Simple Hydrodynamic Model Research Articles

A simple hydrodynamic model for clay

Laboratory description of clay normally distinguishes the scale of atoms from the scale of clay particles and aggregates. Contemporary constitutive models for clay tend to ignore this scale separation, and rather focus on phenomenology. By considering scale separation, this paper introduces a robust physics-based phenomenological constitutive model for clay that qualitatively captures their broad spectrum of rate-dependent mechanical features. The model is derived using the thoroughly rigorous hydrodynamic procedure. While some imagine that by considering rigour and physics, their models would get complicated, the resulting set of equations reveal a surprising degree of simplicity. The derivation strongly benefits from the principle of two-stage irreversibility, which describes energy flow within the material from the continuum scale down to the atomistic micro-scale, through the meso-scale of clay aggregates. While thermal and meso-related temperatures capture atomistic and clay aggregate fluctuating motions, a sink term from the latter to the former underpins the direction of the energy flow. The model’s standout feature is in pinpointing new transport coefficients that drive both volumetric and shear plastic flows in a thermodynamically coupled manner. A novel scheme is then proposed to calibrate these coefficients from conventional steady-state observations. Thanks to the formulation the model shows a remarkable level of predictiveness, despite being relatively simple mathematically. In particular, the model readily explains the broad spectrum of rate-dependent phenomena during transient loading, along with creep and relaxation processes. Given the generality of hydrodynamics, it is anticipated that the new model could be expanded to capture fluid-solid transitions between liquid-like soft mud and plastic-like stiff clay responses, contingent on water content variations.

Modeling JWST MIRI-MRS Observations of T Cha: Mid-IR Noble Gas Emission Tracing a Dense Disk Wind

[Ne ii] 12.81 μm emission is a well-used tracer of protoplanetary disk winds due to its blueshifted line profile. Mid-Infrared Instrument (MIRI)-Medium Resolution Spectrometer (MRS) recently observed T Cha, detecting this line along with lines of [Ne iii], [Ar ii], and [Ar iii], with the [Ne ii] and [Ne iii] lines found to be extended while the [Ar ii] was not. In this complementary work, we use these lines to address long-debated questions about protoplanetary disk winds regarding their mass-loss rate, the origin of their ionization, and the role of magnetically driven winds as opposed to photoevaporation. To this end, we perform photoionization radiative transfer on simple hydrodynamic wind models to map the line emission. We compare the integrated model luminosities to those observed with MIRI-MRS to identify which models most closely reproduce the data and produce synthetic images from these to understand what information is captured by measurements of the line extents. Along with the low degree of ionization implied by the line ratios, the relative compactness of [Ar ii] compared to [Ne ii] is particularly constraining. This requires Ne ii production by hard X-rays and Ar ii production by soft X-rays (and/or EUV) in an extended (≳10 au) wind that is shielded from soft X-rays, necessitating a dense wind with material launched on scales down to ∼1 au. Such conditions could be produced by photoevaporation, whereas an extended magnetohydrodynamic (MHD) wind producing equal shielding would likely underpredict the line fluxes. However, a tenuous inner MHD wind may still contribute to shielding the extended wind. This picture is consistent with constraints from spectrally resolved line profiles.

Flood Risk Assessment of Areas under Urbanization in Chongqing, China, by Integrating Multi-Models

In the context of urbanization, frequent flood event have become the most common natural disasters, posing a significant challenge to human society. Considering the effects of urbanization on flood risk is critical for flood risk reduction and reasonable land planning strategies at the city scale. This study proposes an integrated approach based on remote sensing data using CA, Markov, and simplified hydrodynamic (FloodMap) models to accurately and effectively assess flood risk under urbanization. Taking Chongqing City as a case study, this paper analyzes the temporal and spatial variations in land use/land cover (LULC) in 2010, 2015, and 2018 and predicts the LULC for 2030, based on historic trends. Flood risk is assessed by combining the hazard, exposure, and modified vulnerability. The results suggest that the area of built-up land will increase significantly from 19.56% in 2018 to 25.21% in 2030. From 2010 to 2030, the area of medium and high inundation depths will increase by 10 and 16 times, respectively. Flood damage varies remarkably according to the LULC and return period. The expected annual damage (EAD) has been estimated to increase from USD 68 million in 2010 to USD 200 million in 2030. Flood risk is proportional to population and is significantly inversely proportional to socioeconomic level. The approach used here can provide a comprehensive understanding of flood risk and is significant for land-use policymaking and the management of flood control facilities.

