Ring Baffle Research Articles

Three-dimensional resonant sloshing in an upright cylindrical container with a ring baffle

The effect of ring baffles on suppressing the three-dimensional (3D) resonant sloshing in an upright cylindrical container is experimentally investigated. The main objectives of this work are to examine the effectiveness of various baffle configurations, to establish the stability boundaries of the stable steady-state waves in the unbaffled and baffled containers, to provide accurate experimental data for the verification of the analytical and numerical models, and to prompt future investigations. For this purpose, hundreds of sloshing experiments are conducted in a cylindrical container with or without a ring baffle. An analytical potential-flow solution and an asymptotic multimodal method are used to elucidate the experimental results. It is found that the vertical location of the ring baffle has small influence on the fundamental natural frequency of the system; however, it has a significant influence on the viscous damping and the damping rate increases gradually with the ascension of the baffle. When the distance between the baffle and the free liquid surface is sufficiently large, the system exhibits three types of resonant wave patterns, namely stable planar, stable swirling, and irregular chaotic. These wave patterns are qualitatively and quantitatively similar to those in the unbaffled container. When the baffle is near the free liquid surface, neither the chaotic waves nor the swirling waves take place, but a new wave pattern with the characteristic of multiple wave crests is observed. Probably, this is the first time that the 3D resonant sloshing in the baffled cylindrical container has been systematically investigated.

Numerical design of a flow restrictor for tanked liquid nitrogen undergoing reduced-gravity flights

NASA and the United States are designing multiple reduced-gravity cryogenic payloads to study various two-phase flow phenomena that will be ground-tested and subsequently flight-tested onboard parabolic flights. The setup will undergo 25+ parabolas per flight, during which liquid nitrogen will be cyclically or continuously demanded from a supply Dewar. The minimum gravity level during a parabolic maneuver is 0 ± 0.05 g, which can last around 20 seconds, and the maximum expected gravity is 2 g, which lasts for 40-50 seconds. This Computational Fluid Dynamics (CFD) study focuses on the design and optimization of a bi-directional perforated plate and a ring baffle to help ensure single-phase liquid nitrogen outflow during all flight phases, regardless of supply tank liquid level or gravity level. CFD analyses carried out using ANSYS FLUENT indicate that a double perforated plate with an open area percent equal or less than 0.63% can achieve high values of expulsion efficiency. Structural analyses performed using the ANSYS Static Structural solver determined the minimum plate thickness needed to withstand gravitational and hydrodynamic forces experienced during the flight.

Effect of nuclei particle shape and baffle setting on the drum granulation in iron ore sintering process

Discrete element method is used in this work to investigate the sintering granulation process of different-shaped nuclei iron ore particles and different drum baffle settings in rotating drums. The results show that the nuclei particle shape does not affect the flow pattern much, and the baffle setting can affect the time needed for particle flow to stabilize and the fluctuation intensity of particle collisions. The shape of iron ore nuclei significantly affects the number of attached small particles (per unit area), with the order of sphere > schistose > sphero-polyhedron > ellipsoid > polyhedron. Drums with the inclined baffles and ring baffles have faster water exchange rate. The 4-baffle drum has the highest number of adhered particles on the nuclei particle surface, showing a better granulation performance. The drum baffle setting does not affect the proportion of adhered iron ore, coke, and flux particles much.

Effect of ring baffle on erosion in circulating fluidized bed boiler

Effect of ring baffle on erosion in circulating fluidized bed boiler

Semi-analytical method for liquid sloshing in the rigid super-elliptical tank with the ring baffle

Tanks with super-elliptical cross-sections can improve space utilization. The effect of the submerged ring baffle on liquid sloshing in the tank is studied. The semi-analytical method is developed to solve the three-dimensional (3D) sloshing problem in the baffled non-axisymmetric tank, using linear potential theory by dividing the liquid domain into sub-domains. The formal solutions are obtained analytically for the 3D non-axisymmetric sub-domains with arbitrary cross-sections, allowing for the determination of natural frequencies and modes by substituting the formal solutions into the linearized free surface condition, the boundary conditions on the baffle and tank wall and the continuity conditions at the interfaces of the interconnecting sub-domains. The dynamic response equation is derived using the mode superposition method with the damping term for swaying excitation. The obtained solution is validated by comparing it with a numerical model, demonstrating excellent accuracy and efficiency. Parametric studies are performed to determine the effect of the baffle on liquid sloshing, indicating that the baffle can considerably reduce the liquid sloshing when considering an optimal baffle position and width. This technique can be extended to investigate the sloshing reduction in vertical containers with arbitrary cross-sections.

