Submergence Depth Research Articles

Wave energy dissipation of a submerged horizontal flexible porous membrane under oblique wave interaction

An analytical model associated with oblique wave interaction with a submerged horizontal flexible porous membrane is presented under the assumption of linearized small amplitude and structural response in finite water depth. The expansion formula associated with Green's functions using fundamental source potentials based on reduced wave equation is derived. Further, a physical problem of oblique wave interaction with a moored finite horizontal submerged flexible porous membrane on wave energy dissipation is illustrated to analyse the different design parameter based on matched eigenfunction expansion method. The roots of the complex dispersion relation are obtained by applying a perturbation scheme and the accuracy of the numerical computation is demonstrated by analysing the convergence of reflection, transmission, and dissipation coefficients for different spring stiffness and porous-effect parameters. Further, the correctness of the present solution is checked by validating against analytical, numerical boundary element method, and experimental data available in the literature. The effects of spring stiffness, porous-effect parameter, submergence depth, structural length, angle of incidence, and flow pattern on reflection, transmission, dissipation coefficients, membrane deflection, vertical force, and contour plots are analysed. The present analysis on different design parameters will be helpful for better understanding for engineers to design as an effective breakwater/wave absorber.

The effects of submergence depth on Vortex-Induced Vibration (VIV) and energy harvesting of a circular cylinder

Vortex-Induced Vibration (VIV) is a kind of high-energy phenomena and can be used to harvest energy from ocean/river currents. In this paper, a spring-mounted circular cylinder in VIV was numerically investigated with 2-dimensional simulations to examine the effects of submergence depth on the energy conversion. The flow speed changes from 0.2 m/s to 1.3 m/s (1.61 × 104<Reynolds number<1.05 × 105), covering three different VIV branches (i.e. initial branch, upper branch and lower branch). The submergence depth changes from 0.1 m to 0.5 m. Results indicate that proximity to the free surface significantly affects the VIV responses. As the submergence depth decreases from 0.5 m to 0.1 m, the VIV amplitude is gradually suppressed resulting in a similar drop in energy conversion. The maximum energy conversion efficiency (34.7%) is achieved in the VIV upper branch with the submergence depth S = 0.5 m. When the submergence depth reaches up to the critical submergence depth S = 0.5 m, the VIV amplitude and converted power no longer increase, which means the effects of submergence depth or the disturbance from the free surface can be ignored. It is also found that when the flow speed exceeds 1.2 m/s (Reynolds number>9.7 × 104), the oscillation amplitude of the cylinder decreases to zero. In this case, the oscillation response doesn’t belong to VIV.

X-ray Radioscopic Visualization of Bubbly Flows Injected Through a Top Submerged Lance into a Liquid Metal

We present an experimental study on the formation and behavior of a liquid metal bubbly flow arising from a downward gas injection through a top submerged lance (TSL). A visualization of the bubble dynamics was achieved by the X-ray radiography combined with high-speed imaging. The experiments were carried out in a parallelepiped container (144 × 144 × 12 mm3) using GaInSn, a ternary alloy that is liquid at room temperature. The gas flow rate Qgas was adjusted in a range between 0.033 and 0.1 L/s. Three different injection positions were considered with respect to the submergence depth L. X-ray images allow for a characterization of the flow regimes and provide the properties of the individual bubbles such as size, shape, and trajectory. Formation and entrainment of smaller gas bubbles are observed at the free surface. These small bubbles can be trapped in the fluid for a long time by recirculation vortices. Bubble size distributions are determined for different Qgas. The bubble detachment frequency is measured as a function of Qgas and L. The results are compared with previously published data for water. The X-ray radiography offers an effective method for determining the local void fraction and allows for an estimation of the bubble volume.

Large‐Scale Experiments on the Formation of Surface Vortices with and without Vortex Suppression

AbstractExperiments were carried out in a 50‐m3 cylindrical tank to determine the influence of strong momentum on the formation of large‐scale gas‐core vortices. Gas‐core lengths were measured for varying volume flow rates and submergence depths. The critical Froude numbers were also determined and the efficiency of different vortex suppressors on the gas‐core formation was investigated. The horizontal velocity field inside the vortex core region was additionally recorded using particle image velocimetry. The experimental results were used to verify numerical simulations and compared to vortex models and correlations from literature.

