quasi-3D Modelling Research Articles

50 Years Of Hanbar Concrete Units In Australia And New-Zealand: Lessons Learned From Physical Modelling Studies And Recently Built Structures

During the last 50 years, numerous breakwaters along the eastern coast of Australia, and more recently in New Zealand, have undergone construction, repairs, or upgrades using Hanbar concrete armour units. These units are distinct to Australasia, and there is limited information about their properties in standard coastal engineering literature. This paper first provides a survey and timeline of all known projects using Hanbars. An overview of the Hanbar concrete unit features and manufacturing method is then provided. The paper presents a summary of results of previous modelling studies of Hanbar applications to specific breakwaters, as well as recent research programs completed at WRL, and provides placement density guidelines as well as recommended damage coefficient (Hudson Kd) for design. The paper concludes with a brief overview of two recent case studies which have successfully capitalized on the economical, robustness and manufacturing simplicity of the Hanbar concrete units. The first case study is on the Opotiki Harbour Development (“OHD”) in New Zealand. The OHD scheme comprises twin 400 m long training wall breakwaters to train a dynamic river mouth. A multi-stage approach to physical modelling was adopted by conducting 2D modelling of key sections of the training wall trunks, quasi-3D modelling of the breakwater head, and full 3D modelling of complete structures. The second case study presents the results of a field trial investigating the potential for high-density geopolymer concrete (GPC) coastal armour units. This resulted in the casting and placing of thirteen 16 t GPC Hanbar units (SG 2.6) on the Port Kembla northern breakwater in NSW. The trial proved the viability of production of geopolymer armour units, and allowed long-term monitoring of the integrity of the concrete in the aggressive marine environment.

Computationally Efficient Quasi-3D Model of a Secondary Electrode Particle for Enhanced Prediction Capability of the Porous Electrode Model

Models of Li-ion batteries addressing a particular scale—from atomistic to continuum—have reached a certain level of maturity. Meanwhile, consistent multi-scale modelling approaches are still in their infancy despite their large potential to boost the accuracy and prediction capability of Li-ion battery models. As an answer to this challenge, the paper presents an advanced quasi-3D model of the active electrode material that tackles one of the main deficiencies of the porous-electrode theory (PET) based models which arises from a poor representation of the electrode topology. It is hypothesised that there exists a quasi-3D modelling representation of the active electrode material that adequately virtually replicates intra primary particle Li-distribution and features significantly shorter computational times compared to models featuring a fully 3D meshed electrode topology, which enables its full integration into the porous electrode model. An advanced quasi-3D model is constructed by the integration of the concentration and the chemical potential in each primary particle across its volume and by the introduction of the permeability parameter at the interfaces. Besides compatibility with PET and acceptable computational times, the model also exhibits results that are in good agreement with measured lithium concentration profiles inside secondary particles published in literature.

Modelling the Inundation and Morphology of the Seasonally Flooded Mayas Wetlands in the Dinder National Park-Sudan

Understanding the spatiotemporal dynamics of surface water in varied, remote and inaccessible isolated floodplain lakes is difficult. Seasonal inundation patterns of these isolated lakes can be misestimated in a hydrodynamic model due to the short time of connectivity. The seasonal and annual variability of the Dinder River flow has great impact on what is so called Mayas wetlands, and hence, on the habitats and the ecological status of the Dinder National Park. This variability produces large morphological changes due to sediment transported within the river or from the upper catchment, which affects inflows to Mayas wetlands and floodplain inundation in general. In this paper, we investigated the morphological dimension using a quasi-3D modelling approach to support the management of the valuable Mayas wetlands ecosystems, and in particular, assessment of hydrological and morphological regime of the Dinder River as well as the Musa Maya. Six scenarios were developed and tested. The first three scenarios consider three different hydrologic conditions of average, wet and dry years under the existing system with the constructed connection canal. While the other three scenarios consider the same hydrologic conditions but under the natural system without an artificial connection canal. The modelling helps to understand the effect of human intervention (connection canal) on the Musa Maya. The comparison between the simulated scenarios concludes that the hydrodynamics and sedimentology of the Maya are driven by the two main factors: a) the hydrological variability of Dinder River; and b) deposited sediment plugs in the connection canal.