A comparative numerical study of shell and multi-tube heat exchanger performance with different baffles configurations

This study presents a numerical modeling of a shell and tube heat exchanger to analyze six various baffle configurations for increasing the thermal parameters performance and hydraulic parameters performance. The baffle configurations include conventional single segmental (CSS), staggered single segmental (SSS), Flower segmental (FS), hybrid segmental (HS), circular ring baffle (CR), and circular ring with holes (CRH) baffles. Flow of water field characteristics, pressure loss, and heat transfer performance, including effectiveness (ε) and the heat transfer coefficient (h) are studied with a variation of Reloads numbers from 10500 to 38500 to analyze the best performance. The effectiveness and the heat transfer coefficient increase with increasing the Reynolds numbers. The HS configuration results are the largest shell side pressure loss while HS and CR thermal influence on heat exchanger performance augmentation is found to be more significant compared to other configurations for all test cases. Compared to the CSS and SSS baffle configurations, the dead spaces and the recirculation zones are disappearing in both FS and HS configurations where the RCH is superior in overcoming the dead zones completely. The maximum values of the effectiveness and heat transfer coefficient of STHX are achieved in the case of CRH type with enhancement about 166% and 142% respectively, compared to CSS baffle. The CRH accomplished less friction losses than hybrid and ring baffles where the shell side pressure drop for HS was the highest value. The heat transfer coefficients per pressure loss of the RCH are about 138% higher than that of other configurations.

Numerical Investigation of Sloshing Characteristics in Long Moving Vessels with Embedded Concave Rigid-ring Baffle in Gravity Environment

Flat Rigid–ring Baffle [1] (FRB) is a common slosh suppression device in Long Moving Vessel (LMV) to mitigate against oscillation-induced instability due to sloshing of its content but, its relative low performance is unacceptable for desirable safety standard thus, necessitating continuous efforts to investigate other baffle configurations. Investigation of Concave Baffles of varying geometries was carried out and analysed with the ANSYS/CFX [2] and the Computational Fluid Dynamics (CFD). Results were post-processed with the help of Mat lab [3-5] in a gravity milieu. This work was therefore designed to study the sloshing characteristics of Water-Carrying Cylindrical (WCC) tank equipped with three baffles. Model governing equations based on conservation of mass and momentum were developed and solved using Finite Element Analysis (FEA) technique. The model was used to evaluate Damping Ratio (DR) from Mile's equation [1] at 72, 66 and 59 percent standard positions, in a 75 percent filled WCC tank with slenderness ratio of 1.5 excited at a frequency of 2 Hz. The investigated baffles were Concave Rigid-ring Baffle-1 (CARB1) 0.02 m pitch, Concave Rigid-ring Baffle-2 (CARB2) 0.04 m pitch and Flat Rigid-ring Baffle, FRB (control). Data were presented in term of non dimensional DR and as the main performance index. Numerical results were obtained and compared with FRB results also obtained numerically. The results showed that, the concave baffles exhibited [better damping characteristics at 72 and 59 percent water-filled positions of the cylinder which mostly the critical states hence, Concave-Rigid-ring Baffle have better damping effectiveness than Flat-Rigid-ring Baffle.

