Flow Deformation Research Articles

CWD-Sim: Real-Time Simulation on Grass Swaying with Controllable Wind Dynamics

In this paper, we propose algorithms for the real-time simulation of grass deformation and wind flow in complex scenes based on the Navier–Stokes fluid. Grasses play an important role in natural scenes. However, accurately simulating their deformation due to external forces such as the wind can be computationally challenging. We propose algorithms that minimize computational cost while producing visually appealing results. We do this by grouping the grass blades and then applying the same force to the group to reduce the computation time. We also use a quadratic equation to deform the blades affected by the wind force rather than using a complicated spline technique. Wind force is fully modeled by the Navier–Stokes fluid equation, and the blades react to this force as if they were being swept by the wind. We also propose the AGC interface (Arrow-Guided wind flow Control), which allows the direction and intensity of the wind to be manipulated using an arrow-shaped interface. Through this interface, users can have grass sway in response to user-defined wind forces in a real-time rate. We verified that the proposed algorithms can simulate 900% more grass blades than the compared paper’s algorithms.

Drop deformation in a planar elongational flow: impact of surfactant dynamics.

Drops in extensional flow undergo a deformation, which is primarily fixed by a balance between their surface tension and the viscous stress. This deformation, predicted and measured by Taylor on millimetric drops, is expected to be affected by the presence of surfactants but has never been measured systematically. We provide a controlled experiment allowing us to measure this deformation as a function of the drop size and of the shear stress for different surfactants at varying concentrations. Our observation is that the deformation predicted by Taylor is recovered at zero and high surfactant concentration, whereas it is smaller at concentrations close to the critical micellar concentration. This is in contradiction to the existing analytical models. We develop a new analytical model, taking into account the surfactant dynamics. The model predicts a transition between a deformation similar to that of a pure liquid and a smaller one. We show that the transition is driven by a parameter KL, which compares adsorption and desorption dynamics. Finally, the concentration C*, at which we observe this transition in the extensional flow is in good agreement with the one predicted by independent measurements of KL.

An intuitionistic fuzzy rough model for maritime transportation chains under disaster effects: the case of COVID-19

The outbreak of COVID-19 has caused disruptions in port transport infrastructure and shipping, resulting in higher shipping rates in 2022. This article aims to assess the extent of COVID-19 risks on the capacity and concentration of traffic flows, and evaluate the degree of imbalance in the transport system during 2020-2021 compared to the previous period of 2018-2019. The data is analyzed using the Intuitionistic Fuzzy Rough set, which allows the evaluation of multiple heterogeneous measures to produce an aggregate outcome. The model is based on the intensity of non-stationary incoming and outgoing traffic, as well as the intervals between separate ship calls. The data obtained from the study shows the dynamics of changes in traffic flows under the influence of COVID-19. The results indicate a minimal degree of its influence, which did not lead to any failures or modifications in the composition of traffic flows. The method can also allow for the development of complex simulation models to assess the limit of potential deviations, after which, with a high degree of probability, deformation of traffic flows is possible.

Horizontal borehole azimuth optimization for enhanced stability and coal seam gas production

Horizontal boreholes have been widely used to extract natural gas from coal seams. However, these boreholes can encounter severe instability issues leading to production interruption. Optimizing drilling azimuth is a potential solution for enhancing borehole stability while considering gas production. In this work, we improved and implemented a dual-porosity, fully coupled geomechanical-hydraulic numerical model into COMSOL Multiphysics to investigate into this factor. The sophisticated numerical model incorporates various critical factors, including desorption-induced matrix shrinkage, stress-dependent anisotropic fracture permeability, and the interactions of gas flow and reservoir deformation in matrices and fractures.A suite of simulation scenarios (e.g., varying coal strength) was carried out to quantify the impact of drilling azimuth on coal permeability evolution, cumulative gas production, and the borehole break-out width for Goonyella Middle Seam of Bowen Basin, Australia. The model was calibrated against both theoretical permeability values and field gas production data. Due to the lack of directly measured matrix permeability data, the actual gas production was used to back calculate the best-matched matrix permeability, which is 0.65 μD for this particular work. Moreover, based on the breakout shape and induced volumetric strains around the borehole, drilling along the maximum horizontal stress does not necessarily lead to the best stability of the borehole, as generally believed. A drilling azimuth between 0° and 60° results in similar breakout width, whereas a drilling azimuth between 60° and 90° achieves the most efficient gas production. By considering both gas production efficiency and borehole stability, for this particular reservoir condition, the optimum drilling azimuth is determined to be between 45° and 60°.This study presents a practical approach for determining the optimum drilling azimuth in coal seam gas extraction through in seam boreholes.

