Water Drag Force Research Articles

Study on influencing factors of hydrodynamics based on AUV docking with conical dock

It is necessary to investigate the dynamic performance during autonomous underwater vehicle (AUV) underwater docking to aid in control and to enhance docking safety. Therefore, in this study, the docking hydrodynamic characteristics (including the docking system’s streamline, velocity vector, and surface pressure during the overall docking process) of the AUV with conical hood dock are determined by using the dynamic grid technology, and the water drag force situations of the AUV docking with conical hood dock are studied from the perspectives of different velocities, accelerations, navigation modes, and structures. Additionally, the multiple nonlinear regression fits and the preliminary docking test were examined. Furthermore, brief inferences obtained are as follows: First, the maximum pressure is situated at the upstream surface of the dock conical hood and the head of the AUV, and the maximum rotation angle of the streamline is situated at the outermost ring of dock conical hood. Within a specified range, the rotation angle of the streamline affected by the conical hood progressively declines as the AUV docks deeper into the conical hood. Second, low velocity uniform docking, deceleration docking, and chase docking can reduce the drag force to a certain extent during docking. Finally, both arc shape and mesh structure can decrease the water drag force of docking to a specified degree. This research provides a theoretical basis and reference methods for the dynamic research of the docking system, and other related research can be carried out through the methods and results of this research.

An innovative light-weight gravity installed plate anchor and its dynamic performance in clayey seabed

This paper presents a series of 1g tests to investigate the performance of an innovative light-weight gravity installed plate anchor (L-GIPLA) with the aid of a reusable booster both in normally consolidated (NC) and lightly over-consolidated (LOC) soils. A micro-electromechanical systems (MEMS) accelerometer was used to measure the dynamic penetration process of the L-GIPLA with a booster in clay. Various factors affecting the final penetration depth of the anchor were investigated, including the soil strength characterisation, impact velocity, anchor shape, booster weight, and water entrainment effects. Based on the data obtained from the MEMS accelerometer, the hydrodynamic aspects associated with the water drag force and water entrainment effect during the dynamic penetration of the L-GIPLA were analysed. Besides, theoretical framework and energy-based models were proposed to predict the final penetration depth of the L-GIPLA. The excess pore water pressure induced by the dynamic penetration of the L-GIPLA and the subsequent dissipation around the anchor were investigated, hence the affected regions of the soil due to the dynamic penetration could be estimated. Finally, the penetration depth ratio and capacity-to-weight ratio of the proposed L-GIPLA were compared with that of other gravity installed anchors.

Computational optimization approach to design a water-jet nozzle for a water-jet loom using the design of experiment method

A water-jet nozzle is widely used on a water-jet loom to carry thread from one side of the loom to the other. The nozzle performance is important for the loom design and is measured in terms of the water drag force. A computational approach is proposed to design and optimize a water-jet nozzle using the design of experiment (DOE) method. Computations were carried by solving the incompressible Navier-Stokes equations with the standard k-e turbulence model. ANSYS Fluent software was used to solve the fluid flow with Minitab software, which was used for optimization of the geometric parameters. The computational results show that the optimized nozzle has better performance than the original nozzle. The computational optimization approach was experimentally confirmed to be useful in designing a water-jet nozzle for water-jet looms.

