Single Baffle Research Articles

Numerical Study on the Anti-Sloshing Effect of Horizontal Baffles in a Cargo Hold Loaded with Liquefied Cargo

Sloshing of liquefied bulk granular cargoes weakens the stability of cargo carriers when at sea. Using the horizontal rectangle baffle is a promising way to restrain its sloshing motion. But the location height and optimal baffle area rate to achieve a better anti-sloshing effect should be studied first. The discrete element method was adopted to establish the simulation model, and the direct shear test was used for verification. Through the static tilt tests, the definite relationship between the effects of moisture content on cargo motion and particle friction coefficients was acquired. Then, liquefied cargo motion in a cargo hold without baffles and with one and two pairs of horizontal baffles was simulated. Based on variations in the cargo gravity center offset and the sloshing-induced force on the cargo hold, the anti-sloshing effect of different settings of the baffles was compared. Results show that the baffles have the ability to restrain cargo sloshing, and this is important for sea transportation safety. The anti-sloshing effect is better when the baffle plane is right on the cargo top surface compared to the other location heights. Further, there is an optimal length–width combination, e.g., a single baffle plane with a length of 0.26 L and a width of 0.46 B, at which a better anti-sloshing effect could be achieved with the smallest baffle area rate. This study could be useful for the practical application of horizontal baffles for bulk granular cargo carriers.

Heat transfer analysis in a tube contained with louver-punched triangular baffles

The present research assesses the thermal effectiveness of a heat exchange tube incorporating louver-punched triangular baffle (LPTB) vortex generators under turbulent conditions. For Reynolds numbers between 4760 and 29,270, the heat transfer and flow behaviors in the consistent heat-fluxed tube equipped with LPTBs were studied numerically and experimentally. A single baffle height/blockage ratio (b/D = BR = 0.25) and relative baffle pitch (P/D = PR = 1) were used for both baffle attack angles, (α) 30° and 45°, along with three louver size ratios (e/b = LR = 0.24–0.56) as well as five louver angles (θ = 0°, 20°, 30°, 45°, 60°, and 90°). The results show that as the LR and θ values decrease, the Nusselt number (Nu) and friction factor (f) of the LPTB rise owing to the improved fluid mixing process generated by streamwise vortices with stronger turbulence kinetic energy. The LPTB with LR = 0 and θ = 0° provides the greatest f and Nu of about 22.18 and 5.1 times, respectively, although the one with LR = 0.24 and θ = 45° has the largest TEF of about 2.39 and 2.5 for the α = 30° and 45° LPTBs, respectively. Furthermore, an examination into the thermal and flow patterns was conducted through a three-dimensional computation; the validation of the numerical and experimental data yielded satisfactory results. Using measured data, the f and Nu correlations of the α = 30° and 45° LPTBs were additionally established.

Two-fluid simulations of an aerated lab-scale bioreactor

We report the findings of a detailed assessment of various options for computational two-fluid RANS simulations of an aerated agitated 2-L bioreactor equipped with a single baffle and several dip tubes. The simulations were carried out by using the commercial flow solver ANSYS/Fluent. Our focus was on (1) the outlet condition at the liquid’s surface (i.e., including an air head space in the simulation yes or no); (2) the choice between the steady-state Multiple Reference Frames (MRF) approach for modelling the impeller rotation and the dynamic Sliding Mesh (SM) option; (3) the choice between two computational meshes (mosaic or polyhedral); and (4) the effect of using either the realizable k-ε model or the SST k-ω model for dealing with the turbulence in combination with different values for the fixed bubble size (either 1.8 or 2.8 mm). The final conclusion is that the SM impeller model in combination with a polyhedral computational mesh and the SST k-ω turbulence model is to be preferred. All simulations suffer from the occurrence of spurious velocities larger than the impeller tip velocity.