Thermo-mechanical process variables driven microstructure evolution during additive friction stir deposition of IN625

Additive friction stir deposition is an innovative technique for solid-state additive manufacturing involving complex thermo-mechanical processes such as frictional heating, plastic deformation, and viscoplastic material flow, which repeats layer by layer during material deposition. The present study is an attempt to understand the relationship between the complex thermo-mechanical process attributes and the resultant microstructure in additive friction stir deposition of IN625. The estimation of thermo-mechanical process attributes, primarily temperature and strain rate during multi-layer deposition was based on the already established thermo-pseudo-mechanical description of friction stir based processes. The complex thermo-mechanical interaction associated with multi-layer material deformation, deposition, and flash formation can be attributed to variations in the average deposition temperature and the strain rate. Microstructural examination of the additive friction stir deposited sample was performed using electron backscatter diffraction. As a result of the additive friction stir deposition associated thermo-mechanical conditions, the microstructure exhibited fine equiaxed grains in the plane along the build direction along with bands of very fine grains within the interface regions between deposited layers. The observation of fine equiaxed grains and a lower degree of in-grain misorientation in the additively fabricated sample pointed to dynamic recrystallization as the governing restoration mechanism during the deposition process. The grain size refinement during additive friction stir deposition of IN625 resulted in substantial augmentation in the yield strength compared to IN625 feed material and as-cast IN625.

The result of tangential layered solid-state flow deformation in the middle and lower crust: The Yardoi dome in the eastern Himalayan orogenic belt

The result of tangential layered solid-state flow deformation in the middle and lower crust: The Yardoi dome in the eastern Himalayan orogenic belt

Numerical sensitivity analysis for stress-strain simulation and flow liquefaction assessment of tailings storage facilities using the NorSand constitutive model

With the advent of critical state Soil Mechanics (CSSM), the void ratio began to be recognized as a key parameter, along with the stress state, which defines the mechanical behavior of soils and other particulate geomaterials by using the state parameter. The state parameter is the difference between the current and critical void ratio so that its definition requires the critical state line (CSL) identification. This work presents numerical calibration results, using the NorSand constitutive model, from three sets of triaxial compression tests selected from the literature. The SIGMA/W module of the Geostudio® System was adopted to perform the simulations of the triaxial compression tests, and the results showed adequate fit between real tests and numerical simulations. The parameters necessary for the modeling with NorSand model, defined from the numerical calibration, were used in a stress-strain evaluation of a hypothetical upstream tailings dam. These simulations allowed the evaluation of the differences in the tailings storage facility (TSF) responses in terms of both deformation behavior and flow liquefaction instability. Flow liquefaction instability is described in the literature as a complete loss in shear strength and the development of excessive strains due to the contractive response of tailings when subjected to low confining stress. The results suggest that the use of the NorSand model is, in general, a good option to reproduce the typical strain-softening behavior of such structures. Furthermore, it was clear the high sensitivity of the constitutive model parameters, drawing attention to the importance of best laboratory practices for carrying out triaxial tests to obtain reliable parameters for NorSand modeling.

Mechanics of geodesics in information geometry and black hole thermodynamics

In this paper, we shall discuss the theory of geodesics in information geometry, and an application in astrophysics. We will study how gradient flows in information geometry describe geodesics, explore the related mechanics by introducing a constraint, and apply our theory to Gaussian model and black hole thermodynamics. Thus, we demonstrate how deformation of gradient flows leads to more general Randers–Finsler metrics, describe Hamiltonian mechanics that derive from a constraint, and prove duality via canonical transformation. We also verified our theories for a deformation of the Gaussian model, and described dynamical evolution of flat metrics for Kerr and Reissner–Nordström black holes.

