Hydrodynamic Drag Force Research Articles

Motion through spherical droplet with non-homogenous porous layer in spherical container

The problem of the creeping flow through a spherical droplet with a non-homogenous porous layer in a spherical container has been studied analytically. Darcy’s model for the flow inside the porous annular region and the Stokes equation for the flow inside the spherical cavity and container are used to analyze the flow. The drag force is exerted on the porous spherical particles enclosing a cavity, and the hydrodynamic permeability of the spherical droplet with a non-homogeneous porous layer is calculated. Emphasis is placed on the spatially varying permeability of a porous medium, which is not covered in all the previous works related to spherical containers. The variation of hydrodynamic permeability and the wall effect with respect to various flow parameters are presented and discussed graphically. The streamlines are presented to discuss the kinematics of the flow. Some previous results for hydrodynamic permeability and drag forces have been verified as special limiting cases.

Application of wake oscillators to two-dimensional vortex-induced vibrations of circular cylinders in oscillatory flows

A nonlinear time-domain simulation model for predicting two-dimensional vortex-induced vibration (VIV) of a flexibly mounted circular cylinder in planar and oscillatory flow is presented. This model is based on the utilization of van der Pol wake oscillators, being unconventional since wake oscillators have typically been applied to steady flow VIV predictions. The time-varying relative flow–cylinder velocities and accelerations are accounted for in deriving the coupled hydrodynamic lift, drag and inertia forces leading to the cylinder cross-flow and in-line oscillations. The system fluid–structure interaction equations explicitly contain the time-dependent and hybrid trigonometric terms. Depending on the Keulegan–Carpenter number (KC) incorporating the flow maximum velocity and excitation frequency, the model calibration is performed, entailing a set of empirical coefficients and expressions as a function of KC and mass ratio. Parametric investigations in cases of varying KC, reduced flow velocity, cylinder-to-flow frequency ratio and mass ratio are carried out, capturing some qualitative features of oscillatory flow VIV and exploring the effects of system parameters on response prediction characteristics. The model dependence of hydrodynamic coefficients on the Reynolds number is studied. Discrepancies and limitations versus advantages of the present model with different feasible solution scenarios are illuminated to inform the implementation of wake oscillators as a computationally efficient prediction model for VIV in oscillatory flows.

Hydrodynamic drag force on a sphere approaching a liquid-liquid interface

The difficulties involved in trying to model the motion of a solid particle through surfaces, particularly at the liquid-liquid interface, are mainly due to the continuous deformation of the surface, not only as the particle progresses through the surface, but also before its penetration into the lower liquid. This study investigated experimentally and theoretically, the hydrodynamic drag force on a sphere approaching a liquid-liquid interface. The experiment ball material of steel of different ball diameters ranging from 1.5E-3 to 8.69E-3m in four immiscible liquids of distilled water, kerosene, glycerol and engine oil of densities; 1000 kg/m3, 820 kg/m3, 1260 kg/m3 and 848.3 kg/m3 respectively, were considered. The drop either penetrated the interface without opposition, or spent some time at the interface before penetrating, or it remained at interface maintain a certain interface curvature. The mathematical model of the resulting velocities as a function of the size ratio R/R∗ was obtained. The Stinson and Jeffry technique was modified in the theoretical analysis (one ball internal to the other - the larger ball providing curved surface at contact) and using MATLAB algorithm obtained the correction factor to the velocity and hence the hydrodynamic drag force was obtained. The model mathematical equation for the velocity was found comparable to those obtained experimentally. The hydrodynamic drag forces calculated theoretically and experimentally were further analyzed using ANOVA for same size ratio R/R∗ of 0.83. It was found that for steel balls, the experimental and theoretical results are significantly the same confirming the validity of the mathematical model and this work. This kind of study is valuable in biomechanics in the area of blood flow in arteries and capillaries. It is also important in determining the motion of small particles or macromolecules near permeable surfaces, and determining particle deposits on reverse osmosis, mineral filtration, and dialysis or drip irrigation surfaces.

