Vertical Baffle Research Articles

Sloshing mitigation using vertical cylindrical baffle

This study has looked into the phenomenon of liquid vibrations in a rigid cylindrical container. The impacts of rigid vertical baffle positioned in the container on frequencies have been examined. The container is partially filled with an impermeable and non-viscous fluid. ANSYS software is used to report the mode shapes of the baffle and fluid domain.

Optimizing fish-friendly flow pattern in vertical slot fishway based on fish swimming capability validation

Vertical slot fishways are increasingly common structures for the passage of a wide variety of migratory fish species, which account for 59.2% of all fish passage facilities in China. The slot structures and redirected flow in the pools are of great importance to guide the fish to swim through the fishway. To optimize the design of vertical slot fishways, physical experiments and numerical simulations were used to study the hydraulic characteristics for 10 different geometric configurations (referred to as designs D1-D10), combining with the study of fish behavior in the model. A comparative study on vertical slot fishway with L-shaped baffle (D1) and with a new vertical baffle (D2) was conducted. Flow patterns, velocity fields and other key hydraulic parameters including the maximum velocities and turbulence kinetic energy in the pools were analyzed. No obvious differences in all key hydraulic between designs D1 and D2 present in the study, which suggests an upgrade of the L-shaped baffle to the new vertical baffle with the advantage of being more compact and economical. When modifying design D2 in the baffle thickness and length (D3-D10), three typical flow patterns with the different area ratios of left recirculation region to right recirculation region (Scl/Scr) were observed in the pools, which were denoted as flow pattern 1 (FP1), flow pattern 2 (FP2) and flow pattern 3 (FP3). An analysis of the behavior of grass carp (Ctenopharyngodon Idella) in the scaled model clearly showed that the flow and structure in FP2, with the principal flow in the center position and suitable velocity gradient and recirculation area ratio, were more friendly to fish with better migrating efficiency, which present sufficient velocity gradient and area of cushion zone for migratory fish to pass with less energy consumption.

Turbulence analysis for vertical baffle configurations on prismatic tanks by the MPS method

A series of conceptual baffles have been proposed to attenuate pressure effects provoked by sloshing on the walls of Liquefied Natural Gas (LNG) tanks. However, these structures provoke turbulent behavior that need to be analyzed to avoid non-desired fluid effects. In this work, numerical sloshing analyses are developed by a two dimensional Moving Particle Semi-implicit (MPS) method applying the Sub-Particle-Scale Large Eddy Simulation (SPS-LES) turbulent model to identify the turbulent effects due to global motions on a prismatic LNG tank for two filling fractions. The impact pressure, total force, and total moment on tank walls are compared to a prismatic tank without baffles, one configuration with one baffle and two configurations with two baffles. The results illustrate the turbulence effects generated by the three baffle configurations on partially filled tanks (25% and 50% of filling fraction) showing that the effect of the baffles to reduce sloshing effects is more significant for low filling levels (25% of filling fraction), and also, there is a small difference on the sloshing reduced effects between one baffle or two baffles at different separations. However, important turbulent effects appear for high filling levels (50% of filling fraction) specially at roll motion.

Damping effects of dual vertical baffles on coupled surge-pitch sloshing in three-dimensional tanks: A numerical investigation

Present work aims to explore the inhibiting effects of dual vertical baffles (DVBs) on the coupled surge-pitch sloshing, and the wave behaviour and hydrodynamic load are parametrically identified by applying an in-house Navier-Stokes solver. After sufficient validations, the numerical model is then used to study the coupled surge-pitch sloshing where both surge and pitch are at the first-order resonance. The presentence of resonant pitch can dramatically reinforce the wave intensity of the surge-excited sloshing and cause heavy eccentric load, and special attention should be paid to the tank toe due to the remarkable pressure amplification. To lessen the adverse effect, the DVBs with various heights and widths are equipped in the middle of the tank length. It is found that they can shrink water into the spacing between the DVBs, then create pairs of strong vortices around the sharper tips of the DVBs to dissipate wave energy, and also block the movement of fluid at both baffle sides by separating the fluid domain into two compartments which thus yields less fluid bias. The increase of baffle width can lead to a decrease in the wave amplitude, pressure response as well as fluid bias; and the emersed DVBs are more effective than the submerged ones.

