Flat-bottom Tanks Research Articles

Brittle fracture assessment of the API specification 12F shop welded flat bottom tanks

Above ground storage tanks (AST) are essential equipment in the oil and gas industry. In general, large field erected steel storage tanks have been studied and evaluated to understand their behavior under different loadings and identify possible design flaws. However, deep research is necessary to improve the operation of shop-built storage tanks.Particularly, API 12F storage tanks are commonly used in the upstream, exploration, and production segments of oil and gas projects. The environmental conditions of these projects will depend on their locations and might be harsh and threatening for the equipment operation. This paper investigates the brittle fracture failure of the API 12F shop-welded tanks. An elastic stress analysis using finite element models was developed to determine the response of these equipment to extreme environmental conditions and the API 579 “Fitness-for-Service” rules were implemented to perform the brittle fracture assessment.A brittle fracture evaluation is conducted to inquire the propensity of a material to fail without appreciable plastic deformation. In case of the API 12F tanks, several parameters such as ambient temperature, residual stresses, and material toughness can play significant roles in the behavior of the equipment. Complete 3D models of the current API 12F shop-welded, flat bottom tanks as well as axisymmetric and solid submodels were created to address the brittle fracture evaluation and determine whether these storage tanks can operate safely under extreme conditions. Through-wall and surface crack flaws were considered in the most critical joints of the storage tanks and toughness relative ratios between the response of the steel material and the acceptance criteria of the API 579 standard were calculated to describe the behavior of the equipment.

Effects of hydrodynamic factors on Pecten maximus larval development

Hatchery production of great scallop, Pecten maximus, remains unpredictable, notably due to poor larval survival. Large-scale flow-through systems up to 3500 L have been developed to avoid the use of antibiotics in static systems. Alternatively, small-scale flow-through systems have been successfully applied for oysters but they proved to be unsuitable to rear scallop larvae. By focusing on physical factors presumed to limit P. maximus larval development, this study aimed to optimize great scallop larvae rearing parameters under controlled conditions. First, the influence of aeration on larval performances, energetic metabolism and antioxidant defences were studied both in static and flow-through systems. Aeration depressed larval food intake, regardless of the intensities of flow tested (100 ml/min, 155 ml/min and 270 ml/min). On the other hand, antioxidant enzyme activities remained constant or decreased, suggesting that antioxidant defences were inactivated. The increase in citrate synthase activity suggested an increase in metabolic rate possibly due to a turbulent stressful environment. All larvae exposed to such turbulence died before reaching metamorphosis, whereas those reared without aeration survived well (≈ 95%). The effects of water renewal were thereafter studied in 50-L flow-through flat-bottomed tanks. No differences in survival (20.4 ± 0.5%), growth (3.8 ± 0.2 μm/d), competence (5.6 ± 0.2%), energetic metabolism level and antioxidant enzyme activities were observed when comparing 12.5 and 25 L/hr water renewal. Whereas air bubbling leads to detrimental effects, flow-through in small flat-bottomed tanks appears to be a suitable technique for scallop larvae rearing.

Determination of Failure Pressure Modes of the API Specification 12F Shop-Welded, Flat-Bottom Tanks

Shop–welded, flat-bottom tanks for storage of production liquids are designed and fabricated in specific dimensions and capacities for internal pressures close to atmospheric pressure in accordance with the API 12F specification. This study addresses the failure pressure on the eleven (11) current API 12F shop-welded steel tanks as well as two proposed sizes through finite element and stress analysis of more than 350 different tank models. An elastic analysis was carried out to determine the yielding pressure of the shell-to-bottom and roof-to-shell joints. An elastic buckling analysis and a post-buckling analysis including imperfections was performed to determine the buckling modes of the equipment. The redistribution of stresses due to inelastic deformations and plastic collapse were evaluated through a plastic stress analysis considering the stress–strain hardening of the ASTM A36 mild steel material. Moreover, the design pressure increase to failure pressure or 24 oz/in2 (10.3 kPa) was investigated regarding the stress levels and bottom uplift of the 13 flat-bottom tanks. The presented research provides meaningful insights and engineering calculations to evaluate the current design of the API 12F shop-welded, flat-bottom tanks as well as to establish new design internal pressures guaranteeing a safe performance of the equipment.

