Electromagnetically Forced Flows in Shallow Electrolyte Layers

A large body of scientific effort has been devoted to study the dynamics of homogeneous, non-rotating shallow fluid layers in the laboratory [36]. These experiments are believed to be relevant in order to gain insight into some classes of geophysical flows like coastal and river flows, where the density stratification and rotation of the Earth does not play an important role. Experiments on shallow flows are also performed searching for similarities between real turbulent laboratory flows and idealized two-dimensional (2D) turbulence [81]. Finally, another type of research involves studies of vortex dynamics in shallow layers, where coherent structures like a dipolar vortex are created and measured [75]. These coherent vortices are of a special interest to geophysical flows since they are very frequently observed in such large-scale flow systems. A large ratio between the typical horizontal length scale (e.g. the size of the flow domain) to the typical vertical length scale (e.g. the fluid layer depth) is generally believed to ensure quasi-two-dimensional (Q2D) flow properties of shallow fluid layers. [36, 81, 75, 76, 9, 27]. If this ratio is large enough one usually refers to "geometrical confinement" of the flow. In this case Q2D dynamics practically means that "geometrical confinement" is believed to inhibit vertical velocities relative to horizontal motions and vertical profiles of the horizontal velocities become simply Poiseuille-like [25]. Following this reasoning the majority of the work done in the past focused on the planar properties of motion, usually at the free surface of a shallow fluid layer. Yet relatively little is known about the vertical flow structures inside a shallow fluid layer and their interactions with the horizontal motion of the fluid, including the free surface flows. As a response to that state-of-the-art, the research reported in this PhD thesis concerns the three-dimensional (3D) structures present in shallowflows. The main goal is to elucidate the importance or unimportance of 3D effects in a few shallow-flow configurations. Three typical flow structures are examined: a dipolar vortex colliding with a no-slip vertical wall (Chapter 3), a dipole moving over an inclined bottom (Chapter 4) and decaying turbulence (Chapter 5) in a shallow fluid layer. A dipolar vortex is chosen since it is a frequently occurring flow structure in real geophysical flows or in purely 2D turbulence [50]. Investigations on Q2D turbulence largely disregard the effects of lateral sidewalls and a simple and well-defined problem of dipolewall collision is believed to shed some light on this more complicated turbulence problem. A dipole approaching a no-slip inclined bottom corresponds with the realistic and common flow phenomenon of a vortex in coastal areas. Finally, the 3D flow structures in decaying turbulence provide new insights into this classic experiment with assumed quasi-two-dimensionality. The flows discussed in this thesis are driven by electromagnetic forcing. The flow phenomena are studied both by laboratory experiments and by 3D numerical simulations. Wherever the three components of the velocity vector in a single horizontal plane are measured in the laboratory the technique of Stereoscopic Particle Image Velocimetry (SPIV)was employed. In addition to these measurements, 3D numerical simulations have been performed with a realistic model for the Lorentz force. These experimental and numerical aspects of the three-dimensionality inside shallow fluid layers are summarized in the Chapter 6.

The effect of a thin control wire on the wake properties of the flow around a circular cylinder has been investigated numerically. The governing equations are solved using a spectral element method for a Reynolds number of ReD=100. The diameter ratio of the main cylinder and the wire equals D/d=50 so no vortex shedding is expected to occur for the wire. However, the vorticity introduced by the wire in the vicinity of the upper shear layer of the cylinder still affects the vortex dynamics in the wake of the main cylinder. The primary effect of the wire is the reduction of the velocity fluctuations in the vortex formation region of the main cylinder. The maximum decrement occurs at a wire position of yw/D=0.875. The secondary effect of the wire is observed in the kinematics of the vortices, leading to a modified vortex arrangement and strength difference between the upper and lower vortices. Due to these effects, for yw/D≤0.875, a downward wake deflection is observed, while for larger values of yw/D>0.875, an upward deflection is found. The maximum downward deflection occurs at wire position yw/D=0.75 where the maximum positive mean lift coefficient, minimum drag coefficient, and minimum fluctuating lift coefficient are seen. Based on the observations, it is concluded that the deflection of the wake is primarily caused by a modification of the vortex arrangement in the wake. This modified vortex arrangement is caused by different formation times of the upper and lower vortices, by different vortex strengths, or by both.

