Fluid In Tank Research Articles

Long-time dynamics of internal wave streaming

Abstract

The Finite Element Numerical Investigation of Free Surface Newtonian and Non-Newtonian Fluid Flows in the Rectangular Tanks

In this paper, we develop a new computational framework to investigate the sloshing free surface flow of Newtonian and non-Newtonian fluids in the rectangular tanks. We simulate the flow via a two-phase model and employ the fixed unstructured mesh in the computation to avoid the mesh distortion and reconstruction. As for the solution of Navier–Stokes equation, we utilize the SUPG finite element method based on the splitting scheme. The same order interpolation functions are then used for velocity and pressure. Moreover, the moving interface is captured via the concise level set method. We take advantage of the implicit discontinuous Galerkin method to handle the solution of level set and its reinitialization equations. A mass correction technique is also added to ensure the mass conservation property. The dam break-free surface flow is simulated firstly to demonstrate the validity of our mathematical model. In addition, the sloshing Newtonian fluid in the tank with flat and rough bottoms is considered to illustrate the feasibility and robustness of our computational scheme. Finally, the development of free surface for non-Newtonian fluid is also studied in the two tanks, and the influence of power-law index on the sloshing fluid flow is analyzed.

Free vibration analysis of flexible rectangular fluid tanks with a horizontal crack

This paper proposes a numerical approach using the Rayleigh-Ritz method for the free vibration analysis of three-dimensional flexible rectangular fluid tanks with a surface crack. A hypothetical boundary along the crack is assumed, such that it divides the steel wall of the tank into two regions. The total potential energy is obtained from the summation of the potential energy of two regions and the crack. The discontinuity in the wall is created with the local line-springs along the crack, reducing the flexural strength of the steel wall at the crack location. A set of static beam differential equations is used for the shape function of the tank-wall vibration, where the cracks are modeled along the transverse direction of these beams. The velocity potential of the liquid is estimated through the separation of variables and the superposition method. A numerical study was then conducted based on the proposed method. The results indicate that the crack reduces the natural frequencies of the steel tank. It is also worth mentioning that the calculations are performed with acceptable accuracy and low computational costs.

Numerical Investigation of Freely Falling Objects Using Direct-Forcing Immersed Boundary Method

The fluid-structure interaction of solid objects freely falling in a Newtonian fluid was investigated numerically by direct-forcing immersed boundary (DFIB) method. The Navier–Stokes equations are coupled with equations of motion through virtual force to describe the motion of solid objects. Here, we rigorously derived the equations of motion by taking control-volume integration of momentum equation. The method was validated by a popular numerical test example describing the 2D flow caused by the free fall of a circular disk inside a tank of fluid, as well as 3D experimental measurements in the sedimentation of a sphere. Then, we demonstrated the method by a few more 2D sedimentation examples: (1) free fall of two tandem circular disks showing drafting, kissing and tumbling phenomena; (2) sedimentation of multiple circular disks; (3) free fall of a regular triangle, in which the rotation of solid object is significant; (4) free fall of a dropping ellipse to mimic the falling of a leaf. In the last example, we found rich falling patterns exhibiting fluttering, tumbling, and chaotic falling.

Investigation of Paraffin Wax with ZnO Nanorods for Performance Enhancement of Solar Thermal Energy Storage. (Dept.M)

This paper discusses the influence of paraffin wax inoculated with ZnO-nanorods on the latent heat of thermal energy storage (LHTES) of solar water heating system. The main objective of the experimental study is to determine the percentage increase in thermal storage capacity of using paraffin wax with 0.15 wt.% ZnO-nanorods as nano-composite phase change material (NCPCM) to the raw paraffin wax as base phase change material (PCM). The experiments were performed by 33-liter insulated stainless-steel storage shell TES tank containing 21 copper tubes 5/8-inch in diameter. The TES tank is filled with circulating water and the tubes are filled with either the pure PCM or NCPCM. The water is the heat transfer fluid (HTF) in the TES tank. The experiments were done at different HTF flow rates to study the best flow rate that increases both the amount of heat transfer and melting rate of PCM. It was found that 0.15 wt.% ZnO NCPCM decreases the charging and discharging time compared to the pure PCM, and a percentage increase is achieved in thermal energy storage by 20% when using 0.15 wt.% ZnO nanorods. The results also reveal that the maximum discharge energy was raised from 266 kW for pure paraffin wax to 306 kJ for 0.15 wt.% ZnO NCPCM. The NCPCM at 6 l/min HTF flow rate provides the highest energy recovery ratio (ERR), while the smallest occurs at 9 l/min.