Flow features for two cylinders arranged in tandem configuration near a free surface

Flow past two tandem cylinders near a free surface is studied numerically at a Reynolds number of 180 using level set method and immersed boundary method. Values of Froude number are varied as 0.3,0.4,0.6; inter-cylinder distance varied as 2,3,4,5,6,10; submergence depth varied as 0.3,0.55. Flow characteristics and mean forces are noted with the variation of these parameters. Upon examination, it is observed that cylinder-to-cylinder proximity along with increased Froude number reduces the instabilities in flow. It is also found that mean drag of the rear cylinder reduces or increases at certain inter-cylinder distance depending on the submergence depth. At the same time, mean lift is observed to be sensitive to variation in submergence depth for flows with low Froude number.

Dynamic stall simulation of a pitching hydrofoil near free surface by using the volume of fluid method

In the present research, the turbulent fluid flow around a pitching hydrofoil is studied near the water free surface, numerically. The k−ω SST model is used for turbulence modeling. The finite volume method (FVM) is used for discretizing the Reynolds Averaged Navier–Stokes (RANS) equations and the free surface is captured by the volume of fluid (VOF) method. In order to validate the present simulations, the current results are compared with those of given by experimental test cases. The first experimental test case is a pitching airfoil in the single phase flow and the second one is a stationary hydrofoil near the free surface. Furthermore, the influence of free surface on hydrofoil drag and lift coefficients are investigated. Different submergence depths and oscillation frequencies are investigated. It is found that both submergence depth and frequency of rotation are affected the lift and drag coefficients, significantly.

The reason and prevention measures for the rod and tubing wear of the pumping unit in the Bei 301 operation area

In order to study the effective prevention measures to improve the regulation effect of the anti-deflecting measure in Bei 301 operation area and prolong the pump cycle of the oil well. The calculation of the historical data of the eccentric wear well and the analysis of eccentric wear prevention effect show that eccentric wear condition in Bei 301 operation area of hailaer oilfield is relatively serious and the operating wells’ ratio of rod breakage and tube leakage increases year by year due to eccentric wear [1,2]. In 2014, the proportion of rod breakage and tube leakage in the operating wells of the operation area was 19.4% and 45.2% respectively, and the average pump inspection cycle was around 400 days. The reasons for the serious wear of the rod pipe in Bei 301 operation area are the improper production parameters, the submergence depth, high water content and well fluid properties according to the detailed data analysis of the pump operation. Active eccentric wear prevention measures have some effect, and next research direction for preventing eccentric wear is put forward in this paper: the paraffin-removing technology, bi-directional protected box coupling and low friction pump combined with the problems faced by the operating area.

Hydrodynamics of a rigid stationary flat plate in cross-flow near the free surface

In this work, the flow normal to a rectangular flat plate with sharp angles in the presence of the free surface and gravity has been studied numerically, using a three dimensional (3D) large Eddy simulation methodology. Most of the previous studies on this geometry consider either periodic assumptions or laminar regime Re ∼ O(103). The numerical study described here, with a fully 3D simulation of the flat plate in turbulent regime Re ∼ O(105), had not been reported earlier. Important differences have been found with respect to the laminar case or when periodic boundary conditions are assumed. The influence of the gravity force and the free surface interface on the hydrodynamics of the problem is extremely relevant for industrial applications. The simulations are initially validated using a reference case with a plate with sharp corners and a single phase laminar 3D-periodic configuration. The time averaged drag force, the velocity, and pressure fields are compared as well against the case of the plate with smooth corners. Finally, in the case of the two-phase 3D numerical simulations, the drag force and the vorticity fields in the near wake of the plate are compared to recent experimental work [S. Satheesh and F. J. Huera-Huarte, “Effect of the free surface on a flat plate translating normal to the flow,” Ocean Eng. 171, 458–468 (2019)]. These experiments were used as a guideline for the computational setup; consequently, the values of most of the dimensionless parameters are the same. A second scenario where the free surface is replaced by a solid wall is considered. Two important observations show up after this research: first, the characteristic unsteady frequencies that are found associated with two periodic regimes disappear when 3D cases are evaluated. In such a scenario, no dominant frequencies are found. Second, a critical submergence depth (distance) between the upper part of the plate and the free surface (or solid wall) has been found, where the drag force shows a maximum value. These observations are discussed in relation to the pressure distribution, the vortex structures formed at the wake, and the gap flow formed between the plate and the free surface.

