Side Wall Of Tank Research Articles

Study on the plume flow behavior and air entrainment characteristics of co-burning fires

In most of the fire accidents, there is large oil layer leaking into the fire dike and multiple fire points burning simultaneously. A series of numerical simulations for co-burning of a dike and double tanks (co-burning) with different spacing S have been conducted to study the plume flow behavior and air entrainment characteristics. The simulation results show that there is a conical fuel-rich region on the upper rim of the tank which results in the entrained air to flow circularly along the surface of the conical region. With the increase of S, the restriction effect of tank sidewall on air entrainment from environment enhances, while the restriction degree of air entrainment in the middle area of the double tanks decreases, affecting the distribution of plume velocity field and temperature field. And under the coupling effect of them, the tilt degree of tank flame decreases with the increase of S (from 0.3 m to 0.7 m). The air entrainment restriction coefficient αB, αS are introduced to characterize the restriction effect of air entrainment between the external dike fire and the double tank fires. Based on this, a co-burning plume entrainment model has been established, which can be applicable to different spacing S.

Effects of seismic characteristics and baffle damping on liquid sloshing

The present work concentrates on liquid sloshing in tanks under real seismic excitations with various frequency contents [the ratio of peak ground acceleration (PGA) to peak ground velocity (PGV)] by a finite-difference turbulent model. The turbulence is modeled by the large eddy simulation, and the fluid–structure interaction is resolved by the Virtual Boundary Force method. Thirteen seismic records, covering the low, intermediate and high frequency contents, are adopted to excite nonlinear sloshing waves. Both sloshing wave and hydrodynamic pressure are recorded, and their correlations with the filling level, PGA, PGV and frequency content have been identified. The findings suggest that (1) the sloshing responses are in general positively correlated with the filling level; (2) the sloshing height strongly relates to PGV and frequency content, and the seismic excitation of low frequency and meantime with a larger PGV can trigger more violent sloshing waves than others; and (3) the dynamic pressure along the tank sidewall decreases from the bottom up, which is dominated by PGA at the lower part but the stronger correlation is established with PGV and frequency content at the upper part. Finally, to damp severe sloshing waves, the horizontal, vertical and coupled horizontal and vertical baffles are introduced, and their inhibiting effects are discussed. The present work may guide the design of partially filled storage tanks under seismic excitations.

Experimental study on the buffering effects of urban trees group in dike-break floods

The process of dike-break flood propagation in typical urban street is highly complex. The presence of buildings and trees groups in urban street profoundly alters the flood dynamics, impacting the drainage capacity of the area. In this study, a generalized sink model representing a typical urban street was established, including trees groups, buildings, sidewalks, and stormwater drainage systems. The study measured the fluctuation of water levels within the street block and the pressure variation in the pressurized stormwater drainage network during the dike-break flood propagation. Furthermore, it conducted a comparative analysis to assess the influence of different arrangements of trees groups on the maximum water depth in buildings and the discharge capacity of the pressurized stormwater drainage network. Dike-break floods give rise to large-scale water leaps and the formation of thin layer water sheets near the buildings under the influence of buildings, water tank sidewalls, and tree groups. The water leap zones exhibit lateral migration and superposition on the sidewalks during the flood propagation, gradually dissipating and disappearing in the longitudinal direction of the street. In the presence of tree groups, the water levels significantly decrease in buildings and downstream street, while the discharge capacity of the pressurized stormwater drainage network shows a slight improvement as the road’s flood-carrying capacity increases. The pressure in the main pipes fluctuates due to the switching of the grate inlet drainage mode and the hydraulic transition process in the branch pipes. The research findings not only provide valuable validation data for numerical simulations but also offer theoretical guidance for urban flood management and landscape design.