Liquid Sloshing in a Cylindrical Tank with Multiple Baffles Under Horizontal and Pitching Motions

The sloshing response of fluid in a rigid circular cylindrical tank with multiple rigid annular baffles and subjected to horizontal and pitching excitations is investigated. The subdomain method for fluid sloshing is utilized to obtain exact solutions to the convective velocity potential of liquid. By substituting the velocity potential of liquid into free surface sloshing equation, the response equation under the horizontal excitation is constructed. According to producing the similar lateral force and moment as analytical solutions undergoing horizontal motion, an equivalent mass-spring model is developed to replace continuous liquid. Based on the model, dynamic response of liquid sloshing in the tank under the horizontal and pitching excitations is obtained. Compared with the reported results, the lateral force is in excellent agreement with literature solutions and the overturning moment shows good agreement with available solutions under the excitation with low frequency. The proposed model can be employed to simplify dynamics of complicated liquid-structure systems undergoing pitching motion without tedious derivation and great amount of calculation. The effects of the liquid height, the positions and sizes of the baffles on the influence coefficient factor of pitching motion and the steady-state response are revealed in detail.

JA:2021-11. Exposure, Crashes, and Deaths Related to the Use of All-Terrain Vehicles for Spraying

ABSTRACT Purpose: All-terrain vehicles (ATVs) are valuable assets on farms and ranches, but are associated with a growing proportion of U.S. agricultural work-related deaths and injuries. The objectives of this study were to investigate the experiences of private pesticide applicators in using ATVs for spraying and determine the mechanisms of injury and contributing factors associated with occupational deaths while spraying with ATVs. Methods: Participants of the Iowa 2015–2016 Private Pesticide Applicator Continuing Instruction Course were questioned about their use of ATVs for spraying and their crash experiences on their course evaluation forms. In addition, the Iowa Fatality Assessment & Control Evaluation (FACE) program database was utilized to identify occupational ATV sprayer-related deaths from 1996 to 2014. Descriptive analyses were performed. Results/Findings: A total of 6,344 private pesticide applicators completed the course and evaluation form. Nearly two-thirds (65%) reported having used an ATV for spraying herbicides. Of these, 8% had been in a crash while spraying with an ATV. All occupational ATV-related deaths in the FACE database from 1996 to 2014 (N = 29) were in agriculture. Over two-fifths of the fatalities involved a sprayer, with 10 occurring while spraying with an ATV. Of these ten deaths, eight were male, and one-half were 70 years-of-age and older. All crashes occurred during the day, but many victims were found hours after the event. All fatalities involved a rollover with the individual being pinned under the ATV resulting in compression asphyxia. Eight involved sloped terrain or a ditch, and in the other two the slope of the terrain was not known/recorded. None of the crashes were witnessed or known to involve alcohol. Practical Application: Spraying with ATVs appears to be a major risk factor for ATV-related occupational death. Older applicators may be at greater risk, and spraying on sloped terrain is a major contributing factor. Tanks mounted on the rear rack and the shifting of tank fluid likely cause changes in the center of mass, which are conducive to ATV rollover. Agricultural workers who utilize ATVs for spraying should be targeted for safety education. Courses required for pesticide application may be an important venue to impart this instruction.

Research of self-adaptive PID drilling fluid level control algorithm based on differential flow

Aimed at the puzzle of traditional PID control algorithm not satisfy level control requirement when drilling fluid performance changing, the article proposed adaptive PID level control algorithm based on differential flow. Through monitoring differential flow between slurry pump outlet and buffer pry inlet, the algorithm got optimized PID control parameters and evaluated drilling fluid properties, which could be used for liquid level control under different fluid medium characteristics. In the laboratory test of drilling fluid tank, the proposed algorithm could always keep the level deviation within 5% through self-adaptive modify PID control parameters under different drilling fluid characteristics. The results shows that the algorithm has wide adaptability and high reliability, and can be applied to the liquid level control situation where the characteristics of the fluid medium change.

