Fluid Dynamic Forces Research Articles

Hydrodynamic Mechanism for Stable Spindle Positioning in Meiosis II Oocytes

Cytoplasmic streaming, the persistent flow of fluid inside a cell, induces intracellular transport, which plays a key role in fundamental biological processes. In meiosis II mouse oocytes (developing egg cells) awaiting fertilization, the spindle, which is the protein structure responsible for dividing genetic material in a cell, must maintain its position near the cell cortex (the thin actin network bound to the cell membrane) for many hours. However, the cytoplasmic streaming that accompanies this stable positioning would intuitively appear to destabilize the spindle position. Here, through a combination of numerical and analytical modeling, we reveal a hydrodynamic mechanism for stable spindle positioning beneath the cortical cap. We show that this stability depends critically on the spindle size and the active driving from the cortex and demonstrate that stable spindle positioning can result purely from a hydrodynamic suction force exerted on the spindle by the cytoplasmic flow. Our findings show that local fluid dynamic forces can be sufficient to stabilize the spindle, explaining robustness against perturbations not only perpendicular but also parallel to the cortex. Our results shed light on the importance of cytoplasmic streaming in mammalian meiosis. Published by the American Physical Society 2024

Advancements in mathematical modeling and numerical simulation: Immersed boundary method for Navier-Stokes equations applied to stationary and rotating isothermal cylinders

This study investigates the growing scientific and industrial interest in the dynamics of fluids around bodies, with a particular focus on thermal fluctuations. These phenomena are prevalent in various scenarios, such as oil extraction platforms, power transmission lines, and fluid-structure interactions, necessitating a comprehensive understanding of vortex generation, heat transfer, and fluid dynamic forces. We employ the Immersed Boundary Method (IBM) to simulate two-dimensional, incompressible flows around stationary and rotating heated (isothermal) cylinders. Using a computational framework developed in C/C++, we analyze the effects of variations in cylinder rotation rates on flow dynamics and thermal distributions. This study involves multiple simulations to evaluate the stability of the method and extract relevant parameters, including drag, lift coefficients and Nusselt numbers, along with velocity, pressure, vorticity, and temperature fields. Through systematic comparison with existing literature, we aim to validate our findings and contribute to the continuous improvement of numerical accuracy in this domain. By elucidating these complex phenomena, our research aims to provide valuable insights for practical applications in industrial and engineering contexts. The objective of this work is to analyze the combination of heat transfer phenomena with rotation in isothermal cylinders and their thermofluid-structure interaction. To achieve this, a low computational cost C/C++ code (in terms of memory and computational resources) was developed. Furthermore, numerical simulations indicated that with an increase in the Reynolds number, there is an increase in the drag coefficient, highlighting the significant influence of the pressure distribution downstream of the cylinder. This pressure distribution is strongly affected by vortex formation and detachment, thereby validating the methodology.

Two-phase flow-induced vibration of tilted curved bi-directional functionally graded nanopipe in supersonic airflow

Flow-induced vibration is known as a prevalent phenomenon in various industries. As a result of the flow, dynamic fluid forces are generated, which lead to the excitation of the system. Multiphase flow, found commonly in both natural and industrial settings, including industrial plants, is a significant source of noise and vibration. In the two-phase flow, as a particular case of multiphase flow, flow configuration plays a major role in the system’s traits. Despite recent advancements in flow-induced vibration, it is still considered an unresolved topic. This research develops a new multi-physics simulation for the stability study of a two-directional functionally graded tilted curved cylindrical nanopipe conveying a liquid-gas two-phase flow. Nonlocal stress–strain gradient theory (NSGT) with two size-dependent parameters (nonlocal and length scale) is presented to simulate the current nanostructure. Newton’s second law has been employed to govern the resultant forces that act on a control volume at a differential fluid element of fluid. Hiring the finite element (FE) approach alongside the generalized differential quadrature role (GDQR), both the eigenvector and eigenvalue problems are presented for analyzing the characteristics of the nanosystem under various situations. An exhaustive parametric analysis is also provided to make clear the role of varied parameters such as velocity of fluid flow, aerodynamic pressure, air yaw angle, and gas volume fraction coefficient on the system’s fundamental frequency.