Numerical Investigation of an Optimum Ring Baffle Design to Optimize the Structural Strength of a Tank Subjected to Resonant Seismic Sloshing

This article numerically investigates the sloshing dynamics and structural response of baffled cylindrical tanks subjected to lateral resonant as well as seismic excitations. The study focuses on suppressing the sloshing forces and fluid movement by increasing the tank structural strength with the help of a baffle and explores the optimum baffle design from among various ring baffle designs. Two approaches have been used for the evaluation of effective positions and design: the modal approach and the fluid–structure interaction (FSI) approach. The numerical model is validated using the tank design code Eurocode-8. Based on the detailed fluid and structural analysis of sloshing pressure and fluid velocity, the structural stress optimum baffle position and design are achieved, which change the structural characteristics of the tank positively. Furthermore, the effectiveness of the selected design is also tested against the El-Centro and Kocaeli earthquakes. It is found that the optimum design increases the tank structural strength by up to 2.5 and 4 times under resonant and seismic excitations, respectively.

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.

Sloshing dynamics in cylindrical tank with porous layer under harmonic and seismic excitations

The severe sloshing induced by earthquake in cylindrical liquefied petroleum gas (LPG) storage tank is of great concern for liquid storage design. For suppressing sloshing, porous material attached to inner periphery of the tank wall is proposed and studied numerically by using OpenFOAM. The model was validated against with the available data of sloshing in cylindrical tank without and with ring baffle, and flow through porous media in a U-tube and porous dam break. Fair agreements between them are obtained. Findings show that damping effects of porous material layer was significant in linear sloshing scenario compared with ring baffle. The porous material layer was also proved to be good pressure absorber and energy dissipator as evidenced in pressure distribution and evolution of velocity and kinetic energy. Under 1-D harmonic excitation, nonlinear swirling waves could be effectively changed into planar waves due to the effects of porous material layer inside cylindrical tank. As a demonstration, sloshing damping effects of porous material layer in a real scale upright cylindrical tank under EL-centro earthquake excitation were investigated numerically.

Numerical simulation of baffled circulating fluidized bed with Geldart B particles

As most classical fluidization technologies, Circulating Fluidized Beds (CFB) are widely employed in chemical and physical operations. However, CFB Reactors still have some disadvantages such as the non-uniform solid particles distribution and the backflow of the solid particles near the wall, which deteriorate the system mixing, and lead to low system conversion/heat and mass transfer rate. To improve the CFB performance, we propose in the current work to study the effect of the ring baffle configuration on the fluidization system hydrodynamics using a multifluid Eulerian CFD model, incorporating the Kinetic Theory of Granular Flow. In this approach, two different types of ring baffles, circular and trapezoidal, were considered and the corresponding results were compared. The results revealed that the incorporation of ring baffles improved the system mixing and reduced the backflow near the wall. Nevertheless, the shape of baffles had a limited impact on the system hydrodynamics.

Numerical and Experimental Research on the Anti-sloshing Characteristic of Swash Bulkhead in LNG Independent Type C Tank

The sloshing induced by partial loaded in LNG (Liquified Natural Gas) independent type C tank will threat the structure of tank. For sloshing suppression, installation of swash bulkhead is a good choice. With model experiment, the sloshing suppression mechanism of perforated swash bulkhead is investigated. Comparing to the tank without swash bulkhead, the suppression efficiency is obtained. Base on the CFD (Computational fluid dynamic) theory, a numerical method is used to sloshing simulation of tank with perforated swash bulkhead, which is verified by the model experiment. Thus, with the same permeation ratio, the effect of anti-sloshing is analysed numerically with comparison of ring baffle and perforated bulkhead. It is found that perforated swash bulkhead has a better performance in sloshing suppression at higher filling level than the ring baffle. And there is a small variation in anti-sloshing efficiency of perforated swash bulkhead

Impact of column geometry and internals on gas and particle flows in a fluidized bed with downward solids circulation: Effect of lateral injection profile and baffles