Direct Numerical Simulations of Horizontally Oblique Flows Past Three-Dimensional Circular Cylinder Near a Plane Boundary

Abstract Understanding hydrodynamics of a free-spanning pipeline subjected to omni-directional flows is important to engineering design. In this study, horizontally oblique flows past a three-dimensional circular cylinder in the vicinity of a plane boundary are numerically investigated using direct numerical simulations. Parametric studies are carried out at the normal Reynolds number of 500, a fixed gap-to-diameter ratio of 0.8 and five flow inclination angles (α) ranging from 0 deg to 60 deg with an increment of 15 deg. Two distinct vortex-shedding modes are observed: parallel (α ≤ 15 deg) and oblique (α ≥ 30 deg) vortex shedding. The wake evolution is further divided into two or three stages depending on α. The occurrence of the oblique vortex shedding is accompanied by the base pressure gradient along the cylinder span and the resultant axial flows near the cylinder base. The total hydrodynamic drag and lift force coefficients decrease from being the parallel mode to the oblique mode, owing to the intensified three-dimensionality of wake flows and the phase differences in the spanwise vortex shedding. The independence principle (IP) is found to be valid in predicting hydrodynamic forces and wake patterns when α ≤ 15 deg. This IP might produce unacceptable errors when α > 15 deg. In comparison with the mean drag force, the fluctuating lift force is more sensitive to the inclination angle. The IP validity range is substantially smaller than that in the case of flow past a wall-free cylinder. Such finding would be practically useful for vortex-induced vibration prediction.

Dynamic Response of Swimming Paramecium Induced by Local Stimulation Using a Threadlike-Microtool

In this letter, an approach for realizing local area stimulation of single motile microorganism ( Paramecium ) by a microtool is described. In order to overcome the hydrodynamic drag force acting on the thin and long tool in the fluidic environment, a magnetic compensation approach to improve the positioning accuracy of the metallic microtool is introduced. The permanent magnets’ arrangement that reduced the vertical component and enhanced the horizontal component of the magnetic force is modeled and clarified through numerical simulations and actual experiments on the microtool with a diameter of 50 μm. As a result, the positioning accuracy of the microtool using the magnetic compensation is improved to approximately 200 μm. Finally, the performance and practicality of the integrated platform are confirmed by conducting experiments on a freely swimming Paramecium . By virtue of the low fluidic disturbance generated by the microtool, the stimulation did not cause a tracking failure and the dynamic reaction of the Paramecium is confirmed without any immobilization manners for the first time ever. The avoiding reactions in response to mechanical stimulation are evaluated by analysing the captured image data with a spatial resolution of less than 5 μm and a time resolution of less than 5 ms.

AN ACOUSTIC ANTIFOULING STUDY IN SEA ENVIRONMENT FOR SHIP HULLS USING ULTRASONIC GUIDED WAVES

Biofouling results in a range of adverse issues for ships and boats such as an increase in hydrodynamic drag force and fuel consumption and increased maintenance cost. To address this issue, toxic antifouling coatings have been developed. However, these toxic coatings can pose threats to marine life. This has led to research on less harmful techniques such as acoustic methods in the main implemented as laboratory trials. In fact, there have been relatively few sea trials and these are poorly documented. The current work has performed one of the few implemented field trials and the only one to be fully documented. In this sea trial, an optimised array of transducers generating ultrasound guided waves was attached to a hull representative plate in a port environment. The results of this work are evidenced by the significant reduction in-situ of a wide range of biofouling materials and organisms. The documented photographical evidence makes up for its scarcity in the published records of antifouling advances using acoustic techniques.

Neuro-Fuzzy Dynamic Position Prediction for Autonomous Work-Class ROV Docking.

This paper presents a docking station heave motion prediction method for dynamic remotely operated vehicle (ROV) docking, based on the Adaptive Neuro-Fuzzy Inference System (ANFIS). Due to the limited power onboard the subsea vehicle, high hydrodynamic drag forces, and inertia, work-class ROVs are often unable to match the heave motion of a docking station suspended from a surface vessel. Therefore, the docking relies entirely on the experience of the ROV pilot to estimate heave motion, and on human-in-the-loop ROV control. However, such an approach is not available for autonomous docking. To address this problem, an ANFIS-based method for prediction of a docking station heave motion is proposed and presented. The performance of the network was evaluated on real-world reference trajectories recorded during offshore trials in the North Atlantic Ocean during January 2019. The hardware used during the trials included a work-class ROV with a cage type TMS, deployed using an A-frame launch and recovery system.

Estimation of damping induced by taut mooring lines

A moored floating structure may exhibit resonant motion responses to low-frequency excitations. Similar to the resonant responses of many vibration systems, the motion amplitude of a moored floating structure is significantly affected by the damping of the entire system. In such cases, the damping contributed by the mooring lines sometimes accounts for as much as 80% of the total damping. While the damping induced by catenary mooring lines is well-investigated, few studies have been conducted on the damping induced by taut mooring lines, especially one partly embedded in soil. The present study develops a simple but accurate model for estimating the damping contributed by mooring lines. A typical type of taut mooring line was used as the reference and the hydrodynamic drag force and soil resistance were taken into consideration. The proposed model was validated by comparing its predictions with those of a previously developed model and experimental measurements obtained by a physical model. Case studies and sensitivity studies were also conducted using the validated model. The damping induced by the soil resistance was found to be considerably smaller than the hydrodynamic damping. The superposition of the wave frequency motion on the low-frequency motion was also observed to significantly amplify the damping induced by the mooring lines.