A Numerical Approach for Predicting Temperature Distribution, Heat Flow, and Material Deformation of Printed Circuit Board during Laser Soldering

This paper presents a numerical simulation approach using the finite element method (FEM) in ANSYS software to overcome the limited accessibility of laser soldering machines which are expensive. The study aims to examine the viability of simulating a laser soldering process using ANSYS steady-state thermal simulation. The simulation aims to produce accurate predictions for temperature distribution, heat flow, and deformation of the material during the process. A Gaussian laser beam equation is used to analyse the interaction between the laser beam and metallic components, particularly on PCB boards. This paper evaluates the properties of a laser beam and the Sn-3.0Ag-0.5Cu (SAC305) lead-free solders which are commonly used in electronic industries. As a result of the thermal analysis, the temperature distribution within the solder spots, as well as the copper as printed circuit board (PCB) can be determined, whereas the mechanical analysis of the materials can be determined by looking at their deformation and stress in the system. The results show that the laser beam effectively contains heat within the solder contacts, reducing the risk of excessive heat transfer. The copper acts as an efficient heat sink, managing thermal energy during the process. However, the solder point experiences substantial deformation and stress, indicating potential limitations in its performance. Nonetheless, the neighbouring components and solder joints exhibit a factor of safety, ensuring the overall safety and reliability of the system.

Symmetry-Breaking-Induced Internal Mixing Enhancement of Droplet Collision

Binary droplet collision is a basic fluid phenomenon for many spray processes in nature and industry involving lots of discrete droplets. It exists an inherent mirror symmetry between two colliding droplets. For specific cases of the collision between two identical droplets, the head-on collision and the off-center collision, respectively, show the axisymmetric and rotational symmetry characteristics, which is useful for the simplification of droplet collision modeling. However, for more general cases of the collision between two droplets involving the disparities of size ratio, surface tension, viscosity, and self-spin motions, the axisymmetric and rotational symmetry droplet deformation and inner flow tend to be broken, leading to many distinct phenomena that cannot occur for the collision between two identical droplets owing to the mirror symmetry. This review focused on interpreting the asymmetric droplet deformation and the collision-induced internal mixing that was affected by those symmetry breaking factors, such as size ratio effects, Marangoni Effects, non-Newtonian effects, and droplet self-spin motion. It helps to understand the droplet internal mixing for hypergolic propellants in the rocket engineering and microscale droplet reactors in the biological engineering, and the modeling of droplet collision in real combustion spray processes.

Anisotropic continuum framework of coupled gas flow – adsorption – deformation in sedimentary rocks

AbstractSolid deformation is always a crucial factor of gas transport in sedimentary rocks. While previous studies always adopt the assumption of isotropic poroelastic deformation, anisotropic poroelastoplastic deformation is rarely considered, despite anisotropy being a ubiquitous property of natural sedimentary rocks. In this work, an anisotropic poromechanical model is established to analyze the matrix porosity and apparent permeability evolutions during the process of gas migration. Using a thermodynamic formulation that treats the fluid–solid interface as an independent phase, we derive a rate form for matrix porosity and obtain the new dissipation function that contains three parts: dissipations from solid deformation, gas adsorption, and fluid flow. For gas adsorption, we justify the rationality of the adopted model; for fluid flow, the updated porosity can be substituted into sophisticated apparent permeability models for full‐scale analysis; and for solid deformation, a recently developed constitutive model appropriate for rocks exhibiting transverse isotropy in both the elastic and plastic responses is adopted in this work. Through the novel stress‐point simulation incorporating two effective stress measures and adsorption strain, new patterns of apparent permeability are obtained, which fit the experimental data quite well and cannot be reproduced from the assumption of isotropic poroelasticity. The advantages of our poromechanical model include thermodynamic consistency and the ability to employ finite‐element‐based formulation. Finally, an initial‐boundary value problem of gas production considering anisotropic plasticity is conducted, and the effects of the bedding plane and different adsorption models are highlighted.