Numerical Simulation Study on Root Stones Loss in Dam Buttress Engineering

In order to study the loss of root stones under action of water flow in dam buttress, based on Flow-3D, a mathematical model was established. At first, the physical experiment was carried out about water drag force on a 0.04 m×0.04 m×0.04 m cubic block. And then a numerical flume model about this experiment was established in Flow-3D software. The values of drag force were compared between the numerical and experimental results, and the percentage of error was less than 5%. Thus, the numerical model in Flow-3D was accurate and available. Then, a numerical simulation on root stones loss in an actual dam buttress project was carried out. Since the actual flow is turbulent, the RNGk-εturbulence model was used. And VOF method, FAVOR technology, and GMO model were also used in this simulation. The numerical results showed flow depth, pressure, velocity, turbulent energy, and root stones loss. Because water level of the inflow increased with time continuously, flow depth and velocity also increased, and the root stones would be lost. The increase in flow velocity was the fastest in the dam head, and the start time of root stones loss was also the earliest. The most serious area of root stones loss is the dam head, and the serious second area is the upper cross corner. Those root stones would have the farthest lost distance in the dam head. The root stones loss was also serous in the upstream face. However, the root stones in the upstream face and the down cross corner were less affected by water flow, so there were no root stones loss phenomena. Thus, in the actual project, the dam head, the upper cross corner, and the upstream face should get more attention.

Simulation of Sea-ice Thermodynamics by a Smoothed Particle Hydrodynamics Method

Abstract The paper deals with the problem of sea-ice pack motion and deformation under the action of wind and water drag forces. Differential equations describing the behaviour of ice, with its very distinct material responses in converging and diverging flows, express the mass and linear momentum balances on a horizontal plane (the free surface of the ocean). The thermodynamic effects (ice melting and lead water freezing) are accounted for by adding source terms to the equations describing the evolution of the ice thickness and area fraction (concentration). These thermodynamic source terms are described by means of a single function that idealizes typical ice growth-rates observed in winter in the Arctic. The equations governing the problem are solved by a fully Lagrangian method of the smoothed particle hydrodynamics (SPH). Assuming that the ice behaviour can be approximated by a non-linearly viscous rheology, the proposed SPH model was used to simulate the flow of a sea-ice pack driven by wind drag stresses and varying seasonal temperatures. The results of numerical simulations illustrate the evolution of an ice pack, including distributions of ice thickness and ice area fraction in space and time for assumed temperature distributions.

An innovative booster for dynamic installation of OMNI-Max anchors in clay: Physical modelling

An innovative booster concept is proposed to increase both the kinetic and potential energies and hence to increase the penetration depth of the OMNI-Max anchor within the clayey soil with high strength gradient. This paper carried out 1g model tests to investigate the working efficiency of the booster on the anchor penetration depth both in normally consolidated (NC) and lightly over-consolidated (LOC) soils. The similarity relationships of the anchor dynamic penetration within the soil were first deduced, and then a series of dynamic penetration tests were performed to investigate the parameters that influence the anchor penetration depth. The parameters include the soil strength characterisation, impact velocity, booster weight, inclined impacting angle, and water drag and entrainment effects. The anchor dynamic penetration process within the soil was measured by a micro-electromechanical systems (MEMS) accelerometer, through which the soil strain-rate effect and the hydrodynamic aspects including the water drag force and potential water entrainment along the anchor-soil interface were analysed. Finally, energy-based and force-based prediction models were put forward to estimate the penetration depths of OMNI-Max anchors and hybrid anchors (i.e. an OMNI-Max anchor with a booster).

Ice Loads Impact on Spillway Culverts Piers in Lithuania

On the basis of literature analysis and field investigations it was found that piers in spillway culverts suffer most from the ice impacts. Floating ice is a significant hazard to structures - jamming between piers or rubble pile development will modify the effective size of the structure and possibly increase the loads. Ice loads are generally described as ice forces or pressures acting over an area of structure. Ice loads are classified as: static loads, dynamic loads, global loads, local loads. Local ice loads from ice-structure interaction are highly irregular and very hard to model exact. The aim of this work - to evaluate ice loads formed in the ponds of Lithuania and their impact on the spillway culverts piers structures. The ice loads were analysed in this work: 1) the force of moving ice fields in contact with single pier; 2) the force of standing ice field, in the impact due wind and water drag forces; 3) the force from ice jam cutting by pier; 4) the force of ice jam in the perpendicular contact with structure front, 5) the force, which is cutting pier of the ice plug.DOI: http://dx.doi.org/10.5755/j01.mech.24.3.21067

Numerical Investigation of Water Entry Problem of Pounders with Different Geometric Shapes and Drop Heights for Dynamic Compaction of the Seabed

