On atomistic-to-continuum couplings without ghost forces in three dimensions

In this paper we construct energy based numerical methods free of ghost forces in three dimen- sional lattices arising in crystalline materials. The analysis hinges on establishing a connection of the coupled system to conforming finite elements. Key ingredients are: (i) a new representation of discrete derivatives related to long range interactions of atoms as volume integrals of gradients of piecewise linear functions over bond volumes, and (ii) the construction of an underlying globally continuous function representing the coupled modeling method

Finite element modeling of thermo-hydromechanically (THM) coupled problems in frozen ground engineering: state-of-the-art

Fully coupled Thermo-Hydro-Mechanical (THM) modeling has been widely studied in various areas of geomechanics, owing to the multiphase nature of geomaterials. Several researches have dealt with THM coupled modeling of geomaterials in high temperature regimes, but a limited work is available for geomaterials in low temperature regimes. A review and summary of existing work in the literature on THM coupled modeling of frozen soils is presented here. THM coupled modeling in general and its applications are pointed out. The basic governing equations of a coupled THM model in general form, namely mass, momentum and energy balance equations, are discussed. A review of fully coupled models is made and the numerical aspects of THM modeling are briefly discussed. A mechanical constitutive model makes up an important component of a fully coupled THM model and a brief review of existing constitutive models for frozen soils is presented. The models reviewed range from elastoplastic models to viscoplastic or creep and damage coupled models. Some models that consider different approaches from the plasticity framework are briefly reviewed. The state-of-the-art is summarized by pointing out the main aspects of THM coupled modeling and directions for future work

Grand challenge scientific questions in coupled modeling

Most convective field experiments in the past (e.g., SESAME, CCOPE, CINDE) have attempted to resolve only the immediate scales of moist convection using network arrays that spanned two or three atmospheric scales at most. Furthermore, these scales have been defined more on practical considerations (cost, manpower, etc.) than on a clear understanding of their theoretical significance. Unfortunately, this has precluded a description of the entire life cycle of MCS's and their interaction with larger scale systems, the land surface, and trace species. Fortunately, the following factors now make it possible to attempt to simulate scale contraction processes from the synoptic scale down to the cloud scale, as well as interactions between complex meteorological, land surface, precipitation, chemical, and hydrologic processes with coupled, multiscale models: the availability of new technology to sample meteorological fields at high temporal and spatial resolution over a broad region made possible by the weather observing modernization program; increased computer power and improved numerical approaches to run limited area models with nonhydrostatic precipitation physics so as to explicitly resolve MCS (Mesoscale Convective System) processes; and four dimensional assimilation of non-conventional data to provide dynamically consistent datasets for diagnostic analysis of nonlinear scale-interactive dynamics. Several examples of scale-interactive processes which present grand challenges for coupled, multiscale modeling were presented

3-D CFD-PBM coupled modeling and experimental investigation of struvite precipitation in a batch stirred reactor

A general model has been developed to elucidate the precipitation of struvite crystals in a batch stirred tank reactor. The model, which evaluates reactor performance, also predicts crystal size distribution (CSD) over time by considering the hydrodynamic, thermodynamic, and kinetic aspects of solution in the reactor. A Computational Fluid Dynamics (CFD) model was coupled with Population Balance Modeling (PBM) to model the growth of crystals in the reactor. A thermodynamic equilibrium model for struvite precipitation was consolidated with the reactor model. While the equilibrium model provided information on supersaturation development, the coupled CFD-PBM model captured the crystal growth kinetics and the influence of the reactor hydrodynamics on the overall process. Size distribution is crucial as it determines distinct grades of final struvite crystals, which are to be used as commercial fertilizer. In the simulation, the CFD flow field was solved through a Eulerian multiphase approach and RNG-k-ɛ turbulence model. The population balance equation was solved using a discretized form of the continuous partial differential equation, which transformed the continuous partial differential equation into finite ordinary differential equations as per size classes, which were then solved simultaneously. The growth rate, as a function of the supersaturation index (SI), was employed in the model through User Defined Function. The mean, standard deviation, and skewness of the model predicted CSD after 50 minutes were 20.81 μm, 9.61 μm, and 2.97, respectively and for the experimental CSD were 19.66 μm, 7.13 μm, and 2.46, respectively. The predicted peak-size percent fraction revealed a deviation from experimental results of 1.42%, 0.05%, 2.43%, 14.6%, 11.2%, 11.7%, 13.6%, and 14.2% at 0, 3, 10, 20, 30, 40, 50, and 60 min, respectively