Hydrostructural Phenomena in a Wastewater Screening Channel with an Ascendable Sub-Screen Using the Arbitrary Lagrangian–Eulerian Approach

Wastewater invariably accumulates soluble and insoluble waste and requires treatment at a wastewater treatment plant (WTP) to become reusable. The preliminary screening of insoluble waste occurs through a wastewater screening mechanism (WSM) before entering the WTP. The present study computationally investigates the impact of a WSM, comprising a main screen, sliding sub-screen, and rake, on channel flow distribution, deformation, and stresses. Various sub-screen configurations, fully and partially lowered, are examined. The fluid–structure interaction between sewage water and the WSM was solved using the arbitrary Lagrangian–Eulerian approach. Unlike similar studies in the past which have been conducted in 2D, the present study considers the 3D design and thus captures a greater complexity of the WSM assembly. The velocity distribution inside the channel, structural deformation, and von Mises stresses of WSM components were analyzed for a range of inlet velocities at different stages of the screening process. The results reveal that a fully lowered sub-screen with an inactive rake ensures a uniform flow through the WSM, while a partially lowered sub-screen induces persistent flow separation. Structural analysis reveals significant deformation in the upper mid-region of the sub-screen and fluctuating deformations in the rake, accompanied by elevated von Mises stresses. The study serves as a design guideline for manufacturing and operating a WSM, ensuring the prevention of unfavorable stress and deformation in the WSM and the WTP.

Clustering of Floating Tracers in a Random Velocity Field Modulated by an Ellipsoidal Vortex Flow

The influence of a background vortex flow on the clustering of floating tracers is addressed. The vortex flow considered is induced by an ellipsoidal vortex evolving in a deformation. The system exhibits various vortex motion regimes: (1) a steady state, (2) oscillation and (3) rotation of the ellipsoidal vortex core. The latter two induce an unsteady velocity field for the tracer, thus leading to irregular (chaotic) tracer motion. Superimposing a stochastic divergent velocity field onto the deterministic vortex flow allows us to observe significantly different tracer evolution. An ellipsoidal vortex has ellipsoidal symmetry, and the tracer’s trajectories exhibit the same symmetry inside the vortex. Outside the vortex, the external deformation flow symmetry dominates. Diffusion scattering and chaotic advection give tracers the opportunity to leave the region of ellipsoidal symmetry and form a picture of shear flow symmetry. We use the method of characteristics to integrate the floating tracer density evolution equation and the Euler Ito scheme for obtaining the floating tracer trajectories with a random velocity field. The cluster area and cluster mass from the statistical topography are used as the quantitative diagnostics of a floating tracer’s clustering. For the case of a steady ellipsoidal vortex embedded into the deformation flow with a random velocity field component, we found that the clustering characteristics were weakened by the steady vortex. For the cases of an unsteady ellipsoidal vortex, we observed clustering in the floating tracer density field if the contribution of the divergent component was greater than or equal to that of the rotational (nondivergent) component. Even when the initial floating tracer patch was set on the boundary of the oscillating ellipsoidal vortex, we observed the formation of clusters. In the case of a rotating ellipsoidal vortex, we also observed pronounced clustering. Thus, we argue that unsteady ellipsoidal vortex regimes (oscillation and rotation), which induce chaotic motion of the nearby passive tracer’s trajectories, are still conducive to clustering of floating tracers observed in the density field, despite the intense deformation introduced by strain and shear.

Flow and thermal coupling analysis in metal droplet-based 3D printing: Evolution mechanism and regulation strategy under ultrasonic vibration