Liquid sloshing in a rectangular tank with vertical slotted porous screen: Based on analytical, numerical, and experimental approach

The performance of a porous screen placed in the center of a rectangular tank has been investigated based on an analytical, numerical, and experimental approach for the lateral excitation of the tank. The two-dimensional potential model was solved analytically with the Galerkin method by adding the frictional damping coefficient at the free surface condition and considering the energy dissipation across the porous screen. The comparison of the analytical solution with the experimental results shows a good agreement for the frictional damping coefficient of 0.3. The main physical parameters are the surface elevation, pressure at the tank walls, including hydrodynamic forces on the wall, and the horizontal load on the porous screen for different submergence depths and porosities that were investigated. The presence of screen shifts the sloshing tank natural periods slightly, especially in the lowest mode. The unrevealed phenomena accompanied with linear potential theory, the nonlinear wave profile and screen associated effects were also investigated based on an experimental and numerical method. The results show that the numerical prediction with STAR-CCM+ was in good agreement with the experimental results up to second-harmonics. It was found that the porous slotted screen can be an effective device for the suppression of sloshing motion if properly designed.

Survival and root structure changes of rice seedlings in different cultivars under submergence condition

Abstract. Rachmawati D, Maryani MM, Kusumadewi S, Rahayu F. 2019. Survival and root structure changes of rice seedlings in different cultivars under submergence condition. Biodiversitas 20: 3011-3017. Submergence affects plant growth and fitness in natural and agricultural ecosystem. Plant survival to submergence is strongly influenced by the water level and duration of submergence. The objective of this study was to determine the survivalysiological and root anatomical changes of two rice cultivars seedlings to submergence The experiment used completely randomized design with three factors, cultivar (IR-64’ and ‘Inpara 5’), depth and duration of submergence. Depth of submergence consisted of 3 levels: without, partial and complete submergence. Fourteen days old seedlings were treated for 5, 10 and 15 days of submergence. The observed parameters were seedling survival, chlorophyll content, soluble sugar and starch content, plant biomass, and root anatomical structure. The results showed that seedlings survival of ‘IR-64’ and ‘Inpara 5’ decreased by increasing depth and duration of submergence. Increasing depth of submergence decreased chlorophyll content, soluble sugar content and plant biomass. Anatomically, depth and duration of submergence showed a greater increased in root cortex thickness, aerenchyma tissue diameter and the percentage of cortex to be aerenchyma of rice ‘IR-64’ and ‘Inpara 5’. Fifteen days of complete submergence significantly decreased seedlings survival and increased the diameter of aerenchyma in both ‘IR-64’ and ‘Inpara 5’.

An isogeometric boundary element method for liquid sloshing in the horizontal eccentric annular tanks with multiple porous baffles

Boundary element method (BEM) coupled with the isogeometric boundary based on Non-Uniform Rational B-Splines (NURBS), which is termed IGABEM, is a new numerical method and has attracted wide attention in recent years. In this paper, IGABEM is first applied to the liquid sloshing problem in the horizontal rectangular, circular or elliptical annular tanks with multiple porous baffles, assuming incompressible, irrotational and inviscid flows. As a key improvement compared with the conventional polynomial shape function in BEM, the IGABEM for the analysis of liquid sloshing can exactly represent the geometry no matter how coarse discretize the studied boundary, which then produces no geometrical errors. A zoning method is carried out to study arrangement of the multiple porous baffles in the tanks. Neighboring zones is joined together by the boundary conditions of the porous baffles and virtual interface which correlate the flux and velocity potential. By discretizing boundaries of each zone using the isogeometric function, the governing integral equation on the boundary by using BEM can be formulated into the dynamic equation in frequency domain. Three configurations of baffles are taken into account such as the top-mounted baffles, bottom-mounted baffles and annular baffles. The results obtained by the proposed method are verified by comparing with the reported solutions and very good agreement is obtained. The effects of tank's geometry, liquid filling level and the baffle's parameters with various lengths, submergence depths, number of baffles, and porosities on the natural sloshing frequency, wave surface elevation, sloshing force and velocity field are investigated and several conclusions are achieved.

The interaction of flexural-gravity waves with a submerged rigid disc

In this paper, the interaction of flexural-gravity waves with a submerged disc is studied. The problem is solved by transforming it into a two-dimensional hypersingular integral equation. Initially, wave scattering problem is studied followed by radiation and radiation-diffraction problems. The effects of the rigidity of the ice cover and submergence depth of the rigid disc are investigated for all the three cases. It is observed that the submergence of a rigid disc causes significant changes in the scattered as well as radiated wave profiles. However, the presence of the rigid disc creates high-frequency resonance. The present study appears to be useful for understanding the nature of the flow physics in presence of a rigid disc beneath the ice-covered surface.