The water entry problem of three-dimensional pounders with different geometric shapes of cube, cylinder, sphere, pyramid, and cone was numerically simulated by the commercial software Abaqus, and the effects of pounder shape and drop height from the free surface of water on deepwater displacement and velocity as well as pinch-off time and depth were investigated. An explicit dynamic analysis method was employed to model fluid-structure interactions using a Coupled Eulerian-Lagrangian (CEL) formulation. The simulation results are verified by showing the computed shape of the air cavity, displacement of sphere, pinch-off time, and depth which all agreed with the experimental results. The results reveal that the drag force of water has the highest and lowest effect on cubical and conical pounders, respectively. Increasing the pounder drop height up to the critical height leads to increased pounder velocity while impacting the model bed and more than the critical drop height has a reverse effect on pounder impact velocity. Pinch-off time is a very weak function of pounder impact velocity; but pinch-off depth increases linearly with increased impact velocity.

CFD simulation of the unsteady flow of a single coal log in a pipe

AbstractThis study proposes a numerical simulation of the unsteady turbulent flow of a single coal log in a pipe using a dynamic mesh method. An eccentric two‐dimensional dynamic model is developed in FLUENT 6.2. The model contains a straight section and a bent section. Comparisons of the coal log velocity and the pressure distributions of the pipe and the coal log surface are made between the calculated results and the experimental data. The shear force and the friction coefficient are also calculated to verify changes of the influence of water on the coal log. The results of this simulation display the dynamic motion of the coal log for startup and turning. Water drag force moves the coal log, making the coal log velocity greater than the water velocity. The lifting force lifts the coal log and moves its tail slightly upward. The pressure drop of the whole pipe is respectively larger in the presence of the coal log. The pressure along the coal log surface slowly declines. The appearance of a bend impedes the motion of the coal log and enhances abrasion. The coal log has difficulty being suspended due to decreased lifting force and increased friction. The pressure on the coal log surface rises.

기하 비선형과 항력 효과를 고려한 해상풍력발전기의 지진 응답해석

In this study, the capability of an existing analysis method for the fluid-structure-soil interaction of an offshore wind turbine is expanded to account for the geometric nonlinearity and sea water drag force. The geometric stiffness is derived to take care of the large displacement due to the deformation of the tower structure and the rotation of the footing foundation utilizing linearized stability analysis theory. Linearizing the term in Morison`s equation concerning the drag force, its effects are considered. The developed analysis method is applied to the earthquake response analysis of a 5 MW offshore wind turbine. Parameters which can influence dynamic behaviors of the system are identified and their significance are examined.

The development of an estimation model for energy expenditure during water walking by acceleration and walking speed

The aim of this study was to develop an estimation equation for energy expenditure during water walking based on the acceleration and walking speed. Cross-validation study. Fifty participants, males (n=29, age: 27-73) and females (n=21, age: 33-70) volunteered for this study. Based on their physical condition water walking was conducted at three self-selected walking speeds from a range of: 20, 25, 30, 35 and 40 m/min. Energy expenditure during each trial was calculated. During water walking, an accelerometer was attached to the occipital region and recorded three-dimensional accelerations at 100 Hz. A stopwatch was used for timing the participant's walking speed. The estimation model for energy expenditure included three components; (i) resting metabolic rate, (ii) internal energy expenditure for moving participants' body, and (iii) external energy expenditure due to water drag force. When comparing the measured and estimated energy expenditure with the acceleration data being the third component of the estimation model, high correlation coefficients were found in both male (r=0.73) and female (r=0.77) groups. When walking speeds were applied to the third component of the model, higher correlation coefficients were found (r=0.82 in male and r=0.88 in female). Good agreements of the developed estimation model were found in both methods, regardless of gender. This study developed a valid estimation model for energy expenditure during water walking by using head acceleration and walking speed.