Numerical Simulation of Mechanical Characteristics of a Metal Net for Deep-Sea Aquaculture

The investigation on hydrodynamic characteristics of a cage is important for its application in the deep-sea aquaculture in our country. With finite element method, the beam element is used to simulate a three-dimensional metal chain net, and the connector element is introduced as the interaction between metal net lines. A mechanical model for the metal net is constructed to simulate the hydrodynamic characteristics of a metal net subjected to fluid current forces. The static simulation results show that the relative errors of the displacements are 2.13%, 4.19%, 6.64%, and 11.35% compared with static concentrated load tests under concentrated forces of 20, 40, 60, and 80 N, respectively. Both the transient hydrodynamic deformations and drag forces of the netting structures under different current velocities are obtained by solving the hydrodynamic equation of the netting structure. The average relative error of the current forces obtained by numerical simulations shows an 8.13% deviation from the drag tests of the metal nets in the tank under five current velocities. The effectiveness and precision of the simulation approach are verified by static and dynamic tests. The proposed simulation approach will provide a good foundation for the further investigation of the hydrodynamic characteristics of deep-sea aquaculture metal cages and the parameter design for the safety of such cage systems.

Role of Hydrodynamic Interactions in the Deformation of Star Polymers in Poiseuille Flow

Stretching polymer in fluid flow is a vital process for studying and utilizing the physical properties of these molecules, such as DNA linearization in nanofluidic channels. We studied the role of hydrodynamic interactions (HIs) in stretching a free star polymer in Poiseuille flow through a tube using mesoscale hydrodynamic simulations. As increasing the flow strength, star polymers migrate toward the centerline of tube due to HIs, whereas toward the tube wall in the absence of HIs. By analyzing the end monomer distribution and the perturbed flow around the star polymer, we found that the polymer acts like a shield against the flow, leading to additional hydrodynamic drag forces that compress the arm chains in the front of the star center toward the tube axis and lift the arm chains at the back toward the tube wall. The balanced hydrodynamic forces freeze the polymer into a trumpet structure, where the arm chains maintain a steady strongly stretched state at high flow strength. In contrast, the polymer displays remarkably large conformational change when switching off HIs. Our simulation results explained the coupling between HIs and the structure of star polymers in Poiseuille flow.

Active Floating with Buoyancy of Pseudopodia Versus Passive Floating by Hydrodynamic Drag Force: A Case Study of the Flat-Shaped Spumellarian Radiolarian Dictyocoryne

It has been suggested that the pseudopodia of radiolarians play a role in controlling buoyancy for floating behaviour. To understand the function of pseudopodia in terms of planktonic capability, we performed culture experiments on the flat-shaped radiolarian Dictyocoryne. A glass cell, a stereomicroscope and an X-Y-Z stage were used to observe the behaviour of Dictyocoryne from a lateral view. Under static conditions, Dictyocoryne grounded on the bottom of the glass cell extended pseudopodia from both sides of the flat disc surface. Subsequently, these individuals rose slightly by a length equal to that of the extended pseudopodia but remained attached to the bottom. These results suggest that Dictyocoryne lacks the ability to surface by obtaining buoyancy through the emergence of pseudopodia. Under conditions of convection flow, Dictyocoryne moved in the downstream direction only when pseudopodia were completely extended. When the convection flow moved upward, the individuals moved with the flow to just under the surface. In addition, convection flow changed the direction of a long, thick pseudopodium, called the axoflagellum, to be parallel with the flow. Consequently, the axoflagellum was always oriented towards the downstream side, being the disc face in the axoflagellum side on the upturn. Given that the flat-shaped spumellarians have symbiotic algae inside their cells, their unique planktonic capability leads to the stable efficiency of the algal photosynthesis.