Influence of a vertical baffle on suppressing sway motion response of a tank coupled with sloshing actions in waves

The present work is a direct extension of our previous work in Jiang and Bai (2020) where the sway motion response of a box section coupled with an internal sloshing flow was studied. In the present work, vertical baffles are equipped at the bottom of the internal tank, and the influence of the vertical baffles on suppressing the internal sloshing flow as well as the sway response of the system in waves is assessed. The IRF method and the CFD simulation are applied to consider the internal and external fluid flows, respectively. Numerical simulations show that the increased vertical baffle height can generate a more significant effect on suppressing the coupled sloshing action, where the sway motion amplitudes of the baffled sloshing tank tend to the empty tank results. Whether the internal sloshing flow breaks or not seems to play an important role in affecting the sway response of the tank. The vertical baffle can block the sloshing flow and generate a significant effect on the sway motion response when the sloshing flow is of the breaking pattern. For a specific relative vertical baffle height, the shallow filling depth or the large incident wave amplitude is more prone to generate the breaking sloshing flow, and hence better suppressing action can be obtained. As for the non-breaking sloshing flow motion, the vertical baffle is hard to generate the evident effect on the minimal and maximal sway motion amplitudes, but it can cause the variation of frequency range of the essential coupled sloshing action. Generally speaking, the vertical baffle is an effective method for suppressing the sway motion response of the sloshing tank in waves.

Numerical Simulation Low Filling Ratio of Sway Sloshing in the Prismatic Tank Using Smoothed Particle Hydrodynamics

Sloshing is one of challenging problem in the free surface flow, because is dealing with large deformation of fluid. The present paper was carried out of numerical sloshing in the prismatic tank that resemble of LNG membrane type carrier. Pressure sensor was used to validate the dynamic pressure in low filling ratio of tank. Forced oscillation motion in sway with f = 1.08 Hz and amplitude of motion 6.52 mm. A single, and double vertical baffles are used to reduce dynamic pressure and hydrodynamic force. The ratio of baffle heigh with water depth is 0.9. A meshless computational fluid dynamics (CFD) was used to reproduce sloshing in the prismatic tank. Smoothed particle hydrodynamics (SPH) is one of the major meshless CFD. In addition, The advanced visualization was performed using Blender version 2.92. The results showed the vertical baffles effectively reduce the dynamic pressure and hydrodynamic force. Moreover, the advanced visualisation made sloshing simulation more realistic, and attracting compare conventional SPH post-processing.

Heat Transfer Characteristics in Vertical Tubular Baffle Internal Reboiler through Dimensional Analysis

Heat transfer in shell and tube heat exchangers is in general described in terms of the relationships of Nuselt, Prandtl, and Reynold dimensionless numbers. One of the parameters of heat exchanger performance is convective heat transfer coefficien

Investigation of Effects of Baffle Heights on Flow and Heat Transfer in a Trapezoidal Channel with Vertical Baffles

Bu çalışmada, üst duvarında dik bölmeler bulunan, alt duvarı trapez şeklinde dalgalandırılmış bir kanalda farklı bölme yüksekliğinin akış ve ısı transferine etkileri nanoakışkan ve taban akışkan akışı için sayısal olarak incelenmiştir. Nanoakışkan olarak TiO2 nanopartiküllerin su içerisinde süspansiyonu kullanılmış ve nanopartikül hacim oranı, φ=%1 sabit tutulmuştur. Sayısal çalışma, Hesaplamalı Akışkanlar Dinamiği (HAD) tabanlı FLUENT 15.0 programı ile iki boyutlu gerçekleştirilmiştir. Kanalın bölmeler içeren üst yüzeyinin adyabatik olduğu kabul edilmiş ve alt trapez yüzeyi Tw=360K sabit sıcaklıkta korunmuştur. İki farklı bölme yüksekliği (t=H/2 ve t=2H/3) kullanılarak farklı Reynolds sayıları (200≤Re≤1200) için nanoakışkanın ve taban akışkanın Nusselt sayısı (Nu), sürtünme faktörü (f) ve termo-hidrolik performansı (THP) hesaplanmıştır, ayrıca çalışma bölmelerin olmadığı kanal akışı ile de karşılaştırılmıştır. Kanal içerisinde farklı parametrelerde hız ve sıcaklık görüntüleri elde edilmiştir. Sayısal sonuçlar, trapez bir kanalda bölmelerin yüksekliğine ve nanoakışkana bağlı olarak ısı transferinin önemli ölçüde iyileştiğini, ancak sürtünmenin de bir miktar arttığını göstermiştir. En yüksek termo-hidrolik performans, bölmesiz kanalda taban akışkana göre, TiO2-su nanoakışkan akışında Re=400 ve t=2H/3 bölme yüksekliğinde 1,95 olarak elde edilmiştir.