The study of andesite resources was carried out in Hargowilis village, Kokap sub-district, Kulonprogo regency, Daerah Istimewa Yogyakarta province using geoelectrical data with Schlumberger configuration, as much as 14 point which is spreading on 8 hectares area. Based on regional geological map of Yogyakarta area, study area include on intrusive rock lithology’s unit compose of hipersten andesite to augite-hornblende andesite and trachiandesite. Geoelectrical method is one of geophysical method that used to observed geological condition in subsurface based on rock’s electrical properties. Andesite is one type of igneous rock which have contrast electrical properties with its surrounding rock, generally sedimentary rocks, makes it suitable for geoelectrical method to identify the presence of andesite in subsurface and also estimate its thickness to calculate the resources. Geoelectrical configuration used is 1D Schlumberger configuration where this method have advantage more accurate to calculate the thickness of rock layer especially in shallow area. The result of geoelectrical survey showing that it consist 2 layer of andesite, there are shallow layer and deep layer. This result indicate that the igneous rock in study area not only intrusion type, but also lava flow type. Resources potential of andesite both shallow and deep layer are 5,072,354 tons and resources potential of shallow andesite only is 3,162,566 tons.

Laboratory flume studies on monochromatic wave-fine sandy bed interactions Part 2. Sediment suspensions

Experimental and numerical studies of one-directional and bi-directional flow conditions across tube banks heat exchanger

Vortex dynamics play a central role in most turbulent processes, whether of physical or chemical origin. In the realm of so-called weak turbulence, which encompasses physical, chemical, and electrochemical processes, understanding and monitoring the emergence of vortices in three dimensions remains a significant challenge. In this study, we propose a novel approach with minimal computational cost that enables the characterization of vortex ring formation and screw-like patterns in 3D-turbulent flows. Our method involves analyzing gradient vortex dynamics by measuring phase fluctuations in gradient patterns derived from the 3D-distribution of the corresponding amplitudes. The investigation focuses on transient primary structures generated by the Complex Ginzburg-Landau amplitude equation. The simulations integrate gradient pattern analysis, allowing for a groundbreaking association between phase fluctuations (commonly referred to as phase turbulence) and the helical oscillations induced by vorticity. As our main result, the phase-gradient analysis, combined with aspect ratio measurements of the primary patterns of coherent structures, enables us to identify at least four distinct regimes characterizing vortex dynamics. To further enhance this characterization, spectral measurements and recurrence plots of the phase-gradient fluctuations are introduced as innovative tools for describing weak turbulence and spatiotemporal chaos in nonlinear (3D+1) dynamics. This approach provides new insights into the intricate interplay between phase turbulence and vortex dynamics, offering a new perspective on the systematic study of the formation of coherent structures in three dimensions. It is worth highlighting that this is the first time that 3D screw dynamics have been simulated, visualized and analyzed in detail in a phase turbulence process.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-94832-2.

The influence of inflow perturbations on the wake dynamics and structural response is investigated for a cylinder undergoing vortex-induced vibrations (VIV) in oscillatory flows in the proximity of a solid boundary. Numerical simulations are conducted at a Reynolds number of 200, based on the cylinder diameter and free-stream velocity, for perturbation frequencies fp up to four times the natural shedding frequency fo. Three response regimes are identified: a lock-on regime at fp=2fo, with maximum cylinder displacement and forces, a force-amplification regime for 1.8<fp<2.3 characterized by shedding frequency entrainment, and a weakly coupled regime. The wake and structural response dynamics differ from those for unperturbed VIV in uniform flow. The primary mechanism underlying these differences is due to the symmetric instability of the shear layers forced by the perturbations. This instability results in the shedding of vortex pairs at fp in the cylinder base region, which interact with the Kármán formation process and, in the amplification regimes, reinforce the natural instability at 2fo. These mechanisms give rise to distinct wake topology, which is then related to the structural dynamics.