Formation of uniform pileup morphology and excellent bonding strength between two adjacent metal droplets are essential in droplet-based 3D printing. However, due to the unstable included angle (“gap”) of the pileup droplets generated by the complex coupling effect between the fluid flow and thermal deformation during the printing process, the successive pileup droplets tend to form poor accuracy morphologies, non-uniform properties, and low-quality bonding strength of the formed microstructure. Since the unstable flow and thermal deformation of the liquid metal is inherent properties in droplet-based 3D printing technique with the same parameter conditions, the morphological deterioration or even instability pileup process still remain common challenge in this technique. Here, the effects of velocity and thermal behaviors on the morphology and size of the pileup droplets were revealed. To accomplish this, a droplet pileup numerical model based on the volume of fluid (VOF) was developed to analyze the spreading and solidification mechanism of the pileup process. In addition, a series of printing experiments with the successive pileup of Sn droplets, generated by a self-developed piezoelectric micro-jet device (PMJD), were conducted to demonstrate the effects of impacting velocity and solidified temperature on the pileup morphology. The evolution mechanisms of impacting velocity and heat accumulation effect and its influence on the dimensional accuracy were revealed. Finally, the originality of this work is an ultrasonic-assisted metal droplet pileup (UAMDP) method was first proposed and applied to effectively regulate the pileup morphology and improve the bonding strength. The evolutions of the influence of the velocity field, temperature field, and pileup behaviors during the spreading process were analyzed thoroughly. A surface morphology analysis further showed the effect of ultrasonic vibration on the contact region between two pileup droplets. And experiments showed that such UAMDP (under voltage of VP-P = 15 V) has 5.9 times enhancement in the adhesion tangential force between two pileup metal droplets. This study provides a foundation for further development of metal droplet-based 3D printing technology.

A Novel Deformation Analytical Solution and Constitutive Model for Fractured Rock Masses

In order to study the deformation and stability of a fractured rock mass, existing research suggests that fracture deformation, which is usually obtained by evaluating the equivalent deformation modulus, dominates the deformation of a fractured rock mass. However, this parameter is difficult to obtain in theory and practice, which limits the application of rock mass deformation analysis methods. In order to calculate the deformation of fractured rock masses, the mass of the rock is regarded as a sponge-like material, and it is assumed that the deformation of a water-saturated fractured rock mass under external force load is approximately equal to the net flow of fracture water. Based on this assumption, firstly, the relationship between rock mass deformation and fracture flow is studied through a single-fracture rock mass model. The hydraulic properties of the fracture are characterized by the permeability coefficient, and the fracture deformation in the rock mass is equivalent to the fracture flow. The fracture deformation calculation formula is derived from the fracture hydraulics calculation formula, and this is compared with the measured data. The rationality of the calculation formula was verified. On this basis, the calculation formula for rock mass deformation, including multiple groups of fracture surfaces, is proposed, and the stress-strain constitutive relationship of a complex rock mass is established. The correctness of the calculation method was verified by comparing it with other theoretical calculation results.

Radar internal reflection horizons from multisystem data reflect ice dynamic and surface accumulation history along the Princess Ragnhild Coast, Dronning Maud Land, East Antarctica

Abstract Ice shelves, which regulate ice flow from the Antarctic ice sheet towards the ocean, are shaped by spatiotemporal patterns of surface accumulation, surface/basal melt and ice dynamics. Therefore, an ice dynamic and accumulation history are imprinted in the internal ice stratigraphy, which can be imaged by radar in the form of internal reflection horizons (IRHs). Here, IRHs were derived from radar data combined across radar platforms (airborne and ground-based) in coastal eastern Dronning Maud Land (East Antarctica), comprising three ice rises and adjacent two ice shelves. To facilitate interpretation of dominant spatiotemporal patterns of processes shaping the local IRH geometry, traced IRHs are classified into three different types (laterally continuous, discontinuous or absent/IRH-free). Near-surface laterally continuous IRHs reveal local accumulation patterns, reflecting the mean easterly wind direction, and correlate with surface slopes. Areas of current and past increased ice flow and internal deformation are marked by discontinuous or IRH-free zones, and can inform about paleo ice-stream dynamics. The established IRH datasets extend continent-wide mapping efforts of IRHs to an important and climatically sensitive ice marginal region of Antarctica and are ready for integration into ice-flow models to improve predictions of Antarctic ice drainage.