Fatigue evaluation of the API specification 12F shop welded flat bottom tanks

Shop-built storage tanks are widely used in several industries all over the world. These equipment are fabricated with relatively small dimensions and capacities to facilitate their transportation to production fields. Particularly, API 12F shop-welded, flat bottom tanks are a group of standard equipment with specific sizes and capacities that are commonly used in the upstream, exploration, and production segments of oil and gas projects. The extensive utilization of this equipment has raised the need to investigate their behavior under different load cases and determine their service life due to cyclic loading.Throughout this investigation, a fatigue evaluation was performed following the guidelines of the ASME BPVC Section VIII, Division 2, design-by-analysis rules. The thirteen API 12F tanks were separated in three different groups according to their diameters. Also, different thicknesses as well as pressure cycles including internal pressure and vacuum were considered for the evaluation of each group.An elastic stress analysis using finite elements was conducted on shell models, axisymmetric models and solid submodels to determine the stress components and stress tensor range as well as obtain the effective alternating equivalent stress. Moreover, the fatigue penalty factor and a fatigue strength reduction factor were defined in accordance with the ASME code specifications. Hence, the protection against failure from cyclic loading of these equipment was determined using smooth bar design fatigue curves and the permissible number of operational cycles and location of the most critical joint were computed for each API 12F tank.

Power requirements for complete suspension and aeration in an unbaffled bioslurry reactor

Remediation of contaminated soils is spreading as a matter of crucial importance nowadays. Bioremediation via bioslurry reactors of sites polluted by recalcitrant pollutants has been proved to be a valuable option, although optimization is needed to reduce process costs. Free-surface unbaffled stirred tanks (with central air vortex) have been recently proposed as a promising alternative to the more common systems provided with baffles. In a bioslurry reactor solid-liquid interfacial area, oxygen supply, solid loading per reactor unit volume should be maximized, and, at the same time, operation costs have to be kept low. In this regard, the minimum impeller speeds for complete suspension Njs (suspension of all solid particles) and aeration Nca (air vortex ingested by the turbine and dispersed as bubbles in the system) represents a reasonable compromise between process yield and power requirements. To this purpose, a flat bottomed unbaffled tank with diameter T=0.19 m was investigated. The tank was filled with water up to a height H=T. It was stirred by a radial six- bladed Rushton turbines (RT) with diameter D=T/3 and H=T/3. Mono-dispersed particles with diameter dp=250-300µm and density ?˜2500 kg/m3 were employed. Solid loadings B% ranging from 2.5% (weight of solid/ weight of liquid) up to the very high 160% w/w were tested. The visual Zwietering criterion along with the aid of a digital camera was employed to evaluate Njs values. An acoustic criterion was adopted to assess Nca. A static frictionless granite turntable was employed to measure the impeller torque at Njs and Nca and to assess the relevant specific power requirements ejs and eca. Results show that the dependence of Njs and Nca on B% is much lower at low solids loading (B30%). The relevant specific powers per unit mass of solids (i.e. ejs and eca) were found to exhibit a minimum, at B˜20% for ejs and B˜60% for eca. On overall, data collected suggest that operating a radially stirred unbaffled bioslurry reactor loaded with a concentration B˜30% could be the best compromise to minimize the costs for achieving complete suspension and aeration conditions.

Water acidification activates the innate immune system of Senegalese sole Solea senegalensis

Water acidification activates the innate immune system of Senegalese sole Solea senegalensis

Comparative Risk Assessment for Different LNG-Storage Tank Concepts

LNG can be stored either in flat bottom storage tanks or pressurized storage tanks such as bullets or spheres. Safety levels of atmospheric storage tanks are classified by codes as single containment, and containment. For spherical and bullet tanks an analogical definition by codes is missing and containment philosophies for atmospheric storage cannot be applied to pressurized storage. Therefore a new definition is proposed to describe the safety levels of pressurized tank types and flat-bottom tank types consistently.It is supposed to use the definitions single, double and full integrity instead of single, double and full containment in order not to mix up definitions. The integrity level a storage tank has been assigned to gives a direct link to the consequences that would have to be taken into account in case the primary container fails totally. The advantage of these new containment definitions is having available a normalized basis for the comparison of different tanks fulfilling similar requirements on safety design.It is expected, that the integrity level of the LNG storage vessel has influence on the risk to external population. To evaluate this influence, the risk to external population caused by the different LNG storage alternatives has been calculated by means of a quantitative risk assessment. These calculations show, that in general the risk to external population is the higher the lower the integrity level of the LNG storage. Therefore it can be concluded that high integrity solutions should be chosen where exposure of third party population is high. This should be considered when selecting the tank type (i.e. integrity level) with regard to the distance to populated areas as well as the population density.