Quasi 3D modelling of vadose zone soil-water flow for optimizing irrigation strategies: Challenges, uncertainties and efficiencies

A quasi 3D modelling approach was developed by integrating a crop growth (LINGRA-N) and a hydrological model (Hydrus-1D) to simulate and visualize water flow, soil-water storage, water stress and crop yield over a heterogeneous sandy field. We assessed computational efficiency and uncertainty with low-to high-spatial resolution input factors (soil-hydraulic properties, soil-layer thickness and groundwater level) and evaluated four irrigation scenarios (no, current, optimized and triggered) to find the optimal and cost-effective irrigation scheduling. Numerical results showed that the simulation uncertainty was reduced when using the high-resolution information while a fast performance was maintained. The approach accurately determined the field scale irrigation requirements, taking into account spatial variations of input information. Optimal irrigation scheduling is obtained by triggered-irrigation resulting in saving up to ∼300% water as compared to the current-irrigation, while yield increased ∼1%. Overall, the approach can be useful to help decision makers and applicants in precision farming.

Quasi 3D modelling and simulation of axial flux machines

Purpose– The purpose of this paper is to investigate the theoretical foundation of the so-called quasi 3D modelling method of axial flux machines, and the means for the simulation of the resulting models.Design/methodology/approach– Starting from the first principles, a 3D magnetostatic problem is geometrically decomposed into a coupled system of 2D problems. Genuine 2D problems are derived by decoupling the system. The construction of the 2D simulation models is discussed, and their applicability is evaluated by comparing a finite element implementation to an existing industry-used model.Findings– The quasi 3D method relies on the assumption of vanishing radial magnetic flux. The validity of this assumption is reflected in a residual gained from the 3D coupled system. Moreover, under a modification of the metric of the 2D models, an axial flux machine can be presented as a family of radial flux machines.Research limitations/implications– The evaluation and interpretation of the residual has not been carried out. Furthermore, the inclusion of eddy currents has not been detailed in the present study.Originality/value– A summary of existing modelling and simulation methods of axial flux machines is provided. As a novel result, proper mathematical context for the quasi 3D method is given and the underlying assumptions are laid out. The implementation of the 2D models is approached from a general angle, strengthening the foundation for future research.

Quasi-3D Modelling of Two-Phase Slug Flow in Pipes

In this paper, we present progress obtained by the Quasi 3-Dimensional (Q3D) model for pipe flows. This model is based on a multi-fluid multi-field formulation with construction and tracking of the large-scale interfaces (LSIs). The computational time is significantly reduced compared to full 3D by using a specially adopted slice-averaging technique. However, the slice-averaging generates new terms in the model equations. These terms are related to important mechanisms such as wall shear stress and turbulence production at side walls. We present some basic performance tests of the Q3D model, including single phase wall friction and the velocities of single Taylor bubbles at inclinations ranging from horizontal to vertical. Finally we report the performance of the model for slug flow in horizontal and 10° inclined pipes. The model reproduces the experimental data satisfactorily for both cases in a very short simulation time compared to full 3D.

Spatially constrained inversion for quasi 3D modelling of airborne electromagnetic data – an application for environmental assessment in the Lower Murray Region of South Australia