Anisotropy and Deformation Processes in Southern California From Rotational Observations

AbstractSeismic anisotropy in the upper mantle reveals geodynamic processes and the tectonic evolution of the Earth. The two most powerful methods, surface wave tomography, and shear‐wave splitting observations, cannot investigate the deep local anisotropy with good vertical and lateral resolution, resulting in poor constraints on plate deformation processes of the complex plate boundary beneath the Southern California region. Here, we show that the amplitude ratio of translational displacement and rotation makes it possible to retrieve the local anisotropy in the upper mantle. Azimuthal anisotropy in the asthenosphere is well determined and resolved in lateral and vertical directions. The fast axis retrieved from amplitude observations indicates the local rapid changes in plate deformation and complex pattern of mantle flow, which is compatible with the distributions of horizontal mantle flow illuminated by geodetic measurements, providing new insights on geodynamic processes of the Southern California region.

Mapping Mantle Flows and Slab Anisotropy in the Cascadia Subduction Zone

AbstractThe Cascadia margin is an unusual subduction zone characterized by the downdip movement of young and thin oceanic plates, where mantle flow and intraslab deformation are still unclear. Here we present new anisotropic tomography of the Cascadia subduction zone, in which the hexagonal symmetry axis of anisotropy is tilting rather than horizontal or vertical as assumed in previous studies of seismic anisotropy. Subduction‐induced entrained and toroidal flows under the Cascadia margin are discriminated well by the spatial relationship between tilting‐axis anisotropy and slab geometry. The obliquely entrained flow is trapped in a narrow zone (<100 km wide) above and below the subducting slab and reaches ∼200 km depth, which is surrounded by large‐scale sub‐horizontal toroidal flow. The intraslab anisotropy is trench‐normal above 80 km depth but changes to trench‐parallel at 100–400 km depths, which may reflect fossil anisotropy overprinted by deep deformation beneath the arc, or joint effect of serpentinization and hydrous faulting.

The Stress Strain Analysis of Forward Extrusion Process of Hollow Elements

This paper presents an analysis focused on the stress-strain dynamics within the forward extrusion process for hollow elements. The forward extrusion of hollow elements is characterized by extensive plastic deformation and complex material flow. This process involves splitting the metal continuum, subjecting it to plastic deformation, and merging it into a seamless product with a predetermined cross-sectional shape as it exits the tool. Employing modern numerical finite element methods is essential for designing such processes, as it enables the simulation of metal behavior within the tool. These simulations help predict mechanical parameters within the deformable material continuum, such as stress, strain, temperatures, and strain rates. Additionally, they allow for the optimization of tool designs tailored to the specific product, improving process efficiency and quality. Understanding the stress-strain distribution at individual nodes enables proactive measures to prevent mechanical disruptions within the continuum, ensuring the integrity and quality of the final product—an essential criterion in the forward extrusion process for hollow elements.

Dynamics of surfactant-laden drops in shear flow by lattice Boltzmann method

We developed and applied a diffuse interface lattice Boltzmann method for simulating immiscible liquids with soluble surfactants using a modified Ginzburg–Landau free energy functional. We first validated the approach through simulations of planar interfaces and drop equilibration in quiescent fluid. The proposed method accurately captures the phase and surfactant fields with diminishing spurious velocities of 10−6. We systemically examined the effects of capillary number, comparing viscous to surface forces, the combined effect of surfactant and viscosity ratio (λ) of the drop to the continuous phase, and the bulk surfactant load on the deformation and breakage in a shear flow. At a given capillary number (0.05<Ca<0.32), drop behavior is influenced by reduced surface tension, tip-stretching, Marangoni stresses, and surface dilution. These effects either promote (by tip-stretching) or hinder (via Marangoni stresses, surface dilution) the surfactant distribution at the interface, consequently affecting the final drop morphology. As Ca increases, the competition between the viscosity ratio and the presence of surfactant determines drops' topological changes. The presence of surfactants can overcome the effect of viscosity ratio (when 0.05≤λ≤1.7) and promote drop breakup, whereas highly viscous drops (either λ<0.05 or λ>1.7) do not break. Furthermore, high surfactant loads result in higher drop deformation and earlier drop breakup. In brief, our method successfully captures the dynamics of surfactant-laden drops in shear flow, elucidating the complex interplay between flow hydrodynamics and surfactant transport with 3D quantitative phase and surfactant concentration fields.