Bio-inspired robotic dog paddling: kinematic and hydro-dynamic analysis

Research on quadrupedal robots inspired by canids or felids have been widely reported and demonstrated. However, none of these legged robots can deal with difficult environments that include water, such as small lakes, streams, rain, mud, flooded terrain, etc. In this paper, we present for the first time a kinematic analysis and a hydrodynamic model of dog paddling motion in a robotic system. The quadrupedal paddling gait of dogs was first analyzed based on underwater video recording. Hydrodynamic drag force analysis in a paddling gait cycle was conducted for a prototype robotic dog. The prototype robotic dog was developed using four pre-charged pneumatics soft actuators with consideration of relative positions of CG (center of gravity) and CB (center of buoyancy) and their dynamic variation in paddling. It was found that such soft actuators have great potential in developing amphibious legged robots, because they are inherently water-tight, anti-rusty, simple in structural design, and have large hydrodynamic advantage due to their mostly hemi-cylindrical shape design. Trotting and paddling of the prototype robotic dog was also demonstrated. It is believed that our findings reported in this research will provide useful guidance in future development of amphibious robotic dogs.

Investigation of particle detachment from the rotating wheel in indoor environment

There are various wheels are required for indoor activities, such as spinning bike wheels in the gym, various mechanical equipment wheels in the factory. Obviously, these rotational movements of wheels will cause the detachment of particles adhering to the wheel. This common phenomenon is regarded as an important contributor to particulate matter concentrations in indoor environment. The work performed in this study mainly focused on the description and understanding of the process of particles detachment from the rotating wheel into the air. A set of theoretical models were proposed to clarify particle detachment mechanisms. Since the detachment occurs when the sum of external force moments exceed the maximum adhesion resistance moment, different forces acting on the particles should be considered before the particles detached. There are adhesion forces between the particles and the wheel surface, hydrodynamic forces acting on the particles and centrifugal forces due to the rotating wheel. In order to verify models, the corresponding experiments were carried out and the experimental results were quite consistent with the calculation results of models. Results showed that adhesion force, hydrodynamic drag force and centrifugal force were important and critical detachment diameters of particles adhering to the wheel can be influenced by these forces. Effects of different relevant parameters on these forces, including surface roughness, wheel speed, particle size were analysed. Higher roughness, larger particle and faster wheel speed are more conducive to the detachment of particles.

Investigation of mechanical and magnetophoretic focusing for magnetic flow cytometry

Abstract As an alternative to optical flow cytometry, magnetic flow cytometry has emerged in recent years for single cell analysis with sheath-less flow conditions. Instead of measuring scattered light, magnetic fields of magneticallylabeled cells are recorded and analyzed. To determine microfluidic opportunities to manipulate cell trajectories for in-situ cell focusing we use mechanical guiding structures and magnetophoretic forces. A 3D-microfluidic particle simulation has been implemented that revealed parameters ensuring the crucial balance between hydrodynamic drag and magnetophoretic forces. Experimental measurements verified the 3D particle tracking simulation.

Numerical study on the hydrodynamic drag force of a container ship model

In recent years, importance has been recognized increasingly for the reduction of fuel consumption of ships in a seaway to reduce green-house gas emissions from shipping. From a ship design viewpoint, it is of crucial importance to establish reliable prediction methods for ship’s resistance and propulsive power. The required power for the propulsion unit depends on the ship resistance and speed. There are three solutions for the prediction of ship resistance as follow analytical methods, model tests in tanks and Computational Fluid Dynamics (CFD). The rapid developments in computers and computational methods increased the opportunities of the CFD simulation to be used in the ship design process. The present paper aims at simulating ship resistance using CFD simulations method which is conducted using ANSYS-CFX software package. As a case study, Container ship scale model is investigated. The results show the ship resistance which calculated at various ship speeds and Froude number. Predicted results for resistance components at various Froude numbers were compared against Resistance results computed by using Holtop method. It is shown that the simulation results agree fairly well with the results computed from Holtrop method, and that ANSYS-CFX code can predict ship resistance.

Effect of Magnetic Field on the Steady Viscous Fluid Flow Around a Semipermeable Spherical Particle

An analytical solution is presented for the steady axisymmetrical Stokes flow of an electrically conducting viscous incompressible fluid through a partially permeable sphere subjected to a uniform transverse magnetic field. The considered flow is divided into two regions, outer viscous fluid region and inner semipermeable region, which are governed by modified Stokes and Darcy’s law respectively due to the presence of magnetic field in the flow regions. The boundary conditions used at the interface are continuity of normal component of velocity, vanishing of tangential component of velocity and continuity of pressure at the surface in contact with the fluid and the semipermeable sphere. An expression for drag force acting on the semipermeable sphere in presence of magnetic field is obtained. Enhancement of drag force exerted on the particle is seen on application of magnetic field. The effect of Hartmann numbers, permeability parameter on the hydrodynamic drag force were discussed. Some renowned results are obtained as the limiting cases.