We present an application of spatially constrained inversion (SCI) of SkyTEM (airborne electromagnetic) data for defining spatial patterns of salinisation in the Bookpurnong irrigation area located in the lower Murray Basin of South Australia. SCI uses Delaunay triangulation to set 3D constraints between neighbouring soundings, taking advantage of the spatial coherency that may be present in the dataset. Conductivity information for individual soundings is linked through the spatial constraints, from well determined parameters to locally poorly determined parameters. For the survey presented here, SCI generated maps detail the spatial variability of floodplain salinisation, the extent of floodplain sediments influenced by lateral recharge and flushing along stretches of the Murray River, and the variable quality of groundwater in deeper semi-confined aquifers of the Murray Group. Available borehole and other ancillary information, such as vegetation density and health patterns, match the observed conductivity variations seen in the SCI results, even at the very near surface (≈2m depth). The SCI provides more accurate and spatially consistent results compared with those from single site inversions. They are also more uniform and detailed than maps obtained with single point Layered Earth Inversions or a laterally constrained inversion. In this example, the SCI provided reliable quasi 3D modelling, that confirmed and improved the hydrogeological knowledge of the area, indicating that the technique would have application with helicopter electromagnetic data in similar settings throughout the lower Murray Basin of Australia.

Spatially Constrained Inversion for Quasi 3-D Modelling of AEM Data

The spatially constrained inversion (SCI) produces quasi-3D modelling of geoelectrical and EM data of varying spatial density, using a 1D forward solution. Information migrate horizontally through spatial constraints and allow resolution of layers that would be locally poorly resolved. The constraints are built using the Delaunay triangulation, which ensures automatic adaptation to data density variations. It also allows creation of subsets suitable for parallel computing. In this study the SCI was applied to airborne time domain EM soundings (SkyTEM data from the Island of Lolland, Denmark), but it can be implemented also with all other data types. The field case study proves that the SCI produces laterally c onsistent results that respect the 3D geological variations of the sedimentary settings. The resolution of near surface tills and water bearing sand and gravel layers is greatly enhanced and so is the boarder of the saline groundwater intrusion beneath the island. The SCI also suppresses the elongated artifacts commonly seen in profile oriented data sets.

FEM quasi-3D modelling of responses to artificial recharge in the Bangkok multiaquifer system

Quasi three-dimensional (quasi-3D)modelling plays a major role in analysis of groundwater flow in multiaquifer systems and it can be an efficient tool for artificial recharge modelling. As the role of artificial recharge in groundwater management continues to increase, analysis of responses to artificial recharge has a particular significance. This paper deals with some practical aspects of the development of a general quasi-3D model based on an algorithm employing the combined techniques of Finite Element Method (FEM) and convolution integral. Responses to well recharge in a multiaquifer system were analyzed. The results of flow and consolidation analyses for an idealized hydrogeological section of the Bangkok aquifer system are presented to illustrate the role of artificial recharge in land subsidence control for Bangkok city. Here, land subsidence due to groundwater extraction is a serious issue to be resolved, and artificial recharge has been recommended as a supplemental means of mitigation.

Quasi-3D modelling of suspended sediment transport by currents and waves

A quasi-3D model for suspended sediment transport based on an asymptotic solution of the convection-diffusion equation is developed for currents and waves. The influence of waves on the sediment concentration is included through the diffusion analogy and the boundary condition near the bed. The flow velocity profile is assumed to have a logarithmic shape. An extensive sensitivity analysis concerning the influence of wave and current parameters on the suspended adjustment phenomenon shows that the presence of waves considerably enlarges the suspended load and its adjustment time and length scales. Validity analysis of the quasi-3D formulation results in restrictions for the suspension parameter (modified for waves) and for the time and length scales of changes in hydraulic conditions. The presence of waves eases all the above restrictions and thus enlarges the validity area of the model considerably. The model is compared with 2DV and 3D numerical solutions of the convection-diffusion equation with good agreement and verified with existing measurements.

Quasi-3D modelling of nearshore currents

Existing concepts of wave-induced nearshore current models, in the cross-shore vertical plane (2DV) and depth-integrated (2DH), are combined to a quasi-3D mathematical model. This combination is tested for reproducing correct results in 2DV and 2DH situations. The importance of the various contributions to the wave-induced secondary circulation in the vertical plane is investigated for realistic parameter ranges, which leads to the conclusion that both the non-breaking and the breaking fraction of a random wave field in the surf zone generate important secondary currents. Additional computations show the relevance of a 3D-approach of nearshore currents, even in seemingly simple situations like a plane sloping beach with obliquely incident waves.