This paper investigates how solids flow in a circulating fluidized bed can be modified by adding baffles and modifying gas injection locations, and how these changes suggest strategies for a reduction of liquid carryunder in the stripper in Fluid Cokers™. A Computer-Aided Radioactive Particle Tracking (CARPT) method was used with a pilot unit operated at room temperature with the same flux of recirculating coke particles as in the commercial unit. The lateral bitumen injections, and their impact on superficial gas velocity were simulated with 5 banks of 8 lateral gas injectors. In cokers, wet agglomerates that trapped injected bitumen carry unreacted liquid to the stripper. Radioactive simulated agglomerates were tracked to obtain formation-to-stripper time distribution profiles, for each lateral injection jet. Two methods were investigated to reduce liquid carryunder: the addition of a ring baffle and redistribution of liquid between banks. Experiments showed that carryunder can be reduced by either redirecting the bitumen feed from the lowest injection bank to higher banks, or adding a ring baffle with flux tubes in between the lowest and second-lowest injection banks. Combining both methods does not provide additional improvement.

Experimental Investigation of Spherical Tank Slosh Dynamics with Water and Liquid Nitrogen

Understanding, predicting, and controlling fluid slosh dynamics is critical to safety and improving the performance of liquid propulsion systems for space missions. Computational fluid dynamics simulations can be used to predict the dynamics of slosh. Experimental and numerical studies of water slosh have been conducted; however, cryogenic slosh data relevant for validating computational fluid dynamics are lacking. This paper presents the results of slosh experiments with a spherical tank without and with a ring baffle using both water and liquid nitrogen. The experiments were designed to measure forces from continuous excitation over a relevant range of frequencies and amplitudes, natural frequency, and damping parameters. Analytical models and empirical correlations for slosh damping are constructed and compared to the experimental results. An established analytical model for slosh forces is compared to the experimental results for verification purposes. Experiments with a ring baffle installed show increased damping and attenuation of maximum slosh forces. To provide the greatest utility of these data for future rocket and spacecraft missions, the results are presented in a fully nondimensional framework.

Improvement of UV disinfection reactor performance by ring baffles: The matching between the hydrodynamics and UV radiation

The performance of a UV disinfection reactor can be improved with an optimized configuration but its correlation with the fundamental reactor features (i.e., the hydrodynamics and UV radiation) remains indistinct. In this study, the impact of hydrodynamics/radiation on UV disinfection reactor performance was investigated in reactors retrofitted with ring baffles, by using computational fluid dynamics (CFD) simulations. The results showed that proper baffle allocations could increase reduction equivalent fluences (REFs, a performance indicator for UV disinfection reactors) of the 1-lamp and 3-lamp reactor by 37–45% and 36–69%, respectively, depending on the influent UV transmittance. The optimal baffle width was 10 mm for the 1-lamp reactor (i.d. 90 mm) and 30 mm for the 3-lamp reactor (i.d. 150 mm) which led to a maximal matching between the velocity and fluence rate distributions inside the reactor chamber. It was manifested that for UV disinfection reactors retrofitted with ring baffles it was the matching between the hydrodynamics and UV radiation rather than the mixing of the flow that determined the reactor performance improvement. A new parameter named as the specific fluence rate (SFR, ratio of fluence rate to velocity) was defined to characterize the matching level between the hydrodynamics and UV radiation, and the REF was found to relate linearly (R2 ≥ 0.972) with the 10th percentile SFR of the reactor. This study revealed the contribution of ring baffles to UV disinfection reactor performance and for the first time, correlated it quantitatively with the hydrodynamics and UV radiation in the reactor.

Effect of ring baffle configuration in a self-priming venturi scrubber using CFD simulations

This study uses computational fluid dynamics to survey the gas‒liquid flow hydrodynamics of a self-priming venturi scrubber with and without ring baffles. Based on the simulation results, we explore how the structure and configuration parameters such as baffle height, opening-area ratio, and baffle thickness affect the injection flow rate and the homogeneity of the gas‒liquid mixture. In addition, we report the best structure and configuration parameters for the ring baffle. The best position for the ring baffle is at nearly 7/16 of the length of the diffuser above the throat. Having the baffle too near the throat causes large pressure loss, decreasing the injection flow rate. The decrease in opening-area ratio leads to a lower injection flow rate and a more homogeneous gas‒liquid mixture. The optimal value depends on the requirement of the injection flow rate. For the baffle thickness, 5mm is recommended; an overly thick baffle decreases the homogeneity of the gas‒liquid mixture near the throat. All structure parameters and configuration parameters must satisfy the requirement imposed by the injection flow rate and scrubbing efficiency.