Fundamental Mechanics of Walking of Unanchored Flat-Bottom Cylindrical Shell Model Tanks Subjected to Horizontal Harmonic Base Excitation

Assuming very large slide displacement subsequent to tank rock motion to be a possible scenario of tank walk motion, fundamental mechanics of the walk motion of unanchored flat-bottom cylindrical shell model tanks subjected to horizontal base excitation is examined. First, employing a 3DOF model consisting of a set of two masses connected by flexible columns, equations of motion are derived through a variational approach. The interaction among the translational motion of a harmonic oscillator consisting of the upper mass and the flexible columns, the rock motion of the 3DOF model and the slide motion of it is thoroughly studied. Comparison of the experimental results and their predictions demonstrate applicability of the proposed analysis. A reduction in nominal friction force accompanying the rock motion that plays a primary role in causing the very large slide displacement is also pointed out. Next, drawing an analogy between the mechanics of the walk motion of the 3DOF model and that of an unanchored flat-bottom cylindrical shell model tank, equations of motion for the tank walk motion are derived. Shaker table test and time domain analysis are conducted, employing a model tank whose bottom plate concentrically uplifts for readily evaluating fluid masses contributing to the tank rock motion. Comparison of the experimental and analytical results of the slide displacement and the rotational angle corroborates the applicability of the proposed analysis.

Sedimentation from binary suspensions in a turbulent gravity current along a V-shaped valley

AbstractWe present a study of bidispersed particulate gravity currents at high Reynolds numbers flowing along a V-shaped valley. The speed and width of the currents, the mass deposited by the currents and the density of the deposits were examined by both a box model and lock-exchange experiments in a 5 m long tank. Silicon carbide and glass beads were used for the bidispersed suspension models. The initial conditions of the currents were similar, except that the grain size of the glass beads was successively chosen to be 2, 2.5 and 4 times that of the silicon carbide. For all experiments a Stokes’ settling velocity model, assuming that both particles are spherical, gives a settling rate of the glass beads that is greater than that of the silicon carbide by a factor ranging from 1.6 to 16.5. When the ratio of the Stokes’ settling velocity of the glass beads to that of the silicon carbide is greater than ∼6, we find a complete agreement between the box model and the experiment. In particular, the deposit shows a substantial decline in the mass of the coarser glass beads in the first metre, so that it only contains the finer silicon carbide further downstream. By contrast, when the Stokes’ settling velocity ratio is less than ∼4, only the speed of the current and the total sedimented mass can be well described by the box model. The experimental deposit is otherwise characterized by a slightly increasing density, which the box model fails to match. There is no difference in the deposit density across the valley. For all experiments in the V-shaped valley, the width of the currents decreases with time $t$ according to ${t}^{\ensuremath{-} 2/ 7} $. Analogue experiments in a flat-bottom tank were also performed to assess the influence of the valley on the sedimentation dynamics described above. A similar behaviour with settling velocity ratios was found. This study eventually shows the need for considering particle interactions in even dilute gravity currents at high Reynolds numbers.

Tank spawning of first generation domestic green sturgeon

Summary Green sturgeon Acipenser medirostris from hatchery spawned wild-caught broodfish matured under aquaculture conditions. The first females (three out of four) matured at age 8 years, were successfully induced to ovulate by hormonal injections, and their eggs collected by caesarean surgery for fertilization. While the incision healed completely, unknown complications resulted in mortalities 5–12 months later. To minimize handling stress and to eliminate mortalities associated with surgery, a semi-natural tank spawning technique was used in subsequent years. A female was placed into a 3.7 m diameter flat-bottom circular fiberglass tank, depth 0.7 m, with two or three males, and the fish were injected with gonadotropin-releasing hormone analog (GnRHa) and white sturgeon pituitary extracts to induce spawning. Fuller’s Earth was continually added to the spawning tank using a belt feeder to minimize egg adhesion to other eggs and to the tank surfaces. The tank was checked hourly for oviposition, and the eggs collected using a fine mesh dip net, every 1–3 h. Spawning lasted 15–21 h, and 53–80 000 eggs were collected from individual spawning females. Direct observation of spawning activity was not possible because of the high turbidity caused by Fuller’s Earth. However, the female and males occasionally breached at the water surface and appeared to be interacting. After oviposition was completed, viable milt was collected from all males, and fertilization success ranged from 7% to 83% in five spawning events. Over three consecutive years (2009–2011) all five females and 11 males used in semi-natural tank spawning ovulated or spermiated, and were not subject to post-spawning mortality. The relatively slow deposition of eggs and the continuous addition of Fuller’s Earth minimized the adhesion of eggs into large clumps. While the egg fertility and hatchability varied greatly among individual females, the tank spawning technique presented a feasible alternative to other more invasive methods for obtaining fertilized eggs of green sturgeon, and may be applicable for other sturgeons, particularly endangered species.