A Semi-Analytical Solution of Liquid Response in a Two-Dimensional Rectangular Tank with a Vertical Rigid Baffle Under Pitching Excitation

The present work uses a semi-analytic mathematical model to study the dynamic response of the partially liquid-filled rectangular tank equipped with a vertical rigid baffle at the bottom subjected to pitching excitation. The velocity potential consists of the rigid container velocity potential and the disturbance potential, which contains a Stokes–Joukowski potential. The liquid domain is divided into four simple sub-domains. The formal solution of the Stokes–Joukowski potential in each sub-domain is solved using the superposition principle and the separation of variables method. The dynamic response equation is established by using the free liquid surface equation. The ADINA solution is compared with the present method solution, which verifies the correctness of the proposed method. Finally, the effect of baffle parameters on liquid sloshing for a baffled tank subjected to harmonic and seismic pitching excitations is discussed in detail.

Simulation of a new phase change energy storage tank design with a vertical baffle

In this study, a new phase change water tank (NPCWT) design with a vertical baffle was simulated. Unlike in traditional phase change water tank (TPCWT) designs, the phase change materials (PCMs) of the new design were concentrated on one side of the tank, and the baffle divides the tank into a phase-change zone and a non-phase change zone. The simulation results were first compared with experimental data to verify the accuracy of the simulation. Then, the FLUENT software package was used to compare the performance of the NPCWT with that of a common water tank (CWT) and a TPCWT of the same overall dimensions. The influence of the inlet flowrate on NPCWT performance was also studied. The heat storage and release performance of tanks were analyzed in terms of heat storage and release time, temperature distribution, and the utilization rate of the PCM. The simulation results show that the performance of the NPCWT is better than that of the other two designs. Compared with TPCWT, the heat storage time is reduced by 4.12%, while the heat release time is extended by 4.6%. It can also effectively solve the problem of the low utilization rate of PCM, and the heat storage capacity and other parameters are improved. The overall thermal performance of the NPCWT is at an optimum when the inlet flow rate is set to 0.2–0.3 m/s.

An experimental study on the hydrodynamic performance of the twin vertical baffles underflow breakwater

Recently, with the enhancement of marine environmental protection, the permeable breakwater, which has the advantages of a simple structure, good water permeability, and environment-friendly, has been paid more and more attention. This study experimentally investigated the hydrodynamic characteristics of a twin vertical baffles underflow breakwater in a wave flume. Different parameters including the relative submergence, relative blockage, breakwater width, and water surface condition between baffles have been considered. Their influences on the transmission coefficient, reflection coefficient, relative wave run-up on the front baffle, and energy loss rate of the twin vertical baffles underflow breakwater have been analyzed. Furthermore, the wave resonance phenomenon could occur for the cases with free water surface between the two baffles, which had a significant influence on the hydrodynamic characteristics of the breakwater. Finally, an empirical formula for calculating the transmission coefficient has been given based on the experimental data.

