Modelling a pike (Esox lucius) population in a lowland river using a cellular automaton

Petroleum reservoirs are made of highly heterogeneous rocks. These reservoirs could be described by geostatistical models composed of millions of cells. Currently, fluid flow simulations performed within these media need upscaling (or averaging) techniques. Hence, their results are given by averaging on cells which are much larger than the geological model cells. To overcome this problem, the Dual Mesh Method is proposed here, whose purpose is to solve the pressure equation on a low resolution grid, and then to interpolate pressure over the fine mesh by taking into account small scale heterogeneities of the medium. The aim of this paper is this interpolation step; its implementation is presented and illustrated in a five-spot pattern for three different rock characteristics.

A non-linear two-dimensional vertically stratified cross-sectional model of a constant depth basin without rotation is used to investigate the influence of vertical and horizontal diffusion upon the wind-driven circulation in the basin and the associated temperature field. The influence of horizontal grid resolution, in particular the application of an irregular grid with high resolution in the coastal boundary layer is examined. The calculations show that the initial response to a wind impulse is downwelling at the downwind end of the basin with upwelling and convective mixing at the opposite end. Results from a two-layer analytical model show that the initial response is the excitation of an infinite number of internal seiche modes in order to represent the initial response which is confined to a narrow near coastal region. As time progresses, at the downwind end of the basin a density front propagates away from the boundary, with the intensity of its horizontal gradient and associated vertical velocity determined by both horizontal and vertical viscosity values. Calculations demonstrate the importance of high horizontal grid resolution in resolving this density gradient together with an accurate density advection scheme. The application of an irregular grid in the horizontal with high grid resolution in the nearshore region enables the initial response to be accurately reproduced although physically unrealistic short waves appear as the frontal region propagates onto the coarser grid. Parameterization of horizontal viscosity using a Smagorinsky-type formulation acts as a selective grid size-dependent filter, and removes the short-wave problem although enhanced smoothing can occur if the scaling coefficient in the formulation is too large. Calculations clearly show the advantages of using an irregular grid but also the importance of using a grid size-dependent filter to avoid numerical problems.

A Multiscale Control Volume framework using the Multiscale Restriction Smooth Basis and a non-orthodox Multi-Point Flux Approximation for the simulation of two-phase flows on truly unstructured grids

Hydrodynamic modeling of a complex salt marsh system: Importance of channel shoreline and bathymetric resolution

The reconstruction of a super-resolution (SR) image from multiple low-resolution (LR) frames has drawn a lot of research attention over the past years. The SR reconstruction is an inherent ill-posed minimization problem. Though regularization constraint may be accomplished to derive a single solution, to implement a traditional approach which the data fusing is processed at high-resolution (HR) grids may still be a great challenge due to complexity as well as high computing load. In this paper we introduce a new approach which both the blur and noise removal would be simultaneously carried out at the LR grids by taking pixelwise time average upon the available LR frames after registration. This approach is characterized by simplicity and real-time applicability, and the simulation results demonstrate that the compatible performance can be achieved.

Simulation of eddy-driven deep circulation in the East/Japan Sea by using a three-layer model with wind, throughflow and deep water formation forcings

Numerical and experimental investigation of early stage diesel sprays

In this work the flow field evolution, mixture formation and combustion process in an engine with methane Direct Injection (DI) is investigated using Large Eddy Simulations. The supersonic methane injection is modeled according to Muller et al. (2013) and combustion by a level set approach. The flame propagation showed to be dependent on the grid resolution. Higher grid resolutions have two opposing effects: first the fraction of unresolved turbulence is reduced, which decrease the flame speed and second flame wrinkling is increased resulting in faster flame propagation. For the observed setup the wrinkling effect was stronger. The average in-cylinder pressure traces as well as the cyclic variability thereof were compared to experimental data and very good agreement was found. During the supersonic gaseous injection the turbulence level in the cylinder is significantly increased, which dissipates quickly and thus has only a minor effect on the flame propagation. The introduced momentum showed a larger impact, since it enhances the tumble motion resulting in increased turbulence levels as the tumble decays shortly before ignition. During DI the cyclic differences in the tumble motion are preserved, but the impact on the average tumble level results in changing relative differences of the cyclic turbulence levels at ignition timing. Thus an injection direction supporting the tumble flows is expected to reduce the Cycle-to-Cycle Variations (CCV), while a reduction of the tumble strength could increase the CCV level. Compared to the fluctuations in the turbulence levels, the cyclic variability of the equivalence ratio at the injection location with DI showed a minor effect on the simulated CCVs.