Performance of a slotted hydrofoil operating close to a free surface over a range of angles of attack

In this paper, results of a study of a submerged hydrofoil with a custom-designed internal slot are provided. The performance characteristics of the slotted hydrofoil in the presence of the free surface are investigated both numerically and experimentally, with angles of attack ranging from 0°≤AoA≤30° at a Reynolds number of 105. Lift and drag coefficients of the slotted hydrofoil with submergence depth of one chord length determined from the computational fluid dynamics study correlate well with the corresponding experimentally determined coefficients. Results suggest significant improvements in hydrofoil performance in terms of lift, drag, and lift-to-drag ratio at high angles of attack. By comparing experimental results of slotted hydrofoils operating at different submergence depths, the submergence depth for good performance of the slotted hydrofoil was determined.

Three-dimensional analysis of local scouring induced by a rotating ship propeller

The jet induced by a rotating ship propeller can cause scouring of the seabed and consequent deposition of the scoured material nearby. Despite these effects are extremely important for the operability of a harbour, there is currently limited work concerning a detailed investigation of the three-dimensional (3D) characteristics of the bed topography changes induced by the ship propeller. Thus, this paper presents laboratory experiments with the aim of analysing the effects induced by a propeller on a mobile bed, in different conditions of submergence depth (h0) and rotational speed (n). The equilibrium bed surface topography was acquired with the photogrammetry technique combined with a 3D Terrestrial Laser Scanner (TLS), in order to analyse, for the first time, bed elevation data obtained from high-resolution Digital Elevation Models (DEMs). As a result, it was demonstrated that the swirling jet produced by a rotating propeller causes the development of a bed topography not symmetrical with respect to the propeller longitudinal axis, with a deeper scour hole on one side and a higher deposition mound on the other side. Therefore, the scour hole induced by a propeller cannot be assimilated to that produced by a water jet and this behaviour can be noted only with a comprehensive and detailed analysis of a 3D model of the bed topography. Furthermore, it was shown that increasing n for the same h0 (or reducing h0 by keeping n constant) causes a longer, deeper and wider scour hole and a higher deposition mound, with a greater volume of sediments eroded from the bed and deposited nearby the scour hole. To be precise, this is the first study aiming at estimating the eroded and deposited sediment volumes by a propeller jet, thanks to the use of the high-resolution DEMs. The relationships between all the involved variables were analysed, providing equations, graphs and an abacus for the prediction of the effects induced by the propeller as a function of h0 and the Froude number.

Evolution of water column pulled by partially submerged spheres with different velocities and submergence depths

Abstract The evolution of a water column pulled by a partially submerged sphere, known as the water exit problem, is evaluated by numerical simulation. The lattice Boltzmann method was combined with a mass-tracking algorithm. The accuracy of the numerical method was demonstrated by comparisons with previous experimental results. Moreover, the evolution processes of the water column with different Froude and Weber numbers (0.4134 ≤ Fr ≤ 8.2479, 5.15 × 102 ≤ We ≤ 2.06 × 105), as well as different initial submergence depths (Hs/D = 1/2, 1/4, 1/8), were discussed. Spontaneous breakup of water column was observed for higher Weber numbers. Moreover, vertical stretching of the water column approximately followed a power law in which the power exponent depended on the initial setup of the sphere and its time scales. However, the horizontal evolution of the water column followed an approximately linear rule. Variation in the water column diameter appeared to be irregular at different physical times or in non-dimensional time. Furthermore, the initial submergence depth of the sphere was also a significant factor in the pinch-off dynamics and water column evolution. This study of water exit is of a great importance in designing marine vehicles that take off from a free water surface.

Effectiveness of Field Water Tube for Standardization of Alternate Wetting and Drying (AWD) Method of Water Management in Lowland Rice (Oryza Sativa L.)

