resolving models and their validation against observations. Common metrics used to evaluate ice model skills are by and large an adaptation of a least square "metric" adopted from operational numerical weather prediction data assimilation systems and are most appropriate for continuous fields and Eilerian systems where the observations and predictions are commensurate. However, this class of metrics suffers from some flaws in areas of sharp gradients and discontinuities (e.g., leads) and when Lagrangian treatments are more natural. After a brief review of these metrics and their performance in areas of sharp gradients, we present two new metrics specifically designed to measure model accuracy in representing linear features (e.g., leads). The indices developed circumvent the requirement that both the observations and model variables be commensurate (i.e., measured with the same units) by considering the frequencies of the features of interest/importance. We illustrate the metrics by scoring several hypothetical "simulated" discontinuity fields against the lead interpreted from RGPS observations.
    AGU Fall Meeting Abstracts. 12/2006;
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    ABSTRACT: In recent years, the availability of large volumes of recorded ice motion derived from high-resolution SAR data has provided an amazingly detailed look at the deformation of the ice cover. The deformation is dominated by the appearance of linear kinematic features that have been associated with the presence of leads. These remarkable data put us in a position to begin detailed evaluation of current coupled mechanical and thermodynamic models of sea ice. This presentation will describe the material-point method (MPM) for solving these model equations. MPM is a numerical method for continuum mechanics that combines the best aspects of Lagrangian and Eulerian discretizations. The material points provide a Lagrangian description of the ice that models convection naturally. Thus, properties such as ice thickness and compactness are computed in a Lagrangian frame and do not suffer from errors associated with Eulerian advection schemes, such as artificial diffusion, dispersion, or oscillations near discontinuities. This desirable property is illustrated by solving transport of ice in uniform, rotational and convergent velocity fields. Moreover, the ice geometry is represented by unconnected material points rather than a grid. This representation facilitates modeling the large deformations observed in the Arctic, as well as localized deformation along leads, and admits a sharp representation of the ice edge. MPM also easily allows the use of any ice constitutive model. The versatility of MPM is demonstrated by using two constitutive models for simulations of wind-driven ice. The first model is a standard viscous-plastic model with two thickness categories. The MPM solution to the viscous-plastic model agrees with previously published results using finite elements. The second model is a new elastic-decohesive model that explicitly represents leads. The model includes a mechanism to initiate leads, and to predict their orientation and width. The elastic-decohesion model can provide similar overall deformation as the viscous-plastic model; however, explicit regions of opening and shear are predicted. Furthermore, the efficiency of MPM with the elastic-decohesive model is competitive with the current best methods for sea ice dynamics. Simulations will also be presented for an area of the Beaufort Sea, where predictions can be validated against satellite observations of the Arctic.
    AGU Fall Meeting Abstracts. 12/2006;
  • K. Peterson, G. Nguyen, D. Sulsky
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    ABSTRACT: Synthetic Aperature Radar (SAR) provides a detailed view of the Arctic ice cover. When processed with the RADARSAT Geophysical Processor System (RGPS), it provides estimates of sea ice motion and deformation over large regions of the Arctic for extended periods of time. The deformation is dominated by the appearance of linear kinematic features that have been associated with the presence of leads. The RGPS deformation products are based on the assumption that the displacement and velocity are smooth functions of the spatial coordinates. However, if the dominant deformation of multiyear ice results from the opening, closing and shearing of leads, then the displacement and velocity can be discontinuous. This presentation discusses the kinematics associated with strong discontinuities that describe possible jumps in displacement or velocity. Ice motion from SAR data are analyzed using this framework. It is assumed that RGPS cells deform due to the presence of a lead. The lead orientation is calculated to optimally account for the observed deformation. It is shown that almost all observed deformation can be represented by lead opening and shearing. The procedure used to reprocess motion data to account for leads will be described and applied to regions of the Beaufort Sea. The procedure not only provides a new view of ice deformation, it can be used to obtain information about the presence of leads for initialization and/or validation of numerical simulations.
    AGU Fall Meeting Abstracts. 12/2006;