Adiabatic expansion, local equilibrium and extended Maxwell distribution for fire-ball to describe multiple particle production

We propose a model for multiple particle production of [Formula: see text] and [Formula: see text] collisions at high energies. Most of the processes in the model are reasonable physically and/or with reasoning. A fire-ball of a gas, made of grains, is created in the collision and makes an adiabatic and approximately one-dimensional expansion along the collision axis. The fire-ball at the final state, when the grains are free in the fire-ball, is divided into several domains and the thermal equilibrium is realized in each of the domains with different temperatures. Each grain produces several hadrons at the final state. There are two processes of the grains without and with [Formula: see text] (transverse momentum), and the cross-section of the latter process increases with the incident energy. The grains in the domain at the final state obey the extended Maxwell distributions of the temperature [Formula: see text], and the hadrons in each grain do that of the temperature [Formula: see text]. The values of the adjustable parameters are determined empirically in such a way as to reproduce the data of [Formula: see text] distributions and the rapidity density distributions at various incident energies. The model describes both distributions well at the incident energy of [Formula: see text] to 7000[Formula: see text]GeV. The local equilibrium in each domain and the adiabatic expansion describe the flat plateau and the shrinkage of the forward region, respectively, of the rapidity density distribution. Another important conclusion is that a simple hydro-dynamical model does not describe the flat plateau of the rapidity density distribution of produced hadrons at high energies.

Environmental Flows Assessment Based on the Coupling of Water Level and Salinity Requirements for Maintaining Biodiversity: A Case Study from the Ouémé delta in West Africa.

The present study carried out on the Ouémé delta in West Africa, addresses the implementation of the BBM approach for the determination e-flows in a context of high data limitation. It also highlights the potential challenges for the implementation of the recommended e-flows in West Africa countries. To do this, we first established the current ecological status of the delta based on data collection, measurements and scientists' observations. Then, we formulated ecological objectives for e-flows based on the environmental management vision for the delta. And finally, we determined the water requirements for the sustainability of the biodiversity and ecosystem services using a simple 2D hydrodynamic model. The results indicate that 100 and 50% of the average natural flows are required respectively in low-water and high-water periods (3.4 billion m3 per year) to maintain the Ouémé Delta in its current environmental management class. This recommendation for e-flows allocation is in direct competition with the water requirements for the economic development of the delta, which is estimated to be over 3.0 billion m3 per year in the Master Plan for Water Development and Management. While it is clear that the establishment of e-flows recommendations must be accompanied by measures to limit the degradation of ecological habitats, it is even more clear that the economic development remained the main concern of policymakers. The integration of environmental flows into water resources management policies in developing countries requires linking water needs for economic development with water needs for the ecological sustainability of rivers and their associated ecosystems.

Simple model for self-propulsion of microdroplets in surfactant solution.

We propose a simple active hydrodynamic model for the self-propulsion of a liquid droplet suspended in micellar solutions. The self-propulsion of the droplet occurs by spontaneous breaking of isotropic symmetry and is studied using both analytical and numerical methods. The emergence of self-propulsion arises from the slow dissolution of the inner fluid into the outer micellar solution as filled micelles. We propose that the surface generation of filled micelles is the dominant reason for the self-propulsion of the droplet. The flow instability is due to the Marangoni stress generated by the nonuniform distribution of the surfactant molecules on the droplet interface. In our model, the driving parameter of the instability is the excess surfactant concentration above the critical micellar concentration, which directly correlates with the experimental observations. We consider various low-order modes of flow instability and show that the first mode becomes unstable through a supercritical bifurcation and is the only mode contributing to the swimming of the droplet. The flow fields around the droplet for these modes and their combined effects are also discussed.

Numerical simulation of biogas chemical looping reforming in a dual fluidized bed reactor

Conversion technologies with low environmental impact and high energetic efficiency are needed to ensure clean, efficient, and cost-effective exploitation of renewable carbonaceous fuels like biogas. In the present study, the Chemical Looping Reforming of biogas is proposed and numerically investigated to pursue this goal. Preliminarily, a thermodynamic model was implemented by means of the Aspen Plus® commercial software to identify the conditions where carbon formation and deposition do not occur. A simple hydrodynamic model of a Dual Fluidized Bed reactor coupled with a 1D, static, and isothermal kinetic model was adopted. The effects of variations in biogas composition (namely, CH4:CO2 ratio and water content) and in other relevant process parameters (e.g., the oxygen-to-fuel ratio and FR operating temperature) on the process performances in terms of the reactants conversion degree, syngas yield, and syngas composition were assessed and critically discussed. Very high conversion degree for both CH4 (93%) and CO2 (87%), as well as syngas yield ranging up to 3.74, were evaluated.