Non-linear multimodal model for tuned liquid dampers of arbitrary tank geometry

Tuned liquid dampers (TLDs) utilize sloshing fluid to absorb and dissipate structural vibrational energy. Simple TLD tank geometries may not always be feasible due to space limitations. While the non-linear modelling of sloshing fluid is currently limited to tanks of simple geometries, this paper develops a non-linear multimodal model which describes the sloshing behaviour of a fluid in a flat-bottom tank of arbitrary geometry. The mode shapes of the sloshing fluid are found by solving the Helmholtz equation over the tank domain using the finite element method. The Bateman–Luke variational principle is used to develop a system of ordinary differential equations which account for the coupling of the sloshing modes through the non-linear free surface boundary conditions. Damping is incorporated into the model by considering the drag produced on a set of damping screens inserted in the fluid. The system of ordinary differential equations is solved using the Runge–Kutta–Gill Method to predict the wave heights and sloshing forces. In general, the mode shapes in an arbitrary tank will have components in two orthogonal (x- and y-) directions. This out-of-plane behaviour is an important consideration for TLD design. The model is validated with existing models for the special cases of rectangular and circular tanks. Lastly, new shake table tests are conducted on a tank of complex geometry.

Turbulence Properties of Solid-Liquid Flow in the Near-Wall Region of a Stirred Tank

The experiment was performed in a flat-bottomed cubic tank and equipped with a down-pumping 3-blade CBY propeller, investigating solid–liquid two-phase flow in the near-wall region by using 2D-PIV technique. Flow fields with ten different volumetric particle concentrations were investigated, including the single-phase flow. Because measurement is taken in the plane which is 2 mm from the wall, and root-mean-square velocity in the radial dimension could be omitted compared to the other two dimensions, flow field is considered to be two-dimensional. The mean velocity, turbulent kinetic energy and turbulent dissipation rate and their relationship with particle concentration were obtained and examined in this work. The increasing particle concentration decreases the flow mean velocity but increases the turbulent dissipation rate, while the turbulent kinetic energy (TKE) presents a complicated trend. When the particle concentration is below 0.9%, as in most previous studies did, TKE is attenuated; when the concentration grows up to 4%, TKE increases as well.

Process characteristics for a gas—liquid system agitated in a vessel equipped with a turbine impeller and tubular baffles

AbstractResults of the experimental research on gas hold-up, power consumption for liquid phase and gas—liquid systems, and on residence time of the gas bubbles are presented in the paper for an agitated vessel with a turbine impeller. Distilled water or aqueous solutions of NaCl were used as the liquid phase. Air was dispersed into liquid as the gas phase. The studies were carried out in an agitated vessel of the inner diameter D = 0.634 m. Tubular baffles of the diameter of 0.7D, consisting of 24 vertical tubes of the diameter of 0.016D, were located inside a flat-bottomed tank. Turbines with six blades and the pitch of 90°, 60°, or 45°, respectively, were used for agitation. Measurements were carried out in the range of good dispersion of gas bubbles in the liquid within the turbulent regime of the liquid flow. Effects of the gas bubbles capability to coalesce on the gas hold-up, residence time of the gas bubbles, and power consumption were analyzed. Results of the power consumption (P G-L/P o = f 1(Kg, Fr)) and gas hold-up (φ= f 2(Kg, We, Y)) were approximated mathematically, using Eqs. (5) and (6), respectively. In Eq. (6), parameter Y was introduced in order to describe the influence of the bubbles capability to coalesce on the gas hold-up. The results of the study show that power consumption does not depend on the capability of bubbles to coalesce, but the pitch of the turbine impeller affects the power characteristics in such a physical system significantly. However, the residence time of the gas phase in agitated liquid depends on the pitch of the impeller blade and on the capability of bubbles to coalesce.