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    ABSTRACT: We are developing, testing, and validating a new sea ice dynamics model that treats the ice cover as an elastic/decohesive material in the permanent pack and includes the correct frazil/pancake behavior in the marginal zone. Two salient features of present ice dynamics models are that they do not: 1) reproduce the oriented fracture patterns of openings and closings in the pack ice, and 2) accurately model the effects of frazil/pancake ice formation in the ice margin. These poorly modeled areas account for a substantial portion of the ice growth, turbulent heat flux to the atmosphere, salt flux to the ocean, and energy dissipation due to slippage, ridging, and rafting, in the Arctic. Existing sea ice models have shown limited success in predicting the degree to which a lead will open for prescribed or observed forcing conditions. An important aspect of the new model we are developing is that the existence of cracks, along with their orientation, opening, and closing, is predicted. To put this effort in perspective a short history of ice dynamics modeling and data collection is presented. The RGPS data set is used to validate the model. As part of the testing and validation of the model, we are working on a new metric for comparing linear features (leads and ridges) in the data and model to be used in data assimilation for this model. The model framework is presented as well as some results showing the creation and development of leads in a simulation of ice dynamics in the Beaufort Sea. Other presentations by the authors will show other results from this effort.
    AGU Fall Meeting Abstracts. 12/2006;
  • H. L. Schreyer, D. L. Sulsky, M. D. Coon
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    ABSTRACT: One of the dominant characteristics of Arctic ice as reflected by RADARSAT Geophysical Processor System data is the development and persistence of leads. Experimental data from small specimens as well as in situ data from Arctic ice suggest that failure may occur under compression. Presented here is a decohesive constitutive model for which one of the distinguishing new features is that failure is predicted under uniaxial compression. More generally, the model specifically indicates when a lead is initiated, provides the orientation of the lead, gives the mode of failure, and allows one to numerically determine the width of leads. In addition, the approach allows multiple failure planes, a feature that is necessary to simulate crack branching. Pre-existing planes of weakness such as those formed from previous leads can be incorporated. Sample calculations indicate how such a model can be used for large-scale numerical simulations.
    AGU Fall Meeting Abstracts. 11/2006; -1:04.
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    Michael A Gilchrist, Deborah L Sulsky, Anne Pringle
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    ABSTRACT: Filamentous fungi are ubiquitous and ecologically important organisms with rich and varied life histories, however, there is no consensus on how to identify or measure their fitness. In the first part of this study we adapt a general epidemiological model to identify the appropriate fitness metric for a saprophytic filamentous fungus. We find that fungal fitness is inversely proportional to the equilibrium density of uncolonized fungal resource patches which, in turn, is a function of the expected spore production of a fungus. In the second part of this study we use a simple life history model of the same fungus within a resource patch to show that a bang-bang resource allocation strategy maximizes the expected spore production, a critical fitness component. Unlike bang-bang strategies identified in other life-history studies, we find that the optimal allocation strategy for saprophytes does not entail the use of all of the resources within a patch.
    Evolution 06/2006; 60(5):970-9. · 4.86 Impact Factor
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    E. Love, D. L. Sulsky
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    ABSTRACT: Energy consistency for the material-point method (MPM) is examined for thermodynamically consistent hyperelastic-plastic materials. It is shown that MPM can be formulated with implicit, three- field variational, finite element algorithms which dissipate energy and conserve momentum for that class of material models. With a consistent mass matrix the resulting overall numerical method inherits the energy-dissipative and momentum-conserving properties of the mesh solution. Thus, the proposed MPM algorithm satisfies by construction a time-discrete form of the second law of thermo- dynamics. Properties of the method are illustrated in numerical examples. Copyright © 2005 John Wiley & Sons, Ltd.
    International Journal for Numerical Methods in Engineering 03/2006; 65(10):1608 - 1638. · 2.06 Impact Factor
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    ABSTRACT: 1] One of the dominant characteristics of Arctic ice is the development and persistence of leads. Leads are critically important for climate modeling since they are a source for new ice and an avenue for heat exchange between the atmosphere and ocean. Therefore a specific representation for leads in a constitutive model for pack ice is considered essential. Presented here is an elastic-decohesive constitutive model whose purpose is to specifically indicate when a lead is initiated, to provide the orientation of the lead, to give the mode of failure, and to allow for the numerical determination of the width of leads. Both laboratory and in situ data of sea ice provide the motivation for the basic structure of the model. Sample paths in stress and strain space are used to illustrate how the model can simulate failure. The model can predict multiple failure planes, a feature that is necessary to simulate crack branching. Preexisting planes of weakness such as those formed from previous leads can also be accommodated.
    J. Geophys. Res. 01/2006; 111.

Publication Stats

859 Citations
57.63 Total Impact Points

Institutions

  • 1990–2014
    • University of New Mexico
      • • Department of Mathematics & Statistics
      • • Department of Mechanical Engineering
      Albuquerque, New Mexico, United States
  • 2000
    • Los Alamos National Laboratory
      • Theoretical Division
      Los Alamos, California, United States
  • 1988
    • University of California, Los Angeles
      • Department of Mathematics
      Los Angeles, CA, United States