The influence of initial perturbation power spectra on the growth of a turbulent mixing layer induced by Richtmyer–Meshkov instability

Obstruction grids for spectral wave models

The Western Mediterranean Basin is positioned between the cold Atlantic region and the subtropical high-pressure belt, creating a distinctive climate characterised by irregular heavy rainfall. These extreme precipitation events are often associated with cut-off polar fronts interacting with warm, moisture-laden air masses from the Mediterranean Sea, triggering intense convective storms. This study examines one of the most significant flood events in the region’s recent history, which occurred between 11 and 14 September 2019 over the Southeast of the Iberian Peninsula. To enhance our understanding of the processes driving such extreme weather, we employed the WRF model to evaluate different cumulus parameterization schemes. Specifically, we aimed to identify which scheme most accurately reproduces observed precipitation and cumulus formation and to assess the influence of cumulus parameterization activation in the higher-resolution grid on model performance. Our findings highlight the crucial role of orography in precipitation estimation, as it significantly influences convective initiation. Despite the high spatial resolution of the inner grid (3 km), results indicate that parameterized convection remains beneficial for resolving sub-grid processes. Among the tested schemes (Kain-Fritsch, Betts-Miller-Janjic, and Grell-Freitas), scale-aware parameterizations, such as Grell-Freitas, exhibited the best performance in high-resolution models due to their ability to dynamically adjust convective processes to the model’s spatial scale. The insights gained from this study contribute to a better understanding of extreme weather dynamics in the Mediterranean region, offering valuable guidance for improving the modelling and forecasting of torrential convective storms in the region.

On divergence- and gradient-preserving coarse-graining for finite volume primitive equation ocean models

Abstract. Limited resolution in chemistry transport models (CTMs) is necessarily associated with systematic errors in the calculated chemistry, due to the artificial mixing of species on the scale of the model grid (grid-averaging). Here, the errors in calculated hydroxyl radical (OH) concentrations and ozone production rates 3 are investigated quantitatively using both direct observations and model results. Photochemical steady-state models of radical chemistry are exploited in each case to examine the effect on both OH and 3 of averaging relatively long-lived precursor species, such as O3, NOx, CO, H2O, etc. over different spatial scales. Changes in modelled 3 are estimated, independently of other model errors, by calculating the systematic effect of spatial averaging on the ozone production efficiency 1, defined as the ratio of ozone molecules produced per NOx molecule destroyed. Firstly, an investigation of in-flight measurements suggests that, at least in the northern midlatitude upper-troposphere/lower stratosphere, averaging precursor species on the scale of a T42 grid (2.75° x 2.75°) leads to a 15-20% increase in OH concentrations and a 5-10% increase in 1. Secondly, results from CTM model experiments are compared at different horizontal resolutions. Low resolution experiments are found to have significantly higher [OH] and 3 compared with high resolution experiments. The extent to which these differences may be explained by the systematic error in the model chemistry associated with grid size is estimated by degrading the high resolution data onto a low resolution grid and then recalculating 1 and [OH]. The change in calculated 1 is found to be significant and can account for much of the difference in 3 between the high and low resolution experiments. The calculated change in [OH] is less than the difference in [OH] found between the experiments, although the shortfall is likely to be due to the indirect effect of the change in modelled NOx, which is not accounted for in the calculation. It is argued that systematic errors caused by limited resolution need to be considered when evaluating the relative impacts of different pollutant sources on tropospheric ozone.

We have investigated the role of high-frequency cycles (HFCs) in carbonates during water flooding. These are normally sub-seismic and therefore below grid resolution and must be upscaled, both in terms of single- and multiphase flow behaviour, to predict time to water breakthrough, recovery factors, and the habitat of remaining oil properly. Particularly the latter could be important when designing appropriate enhanced oil recovery schemes that target the remaining oil. The importance of selecting a high vertical resolution grid has been demonstrated for HFCs with continuous petrophysical log gradients and discontinuities, and the consequence these high permeability ranges have on waterflood velocity has been presented: capturing all of a continuous gradient requires increasing the vertical resolution so as to predict a fast enough water front, and a realistic distribution of the residual oil within the HFCs. In addition, the importance of selective diagenesis has been investigated by considering the effect of early-stage diagenesis at the top of HFCs in end-member Greenhouse and Icehouse climates. HFCs are very common in carbonates, even if they are nested within larger-scale heterogeneous geobodies, and the value of this investigation is in its application to real reservoir models.

Industrial landscape (IL) is the spatial consequence of industry behaviors. Aboundance of industrial spatial pattern and dependence can be observed due to the variation of different geographical factors. Location of work-force and capital also differ along the earth surface. Because of data collection difficulty, administrative area is often used as the basic spatial analysis unit and high spatial resolution less introduced. In the paper, data of the 2nd National Economic Sensus of China are employed to carry out high spatial resolution IL analysis. Spatial statistics methods are conducted to find industry cluster, special industry zone and spatial dependence at 1Km <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> resolution grid in GIS software. It's argued that subtle spatial segmentation will violate industry characters in some spatial cells in which only few enterprise sites. Therefore supernumerary filters should be introduced to exclude these cells.