Fluid Pressures on Unanchored Rigid Flat-Bottom Cylindrical Tanks Under Action of Uplifting Acceleration

To protect flat-bottom cylindrical tanks against severe damage from uplift motion, accurate evaluation of accompanying fluid pressures is indispensable. This paper presents a mathematical solution for evaluating the fluid pressure on a rigid flat-bottom cylindrical tank in the same manner as the procedure outlined and discussed previously by the authors (Taniguchi, T., and Ando, Y., 2010, “Fluid Pressures on Unanchored Rigid Rectangular Tanks Under Action of Uplifting Acceleration,” ASME J. Pressure Vessel Technol., 132(1), p. 011801). With perfect fluid and velocity potential assumed, the Laplace equation in cylindrical coordinates gives a continuity equation, while fluid velocity imparted by the displacement (and its time derivatives) of the shell and bottom plate of the tank defines boundary conditions. The velocity potential is solved with the Fourier–Bessel expansion, and its derivative, with respect to time, gives the fluid pressure at an arbitrary point inside the tank. In practice, designers have to calculate the fluid pressure on the tank whose perimeter of the bottom plate lifts off the ground like a crescent in plan view. However, the asymmetric boundary condition given by the fluid velocity imparted by the deformation of the crescent-like uplift region at the bottom cannot be expressed properly in cylindrical coordinates. This paper examines applicability of a slice model, which is a rigid rectangular tank with a unit depth vertically sliced out of a rigid flat-bottom cylindrical tank with a certain deviation from (in parallel to) the center line of the tank. A mathematical solution for evaluating the fluid pressure on a rigid flat-bottom cylindrical tank accompanying the angular acceleration acting on the pivoting bottom edge of the tank is given by an explicit function of a dimensional variable of the tank, but with Fourier series. It well converges with a few first terms of the Fourier series and accurately calculates the values of the fluid pressure on the tank. In addition, the slice model approximates well the values of the fluid pressure on the shell of a rigid flat-bottom cylindrical tank for any points deviated from the center line. For the designers’ convenience, diagrams that depict the fluid pressures normalized by the maximum tangential acceleration given by the product of the angular acceleration and diagonals of the tank are also presented. The proposed mathematical and graphical methods are cost effective and aid in the design of the flat-bottom cylindrical tanks that allow the uplifting of the bottom plate.

Fluid Pressures on Unanchored Rigid Rectangular Tanks Under Action of Uplifting Acceleration

Although uplift motion of flat-bottom cylindrical shell tanks has been considered to contribute toward various damages to the tanks, the mechanics were not fully understood. As well as uplift displacement of the tanks, fluid pressure accompanying the uplift motion of the tanks may play an important role in the cause of the damage. An accurate estimate of the fluid pressure induced by the uplift motion of the tanks is indispensable in protecting the tanks against destructive earthquakes. As a first step of a series of research, this study mathematically derives the fluid pressure on a rigid rectangular tank with a unit depth accompanying angular acceleration, which acts on a pivoting bottom edge. The rectangular tank employed herein is equivalent to a thin slice of the central vertical cross section of a rigid flat-bottom cylindrical shell tank. Assuming a perfect fluid and velocity potential, a continuity equation is given by the Laplace equation in Cartesian coordinates. The fluid velocities accompanying the motions of the walls and bottom plate constitute the boundary conditions. Since this problem is set as a parabolic partial differential equation of the Neumann problem, the velocity potential is solved with the Fourier-cosine expansion. The derivative of the velocity potential with respect to time gives the fluid pressure at an arbitrary point inside the tank. A mathematical solution for evaluating the fluid pressure accompanying the angular acceleration acting on the pivoting bottom edge of the tank is given by an explicit function of a dimensional variable of the tank, but with the Fourier series. The proposed mathematical solution well converges with a few first terms of the Fourier series. Values of the fluid pressure computed by the explicit finite element (FE) analysis well agrees with those by the proposed mathematical solution. For the designers’ convenience, diagrams that depict the fluid pressures normalized by the maximum tangential acceleration given by the product of the angular acceleration and diagonals of the tank are also presented. Consequently, the mathematical solution given by the Fourier series converges easily and provides accurate evaluation of the fluid pressures on a rigid rectangular tank accompanying the angular acceleration acting on the pivoting bottom edge. Irregularity in the fluid pressure distribution increases as the tank becomes taller.