Research on vibration characteristics of cone valve based on steady state hydrodynamics

The steady-state fluid dynamic force of the cone valve core reduces the stability of the cone valve, thereby affecting its vibration characteristics. This study first derived the formula for calculating the steady-state fluid dynamic force of the valve core using the momentum theorem. Then, the study used the Computational Fluid Dynamics (CFD) method to explore the variation of steady-state fluid dynamic force with the opening degree of the cone valve and the pressure difference at the inlet and outlet. The study also analyzed the steady-state fluid dynamic force of the improved structure cone valve. Combining the CFD calculation results with the established axial vibration and dynamic models of the valve core spring system, a system dynamics simulation model was developed. Innovatively, the study combined experimental and simulation methods to investigate the vibration characteristics of the cone valve and the impact of steady-state fluid dynamic force on these characteristics. The experimental results aligned well with the simulation results, showing that the influence of steady-state fluid dynamic force on vibration characteristics is similar to that of spring force. At a small opening degree, the compensation structure of steady-state fluid dynamic force can reduce axial vibration amplitude. Increasing the inlet pressure from 2.0 MPa to 2.5 MPa results in a decrease in axial amplitude and an increase in the numerical value of the vibration balance position. Increasing the outlet pressure from 0.5 MPa to 0.9 MPa initially decreases axial amplitude and axial waveform factor, followed by an increase. Increasing the spring preload from 9.4 mm to 13.4 mm leads to a decrease in the numerical value of the balance position, a reduction in amplitude, and a decrease in the waveform factor of the axial vibration of the valve core. The study reveals systematic effects of inlet pressure, outlet pressure, and spring preload on the vibration characteristics of the cone valve. The research results in this paper can provide theoretical support for the structural design of hydraulic valves, reduce the impact of fluid dynamics on vibration, and thereby improve the stability of hydraulic system operation.

Suspension of a point-mass-loaded filament in non-uniform flows: Passive dynamics of a ballooning spider

Spiders utilize their fine silk fibers for their aerial dispersal, known as ballooning. With this method, spiders can disperse hundreds of kilometers, reaching as high as 4.5 km. However, the passive dynamics of a ballooning model (a highly flexible filament and a spider body at the end of it) are not well understood. Here, we introduce a bead–spring model that takes into account the anisotropic drag of a fiber to investigate the passive dynamics by the various non-uniform flows: (i) a shear flow, (ii) a periodic vortex flow field, and (iii) a homogeneous turbulent flow. For the analysis of the wide range of parameters, we defined a dimensionless parameter, which is called “a ballooning number.” The ballooning number is defined as the ratio of Stokes’ fluid-dynamic force on a fiber by the non-uniform flow field to the gravitational force of a body. Our simulations show that the present model in a homogeneous turbulent flow exhibits the biased characteristic of slow settling with increasing turbulence. Upon investigating this phenomenon for a shear flows, it was found that the drag anisotropy of the filament structure is the main cause of the slow settling. Particularly, the cause of slow settling speed lies not only in the deformed geometrical shape but also in its generation of fluid-dynamic force in a non-uniform flow. Additionally, we found that the ballooning structure could become trapped in a vortex flow. These results help deepen our understanding of the passive dynamics of spiders ballooning in the atmospheric boundary layer.

On aeroelastic flutter assessment of thick nanoshell convening two-phase fluid flow using mathematical simulation and deep-neural networks

It is well known that flow-induced vibration occurs often in many different sectors. Dynamic fluid forces are produced by the flow, and these forces cause the system to become excited. One of the most prominent flows in nature and industrial domains, such as industrial facilities, is the multiphase flow which may contribute to creating noise and vibration. As one specific example of a multiphase flow, a two-phase flow relies heavily on flow arrangement for its characteristics. Furthermore, despite the most recent developments and advancements, flow-induced vibration is still considered an open topic. So, in this work, for the first time, frequency analysis of a thick nanoshell convening two-phase fluid flow subjected to aerodynamic pressure is presented. Via nonlocal strain gradient theory (NSGT), Hamilton's principle, trigonometric shear deformation theory, the reappraisal of the fluid-structure interaction relation, and non-conservative aerodynamic pressure formulation, the governing equations, and various boundary conditions of the system are presented. After that, using the generalized differential quadrature method (GDQM) the obtained governing equations are solved, numerically. For more verification of the results, the results are compared with the outcomes of the artificial neural network (ANN) model. For this purpose, the obtained results using mathematical modeling are presented to generate the training dataset and test dataset of the neural network in batches. Finally, some suggestions for improving the stability of the thick nanoshell convening two-phase fluid flow subjected to aerodynamic pressure are presented for future handbooks.