Моделирование мехатронных систем производства инстантированных напитков с добавлением амарантовой муки

Introduction. The world market of instant drinks is a highly competitive environment. New mechatronic production systems can help food companies maintain their competitiveness: they determine process modes, analyze them, and choose the optimal parameters, thus increasing the efficiency of the whole food enterprise. Another problem is the low biological and nutrient value of the finished product. New biologically active instant drinks could solve the problem that occurs in conditions of unsocial hours and unbalanced diet. Products of plant origin contain a lot of useful substances. Amaranth flour increases the biological value of the final products. The research objective was to develop mechatronic systems that could be used to produce instant drinks fortified with amaranth flour at the granulation stage. 
 Study objects and methods. The present research featured a new line of production of instant granular drinks fortified with amaranth flour. The study focused on the granulation section. A drum vibro-granulator with controlled segregated flows was used to make a hardware design of the granulation process. The granulation process often demonstrates an unstable particle size distribution, which is associated with non-uniform mixing of the dry bulk components with the binder solution. A mechatronic module can solve this problem. However, it requires detailed information about the process conditions. 
 Results and discussion. The research determined the specific energy consumption on the operating and design parameters for the granulation process in the new drum vibro-granulator. The experiment made it possible to obtain the optimal process parameters and improve the quality of the finished product. The flow rate of the binder solution depended on the readings of the power consumed by the kneading body engine, which stabilized the system. The value of this parameter is so small that its direct regulation is technically impossible. The paper introduces a block diagram of a multi-circuit cascade system to control the quality of the mixture automatically. The authors installed a valve on the pipeline that feeds the binder fluid in the pressure tank. The valve made it possible to control the process with sufficient accuracy. 
 Conclusion. In the new mechatronic module of the drum vibro-granulator, the quality indicators of the resulting mix depend on the amount of power consumed by the kneading body engine and on the level of the binder solution in the pressure vessel.

Performance of Closed Loop Venturi Aspirated Aeration System: Experimental Study and Numerical Analysis with Discrete Bubble Model

In wastewater treatment plants, aeration plays a significant role as it encourages aerobic respiration of microbes, which are necessary to break down carbonaceous matter in the waste stream. This process can account for the majority of energy use in wastewater treatment plants. The aeration process is also necessary in odor control in lagoons and in the aquaculture industry. Generally, the aeration process is accomplished with compressors or blowers which can be of low efficiency due to ideal gas laws. This study introduces the idea of increasing aeration efficiency by looping water from a reservoir through a piping network which includes a venturi aspirator at its inlet. For this purpose, an experimental study has been conducted in a laboratory setup with a pump which pulls water from a tank, passes it through a Venturi aspirator and a helical piping network intended to increase bubble residence time, before depositing it back into the bulk fluid tank. This same process is modeled computationally, using a discrete bubble method (DBM), with good agreement with experiments. The overall purpose here is to determine the optimal configurations for standard aeration efficiency (SAE) and the standard oxygen transfer rate (SOTR). A parametric study has been implemented using the DBM based on different hydraulic and flow parameters. The model is also used to predict the SAE of a hypothetical aeration system. Results indicate that it is possible to achieve SAE values in the range of surface aerators or submersed jet aerators using the proposed aeration system with less complex components, thereby decreasing overall costs.

Improving the energy efficiency of ship tank heating systems

One of the challenges for creating objects of marine equipment operating in arctic conditions is to prevent freezing of fluids in tanks at extremely low temperatures as it may cause damage to the ship and its systems. This problem can be solved with efficient heating systems for ship tanks. In the paper the ballast tank heating simulation and optimization of heating coil position is discussed. The considered heating coil is typical for icebreakers and ice-class vessels (Arc 5 and above). On the basis of the performed computations the recommendations for improving the energy efficiency of ship heating systems are formulated.

Analytical Solution for Dynamic Response of Underground Rectangular Fluid Tank Subjected to Arbitrary Dynamic Loads

AbstractIn this paper, the dynamic response of underground rectangular fluid tank resting on an elastic foundation and subjected to arbitrary dynamic loads is developed in the form of analytical so...