AbstractA field study was conducted to discover the effectiveness of a field water tube as a practical indicator for water management in lowland rice (Oryza sativa L.). The field water tube was of 40 cm length and 15 cm in diameter so that the groundwater table could be easily visible. This tube with perforations was inserted into the ground until 20 cm protruded above soil level. It enabled monitoring of the water level inside the tube as and when the ponded water level drops to a certain permissible level, i.e. 5–15 cm‐surface. Practical indicators used in the experiment to find out the effectiveness of the field water tube were water stress parameters, viz. soil penetration resistance, soil crack width, soil siltation depth and days needed for ponded water to drop to a designated level in the field water tube. Field trials revealed that with 5 cm submergence depth and a threshold of 5 or 10 cm water depth below the ground level in the field the water tube was found to be a safe alternate wetting and drying practice in view of the higher yield (7060–7210 kg ha−1), considerable water saving (26.6–35.0%) and higher water productivity (1.15–1.27 kg m−3). © 2019 John Wiley &amp; Sons, Ltd.

Optimization and Application of Reciprocating Direct-Drive Electric Submersible Plunger Pump Lifting System in the Xinjiang Oilfield

Background: A reciprocating direct-drive electric submersible plunger pump (RDD-ESPP) lifting system is an innovative rodless lifting method, which uses a downhole linear motor to directly drive the plunger pump to lift the fluid. This method effectively overcomes the problems encountered in a conventional sucker rod pumping system, such as severe eccentric wear between the sucker rod and the tubing, higher energy consumption and frequent pump maintenance. Objective: In this manuscript, the objective is to propose a methodology on optimizing the working parameters of RDD-ESPP lifting system and validate the theory with field case. Methods and Results: Mathematical models for the wellbore temperature distribution, lifting load, pump efficiency, system efficiency and tubing strength validation are established. A selection process for the optimal working parameters is proposed, and a parameter sensitivity analysis is implemented. The results show that pump efficiency is largely affected by gas and leakage, and there are reasonable pump submergence depths in oil wells for different produced gas-to-oil ratios. A field application test in a low-production well resulted in a 33.5% power savings rate and 41.6% improvement in the pump efficiency. Conclusion: RDD-ESPP lifting system has a promosing potential on power savings and consumption reduction compared with conventional sucker rod pumping system.

Experimental investigation on a flapping beam with smart material actuation for underwater application

This paper presents an experimental investigation of flapping beam for thrust generation. The beam is studied in current of water and actuated by the “Macro-Fiber Composite (MFC)” based smart material to undergo flapping and undulatory motions, mimicking a fish. The results obtained are expected to be useful in designing process of robotic fish in different marine environment. Herein, the average power spent for actuation is measured and it is observed that the maximum efficiency obtained is 55% for the frequency of 2.0 Hz. The set of experiment of the undulatory smart beam conducted at different depths of submergence showed that an increase in depth of submergence lead to increase of the thrust. However, in the region between the free surface and bottom of the channel (i.e. mid-depth) the thrust is low. By analyzing the measured data, threshold value of “Elastio-Inertia” number for low input power and high efficiency is determined. The results obtained are expected to help in better understanding the swimming pattern, locomotion of fish and other sea creatures. Also, it contributes to the design and development of motor-less and gearless thrust generation mechanisms for the marine vehicles and robots.

On the drag reconfiguration of plates near the free surface

Rectangular foils of different flexural rigidities were towed normal to the flow at a fixed speed in a quiescent fluid in order to study the effect of the proximity of the upper edge of the models to free surface. It was found that flexibility ensured drag reduction due to the reconfiguration process at all submergence depths, with certain foils exhibiting depth-independent behavior. The study of Vogel exponents also showed that a sublinear or even a depth independent relationship between drag and velocity can be attained at specific flexural rigidity values. A modified classical beam theory model using a power-law based load distribution was utilized to obtain an empirical relationship between the loading exponent and Cauchy numbers and to identify the foil tip location. Particle image velocimetry was also undertaken to interpret and further understand the force results. The experiments showed the existence of 2 ranges of Cauchy numbers with a small degree of overlap in ranges wherein the drag coefficient and Vogel exponents are independent of submergence depth.

Pressure flow and weir scour beneath a bridge deck

In this study, a series of experiments in a flume was conducted to investigate the maximum scour hole depth that occurred due to the vertical contraction of the flow underneath a bridge deck model without a pier. The bridge model was tested under pressurized and weir type of flows governed by clear water conditions. Various parameters of flow, sediment, and geometric features of the bridge, such as approach flow depth, discharge, sediment size, girder depth and degree of submergence were varied to investigate their effects on the maximum depth of scour hole. A total of 102 experiments were conducted and two empirical equations were developed separately for pressure and weir flow types with the use of experimental data. Effects of the aforementioned parameters on the scour hole were also analyzed and discussed.