Dynamic capture behavior of ferromagnetic particles based on fully coupled multiphysics model of particle-fluid interactions

Wet low-intensity magnetic separation (LIMS) is used in the magnetic separation of ferromagnetic minerals. The performance of the separation is controlled primarily by the internal flow in the separator, governed by the process and machine settings. However, these factors change with the properties of the magnetic material and the operating conditions. Therefore, the numerical calculation of the multiphysics coupling separation process of such dynamic captures becomes crucial for wet LIMS. In this study, we present a novel and straightforward fully coupled multiphysics modeling approach for the simulation of LIMS. In this model, particle tracing in the fluid flow module is used to calculate the location and dynamic capture behavior of ferromagnetic particles under the determined magnetic and flow fields. In particular, while calculating the magnetic force, hydrodynamic drag force, gravity, and centrifugal force, the model also inherently retains its ability to simulate the influence of ferromagnetic–particle–fluid interactions.The model is compared with experiments and the particle capture theory, and is demonstrated to be realistic for studying ferromagnetic suspensions in mineral processing applications. The model provides new possibilities to understand and predict the efficiency of mineral separation processes through detailed computational simulations of the effects of the respective operating conditions on the dynamic capture behavior of the particles.

Axisymmetric creeping motion caused by a spherical particle in a micropolar fluid within a nonconcentric spherical cavity

Abstract The problems of the quasisteady translation and steady rotation of a solid spherical particle located at a non-concentric position of a spherical cavity filled with an incompressible micropolar fluid are investigated semi-analytically in the limit of low Reynolds numbers. General solutions are constructed from the superposition of the basic solutions in the two spherical coordinate systems based at the centers of the particle and cavity. The boundary conditions on the particle surface and cavity wall are satisfied by a collocation numerical method. The hydrodynamic drag force and torque exerted by the fluid on the particle which are proportional to the translational and angular velocities respectively are obtained numerically with good convergence for a range of values of the ratio of particle-to-cavity radii, the relative distance between the centers of the particle and cavity and micropolarity parameter. In the limit of the motion of a spherical particle in a concentric position in the cavity and in the lubrication limit, the hydrodynamic drag force and torque are in good agreement with the available results in the literature. As expected, the boundary-corrected drag force and torque exerted on the particle is a monotonic increasing function of the micropolarity parameter.

Hydrodynamic drag force on porous sphere(s) moving in a Newtonian fluid: Two case studies

Abstract This paper is the first to evaluate numerically the hydrodynamic forces that apply in two case studies that involve a Newtonian fluid and three in-line spheres (case 1) and a sphere that moves in a circular cell (case 2). The hydrodynamic interactions between the spheres in case 1 or between the central sphere and the surrounding spherical wall in case 2 can be ignored at β (= d f 2 k , where df and k are the diameter and permeability of the sphere, respectively) 50 (solid sphere limit). At 0.5 2, in neither case 1 nor case 2 can a steadily moving system form; in the former case, sweep coagulation-like behavior occurs, and in the latter, zone settling-like behavior occurs.

A nonlinear two-degree-of-freedom mass–damper–spring model to predict the isolation of circulating tumor cells in microfluidic-elasto-filtration devices

Circulating tumor cell (CTC) isolation has made positive impacts on metastatic detection and therapy analysis for cancer patients. Microfluidic-elasto-filtration (MEF) device based on the critical elasto-capillary number (Ca * ) has been proposed to utilize the optimal multi-parameter conditions, including cell diameter (dc), the diameter of cylindrical filter pores (dp), nonlinear cell elasticity and hydrodynamic drag force, for selectively capturing CTCs and depleting white blood cells (WBCs). In this paper, we propose a novel two-degree-of-freedom nonlinear mass–damper–spring (m–c–k) model to predict the dynamic behaviors of CTCs and WBCs in a generic MEF device. This model enables the optimization of the device design to achieve extremely high CTC capture efficiency and WBC depletion efficiency. In particular, the function of nonlinear cell stiffness specific to different cell types and MEF’s pore diameters is first determined by finite element method with neo-Hookean hyperelastic model, based on which the mechanical behaviors of CTCs and WBCs in MEF devices are systematically studied. Herein, the predicted normalized deformations of a CTC and WBC as a function of Cae are used to determine the optimized Cae of 0.043, consistent with the experimental results from the fabricated MEF devices using MCF-7 cells (0.04 ± 0.006). In addition, the normalized cell diameter versus Cae phase diagram is proposed for the first time as a useful tool for design optimization of MEF devices and other microfiltration devices.