Heat transfer and power consumption of Newtonian and non-Newtonian liquids in stirred tanks with vertical tube baffles

Agitation and heating of Newtonian and non-Newtonian fluids are commonly used processes in various industrial sectors. Traditionally, heating is mediated using jackets and helical coils. Compared to these conventional techniques, a vertical tube baffles offers geometrical advantages that favor mixture quality and heat-transfer efficiency. However, the available literature on this subject is scarce. Therefore, this study aims to determining expressions for calculating the Nusselt number. To this end, plots of the power number were obtained as functions of the Reynolds number during the agitation and heating of Newtonian and non-Newtonian fluids in batch-operated tanks with vertical tube baffles. Two tanks (10 and 50 L) were used along with pitched blade turbine (PBT) and Rushton turbine (RT) mechanical impellers. The Newtonian (water and aqueous sucrose solutions) and non-Newtonian (carboxymethyl cellulose and Carbopol solutions) fluids were heated at different rotational speeds using the transient technique for heat transfer. The power consumed by the turbine was measured experimentally in terms of the torque generated during motor agitation. Non-linear regression analyses were used to develop models to plot Nusselt as a function of the Reynolds, Prandtl, and the corrective factor of viscosity. The models demonstrated good fit with the experimental results. The power number, a function of Reynolds, was found to vary in the range of 2–5 for the PBT and 5–9 for the RT. The developed heat-transfer models were found to be valid across a wide Reynolds range of 20–200,000 for both impellers in the laminar and turbulent regions, which were delimited at a critical Reynolds of 10,000.

Procedures of Fatigue Analysis by Supporting Direct Load Application on Midship Sections

Fatigue evaluation of ship structures using direct calculation methods to calculate fatigue loads are standard practice today. There are several numerical codes available for use in analyses of these fatigue loads. In addition to the varying degrees of computational complexity associated with fatigue prediction methods, the inherent uncertainties of these procedures are also large. This paper introduces the procedure for stochastic fatigue analysis of typical midship models with direct load transfer applied, where an oil tanker is considered. It also covers a comparison of the results with the component-based approach included in the DNVGL Class Note 30.7: “Fatigue Assessment of Ship Structures”. The "real" case analysis includes both internal pressure loads from tank fluids as well as external pressure adjusted for wet and dry surfaces in the waterline area, according to DNVGL Class Note 30.7. Local fine mesh models of fatigue details have been analysed using the sub-modelling technique. The procedure performs well on a typical midship model apart from the file sizes of the generated load transfer files. With 25 wave periods and 12 different headings, the analysed 3-cargo-hold model (1/2 + 1 + 1/2) in the midship area had to be split into four super elements in order to get the analysis through finite element analyses. The procedure is suitable for vessels where warping (torsion) is of less importance. The described procedures are supported by a developed tool to be used in the analysis procedures. Three details of local fine mesh models such as deck erection butt weld, longitudinal stiffener through web-frame, and bottom erection butt weld have been analysed. The results have been compared with the component-based approach. For some of the details there are comparable results, but for others the results vary significantly. The typical trend is that the details heavily influenced by the external pressure (side longitudinal) give less comparable results than e.g. a detail in the main deck mainly influenced by global loads. A comparison of the effect of reducing versus not reducing the pressure amplitude in the waterline on the fatigue life has also been performed and discussed.

Distributed model predictive control with guaranteed performance for reconfigurable power flow systems based on passivity

AbstractThis paper presents a passivity‐based distributed model predictive control algorithm that can provide minimum performance bound on power flow systems. The dynamics of large‐scale power flow systems can be described by the transportation, conversion, and storage of energy among and across subsystems. By strategically choosing a passive output for each subsystem and augmenting each local model predictive controller with a special passivity constraint, the passivity property of each closed‐loop subsystem can be guaranteed; in addition, the corresponding passivity index can be characterized by the designed parameters of the local controller. The passivity‐preserving coupling between subsystems can be utilized to maintain passivity and the stability properties of the overall system. Moreover, the passivity index of the overall system can be characterized by the transition of passivity indices of subsystems based on interconnection topology. Based on the passivity index, the minimum performance bound of the overall power flow system can be characterized. Even if the structure of the power flow system changes, the entire system can remain stable and achieve a certain performance level. Simulation results of a fluid tank system show the effectiveness of the proposed algorithm.