INVESTIGATION OF SLOSHING IN THE PRISMATIC TANK WITH VERTICAL AND T-SHAPE BAFFLES

The demand for liquid carriers, such as liquefied natural gas (LNG), has increased in recent years. One of the most common types of LNG carriers is the membrane type, which is often built by a shipyard with a prismatic tank shape. This carrier is commonly known for its effective ways to mitigate sloshing using a baffle. Therefore, this study was performed to evaluate sloshing in a prismatic tank using vertical and T-shape baffles. The sloshing was conducted with 25% and 50% filling ratios because it deals with the nonlinear free-surface flow. Furthermore, the smoothed particle hydrodynamics (SPH) was used to overcome sloshing with ratio of a baffle and water depth is 0.9. A comparison was made for the dynamic pressure with the experiment. The results show that SPH has an acceptable accuracy for dynamic and hydrostatic pressures. Baffle installation significantly decreases the wave height, dynamic pressure and hydrodynamic force.

Analysis and Reduction of the Sloshing Phenomena Due To Sudden Movement of Spray Mixture Tanker

The sloshing phenomenon occurs in partially filled tankers due to sudden movement can affect the tank structure integrity and impair the dynamic stability of the tanker. The effects of sloshing phenomena in a spray mixture tank due to acceleration or deceleration of the agricultural vehicle is investigated under three filling levels of 25%, 50%, and 75%. The pressure time distributions on the tank wall were evaluated by using a multiphase transient model (water and air as an ideal gas) and a free surface flow in a homogeneous model. It was possible to verify the wave behavior of sloshing. The condition of 75% tank filling volume generated the highest pressure on the tank wall. The effectiveness of two types of vertical baffles in suppressing pressure was numerically investigated. Shear stress on the tank bottom wall under these proposed arrangements was analyzed by steady-state models and mechanical agitation, considering a filled tank. The proposed solution based on two partial vertical baffles and a central gap was the most effective. It promotes the higher reduction of wall impact pressure and other sloshing instabilities and maintains similar results of mixture agitation of the tank without baffles.

Capture of released alkali metals and its simultaneously catalytic performance on secondary reactions of volatiles during biomass pyrolysis

Limiting the corrosion of alkali metals and making full use of their catalytic activity on biomass pyrolysis are valuable to the development of biomass pyrolysis technology. In this study, γ-Al2O3 was used to capture the released alkali metals and its simultaneously catalytic performance on the secondary reactions was investigated in a special reactor equipped with a vertical baffle. The results showed that a nearly opposite catalytic effect on secondary reactions was presented between gaseous phase and adsorbed KCl. KCl vapor reduced the yield of water, improved the yield of gas and bio-oil, and accelerated the production of CO2, olefins and aldehydes. The adsorbed KCl over γ-Al2O3 limited the formation of CO2 and enhanced the formation of methyl-phenol and water. A possible catalytic mechanism of released alkali metals during biomass pyrolysis was proposed. This study can provide a basis for simultaneous capture of alkali metals and in-situ regulation of volatiles during biomass pyrolysis.

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.

Mass and heat transfer in stirred tank equipped with a horizontal tubular cruciform baffle

The effect of impeller rotational speed and blades geometry on mass and heat transfer on the surface of different sizes of a horizontal cruciform tubular baffle placed at the bottom of a stirred tank reactor was studied by the electrochemical technique. Results highlighted the favorable hydrodynamic conditions associated with using the 90° four-blade turbine which leads to higher rates of mass transfer than that obtained in case of the 45° four-blade turbine. On the other hand, it was found that the 45° turbine is 3 times energy efficient more than the 90° turbine in enhancing rates of mass transfer. Data obtained were correlated by the following dimensionless equations:For 90° turbine:Sh=0.0415 Sc0.33 Re0.54(d/T)-0.192For 45° turbine:Sh=0.0676 Sc0.33 Re0.477(d/T)-0.148The importance of the above equations in designing a horizontal auxiliary tubular baffle cooler was highlighted. Comparing the performance of the present system against existing reactors with vertical baffles highlights the merits of using horizontal baffles in terms of mass transfer and energy consumption. Additionally, it was found that drag-reducing polymers, which may exist in the solution or be added intentionally to reduce power consumption, decrease the rate of heat and mass transfer at the horizontal baffle by an amount ranging from 6 to 37% depending on the operating conditions.