Numerical research on the anti-sloshing effect of a ring baffle in an independent type C LNG tank

Liquid sloshing can be suppressed by the installation of baffles. The influence of a ring baffle on sloshing reduction is investigated based on an analysis of parameter sensitivity through computational fluid dynamics (CFD) simulation. Firstly, a series of liquid sloshing experiments with a liquefied natural gas (LNG) independent type C model tank is designed to validate the numerical method. Four definition parameters of the ring baffle, the height (H), the position installation (P), the inclined angle (θ), and the thickness (t), are selected as effective factors, and the efficiency of sloshing reduction is used as the comparison criterion. Research cases of parameter sensitivity are designed by orthogonal tests and computed by a validated numerical method. It is found that the thickness has little effect but the other parameters, especially the height, have significant influence in suppressing sloshing. The directions of improvement of the significant actors are analyzed. The effective height of the ring baffle is discussed numerically with different excitation angles. It is demonstrated that increasing the height of the ring baffle will not bring further improvement in efficiency of sloshing reduction after it exceeds 20% of the tank diameter.

Dynamic response of AP1000 water tank with internal ring baffles under earthquake loads

AP1000 is a standard design developed by Westinghouse for an advanced generation III+ nuclear power plant (NPP) utilizing passive features. Water storage tank of AP1000 plays an important role in cooling down the temperature of the inside of the NPP. However, the water sloshing and fluid-structure interaction effects of AP1000 water storage tank have an important influence on the dynamic response and safety of the nuclear power plant under strong ground motions. In this study, a fluid-structure interaction algorithm of finite element technique is employed to investigate the seismic response of water tank with internal baffles. Four schemes of ring baffle types are considered and the effects of various parameters, such as vertical baffle height, arrangements, and length of baffle on the dynamical response of shield building are investigated. It is indicated that the case 1 with vertical ring baffle near the bottom of tank is the best scheme for reducing dynamic response of shield building in AP1000.

Seismic mitigation performance and optimization design of NPP water tank with internal ring baffles under earthquake loads

The shield building of AP1000 is designed to protect the steel containment vessel of nuclear power plant. Therefore, the safety and integrity must be ensured during the plant life in any conditions such as earthquake. The purpose of this paper is to study the fluid-structure interaction of water in water tank and effects of internal ring baffle on the response of AP1000 shield building under strong ground motions. For this purpose, a fluid-structure interaction algorithm of finite element technique is employed to investigate the seismic response of water tank with internal baffles of different shapes and arrangements under artificial, El-Centro and Kobe earthquakes with peak acceleration of 0.3g. Four optimal designed schemes of different ring baffle types are considered and the influences of various parameters such as vertical baffle height, arrangement locations, baffle height ratio and length of baffle on the dynamical response of shield building are discussed. The numerical results clearly show that the water tank with vertical ring baffle near the bottom of tank can limit the vibration of shield building and can more efficiently dissipate the kinematic energy of the shield building under different earthquake.

The design of the floating baffle for Cassini tank and the analysis of restraining sloshing

In this article, a new floating plate structure with “drive ring” is presented, which breaks the traditional idea of installing fixed baffle in a tank. In order to analyze the performance of this anti-sloshing structure, the effect of sloshing suppression and the liquid sloshing dynamics of this structure in a Cassni tank with numerical simulation is investigated. Liquid sloshing frequencies of the floating plate with different fill ratio under the circumstances of normal weight and micro-gravity were studied. At last aiming at the liquid sloshing amplitude, the suppression effect of the floating plate and rigid ring baffle was also studied under the circumstances of instantaneous angular and “Bang-Bang” transverse acceleration incentives with different fill ratios. The result of the numerical simulation shows that the movable-type floating plate structures can increase the liquid sloshing frequency and can effectively absorb the kinetic energy of the liquid sloshing and reduce liquid sloshing amplitude.