DEVELOPMENT OF A MODERN LABORATORY INFORMATION MANAGEMENT SYSTEM FOR THE OIL AND GAS INDUSTRY

Preparing an economic assessment for the development of new oil and gas equity is an important task that affects many different design decisions. At the same time, at the early stages of project implementation, there are the greatest levers to increase their final economics, but unfortunately, the insufficient knowledge of the field does not allow making accurate forecasts.To obtain production profiles in such conditions, a simplified hydrodynamic model (HDM) is usually used, on which an analysis of the uncertainties of the input data is carried out. To do this, the ranges of change of the most significant parameters affecting the production are determined (porosity, permeability, PVT-properties of oil, etc.). Further, the set of production profiles for all possible variations of each uncertain parameter is averaged. At the same time, an increase in the number of variable parameters leads to an exponential increase in labor costs. Additional complexity in carrying out such calculations is created by the need to involve specialists of various profiles employees of the services of the chief geologist responsible for the design of the field development, and the chief engineer responsible for the well completion design. This makes it possible to consider both the potential of the reservoir and the limitations of surface infrastructure in the overall solution. The latter is critical for offshore fields, since oil platforms do not have the same flexibility in terms of modification as surface facilities.Offshore deposits are also of particular interest from the point of view of the need to replenish Russia's raw material base due to the depletion of more accessible onshore deposits in the medium term.In this way, the development of an engineering calculator for calculating the production profile for an oil platform is a complex but important task for the oil industry. This article presents the results of its formalization and solution.

Coseismic river avulsion on surface rupturing faults: Assessing earthquake-induced flood hazard.

Surface-rupturing earthquakes can produce fault displacements that abruptly alter the established course of rivers. Several notable examples of fault rupture-induced river avulsions (FIRAs) have been documented, yet the factors influencing these phenomena have not been examined in detail. Here, we use a recent case study from New Zealand's 2016 Kaikōura earthquake to model the coseismic avulsion of a major braided river subjected to ~7-m vertical and ~4-m horizontal offset. We demonstrate that the salient characteristics of the avulsion can be reproduced with high accuracy by running a simple two-dimensional hydrodynamic model on synthetic (pre-earthquake) and "real" (post-earthquake) deformed lidar datasets. With adequate hydraulic inputs, deterministic and probabilistic hazard models can be precompiled for fault-river intersections to improve multihazard planning. Flood hazard models that ignore present and potential future fault deformation may underestimate the extent, frequency, and severity of inundation following large earthquakes.

Marangoni destabilization of bidimensional-confined gas–liquid co-flowing streams in rectangular microfluidic channels

In microchannels, the stability of a fluid jet injected into another immiscible fluid strongly depends on its degree of geometric confinement. When the width of the jet, w, is larger than the channel height, H, the surface tension driven Rayleigh–Plateau instability is suppressed so that the 2D (bidimensional)-confined jet is absolutely stable and never collapses into bubbles (or drops) in contrast to what occurs when w ≤ H [Dollet et al., “Role of the channel geometry on the bubble pinch-off in flow-focusing,” Phys. Rev. Lett. 100(3), 034504 (2008); Guillot et al., “Stability of a jet in confined pressure-driven biphasic flows at low Reynolds number in various geometries,” Phys. Rev. E 78(1), 016307 (2008)]. We here demonstrate both experimentally and theoretically that this picture is, indeed, no longer valid when Marangoni effects are considered. We experimentally show that the addition of small length alcohol molecules into the liquid phase destabilizes a 2D-confined gas–water microfluidic stream ( w > H), leading to the generation of steady non-linear waves and further to the production of bubbles. Using a simple hydrodynamic model, we show through a linear analysis that the destabilization of the gas stream may result from a Marangoni instability due to the fast adsorption of the alcohol molecules, which occurs on a timescale comparable to that of the microfluidic flow.

Considerations about the gas fraction in two-phase electrochemical reactors by using a rigorous hydrodynamic model

The experimental evidence that a limiting value of gas fraction is achieved in a gas-liquid dispersion as the gas volumetric flow rate is increased is explained by means of a rigorous hydrodynamic model. The mathematical treatment, based on the Eulerian concept applied to each phase, considers a population balance with a range of bubble sizes allowing the coalescence and breakup between them; and it is implemented in the OpenFOAM framework. It is concluded that the limiting gas fraction is a consequence of the increase of the gas velocity and the constancy of the drag term of the interfacial exchange moment as the volumetric gas flow is enlarged. A simplified hydrodynamic model is also reported that closely matches both the rigorous one and the experimental results under limiting operating conditions.