Optimal design of vertical porous baffle in a swaying oscillating rectangular tank using a machine learning model

The sloshing-induced impact loads on the tank wall are significant when the liquid in a tank is excited at and around its natural frequencies, which are highly reliant on the tank's geometry and liquid fill level. Herein, To design the optimal porous baffle for mitigation of liquid sloshing, a machine learning algorithm based on the MLPR model is adopted. First, a sloshing database comprising of different features such as porosity, baffle arrangement, submergence depth of the baffle, motion period, and free-surface elevation at the tank wall is prepared from the sloshing experiments in a swaying rectangular tank with the vertical porous baffle. Then, the detailed feature study is conducted on the database. The MLPR model is trained and validated after preprocessing the data, and the predictions on the free-surface elevation are made for 3520 combinations of feature values using the trained model. A comparison with the available experimental data shows that a well-trained machine learning model can predict well the physical characteristics that occurred in a sloshing tank. A fully submerged single baffle with a porosity of 0.1375 is obtained as the optimal baffle. It reduces significantly the liquid sloshing at resonance, especially the first-mode resonance peak, compared to the no-baffle tank.

NUMERICAL SIMULATION OF SLOSHING IN THE PRISMATIC TANK WITH VERTICAL BAFFLE USING SMOOTHED PARTICLE HYDRODYNAMICS

The capacity of LNG carriers is increasing year by year due to the demand for liquified natural gas (LNG). One of the types of LNG carriers is membrane type that the tank is prismatic. A natural phenomenon in a liquid carrier such as LNG is sloshing. Sloshing is a violent phenomenon in fluid dynamics caused by excitation force. The present study will conduct sloshing with a baffle shape to reduce the free surface inside the tank and impact pressure. In this study, a single vertical baffle and a double vertical baffle are used to reduce sloshing. In the present study, the meshless approach, so-called Smoothed particle hydrodynamics (SPH), is used to reproduce sloshing in the prismatic tank. The three-dimensional prismatic tank was used to capture sloshing with the baffle. Regular roll motion with one pressure sensor uses to validate the SPH results. The result shows that vertical baffle effectively reduced fluid movement inside the tank and impact pressure. As a result, the hydrodynamic force and moment decreased. The ratio of the baffle and the water depth 0.9 shows has significant influence to sloshing.

Investigation on the effects of vertical baffles on liquid sloshing based on a particle method

This study adopts the numerical simulations of Moving Particle Semi-Implicit Methods (MPS), which are meshless methods based on Lagrange particles. Using Lagrange particle has an advantage that it can avoid numerical dissipation problems without directly discretizing the convection term in the governing equation. First of all, a numerical model of a liquid sloshing tank without baffles is used to confirm the effectiveness of the MPS by comparing the numerical results with the experimental data of Kang and Li. And the pressure curves obtained with MPS method were in good agreement with the experimental findings, which confirmed its effectiveness. On that basis, simulations of liquid sloshing movements with one baffle, two symmetrical baffles, and three baffles are performed, respectively. The results indicate that the addition of vertical baffles in the tanks effectively enhanced the ability to reduce liquid sloshing.

Numerical Investigation of Shallow Liquid Sloshing in a Baffled Tank and the Associated Damping Effect by BM-MPS Method

Understanding the damping mechanism of baffles is helpful to make more reasonable use of them in suppressing liquid sloshing. In this study, the damping effect and mechanism of vertical baffles in shallow liquid sloshing under a rotational excitation are investigated by an improved particle method. By incorporation of a background mesh scheme and a modified pressure gradient model, the accuracy of impact pressure during sloshing is significantly enhanced. Combined with the advantages of the particle method, the present numerical method is a wonderful tool for the investigation of liquid sloshing issues. Through the analysis of impact pressure, the influences of baffle height and baffle position on the damping mechanism are discussed. The results show that the damping effect of vertical baffles increases with the increase of the elevation of baffle top and decreases with the increase of the elevation of the baffle bottom. Moreover, the resonance characteristics of sloshing are altered when static water is divided into two parts by the vertical baffle. The dominant damping mechanism of vertical baffles depends on the configurations.