Experiments and modeling of the temperature profile of turbulent diffusion flames with large ullage heights

In the last decades, several major fire accidents involving storage tanks occurred, particularly for the tanks with a low fuel level (large ullage height). In case of a tank fire, the axial temperature profile is affected by the ullage because of the restriction in air entrainment by the tank sidewall. This work is aimed at examining the temperature profile of turbulent diffusion flames with large ullage heights. A series of experiments were conducted with different ullage heights (h = 16–42 cm) and fuel supply rates. The temperature profiles both inside and outside the fuel tray were measured and analyzed. Five regions were identified based on flame intermittencies: namely 1) fuel vapor, 2) down-reaching intermittent flame, 3) continuous flame (down-reaching and upper flame), 4) upper intermittent flame and 5) buoyant plume. It was found that for a given fuel supply rate the length of the fuel vapor region increases linearly with the ullage height. The lengths of the fuel vapor and continuous flame regions both increase with the fuel supply rate, whereas that of the down-reaching intermittent flame region shows an opposite trend. Based on the experimental data and dimensionless analysis, new correlations for the virtual origin were proposed, which were then incorporated in the predictions of the temperature profiles in both upper and down-reaching flames. The present results could not only contribute to the understanding the effects of the ullage height on the axial temperature profile in storage fuel tank fires with large ullage heights but are also of practical importance in the thermal hazard assessment of fire accidents involving tank liquid fuels.

Mitigation of liquid sloshing by multiple layers of dual horizontal baffles with equal/unequal baffle widths

Present work aimed to discover the inhibiting efficacy of multiple layers of dual horizontal baffles (multiple DHBs) on liquid sloshing under harmonic and seismic excitations by applying a Navier-Stokes solver. The multiple DHBs with equal/unequal baffle width (EBW/UBW) were considered, where that of UBW was divided into two categories — oblique and concave UBW schemes. Their damping effects were illustrated by estimating the free surface and pressure results, and the velocity and vortex fields were also discussed. The results showed that the EBW scheme with wider width was better than the narrow one. Both UBW schemes could effectively inhibit the resonant sloshing wave and were also superior to the EBW scheme in damping the sloshing amplitude and hydrodynamic load at lower parts of the tank sidewall. Overall, all baffle schemes could effectively suppress the total forces acting on the tank sidewall. Finally, El Centro earthquake was imposed on the charging system to guarantee a violent sloshing wave, and the damping efficacy of various baffles on such wave was numerically investigated.

The Effects of Contrast between Dark- and Light-Coloured Tanks on the Growth Performance and Antioxidant Parameters of Juvenile European Perch (Perca fluviatilis)

European perch (Perca fluviatilis) is a predatory fish species with a high degree of stress sensitivity during rearing in intensive systems. Our study was focused on the effects of contrast between two colours (black and light grey) in different parts of a tank (bottom and sidewall) on the production and antioxidant parameters of juvenile European perch during intensive rearing. The duration of the experiment was 8 weeks. In the first treatment, the bottoms of the tanks were black (DB); in the second treatment, the sides of the tank were black (DS); in the control treatment, the fish were kept in light-grey tanks (K). There were three replicates per treatment, and a total of 180 individuals were used; therefore, 60 individuals were used per treatment, with 20 individuals per tank. The mean body weight of the fish at the start of the experiment was 32.01 ± 0.79 g. At the end of the experiment, the antioxidant parameters (cortisol, glucose, MDA, catalase, vitamin C, GPx, GR, GSH, GSSG, and HSP70) of the fish were determined from blood samples. The results of our experiment show that different levels of contrast between the dark and light tank colours significantly influenced the production and antioxidant parameters of the juvenile European perch.