Study of the Sloshing Dynamics in Partially Filled Rectangular Tanks with Submerged Baffles Using VOF and LES Turbulence Methods for Different Impact Angles

This research studies how the angle and dimensions of a single baffle affect the dynamics of a fluid in a closed rectangular tank under an accelerated harmonic vibration in resonance. A half-filled non-deformable rectangular tank with a single centered submerged baffle has been simulated using ANSYS® FLUENT. The study aims to characterize the effect of changing the baffle’s angle; hence, 10 simulations have been performed: without a baffle, 90°, 30°, 60°, 120° and 150°, either maintaining the baffle’s length or the projected height constant. The computational fluid dynamics (CFD) method using volume of fluid (VOF) and large eddy simulation (LES) are used to predict the movement of the fluid in two dimensions, which have been benchmarked against experimental data with excellent agreement. The motion is sinusoidal in the +X direction, with a frequency of oscillation equal to its first vibration mode. The parameters studied have been the free surface elevation, values at three different points and maximum; the center of gravity’s position, velocity, and acceleration; and the forces against the tank’s walls. It has been found that the 90° angle has the most significant damping effect, stabilizing the free-surface elevation, reducing the center of gravity dispersion, and leveling the impacting forces. Smaller angles also tame the sloshing and stabilize it.

Power number and hydrodynamic characterization of a stirred vessel equipped with a Retreat-Blade Impeller and different types of pharmaceutical single baffles

• Vessels with single baffles are commonly found in pharmaceutical facilities. • The experimental Power Numbers (Po) for an RBI in single-baffle vessels were determined. • Results for beavertail, D-type, H-type, finger-type, fin-type baffles were obtained. • CFD predictions for Power Numbers were in good agreement with experiments. • A power-law correlation for Po vs. the area of the baffles in the liquid was derived. Many operations conducted in the pharmaceutical industry take place in glass-lined vessels provided with a Retreat-Blade Impeller (RBI) and one of different types of single baffles. Little information is available on the power dissipated by the RBI and on the hydrodynamic of such systems. Here, the turbulent Power Numbers, Po’s, for an RBI in a scaled-down vessel equipped with one of the different types of single baffles used in the pharmaceutical industry (beavertail, D-type, H-type, finger-type, fin-type baffles) were experimentally determined for different positions of the baffles and computationally obtained, together with the velocity distribution. Vortex formation, occurring with the beavertail baffle, was also quantified experimentally and computationally. The experimental Po values were in close agreement with the computational predictions. Additionally, a simple power-law correlation was established between Po and the dimensionless vertical cross-sectional area of the baffles, resulting in an equation with a good fit with the experimental data.

A new combination approach for optimal design of sedimentation tanks based on hydrodynamic simulation model and machine learning algorithms

The current study aims to propose a novel approach to design rectangular primary sedimentation tanks using computational fluid dynamics (CFD) and artificial intelligence. Hybrid adaptive neuro-fuzzy inference system and particle swarm optimization algorithm (ANFIS-PSO) is trained using CFD model's results. ANFIS-PSO is coupled with two multi-objective algorithms to optimize two objectives: Mean velocity and baffles' configurations. For the single-baffle tank, the optimal baffle position regarding flow velocity was approximately at 0.13 of the basin length, with the height ratio (ratio of baffle height to weir height) of 0.21, but the most cost-effective design was obtained when the single baffle was placed at about 0.06 of total length, with the height ratio of 0.17. Using two baffles could enhance the tank's hydraulic performance, especially when the first and second baffles were at 0.11 and 0.25 of the tank's length, respectively, with the height ratio of 0.33 and 0.22, respectively.

Numerical optimizing noise damping performances of Helmholtz resonators with a rigid baffle implemented at neck in presence of a grazing flow

As an applicable noise attenuator, Helmholtz resonator is mainly used to dampen acoustic noise at low- and medium-frequency ranges. It is typically implemented in combustion-engines and gas turbines to dampen thermoacoustic instabilities. However, it has a narrow effective frequency range and does not work effectively at off-design conditions. In this work, we consider a modified structured Helmholtz resonator (HR) at its neck by applying a rigid baffle in order to maximize its’ noise damping effect and to broaden its frequency bands. The resonator is attached to a cylindrical duct/pipe in presence of a mean flow (grazing flow), aiming to simulate the practical engines flow configuration. For this, a two-dimensional frequency domain numerical model is developed by using COMSOL V5.3. The numerical simulations are carried out by solving the linearized Navier–Stokes equation in frequency domain with low computational cost and time. In order to obtain an optimum design in terms of the maximum noise damping performances, 10 new different configurations/designs are proposed. The effects of 1) the single baffle attached to the upstream or downstream sidewall of the neck ends, that is, Design A, B, C, and D or double baffles, that is, Design E, F, G, and H), 2) the baffle implementation location, 3) the length of the rigid baffle, and 4) the grazing flow low Mach number are evaluated and compared. It is found that Design C is associated with improved TL by 50% and decreased resonant frequency by 20% comparing with the conventional HR. The present preliminary study shows that Design C is the better design. Further experimental and optimization researches are needed to sheds light on the optimum design of a Helmholtz resonator with neck structure being modified, as there is a low Mach number grazing flow.