Fluid dynamics is a research area lying at the crossroads of physics and applied mathematics with an ever-expanding range of applications in natural sciences and engineering. However, despite decades of concerted research efforts, this area abounds with many fundamental questions that still remain unanswered. At the heart of these problems often lie mathematical models, usually in the form of partial differential equations, and many of the open questions concern the validity of these models and what can be learned from them about the physical problems. In recent years, significant progress has been made on a number of open problems in this area, often using approaches that transcend traditional discipline boundaries by combining modern methods of modelling, computation and mathematical analysis. The two-part theme issue aims to represent the breadth of these approaches, focusing on problems that are mathematical in nature but help to understand aspects of real physical importance such as fluid dynamical stability, transport, mixing, dissipation and vortex dynamics.This article is part of the theme issue ‘Mathematical problems in physical fluid dynamics (part 2)’.

Fluid dynamics is a research area lying at the crossroads of physics and applied mathematics with an ever-expanding range of applications in natural sciences and engineering. However, despite decades of concerted research efforts, this area abounds with many fundamental questions that still remain unanswered. At the heart of these problems often lie mathematical models, usually in the form of partial differential equations, and many of the open questions concern the validity of these models and what can be learned from them about the physical problem. In recent years, significant progress has been made on a number of open problems in this area, often using approaches that transcend traditional discipline boundaries by combining modern methods of modelling, computation and mathematical analysis. The two-part theme issue aims to represent the breadth of these approaches, focusing on problems that are mathematical in nature but help to understand aspects of real physical importance such as fluid dynamical stability, transport, mixing, dissipation and vortex dynamics.This article is part of the theme issue ‘Mathematical problems in physical fluid dynamics (part 1)’.

A binding phase based on the clay mineral montmorillonite (MT) was used as a sorbent in this work, which employed diffusive gradients in thin-film (DGT) devices to determine the lability of trace elements in natural waters. Montmorillonite exhibits low cost, wide availability, ease of handling, high ion-exchange capacity, and reusability. As(V), Ba2+, Cd2+, Co2+, Cr(III), Cu2+, Mn2+, Ni2+, Pb2+, Sr2+, V(V), and Zn2+ were quantitatively sorbed by MT and eluted with 1.0molL-1 HNO3, which provided efficiency above 70% of recovery. Validation tests were performed with synthetic solutions. The recovery of known concentrations ranged from 83 to 110%. The performance of modified DGT was compared with conventional DGT devices in experiments lasting 6 and 48h. The results obtained with both DGT devices showed no significant differences with 95% confidence. DGT samplers with MT were deployed in the determination of labile forms of the elements in water samples from Iguaçu River (Paraná, Brazil). The measured masses of elements in MT for various durations showed good fit to a theoretical line, indicating that the results agreed with the principle of the DGT technique. The concentrations of labile species in the sample proceeded as follows; Sr > Cd > Ba > Cu > Cr > Mn > Zn > Pb. The results suggest that DGT devices with MT are an effective alternative for speciation analysis of a wide range of elements (cations as well as anions) in natural waters.

Biopolymers with piezoelectric properties are widely attractive nowadays owing to their direct and indirect effects of piezoelectric behavior in addition to biocompatibility and biodegradability. Although a wide range of polymers such as polyvinylidene fluoride, are used to enhance the power generation, conversion efficiency, and storage capacity of different piezoelectric devices, biocompatibility is the significant property when bio-nanogenerators are considered. Biopolymers are notable for their wide availability, ease of handling and biodegradability, however durability and poor mechanical strength are some of the challenges associated with them. This chapter briefly illustrates the recent advances in developing biopolymer nanocomposites for piezoelectric applications and the influence of different nanomaterials in regulating the piezoelectric properties of biopolymers.