Numerical simulation of Faraday waves in a rectangular tank and damping mechanism of internal baffles

Parametric sloshing and damping mechanism of internal baffles were systematically investigated through an in-house numerical model NEWTANK (developed by Xue and Lin, 2011). The internal baffles were modelled by the Virtual Boundary Force method. A good agreement of validation was achieved, then the numerical model was applied to investigate the mode 2 to mode 5 Faraday waves in tanks with various baffles, and the damping mechanism has been uncovered. Four kinds of baffles, including vertical, horizontal, ring and T-shape baffles, have been considered. The wave was divided into two categories: symmetric and asymmetric modes. The effectiveness of those baffles was identified by estimating the waveform, velocity and vortex fields; and the effective baffle configurations for various waveforms were proposed. The key issue was to suppress the vertical motion at the tank sidewalls for the symmetric mode; as for the asymmetric mode, the constraint of the horizontal movement at the wave nodes was proved to be more vital. The ring baffle was effective to suppress the mode 2 Faraday wave but lost efficacy for the mode 3 Faraday wave; the horizontal baffle was applicable for both mode 2 and mode 3 Faraday waves; and the vertical baffle was superior to the T-shape baffle in mitigation of the mode 2 Faraday wave, but was inferior to the latter as for the mode 3 Faraday wave. The effectiveness of the T-shape baffle in/close to the wave nodes was further identified through simulations of higher modal Faraday waves. Finally, the mitigation of the sloshing under coupled resonant surge and unstable heave excitations was presented and discussed.

Turbulent cylinder-stirred flow heat and momentum transfer research in batch operated single-phase square reactor

Heat transfer and momentum transfer due to water flow in a cylinder-stirred reactor of square cross section were investigated. Important industrial processes like mixing depend on combined effects of heat transfer and fluid flow which can be understood by analyzing the turbulence structure. A reactor of aspect ratio η = 0.21 (diameter of cylinder to tank side wall) was considered. It uses a small-diameter cylinder to stir the water in batch condition with rotating Reynolds number in a range 1.68 × 104 <Re < 10.1 × 104. The cylinder released a constant heat flux rate of 158 W/m2 through its surface. The steady state mean flow was numerically simulated using two models for turbulence, isothermally with a k-ε and thermally with the RSM model. The results revealed a fluid motion like Taylor-Couette vortex which was validated with PIV streamlines for Re = 6.1 × 104 and 10.1 × 104. Turbulent angular momentum and shear rate revealed differences for the corner direction as the Re number increased compared with the wall direction. Temperature fluctuations and thermal gradient in the gap allowed to analyze the turbulent heat diffusivity coefficient and the ratio to predicted diffusivity for momentum. The results revealed that heat and momentum diffusivity increase for higher Re number and show that heat diffusivity is faster than momentum in the gap. The main frequencies of fluid motion showed large-scale structures and secondary cells of fluid motion. The averaged heat transfer as a function of Re number indicate that this reactor is an enhanced mean for mixing process compared to concentric cylinders reactors.

Nonlinear scattering of crossed ultrasonic beams in the presence of a turbulent bubbly jet flow in water

Experiments involve the nonlinear scattering of mutually perpendicular crossed ultrasonic beams of primary CW frequency components: f1 = 2.240 MHz, f2 = 2.293 MHz; interacting nonlinearly with turbulent bubbly shear flow generated by a circular water jet (nozzle exit diameter D = 1.6 mm and volume flow rate 32 cc/s). The jet axis is perpendicular to the crossed beam axes. The nozzle exit is downward (5 mm above the surface). The water pump’s suction port was at the bottom center of the 10 cm cubic acrylic water tank (wall thickness 4.8 mm). Identical 1.27 cm diameter quartz transducers (T1 and T2) were epoxied at the centers of adjacent vertical tank sidewalls generate the primary beams (in the i or j directions). Identical 4.5MHz receiving transducers (6.35 mm diam PZT-4) measure nonlinear scattering in the forward or backscattered directions. Receiver Rf located in the plane formed by the primary acoustic beam axes) detects in the i cos 45 + j sin 45 direction. Receiver Rb was located in the opposite direction. In the absence of turbulence virtually no radiated sum frequency component exists. Doppler shift, frequency broadening, skewness and kurtosis from the received sum frequency power spectrum were measured.