Fluid–structure interaction with a Finite Element–Immersed Boundary approach for compressible flows

This paper presents the mathematical modeling and numerical simulations of fluid–structure interaction (FSI) problems. The fluid domain is discretized using a Cartesian block-structured mesh and solved using the Finite Volume Method (FVM), using the LES methodology with Smagorinsky turbulent closure model. The fluid flow in the system is considered compressible, with properties that vary. The Immersed Boundary Method (IBM) is used to model the solid–fluid interface, and the structure deformation was solved using the Finite Element Method (FEM). The Multi-direct Forcing Scheme is used to calculate the fluid-dynamics forces through the IBM. After calculating the fluid forces exerted on the solid, the forces are interpolated and transferred to the FEM model, providing the deformation of the structure at each time step. The structural domain was discretized with Hexahedral eight-noded element with extra shape functions. The simulations were carried out using MFSIm (in-house code), a multiphysics simulation framework developed by the Fluid Mechanics Laboratory of the Federal University of Uberlândia with financial support from Petrobras. This paper demonstrates the practical application of FSI analysis in an industrial context, specifically focusing on a pipeline system within a Fluid Catalytic Cracking Unit (FCCU) used in the oil and gas industry. The analysis involves the use of butterfly valves positioned at different angles of opening. The results are treated statistically, and a surface response is generated. Machine learning is employed to predict the surface response, showing the valve configurations that yield the maximum and minimum displacement magnitudes of the evaluated structural probes.

Visual analysis of interface deformation in multiphase flow

In multiphase flows, the evolution of fluid-fluid interfaces is of interest in many applications. In addition to fluid dynamic forces governing the flow in the entire volume, surface tension determines droplet interfaces. Here, the analysis of interface kinematics can help in the investigation of interface deformation and the identification of potential breakups. To this end, we developed a visualization technique using metric and shape tensors to analyze interface stretching and bending. For interface stretching, we employ the eigenpairs of the metric tensor defined for the deformation rate of the fluid surface. For interface bending, we present a technique that locally captures the interface curvature change in terms of a shape tensor, extracting its principal directions and curvatures. We then visualize interface deformation by combining both representations into a novel glyph design. We apply our method to study multiphase flow simulations with particular emphasis on interface effects. These include the interplay between fluid dynamics and surface tension forces leading to breakup processes following droplet collisions, as well as droplet-droplet interactions of different fluids where Marangoni convection along the surface is explicitly taken into account.Graphical abstract

Compression and consolidation characteristics analysis of waste tire powder bed during gas pressurization

Pressurized conveying of waste tire powder was one of the key challenges in the feeding process. In this paper, the characteristics of powder bed compression behaviors during gas pressurization were studied by a visualization tank. Compared with the pulverized coal, the higher compressibility of waste tire powder bed revealed the serious consolidation problem in the high-pressure hopper. The source of bed consolidation was fluid dynamic force and constrained space. The intrusion probe was applied to the consolidation test of the compressed powder bed. The results showed that the gas pressurization enhanced the consolidation and the consolidation distribution existed along the axial direction. The maximum relative intrusion resistance was located at the compaction height of bed from 10.2 % to 22.2 %. This study was helpful in further optimizing the operation of pressurized conveying in the dry-fed gasification process of waste tire powder.