Cardiorespiratory and Neuromuscular Responses during Water Aerobics Exercise Performed with and without Equipment

The aim of the study was to compare the cardiorespiratory and neuromuscular responses to water aerobics exercise performed with and without equipment. 15 women performed stationary jogging combined with elbow flexion/extension without equipment, with water-drag forces equipment and with water-floating equipment, at 2 submaximal cadences and at maximal cadence. Heart rate, oxygen uptake and electromyographic signal from biceps brachii, triceps brachii, biceps femoris and rectus femoris were collected during the exercise. The heart rate and oxygen uptake showed significantly higher values during the execution of the water aerobics exercise with either equipment compared to the execution without equipment. In addition, significant difference was found between submaximal cadences. For neuromuscular responses, no significant differences were found between the submaximal cadences for all muscles analyzed; however, significant differences were found between these submaximal cadences and the maximal cadence. Similarly, the results showed no significant differences between the execution of the exercise with or without equipment, except in the muscle activation of triceps brachii and biceps femoris, which was higher when using water-floating and water-drag forces equipment, respectively. In conclusion, the water aerobics exercise presented higher cardiorespiratory responses with equipment and also increased the cadence of execution. Nevertheless, neuromuscular responses were higher only at maximal cadence.

The Modulation of Verbal Information As a Factor Stimulating Conscious Differentiation of Kinaesthetic Sensations in the Aquatic Environment

Background: This study aims to find a relationship between the amplitude and duration of verbal information, and a conscious reaction to the kinaesthetic learner. Material/Methods: Research participants in this study consisted of 40 children from elementary school No. 1 in Swidnica (Poland). The group consisted of 16 boys and 24 girls. The respondents’ age ranged from 9 to 10 years. Children regularly attended swimming classes 3 times a week for 45 minutes. The method used for the research was the laboratory experiment method, where the aim was to assess the level of differentiation of kinaesthetic sensations in the aquatic environment. Study participants had to perform 10 repetitions of force differentiation of their upper limb adduction movements, under the influence of water resistance felt on the surface of the palm of their hands. The task was to move from the slightest perceptible drag force of water (sensory threshold), through intermediate values to the maximum strength. Results: The results confirmed the hypothesis that the intentional modulation of verbal information affects the level of conscious differentiation force in the aquatic environment. The magnitude of the force registered during the measurements significantly correlated with the intensity of the amplitude of individual words and their duration. Conclusions: The participants’ conscious reactions were therefore a response to the teacher’s intentional and planned actions. This issue is worth addressing in more detail in subsequent studies. Verbal information should be supplemented with suitably chosen content and then evaluated in terms of its effectiveness relating to the teaching process.

Muscle Activity During the Typical Water Polo Eggbeater Kick

The muscle activity of the Tibialis Anterior, Gastrocnemius Medialis, Adductor Longus, Vastus Medialis, Tensor Fasciae Latae, and Biceps Femoris muscles in the typical water polo eggbeater kick were evaluated for four national level water polo players. The surface electromyographic (EMG) signals were collected during an intermittent protocol in which the basic position with arms up and horizontal position variations were performed. Descriptive and inferential statistics (including ANOVA) were calculated using the p < .05 significance level. We observed that different muscles have different relevance during the eggbeater kick cycle, changing as a function of the movement phase. When comparing the three variations of eggbeater kicks, differences were noticed within each phase: the outward phase and the power phase seem to impose higher muscular activity than the recovery phase for most of the muscles studied. Considering the eggbeater kick variations, arms up seems to produce higher EMG values, while the basic position and the horizontal position seem to create similar EMG values. The eggbeater kick is a basic and commonly used water polo technique, being similar to the breaststroke kick, with the exception that the limbs move alternately instead of moving symmetrically together (Clarys, 1975). It allows the player to raise (and sustain) the body out of the water or move it in any desired direction by generating a force to counteract the gravitational pull on body weight or any other resistance (e.g., the opponent player or simply the water drag force). Consisting of cyclic actions, this specific technique implies that the right and left lower limbs move in a circular trajectory in opposite directions and out of phase, which means that while one limb is executing its power phase (extension), the other is making the opposite recovery phase action (Sanders, 1999a), allowing a continuous propulsion. The eggbeater kick is a complex combination of hip, knee, and ankle motions, which demands coordination and different levels of muscle activation. Following Sanders (1999b), its distinct cycle phases are characterized by the different foot directions: (a) the outward phase, when the foot (with the flexed knee) starts rotating laterally and moving outward (Figure 1, left panel); (b) the power phase, the most propulsive one (Sanders, 2005), starts after the outward phase when the foot begins its movement downward and inward (Figure 1, central panel); and (c) the