A new method for optimizing the preheating characteristics of storage tanks

Storage tanks are among the most important components of heat storage systems. Long preheating time causes low operating efficiency and high economic costs. In this work, the temperature distribution, thermal stress distribution, and related influencing factors of storage tanks are studied by the computational fluid dynamics (CFD) method. In addition, a new preheating scheme is proposed to optimize the preheating process of a storage tank. The results show that as preheating proceeds, the temperature distribution of most parts of the tank becomes increasingly uniform, and the thermal stress greatly increases. Local thermal stress can be concentrated at the joint of the tank sidewall and tank bottom. Increasing Ta and Gg can shorten the preheating time of the tank but also increase the risk of thermal stress concentration in the tank. With traditional preheating methods, decreasing the TD can improve tank preheating characteristics but may possibly cause local thermal stress concentration in the tank. The equal difference-variable stepped preheating method is proposed to optimize preheating characteristics. The optimal preheating scheme to efficiently and safely preheat the tank is when T = 15 K, which is reduced by 55.1% in comparison with the preheating scheme of the actual project.

Optical Measurements on Thermal Convection Processes inside Thermal Energy Storages during Stand-By Periods

Thermal energy storages (TES) are increasingly important for storing energy from renewable energy sources. TES that work with liquid storage materials are used in their most efficient way by stratifying the storage fluid by its thermal density gradient. Mixing of the stratification layers during stand-by periods decreases the thermal efficiency of the TES. Tank sidewalls, unlike the often poorly heat-conducting storage fluids, promote a heat flux from the hot to the cold layer and lead to thermal convection. In this experimental study planar particle image velocimetry (PIV) measurements and background-oriented schlieren (BOS) temperature measurements are performed in a model experiment of a TES to characterise the influence of the thermal convection on the stratification and thus the storage efficiency. The PIV results show two vertical, counter-directed wall jets that approach in the thermocline between the stratification layers. The wall jet in the hot part of the thermal stratification shows compared to the wall jet in the cold region strong fluctuations in the vertical velocity, that promote mixing of the two layers. The BOS measurements have proven that the technique is capable of measuring temperature fields in thermally stratified storage tanks. The density gradient field as an intermediate result during the evaluation of the temperature field can be used to indicate convective structures that are in good agreement to the measured velocity fields.

Development of Seismic Device for Stainless Steel Rectangular Water Tank at Short Period Earthquake

ABSTRACTThe seismic device effective for an existing stainless steel rectangular water tank was developed to prevent the damage of tank by earthquake, especially focusing on the short period earthquake where the impulsive pressure acts on the side wall of tank. The seismic device consisted of a thin high damping rubber plate, sandwiched with two metal plates, which were attached on both the surfaces of the rubber plate. These seismic devices were expected to be set between the base frame of tank and the anchor block.First, a shaking table test of a small water tank (1,000 mm×1,000 mm×1,000 mm) made of stainless steel panels was performed under the several conditions of the number, shape and rubber thickness of the seismic devices. Then, eight seismic devices were set to a large water tank (3,000 mm×3,000 mm×3,000 mm) constructed from nine stainless steel panels for each side wall. These tanks were put on the shaking tables and dynamic shaking tests were performed. The shaking frequency was varied from DC to 12 Hz with a given interval step and the water pressure on the side wall of tank was measured.In this study, by setting the seismic devices to both the small and large water tanks, the natural impulsive frequencies of tanks became a little lower, and the impulsive pressure at the natural frequency became smaller with increasing rubber thickness and with increasing surface pressure. When the HYOGOKEN‐NANBU earthquake waves were given to the large water tank with the seismic devices, the impulsive pressure at the short period oscillation was largely suppressed but the sloshing pressure at the long period oscillation was scarcely enhanced.

Experimental Study on the Influence of External Excitation Frequency Change on Liquid Sloshing Impact in Elastic Tank

The sloshing impact of liquid in elastic tank under combined excitation was studied by physical model experiments, and the sloshing impact characteristics of liquid on the side wall of tank with low liquid loading rate under different external excitation frequencies were analyzed. The results show that under the combined excitation of rolling and pitching motion, the sloshing impact load at the free surface is the largest, while the sloshing impact load far from the free liquid surface is smaller. However, when the external excitation frequency of rolling and pitching motion is located at the resonant frequency and larger than resonant frequency, the sloshing impact load in individual regions appears abnormal phenomenon. When the external excitation frequency of rolling and pitching moves from far away from the resonance frequency to near or even slightly beyond the resonance frequency, the sloshing impact load at the free liquid surface presents a small decline stage, a sharp rise stage and a small rise stage, respectively.