Turbine Inlet Valve’s Self-Excited Vibrations Risk the Safe Operation of Hydropower Plants

PurposeThe main function of the turbine inlet valve (TIV) in a hydroelectric power plant is to prevent flow of water to the turbine whenever the turbine is not operating. Usually, the valve responsible for this operation is spherical with annular seals to perform the sealing function. Occasionally, when the valve is set into a closed orientation, the annular seal may not execute its sealing function properly though develop periodic oscillations accompanied by periodic leakage flows. These seal vibrations cause pressure fluctuations in the penstock pipeline, which risks the plant’s reliable and safe operation. Therefore, the primary goal of this research is to present a simplified theoretical model, able to clarify the excitation mechanism of the periodic seal vibration and simulate the plant’s transient behavior. Afterwards, develop some recommendations to enhance the stable operation of the (TIV).MethodsThe system governing equations comprises the water hammer equations to model the water flow through the various pipelines, the vibrating seal equation of motion, and the system boundary conditions.ResultsThe dynamic instability of the (TIV) vibrations is more likely to arise at higher input reservoir energy levels and at the first harmonic of the seal oscillation. In addition, modifying the (TIV) by increasing pilot pipeline head losses and reducing its diameter can eliminate the (TIV) vibrations and warrant the plant’s safe operation.ConclusionResults revealed that fluid compressibility and acoustic transmission have a decisive effect on the fluid-dynamic forces acting on the seal and the (TIV) stability. In addition, the origin of the (TIV) vibrations is the valve leakage flow through the service seal.

Regulation of the swimming kinematics of lampreys Petromyzon marinus across changes in viscosity.

The bodies of most swimming fishes are very flexible and deform as result of both external fluid dynamic forces and internal musculoskeletal forces. If fluid forces change, the body motion will also change unless the fish senses the change and alters its muscle activity to compensate. Lampreys and other fishes have mechanosensory cells in their spinal cords that allow them to sense how their body is bending. We hypothesized that lampreys (Petromyzon marinus) actively regulate body curvature to maintain a fairly constant swimming waveform even as swimming speed and fluid dynamic forces change. To test this hypothesis, we measured the steady swimming kinematics of lampreys swimming in normal water, and water in which the viscosity was increased by 10 or 20 times by adding methylcellulose. Increasing the viscosity over this range increases the drag coefficient, potentially increasing fluid forces up to 40%. Previous computational results suggested that if lampreys did not compensate for these forces, the swimming speed would drop by about 52%, the amplitude would drop by 39%, and posterior body curvature would increase by about 31%, while tail beat frequency would remain the same. Five juvenile sea lampreys were filmed swimming through still water, and midlines were digitized using standard techniques. Although swimming speed dropped by 44% from 1× to 10× viscosity, amplitude only decreased by 4%, and curvature increased by 7%, a much smaller change than the amount we estimated if there was no compensation. To examine the waveform overall, we performed a complex orthogonal decomposition and found that the first mode of the swimming waveform (the primary swimming pattern) did not change substantially, even at 20× viscosity. Thus, it appears that lampreys are compensating, at least partially, for the changes in viscosity, which in turn suggests that sensory feedback is involved in regulating the body waveform.

A study on unsteady fluid-dynamic force characteristics of a pitching wing with leading edge protuberance

A study on unsteady fluid-dynamic force characteristics of a pitching wing with leading edge protuberance

Vortex force map for incompressible multi-body flows with application to wing–flap configurations

The vortex force map method for incompressible viscous flows with multiple bodies is derived in this work. The method breaks the fluid force into inertial, vortex-pressure, viscous-pressure and skin-friction components, and it could be used to analyse the fluid dynamic forces on individual bodies in a multi-body assembly. For the first time, we provide a graphical representation of the vortex-pressure force – the vortex force map – for individual bodies in a multi-body assembly. We have shown that the vortex force map in a multi-body set-up differs from single-bodied counterparts from modifications to their hypothetical potential through a nonlinear cross-coupling, and that the inertial and viscous-pressure contributions contain influences from other bodies explicitly. We then demonstrate the multi-body vortex force decomposition method with a wing–flap starting flow problem using computational fluid dynamics data, identifying the positive and negative force-generating critical regions or directions. It is found that the dominant force is the vortex-pressure force, and the force variation against time is closely related to the evolution of the vortex structures. Furthermore, we showed that the existence of another body significantly alters the force contribution roles of vortices in the flow.

Study on the Model and Law for Radial Leakage of Drilling Fluid in Fractured Formations.