Dynamic Model of the Octopus Arm. I. Biomechanics of the Octopus Reaching Movement

The octopus arm requires special motor control schemes because it consists almost entirely of muscles and lacks a rigid skeletal support. Here we present a 2D dynamic model of the octopus arm to explore possible strategies of movement control in this muscular hydrostat. The arm is modeled as a multisegment structure, each segment containing longitudinal and transverse muscles and maintaining a constant volume, a prominent feature of muscular hydrostats. The input to the model is the degree of activation of each of its muscles. The model includes the external forces of gravity, buoyancy, and water drag forces (experimentally estimated here). It also includes the internal forces generated by the arm muscles and the forces responsible for maintaining a constant volume. Using this dynamic model to investigate the octopus reaching movement and to explore the mechanisms of bend propagation that characterize this movement, we found the following. 1) A simple command producing a wave of muscle activation moving at a constant velocity is sufficient to replicate the natural reaching movements with similar kinematic features. 2) The biomechanical mechanism that produces the reaching movement is a stiffening wave of muscle contraction that pushes a bend forward along the arm. 3) The perpendicular drag coefficient for an octopus arm is nearly 50 times larger than the tangential drag coefficient. During a reaching movement, only a small portion of the arm is oriented perpendicular to the direction of movement, thus minimizing the drag force.

Creep Buckling of a Wedge-Shaped Floating Ice Plate

The paper is concerned with the problem of creep buckling of a floating ice plate pressing against a rigid, vertical-walled, engineering structure of a finite length. The plate is modelled as a truncated wedge of a semi-infinite length and constant thickness, resting on a liquid base and subjected to transverse bending due to the elastic reaction of the base and in-plane axial compression due to wind and water drag forces. The ice is treated as a viscous material, with the viscosity varying with the depth of the ice cover. The results of numerical calculations, carried out by the finite-element method, show the evolution of creep buckles in the plate, and also illustrate the behaviour of the ice cover at different levels of the in-plane axial loading, at different temperatures across the ice, and for different geometries of the wedge-shaped plate.

Evaluation of Viscoelasticity of Biological Cells in Liquid by Scanning Probe Microscopy.

An analytical method is proposed to evaluate the viscoelasticity of a biomaterial in water by the scanning probe microscope. The proposed method utilizes the dependence of amplitude and phase lag of cantilever vibration on the viscoelasticity when the tip on the cantilever cyclically penetrates into the cell. The cyclical penetrations are carried out in two ways; one is by excitation of the cantilever fixed end, and other by that of the table. The analysis takes the drag force of water due to the cantilever vibration into account. The stiffness and the viscosity of the cell are analytically related with the amplitude and the phase lag of the cantilever vibration. The results shows that the relations among the amplitude, the phase lag, stiffness and viscosity vary significantly depending on the excitation frequencies of the cantilever fixed end and the table.

Chemigation Pipeline Transport Model for Nonsoluble Pesticide I. Theory

A mathematical model of dispersed phase transport of a nonsoluble pesticide in an irrigation pipeline is derived. Eulerian and Lagrangian approaches are used at high and low turbulence intensities, respectively. An equation is derived by equating pesticide surface tension and viscous forces to irrigation water drag force at the injection nozzle in order to estimate mean dispersed-phase chemical drop size within the irrigation pipeline.