A method for reducing mean flow in oscillating-grid turbulence

Oscillating-grid turbulence (OGT) is an experimental tool that has been widely used to study the role of turbulent fluctuations under conditions of small mean flow. We report experiments to investigate the structure of the turbulent flow produced by an oscillating grid, using velocity measurements obtained through the application of two-dimensional particle image velocimetry in the vertical plane through the centre of the grid. Ensemble averages of the fluid velocity measurements at specific stages of the grid’s oscillation indicate that mean flow is induced in OGT by the merging of grid-induced jets close to the tank sidewalls. The installation of an open-ended ‘inner box’ (with its top edge positioned just below the bottom of the grid’s oscillation) is shown to inhibit the merging of the jets, thereby resulting in a reduction in the magnitude of the mean flow within the interior of the inner box region. Measurements of the time-averaged root-mean-square turbulent velocity components and the time-averaged turbulent kinetic energy flux indicate that the installation of the inner box results in turbulence that is in good agreement with the well-established models of OGT across the central 50% of the inner box’s width, but that distinct anisotropic regions exist adjacent to the vertical sidewalls. We anticipate that this simple amendment to reduce the mean flow present in OGT can be readily used in future work that utilises OGT to isolate the effects of turbulent fluctuations from those of the mean flow.Graphical abstract

A method to correct shallow-water model tests for tank wall effects

A new method is proposed to correct shallow-water model resistance tests for the effect of the tank side walls, i.e. to correct the resistance curve towards shallow water of infinite width. From computed flow fields along ships in shallow water and channels, the tank or channel walls are found to increase the overspeed along the ship (return flow) by an amount that is roughly constant over the channel section. An algebraic equation is derived from which this amount can be solved, using a volume flux derived from a single potential-flow computation. The effect of the tank walls on the resistance curve is represented by a speed shift corresponding with this overspeed. The assumptions made are checked against computed flow fields and resistances. The overspeed increment is very well predicted; its effect on the resistance is fairly well estimated as long as it is not too strong. The method, in routine use for shallow-water tests at MARIN, is most practical; and in view of the large tank wall effects in shallow water, it is essential for good predictions.

Dependence of critical filling level on excitation amplitude in a rectangular sloshing tank

A series of experiments has been conducted to investigate the fluid sloshing at the first mode (i.e. half wavelength exists inside the tank) for different filling levels in a rectangular tank. For each filling level, fluid sloshing was driven by forced tank motions in the horizontal plane with excitation amplitudes of 0.127 cm, 0.254 cm, 0.508 cm and 0.635 cm, respectively. Pressure variations on the side wall of the tank and wave elevation inside the tank were measured simultaneously using four pressure sensors and a wave gauge. It was found that the filling level at which the maximum sloshing amplitude occurs, namely the critical filling level, decreases as the excitation amplitude increases. A theoretical analysis was conducted to provide a physical explanation for this trend. It was also found that an increase in the damping of the system leads to a shift of the critical filling level to a higher value. The pressure on the tank sidewall is found to correlate well with the response amplitude of the water level in the tank since small excitation amplitudes were used in this study.