Nonlocal Fourier modal method for analyzing nonlocal plasmonic periodic nanostructures

In accordance with growing scientific interests in nanoplasmonic structures, along with the increasing ability to fabricate them using proper nanotechnologies, we have developed a methodology to incorporate nonlocal optical responses, described with a simple hydrodynamic model, into the numerical Fourier modal method (FMM) technique to enable broadening of the simulation portfolio of such physical phenomena in plasmonic nanostructures. Here, we have newly incorporated the nonlocal response approximation (NRA) into the periodic FMM technique (called NonLocFMM) described with a proper hydrodynamic model, and we show in several examples that this implementation is capable of numerically analyzing periodic plasmonic systems, such as nonlocal periodic multilayers and resonant gratings. The implementation was performed in such a way that a future possible generalization of the hydrodynamic nonlocal description will be feasible, as well as the aperiodization of the technique. Such an extension is, indeed, viable and will be the subject of a subsequent paper.

Characterisation of the conveying effect of turned radial shaft seal counter-surfaces using a simplified hydrodynamic simulation model

AbstractA typical sealing system for rotating shafts consists of the radial shaft sealing ring (RSS), the lubricant and the shaft counter-surface (SCS) of the rotating shaft. The properties of the machined surface of the SCS have an impact on the sealing system. The structural pattern of the SCS influences the lubricant flow along the axial direction. In this paper, a simplified micro scale hydrodynamic simulation model is presented in order to study and determine the axial flow of the lubricant induced by the SCS of the sealing system, isolated from the effects induced by the seal, to allow for a rating of the shaft surface. The influence of the seal was neglected to allow for a simplified simulation. Simulated shaft surfaces corresponding to different machining parameters of machined SCS are used as input. These variants of SCS were created using a kinematic model which simulates an ideal surface machining process of the shaft. A micro scale hydrodynamic simulation model is used to investigate the influence of machining parameters on the lubricant flow along the axial direction across the tribo-contact. From this investigation, the connection between parameters applied for machining of the SCS and conveying effects can be estimated. The simulation model is also validated with experimental results of hard turned shafts of different machining parameters. Differences between manufactured real surfaces and kinematically simulated surfaces are the cause of deviations between the results.

Pulsed Plasma Accelerator

In this paper, we consider the acceleration of plasma fluxes in crossed electromagnetic fields. The possible technical approach to a prospective plasma accelerator is discussed. A simple hydrodynamic model describing the dynamics of the plasma ring in these fields is proposed. Based on this model, the estimations of basic characteristics for the accelerated flux are calculated for typical experimental conditions.

Larval fish counteract ram and suction to capture evasive prey.

A simple hydrodynamic model of predator-prey interactions between larval clownfish and copepod prey is used to elucidate how larval fish capture highly evasive copepods. Fish larvae are considered to be suction feeders; however, video observations revealed that successful captures by clownfish larvae were preceded by rapidly accelerating lunges (ram), while the role of suction to draw prey into the fish's mouth was less clear. Simulations were made of the fish's strike, varying strengths of ram and suction to characterize optimal strategies for copepod capture given known evasive capabilities. Our results suggest that, contrary to expectations, suction feeding is dominant only in older larvae, whereas ram feeding is the dominant mode for early larvae. Despite the relatively weak suction produced by smaller larvae, it still plays a crucial role in prey capture through hydrodynamic stealth. Escape-triggering water deformations from the strike can be cancelled through controlled suction. Experimental data obtained from larval clownfish agree with model results, suggesting that the primary role of suction in early larvae is providing hydrodynamic stealth rather than capture.

Implementation of printability for magneto-active soft materials based on programmed 3D printing technique

Magneto-active soft materials fabricated by new paradigms of 3D printing have received considerable interest for various applications owing to their remarkable complex deformation and extraordinary magneto-mechanical properties. The morphology and magneto-mechanical properties of materials prepared by direct ink writing (DIW) 3D printing, on the other hand, are closely related to process and material parameters that are critical in this printing technique. In this study, the morphology of ink filaments printed under different parameters was investigated through theoretical analysis and experimental tests to achieve the implementation. The results demonstrated that the prepared magnetic inks are suitable for DIW, and the predictions based on a simplified hydrodynamic model are basically consistent with the measured data in the experiments. It also showed that the diameter of the extruded ink filaments increases with increasing extrusion pressure, and decreasing printing speed, layer height, and magnetic particle content. Similarly, the magnetic property varies with the nozzle diameter and material composition variations. Using the obtained optimal parameters, several magneto-active rods and plate-like structures with a specific arrangement of microscopic magnetic domains were successfully fabricated. Their magnetically driven behavior further was investigated experimentally and numerically, which revealed a programmed, non-contact remote control, reversible, and multimodal large deformation characteristics. The findings of this study allow a more in-depth understanding and analysis of processing-structure-property correlations of printed magneto-active soft materials, laying the groundwork for personalized customization and versatile development of magneto-mechanical performance.