Numerical simulation and experiment verification of the static boil-off rate and temperature field for a new independent type B liquefied natural gas ship mock up tank

In this paper, a new independent type B liquefied natural gas (LNG) ship mock up tank with the net capacity of 40 m3 and an insulation thickness of 400 mm was taken as the research target. After reasonable simplification, two-phase flow and phase change heat transfer of cryogenic fluid in the mock up tank was simulated by using unsteady three-dimensional CFD method. Volume of fluid (VOF) model was selected to track the vapour-liquid interface, Lee model was used as the phase change model, and the influence of the static pressure on the phase change model was considered. The temperature distribution and the static boil-off gas (BOG) generation rate of the mock up tank was calculated, and working conditions of the simulated tank under different liquid levels and partial insulation system damage were discussed. The pressurization characteristics of the mock up tank under closed conditions was also studied. Comparing the simulation with the experimental results, it showed that this model could effectively simulate the evaporation process of cryogenic liquids in the mock up tank under stationary conditions, which provides an important reference for the design and improvement of the new independent type B LNG ship.

Linear analysis of the dispersion relation of surface waves of a magnetic fluid in a square container under an external oblique magnetic field

In this study, free surface evolution of a magnetic fluid in a finite size tank which is subjected to an external magnetic field was investigated. The physical problem and equations governing fluid motion and magnetic field were given with boundary conditions. Using proper selection of variables, dimensionless equation system governing magnetic fluid sloshing were written. Resolution method based on multiple scale variables was presented and solution of the linear problem was given. The dispersion relation obtained in the finite depth case was compared with that corresponding to an infinite depth calculated with the same assumptions. Direction and magnitude of the external magnetic field, magnetic permeability ratio and surface tension effects on magnetic fluid free surface stability were analysed and important results were discussed.

Effect of impeller blade curvature on the hydrodynamics and power consumption in a stirred tank

The performance of curved bladed turbines (CBTs) for the agitation of Newtonian fluids in cylindrical tanks is investigated. The efficiency of CBT is compared with that of the standard Rushton turbine. Also, effects of the blade height of the new designed impeller are highlighted. The computational fluid dynamics (CFD) study is performed to observe the axial, radial and tangential components of velocities, flow patterns and power consumption. The obtained results revealed that the increase of blade curvature reduces the power consumption. Also, a slight decrease of power number is observed in the turbulent flow regime within unbaffled tanks. In a comparison between the cases studied, the best axial circulation of fluid is given by the impeller with flat blades. The increase of the height of curved blades has generated a stronger tangential flow and enhanced the axial movement of fluid particles, but with further penalty in power input.

Fluid Oscillations in Cylindrical Tanks with Longitudinal Damping Partitions

An asymptotic method for investigating small oscillations of fluids in cylindrical tanks with longitudinal damping partitions is presented. The effect of the number and width of partitions on the hydrodynamic parameters and the damping coefficients of fluid oscillations is studied in detail for the case of a circular cylindrical enclosure with a plane bottom. The numerical results are obtained using the finite element method. Basing on the asymptotic theory of vortex resistance a perturbation method applicable for determining the fluid oscillation damping in tanks of arbitrary shape with partitions of small relative width is developed.

Investigation on the equivalent mechanical longitudinal fluid sloshing model for a partially filled tank vehicle

This paper aims to investigate the equivalent mechanical model of longitudinal fluid sloshing for a partially filled tank vehicle. A one-degree-of-freedom (1DOF) mass-spring-damping (MSD) equivalent mechanical model proposed in the literature is first evaluated. To improve the precision of the MSD model, two 2DOF models those are the serial 2DOF (2DOF-S) model and the parallel 2DOF (2DOF-P) model, and a hybrid 3DOF (3DOF-H) model have been proposed, formulated and evaluated. Comparisons demonstrate that the 3DOF-H model can provide rather satisfying precision in broad ranges of tank ellipticity and fill level. Finally, the proposed 3DOF-H MSD sloshing model is further evaluated from the viewpoint of vehicle dynamics response. It is revealed that it is easy to integrate the 3DOF-H model with vehicle dynamics to build a fluid tank vehicle model which can reflect the basic dynamics property of a tank vehicle.