The wide availability, ease of handling and structural and functional diversity make carboxylic acids prized building blocks in organic synthesis. The past two decades has seen an explosion of interest in the development of new modes of reactivity of carboxylic acids and their derivatives. Of these, metal‐mediated decarboxylation reactions are attractive as they produce organometallic intermediates that can subsequently be used in C−X (where X=C, N, S etc) bond coupling reactions. Here the results of mechanistic studies integrating both gas‐ and condensed‐phase work are described for development of new extrusion‐insertion (ExIn) classes of reactions for the synthesis of amides, thioamides, amidines, alkenes and ketones from arylcarboxylic acids and suitable (hetero)cumulenes.

Biopolymers with piezoelectric properties are widely attractive nowadays owing to their direct and indirect effects of piezoelectric behavior in addition to biocompatibility and biodegradability. Although a wide range of polymers such as polyvinylidene fluoride, are used to enhance the power generation, conversion efficiency, and storage capacity of different piezoelectric devices, biocompatibility is the significant property when bio-nanogenerators are considered. Biopolymers are notable for their wide availability, ease of handling and biodegradability, however durability and poor mechanical strength are some of the challenges associated with them. This chapter briefly illustrates the recent advances in developing biopolymer nanocomposites for piezoelectric applications and the influence of different nanomaterials in regulating the piezoelectric properties of biopolymers.

Water is the most commonly used injection fluid for flooding/energizing oil reservoirs. Despite oil price fluctuations, water use has continued because of its wide availability, relatively low cost, and ease of handling. Decades of research and field application experiences have yielded a sound theoretical approach and practical knowledge of the subject. Nevertheless, water injection deployment and operations can still benefit from optimization. This paper discusses the state-of-the-art use of numerical optimizers based on smart algorithms and stochastic machines that couple subsurface, surface, and economic models. During planning and operations of waterflooding projects, many decisions are made, such as the number, location, and drilling sequence of new injector and producer wells, total and per well injection rates, well conversion, and fluid withdrawal rates. In addition, each decision variable has multiple options, which combined can generate hundreds or thousands of scenarios, raising the key question of how the optimum scenario can be determined in a timely manner. Furthermore, the optimum scenario selection process should consider uncertainty (e.g., reservoir properties and oil prices) as well as operational constrains. Based on previous experience, a general workflow was developed and fine-tuned to help identify optimum scenarios. The workflow begins by defining the scenario matrix using available validated history-match models. Models are coupled with an automatic optimizer/stochastic machine. The study cases considered reservoirs with heavy-to-medium oil, injection by pattern and flank, large variations in original oil in place (OOIP), and number of wells for waterflooding implementation and reactivation planning. Optimization runs typically require hundreds of iterations to approach the maximum or minimum objective business function. Each iteration corresponds to a scenario. To identify the optimal scenario quickly, various strategies were tested: parallel computing and new methodologies of sequential optimization with reduced number of decision variables, initial exploratory runs with a shortened economic horizon time, and stochastic analysis of selected scenarios of the optimization run. All of these strategies proved successful, depending on the specific situation. The workflow application in three case studies yielded approximately 30% cumulative production and net present value (NPV) increments, with less economic risk than the traditional deterministic simulation approach and reduced water cut up to 40%; compared to base scenarios, Np and NPV increases higher than 200% were obtained. Furthermore, the workflow application generated a large number of scenarios that provided flexibility to modify operations during unexpected events. Optimizers/stochastic machines were determined to be a valid means to quantitatively estimate the economy and risks and are a fundamental tool for managing waterflooding projects, resulting in better scenarios than the traditional deterministic approach. The approach is also applicable to all types of enhanced oil recovery (EOR) projects.

Numerical simulations of the transition from laminar to chaotic behaviour of the planar vortex flow past a circular cylinder