Brief communication: Impact forecasting could substantially improve the emergency management of deadly floods: case study July 2021 floods in Germany

Abstract. Floods affect more people than any other natural hazard; thus flood warning and disaster management are of utmost importance. However, the operational hydrological forecasts do not provide information about affected areas and impact but only discharge and water levels at gauges. We show that a simple hydrodynamic model operating with readily available data is able to provide highly localized information on the expected flood extent and impacts, with simulation times enabling operational flood warning. We demonstrate that such an impact forecast would have indicated the deadly potential of the 2021 flood in western Germany with sufficient lead time.

Fractal structure of chaotic scattering in a simple hydrodynamic model with a point vortex embedded in a time-(quasi)periodic background flow

This paper is a study of a nonlinear dynamical system with 3/2 degrees of freedom consisting of a point vortex and an unsteady background flow. This background flow consists of two parts, a steady and a (quasi)periodic with two sinusoidal components with different frequencies and amplitudes. The considered system with a separatrix loop in the phase portrait is the simplest model of chaotic scattering of passive tracers on a topographic vortex, captured by a seamount, in the ocean. We have found that depending on variation of amplitudes of two sinusoidal components, the passive tracers enters and leaves the vortex region in portions. The frequency of escape and the size of such portions depend on the parameters of the background flow. It is shown that the structure of the fractal-like scattering function changes at low levels through the formation (disappearance) of segments according to two mechanisms, the action of which is determined by the relation between two frequencies of the perturbation.

Detection of particles of dark matter from the spectrum of secondary particles in high-energy proton-proton collisions in a thermodynamic model

In a simple hydrodynamic model, the transverse momentum distributions are found for A hyperons formed in pp collisions at ultrarelativistic energies. The calculated spectra are compared with the experimental data obtained for various colliders in a wide range of proton collision energies, including the data from experiments at the Large Hadron Collider. An interpretation of the transverse momentum spectra of soft photons in pp collisions is proposed, taking into account the X17 boson with a mass of 17 MeV - a new particle, a possible candidate for the role of dark matter particles. A tube model is proposed on the basis of combining two-dimensional quantum chromodynamics and quantum electrodynamics. An interpretation is proposed for the detection of a 38 MeV boson in the spectra of photons emitted in the reactions of protons with carbon nuclei at an incident proton momentum of 5.5 GeV/c. The X38 boson with a mass of 38 MeV has a mass close to the boson mass obtained by us, equal to 35 MeV for an electromagnetic tube. This new particle was discovered in experiments carried out recently in Dubna for the reactionp p + C→2γ + X. To interpret the obtained experimental data on the spectra of emitted photons depending on their mass, it is proposed to use the formulas obtained for massive particles, setting the mass of a boson decaying into two photons equal to 38 MeV. It was proposed to consider bosons X17 and X38 as particles of dark matter.

A snapshot of the oldest active galactic nuclei feedback phases

Active Galactic Nuclei (AGN) inject large amounts of energy into their host galaxies and surrounding environment, shaping their properties and evolution. In particular, AGN jets inflate cosmic-ray lobes, which can rise buoyantly as light `bubbles' in the surrounding medium, displacing and heating the encountered thermal gas and thus halting its spontaneous cooling. These bubbles have been identified in a wide range of systems. However, due to the short synchrotron lifetime of electrons, the most advanced phases of their evolution have remained observationally unconstrained, preventing us to fully understand their coupling with the external medium, and thus AGN feedback. Simple subsonic hydrodynamic models predict that the pressure gradients, naturally present around the buoyantly rising bubbles, transform them into toroidal structures, resembling mushroom clouds in a stratified atmosphere. The way and timescales on which these tori will eventually disrupt depend on various factors including magnetic fields and plasma viscosity. Here we report LOFAR observations below 200 MHz, sensitive to the oldest radio-emitting particles, showing the late evolution of multiple generations of cosmic-ray AGN bubbles in a galaxy group with unprecedented level of detail. The bubbles' buoyancy power can efficiently offset the radiative cooling of the intragroup medium. However, the bubbles have still not thoroughly mixed with the thermal gas, after hundreds of million years, likely under the action of magnetic fields.