Experimental and numerical measurements of wave forces on a 3D offshore stationary OWC wave energy converter

In this paper, wave forces on a 1:50 model–scale of an offshore stationary Oscillating Water Column (OWC) device are studied in 3D physical and numerical wave tanks. In total 310 physical experiments including repetition were performed in a wave tank for regular waves of different heights and periods, and several turbine–induced pneumatic damping conditions simulated via orifice plates. A Computational Fluid Dynamics (CFD) model based on the RANS equations and the VOF surface capturing scheme was constructed and validated against the tank measurements. The validated CFD model was then utilized to investigate the effects of tank sidewalls on the predicted wave forces. It was found that the horizontal wave force acting on the OWC device was always larger than the vertical force. The total horizontal and vertical forces were maximum and minimum, respectively at the intermediate wavelength. In addition, the pneumatic damping had a significant impact on the measured vertical force, whereas negligible effects were observed on the horizontal force. Increasing the wave height increased nonlinear effects on the forces measured, especially the vertical force. It was concluded that a tank width of less than five times the OWC device breadth will likely provide misleading wave forces due to blockage effects.

Optimization of linear and nonlinear sidewall storage units using coupled boundary element-finite element methods

In this research, a numerical model is developed for optimization of storage tanks based on sloshing phenomenon. The sloshing of the liquid can increase the dynamic pressure on the partially filled storage tank sidewalls and bottom to endanger its integrity. The coupled boundary element-finite element methods were used to solve the Laplace equation as governing equation and nonlinear free surface boundary conditions. The numerical model is validated against available data. Different sections for the liquid storage tanks such as rectangular tank with different aspect ratios, trapezoidal tanks with linear and nonlinear sidewalls, different sidewall angles and different widths were examined. Finally the best cross sections of storage tank based on minimization of the pressure and forces exerted on the perimeter of the tank due to sloshing phenomenon were suggested. The results showed that using nonlinear sidewalls in storage tank dramatically decreases the sloshing pressure on the perimeter of the tank.

Thermal performance-based analysis of minimum safe distances between fuel storage tanks exposed to fire

This paper presents a numerical investigation aimed at assessing the safety of fuel storage tank farms subjected to elevated temperatures caused by fire conditions. In particular, the work addresses the ways of given pool-fire scenarios, occurring from the fuel ignition of pre-defined source tanks, are able to propagate to adjacent target tanks, i.e., examining the possibility of a domino effect. The proposed analysis involves a sequential two-step procedure, corresponding to the application of: (i) a semi-empirical model—to obtain the equivalent temperature of the large pool-fire flame (source tank), assumed as a solid cylinder with a homogeneous and constant temperature distribution, dependent on the smoke ratio generated from fuel burning, with determined geometric flame features based on data extracted from literature and, (ii) Abaqus finite element transient heat transfer model—to determine the temperature variation on the target tank sidewall as a function of fire elapsed time. After validating the numerical model adopted, through the comparison with results of simulations reported in the literature and based on CFD (Computational Fluid Dynamics) model, the paper presents results concerning the safety assessment of a proposed case study corresponding to two adjacent tanks (source and target). The analysis considered the influence of a combination of various parameters: (i) type of stored fuel (gasoline or ethanol), (ii) structural tank sidewall material (steel or concrete), (iii) incidence of wind and (iv) several distances between the tanks. Finally, the temperature field evolution and ultimate temperature (mostly) resulting from the target tank sidewall data gathered in this study indicate that the current NFPA 30:2012 design recommendations need to be modified in order to achieve a satisfactory failure prediction for different ethanol and wind incidence.

A free surface frequency domain green function with viscous dissipation and partial reflections from side walls

The free-surface Green function method is widely used in solving the radiation or diffraction problems caused by a ship or ocean structure oscillating on the waves. In the context of inviscid potential flow, hydrodynamic problems such as multi-body interaction and tank side wall effect cannot be properly dealt with based on the traditional free-surface frequency domain Green function method, in which the water viscosity is omitted and the energy dissipation effect is absent. In this paper, an open-sea Green function with viscous dissipation was presented within the theory of visco-potential flow. Then the tank Green function with a partial reflection from the side walls in wave tanks was formulated as a formal sum of open-sea Green functions representing the infinite images between two parallel side walls of the source in the tank. The new far-field characteristics of the tank Green function is vitally important for improving the validity of side-wall effects evaluation, which can be used in supervising the tank model tests.