Particulate gravity currents along V-shaped valleys

This paper extends previous studies of saline gravity currents at high Reynolds number flowing along a tank with a V-shaped valley. We use experiments and a box model to determine the primary features of the flow. The particulate gravity currents were initiated by releasing a fixed volume of fluid consisting of pure water mixed with silicon carbide particles from a lock at one end of the tank. The resulting motion and deposit pattern differ significantly from those for the propagation of a particulate gravity current along a flat-bottomed tank. The front of the current, seen from above, is approximately parabolic (with axis parallel to the flow direction) in contrast to the current in a flat-bottomed tank where it is nearly a straight line perpendicular to the flow. This feature mimics the results for pure saline currents. When seen in profile the currents do not have a clearly defined raised head, which is a feature of the flat-bottomed currents. The mass deposited per unit area varies nearly monotonically with respect to distance down the tank, again in contrast to the case of the flat-bottomed tank. The exceptions to this are the two experiments which have the highest ratio of lock height to length. The mass deposited per unit area across the V-shaped valley is much larger in the central part of the valley than it is on the flanks for any position along the valley. We find that the results can be described with remarkable accuracy by a box model using a generalization of the equation for sedimentation from a turbulent medium due to Martin and Nokes. Our results further show that the factor used in the deposition rate equation which is commonly assumed to be 1 should be smaller, typically 0.7.

Theoretical Modeling of TLD With Different Tank Geometries Using Linear Long Wave Theory

Abstract This study focuses on the modeling of tuned liquid dampers (TLDs) with triangular-bottom, sloped-bottom, parabolic-bottom, and flat-bottom tanks using the linear long wave theory. The energy dissipated by damping screens is modeled theoretically utilizing the method of virtual work. In this proposed model, only the fundamental sloshing mode is considered, and the assumption of small free surface fluid response amplitude is made. Subsequently, the equivalent mechanical properties including effective mass, natural frequency, and damping ratio of the TLDs, having different tank geometries, are compared. It is found that the normalized effective mass ratio values for a parabolic-bottom tank and a sloped-bottom tank with a sloping angle of 20 deg are larger than the normalized effective mass ratio values for triangular-bottom and flat-bottom tanks. An increase in the normalized effective mass ratio indicates that a greater portion of the water inside the tank participates in the sloshing motion. The derived equivalent mechanical models for the TLD tank geometries considered in this study can be used for the preliminary design of structural-TLD systems.

Fluid pressure on unanchored rigid flat-bottom cylindrical tanks due to uplift motion and its approximation

As well as the uplift displacement of the tanks, the fluid pressure accompanying the uplift motion of the unanchored tanks has been considered to contribute toward their various damages. Its accurate estimate is indispensable to secure the safety of the tanks at an earthquake event. Assuming the ideal fluid and velocity potential, a mathematical solution for evaluating the fluid pressure on a rigid flat-bottom cylindrical tank accompanying the angular acceleration that acts on a pivoting bottom edge is derived. In actual case scenarios, practitioners should calculate the fluid pressure accompanying the rocking motion of the tank which possesses a crescent-like uplift region in a plan view of the bottom plate. To satisfy this demand, this paper also proposes an approximation method featuring a rectangular tank with a unit depth off and parallel with the center line of the rigid flat-bottom cylindrical tank, denoted a slice model. The mathematical solution is given by the explicit function of aspect of the tank but is a Fourier series. It well converges with a few first terms of the Fourier series. A comparison with the FE analysis with a three-dimensional half tank model reveals the analytical accuracy for evaluating values of the fluid pressure on the rigid flat-bottom cylindrical tank. In addition, the slice model reasonably approximates the values of the fluid pressure on the shell off and parallel with the center line of the rigid flat-bottom cylindrical tank. For designer’s convenience, diagrams that depict the normalized fluid pressure are also presented. The curved component of the fluid pressure distribution increases as the tank becomes taller or the azimuth angle approaches to 0 or 180 degrees.

Usefulness of flat bottom tanks on the settlement of spider crab (Maja squinado, Herbst) larvae

Usefulness of flat bottom tanks on the settlement of spider crab (Maja squinado, Herbst) larvae

平底円筒貯槽の浮上り挙動への陽解法の適用性に関する基礎的研究

The uplift of the flat-bottom cylindrical shell tank has been considered to contribute to the various damage of the tanks. The motion of the free surface and the fluid pressure characterize dynamical effects of the fluid on the tank induced by the uplift motion. Therefore, to properly evaluate the seismic-resistance performance of the tank, account must be made of these behaviors mathematically and numerically. The present paper examines the applicability of the explicit FE-Analysis to numerically compute these behaviors. As we shortly see, the explicit FE-Analysis accurately predicts the motion of the free surface observed during the free rocking test of the tank and the fluid pressure on the tank mathematically derived based on Laplace equation and associate boundary conditions.