The economic loss caused by fracture leakage accounts for 90% of all leakage costs; thus, it is necessary to find the factors that affect the leakage and to study the leakage laws of fractured strata. The advantage of this article is that we introduced fracture index deformation and fracture tortuosity parameters to characterize fracture roughness and fracture characteristic parameters using the logging data analysis method. To explore the mechanism of leakage in essence, this paper, based on fluid mechanics, improves the radial leakage model by adopting the Herschel-Bulkey (H-B) flow type drilling fluid with high calculation accuracy and comprehensively considering the factors such as drilling fluid performance parameters, fracture roughness characteristic parameters, pressure difference between the wellbore and formation, and radial extension length of the drilling fluid. The advantage of the model is that it is solved in an absolutely stable backward Euler difference format. The numerical simulation is carried out by MATLAB. The simulation results revealed that the leakage rate increased as the fracture index deformation coefficient and the fracture opening increased. The leakage rate also increased as the fracture tortuosity parameters decreased and as the fracture smoothened. However, the leakage rate decreased as the drilling fluid consistency coefficient increased. Drilling fluid dynamic shear force had a minor effect on the leakage rate. The higher the pressure difference between the wellbore and the formation, the higher the leakage rate. As the drilling fluid intrusion depth increased, the leakage rate decreased until it reached 0. Two parameters were mainly controlled in order to control the degree of leakage: differential pressure and fracture static width, which has important guiding for adjusting the drilling fluid density and predicting leaks in the field. The solution method of the model in this paper has a certain reference value for the solution of other models in the future. The conclusion can provide reference for numerical simulation, laboratory test, and field application in the future.

Increasing vortex-induced vibration-based energy harvesting using a nature-inspired bluff body: An experimental study

The present study investigates the effect of changes on the cross-sectional geometry of a flow-induced vibration-based energy harvester. To do so, a bio-inspired geometry, which is adopted from the ‘Amaryllis’ flower is utilized. The fluid dynamic acting forces are numerically studied for the Reynolds numbers between 100 and 5000. Based on the attack angles of the so-called convex and concave petal cylinders are proposed, and three geometrical configurations with six, eight, and ten petals are considered. Furthermore, the concave and the convex cylinders’ vortex interaction and near wake flow are experimentally studied for two Reynolds numbers, employing Particle Image Velocimetry (PIV). A proportional relation was found between the enhancement of fluid dynamic forces and the shortening of vortex formation length that would improve Vortex-Induced Vibration (VIV). Finally, validated lift coefficients are employed in the analytically derived electromechanical equation of motion for the VIV-based energy harvester. It is shown that the newly proposed nature-inspired system can effectively increase the amount of harvested energy.

Mechanical fragmentation and thermal erosion of dyke adjacent host rocks induced by fluid-dynamic shear stress and latent heat release in response to turbulent magma flow

We present a quantitative account of the thermodynamical and fluid-mechanical aspects of granitic host rock erosion related to dyke emplacement by considering the latent heat released from the dyke, subsequent thermal damage, and erosion processes. When these processes are coupled with the fluid-dynamic shear forces induced by magma turbulence, they provide the main driving force for mechanical fragmentation and xenolith entrainment. To make these inferences, we have estimated the Reynolds Number related to magma flow in a series of well-exposed dykes in Eastern India. We define the thresholds of turbulent to laminar flow based on Reynolds Numbers, where values over 2000 indicate that the magma had flowed turbulently. In these cases, both thermal erosion and fluid-dynamic shear stresses would have combined to fragment the adjacent host rock. Equations for the conservation of mass are derived and presented in order to quantify the complex interactions between magma and cold host rock. We further propose a novel linear integro-differential equation to determine xenolith size resulting from internal collisions and secondary fragmentation. Our model and results will be helpful in interpreting magma flow characteristics, magmatic evolution, and host rock entrainment processes in exposed outcrops of magmatic intrusions.

The role of adhesive receptor patterns on cell transport in complex microvessels.