Coupled modeling for investigation of blast induced traumatic brain injury

Modeling of human body biomechanics resulting from blast exposure is very challenging because of the complex geometry and the substantially different materials involved. We have developed anatomy based high-fidelity finite element model (FEM) of the human body and finite volume model (FVM) of air around the human. The FEM model was used to accurately simulate the stress wave propagation in the human body under blast loading. The blast loading was generated by simulating C4 explosions, via a combination of 1-D and 3-D computational fluid dynamics (CFD) formulations. By employing the coupled Eulerian-Lagrangian fluid structure interaction (FSI) approach we obtained the parametric response of the human brain by the blast wave impact. We also developed the methodology to solve the strong interaction between cerebrospinal fluids (CSF) and the surrounding tissue for the closed-head impact. We presented both the arbitrary Lagrangian Eulerian (ALE) method and a new unified approach based on the material point method (MPM) to solve fluid dynamics and solid mechanics simultaneously. The accuracy and efficiency of ALE and MPM solvers for the skull-CSF-brain coupling problem was compared. The presented results suggest that the developed coupled models and techniques could be used to predict human biomechanical responses in blast events, and help design the protection against the blast induced TBI

Near Real-Time Sub/Seasonal Prediction of Aerosol and Air Quality at the NASA Global Modeling and Assimilation Office

Version 2 of the coupled modeling and analysis system used to produce near real time subseasonal to seasonal forecasts was released almost two years ago by the NASA/Goddard Global Modeling and Assimilation Office. The model runs at approximately 1/2 degree globally in the atmosphere and ocean, contains a realistic description of the cryosphere, and includes an interactive aerosol model. The data assimilation used to produce initial conditions is weakly coupled, in which the atmosphere-only assimilated state is coupled to an ocean data assimilation system using a Local Ensemble Transform Kalman Filter. Results of aerosol-derived air quality (Particulate Matter) from an extensive series of retrospective forecasts will be shown, with particular focus on the continental United States and eastern Asia. In addition, under some circumstances, the interactive aerosol is shown to improve seasonal time scale prediction skill. Plans for a future version of the system with predicted biomass burning from fires will also be discussed

Session on cumulus parameterization

The session on cumulus parameterization from the Colloquium and Workshop on Multiscale Coupled Modeling is covered. The ten major issues raised that were suggested to be critical unknowns requiring immediate attention are presented

Insights on Simulating Summer Warming of the Great Lakes: Understanding the Behavior of a Newly Developed Coupled Lake-Atmosphere Modeling System

The Laurentian Great Lakes are the world\u27s largest freshwater system and regulate the climate of the Great Lakes region, which has been increasingly experiencing climatic, hydrological, and ecological changes. An accurate mechanistic representation of the Great Lakes thermal structure in Regional Climate Models (RCMs) is paramount to studying the climate of this region. Currently, RCMs have primarily represented the Great Lakes through coupled one-dimensional (1D) column lake models; this approach works well for small inland lakes but is unable to resolve the realistic hydrodynamics of the Great Lakes and leads to inaccurate representations of lake surface temperature (LST) that influence regional climate and weather patterns. This work overcomes this limitation by developing a fully two-way coupled modeling system using the Weather Research and Forecasting model and a three-dimensional (3D) hydrodynamic model. The coupled model system resolves the interactive physical processes between the atmosphere, lake, and surrounding watersheds; and validated against a range of observational data. The model is then used to investigate the potential impacts of lake-atmosphere coupling on the simulated summer LST of Lake Superior. By evaluating the difference between our two-way coupled modeling system and our observation-driven modeling system, we find that coupled-lake atmosphere dynamics can lead to a higher LST during June-September through higher net surface heat flux entering the lake in June and July and a lower net surface heat flux entering the lake in August and September. The unstratified water in June distributes the entering surface heat flux throughout the water column leading to a minor LST increase, while the stratified waters of July create a conducive thermal structure for the water surface to warm rapidly under the higher incoming surface heat flux. This research provides insight into the coupled modeling system behavior, which is critical for enhancing our predictive understanding of the Great Lakes climate system

A coupled modeling framework for sustainable watershed management in transboundary river basins

There is a growing recognition among water resource managers that sustainable watershed management needs to not only account for the diverse ways humans benefit from the environment, but also incorporate the impact of human actions on the natural system. Coupled natural– human system modeling through explicit modeling of both natural and human behavior can help reveal the reciprocal interactions and co-evolution of the natural and human systems. This study develops a spatially scalable, generalized agent-based modeling (ABM) framework consisting of a process-based semi-distributed hydrologic model (SWAT) and a decentralized water system model to simulate the impacts of water resource management decisions that affect the food–water–energy–environment (FWEE) nexus at a watershed scale. Agents within a river basin are geographically delineated based on both political and watershed boundaries and represent key stakeholders of ecosystem services. Agents decide about the priority across three primary water uses: food production, hydropower generation and ecosystem health within their geographical domains. Agents interact with the environment (streamflow) through the SWAT model and interact with other agents through a parameter representing willingness to cooperate. The innovative twoway coupling between the water system model and SWAT enables this framework to fully explore the feedback of human decisions on the environmental dynamics and vice versa. To support non-technical stakeholder interactions, a web-based user interface has been developed that allows for role-play and participatory modeling. The generalized ABM framework is also tested in two key transboundary river basins, the Mekong River basin in Southeast Asia and the Niger River basin in West Africa, where water uses for ecosystem health compete with growing human demands on food and energy resources. We present modeling results for crop production, energy generation and violation of ecohydrological indicators at both the agent and basin-wide levels to shed light on holistic FWEE management policies in these two basins