Cell transport is governed by the interaction of fluid dynamic forces and biochemical factors such as adhesion receptor expression and concentration. Although the effect of endothelial receptor density is well understood, it is not clear how the spacing and local spatial distribution of receptors affect cell adhesion in three-dimensional microvessels. To elucidate the effect of vessel shape on cell trajectory and the arrangement of endothelial receptors on cell adhesion, we employed a three-dimensional deformable cell model that incorporates microscale interactions between the cell and the endothelium. Computational cellular adhesion models are systematically altered to assess the influence of receptor spacing. We demonstrate that the patterns of receptors on the vessel walls are a key factor guiding cell movement. In straight microvessels, we show a relationship between cell velocity and the spatial distribution of adhesive endothelial receptors, with larger receptor patches producing lower translational velocities. The joint effect of the complex vessel topology seen in microvessel shapes such as curved and bifurcated vessels when compared to straight tubes is explored with results which showed the spatial distribution of receptors affecting cell trajectory. Our findings here represent demonstration of the previously undescribed relationship between receptor pattern and geometry that guides cellular movement in complex microenvironments.

Aerodynamic coefficients of irregular non-spherical particles at intermediate Reynolds numbers

In industrial processes such as those related with paper industry, coal or biomass combustion, particles can take irregular non-spherical shapes. However, in related numerical computations the assumption of spherical particle is customary, mainly because the fluid dynamic forces acting on such irregular particles are unknown to a large extent. This contribution aims to generate new information about the flow resistance coefficients (forces and torques) experienced by non-spherical irregular-shaped particles with three different degrees of sphericity ψ (0.7, 0.8 and 0.89) immersed in a uniform flow at intermediate Reynolds numbers (i.e. Re = 1–200). For this purpose, Particle Resolved Direct Numerical Simulations (PR-DNS) are carried out by means of the Ansys-Fluent code using body fitted meshes where the irregular particle is well resolved. The flow coefficients are computed for a set of different particles belonging to the same sphericity group, considering a large number of orientations, which allows the construction of the corresponding distribution functions. Such distributions depend on Reynolds number and particle sphericity and can be reasonably well approximated by Gaussian distributions, which are determined by a mean value and a standard deviation. The obtained drag, lift and torque coefficients display expectedly a scattering around the mean values with a high sensitivity to the irregularity of the surface and particle intrinsic aspect ratio (φ). Additionally, the distribution of the angle formed between the transverse lift force and the transverse torque in the plane orthogonal to the flow direction is computed. The generated information will be used to further pursue a novel statistical model for the fluid dynamic forces and torques acting on irregular particles in the frame of the Lagrangian approach.

Vortex Ring Formed by a Butterfly Wing and Dynamic Forces

Butterfly generates unsteady dynamic fluid force with a pair of vortex rings. In order to elucidate the flight mechanism of butterflies, it is necessary not only to clarify the vortex rings formed around the wings but also elucidate the characteristics of the unsteady fluid force generated by the flapping motion. By applying the momentum theory to the vortex rings formed during flapping motion, it is possible to estimate the force generated by flapping motion. In this study, we reconstruct a pair of vortex rings formed by flapping motion based on a small number of visualization results and elucidate dynamic fluid force characteristics. A part of estimation result of Lift estimated by the rough shape vortex rings generated by downstroke and upstroke do not match with the direct measurement result. But not only the peak value of estimation result of Lift is near with the direct measurement result quantitatively but also the value of estimation result between upstroke is a small negative as well as the direct measurement result. Although there is a phase difference between the estimation result and direct measurement result, there is a qualitative and quantitative agreement between estimation results and direct measurement result. From those results, butterfly generate the unsteady dynamic Lift between downstroke, especially at butterfly spread wing maximum (t/T = 0.40). After that, the unsteady dynamic Lift decrease and become 0 at upstroke.

IMMERSED BOUNDARY METHODS FOR THERMOFLUIDS PROBLEMS

We review the progress in the development and application of immersed boundary (IB) methods to thermofluids problems achieved in the last three decades. The implementation of different heat transfer boundary conditions, ranging from Dirichlet, Neumann, and Robin to conjugate heat transfer, are discussed for continuous as well as discrete forcing immersed boundary methods. We review several key studies that developed and employed IB methods with stationary boundaries for a variety of heat transfer scenarios such as forced convection, natural or mixed convection, radiation, and combustion. The computational challenges associated with the approaches employed for thermofluids problems with moving boundaries are discussed in detail. These include problems with rigid bodies that move under the influence of fluid dynamic forces as well as flow-induced deformation of compliant bodies. We conclude the article by briefly discussing the implementation of immersed boundary methods in two emerging areas: bioheat transfer and high-speed compressible flows.