Flash Smelting Settler Design Modifications to Reduce Copper Losses Using Numerical Methods

A mathematical modeling approach was used to test different design modifications in a flash smelting settler to reduce the copper losses in slag, which is economically disadvantageous for copper processing using the pyrometallurgical route. The main purpose of this study was to find ways to reduce copper losses in slag by improving the settling and coalescence of copper matte droplets, in particular, the smallest droplet sizes of ≤100 µm. These improvements inside the flash smelting (FS) settler were targeted through different settler design modifications. Three different design schemes were tested using the commercial computational fluid dynamics (CFD) software, Ansys Fluent. These settler design modification schemes included the impact of various baffle types, positioning, the height inside the settler, and settler bottom inclinations. Simulations were carried out with and without coalescence and the results were compared with normal settler design. The results revealed that the settling phenomenon and coalescence efficiency were improved significantly with these design modifications. It was concluded that a single baffle design was optimal for reducing copper losses and increasing coalescence efficiency instead of using multiple baffle arrangements. The top-mounted baffle outperformed the bottom-mounted baffle and inclined settler design.

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.

Optimization of Tidal-Combined Flow Constructed Wetland System and Its Removal Effect on Antibiotic Resistance Genes

Antibiotic resistance genes (ARGs) pose a serious threat to environmental biology and public health, along with the discharge and spread of wastewater. The advanced treatment of ARGs in wastewater therefore deserves special attention. In our previous study, we found that tidal flow constructed wetlands can effectively remove multiple ammonia from wastewater. In this study, we further optimized tidal flow constructed wetland systems by adding baffles and cultivating plants; we investigated the influence of process optimization on the removal of ARGs and the influence of functional microorganism distribution on nitrogen removal. The results show that the addition of baffles and plants can effectively improve the removal efficiency of ARGs, with the maximum removal rate of 21 resistance genes, in 7 categories, reaching 83.82%-100.0% with the simultaneous addition of baffles and plants. These removal rates were significantly higher than the increase resulting from a single baffle or plant group. From the comparison of the absolute abundance of ARGs in the substrate and plants, it is clear that the baffles can promote the enrichment of ARGs in the wetland substrate, while uptake by plants is also a way of removing ARGs. Combined with the results of nitrogen-cycle functional gene sequencing, system optimization can increase the diversity and richness of nitrification and denitrification functional microorganisms in the substrate, which is consistent with the higher removal rate of nitrification and total nitrogen in wastewater.

Optimization of static defoaming structure in gas-liquid separator

ABSTRACT The foam generated in the CO2 flooding-produced fluids causes considerable oil and gas treatment problems, especially in the separation process. The foam in the gas-liquid separator is detrimental to the liquid level control and can also reduce the gas-liquid separating efficiency. To accelerate the defoaming process and increase the gas-liquid separating efficiency, different defoaming structures were evaluated and optimized experimentally within a horizontal separator with a gas-liquid cylindrical cyclone (GLCC) at the inlet. When the gas-phase flow is constant at 2 m3/h and the gas-liquid ratios are 0.4, 0.8, 1.2, 1.6, 2.0, and 2.4, the effects of the type, the quantity of defoaming baffles, and the spacing between defoaming baffles were investigated. The defoaming effect of the perforated folded baffle is better than that of the ordinary baffle and multi-cone baffle, reducing up to 11% of the time. With three defoaming baffles, the foam can be broken by sufficient interception and squeeze, and the defoaming effect is much better than a single baffle or two baffles, reducing up to 8% of the time. The relative increase of the defoaming distance is beneficial to the defoaming. Moreover, the defoaming effect of 120 mm spacing is better than 40 mm and 80 mm spacing, reducing up to 9% of the time.

Accuracy of Prediction Methods for Sound Insulation of Homogeneous Single Baffles

Accuracy of Prediction Methods for Sound Insulation of Homogeneous Single Baffles

Parametric & CFD Analysis of Shell and Tube Heat Exchanger by Varying Baffles Geometry

The Shell and Tube Heat Exchanger are most commonly used in current industrial production. In this study, the effect of baffle spacing on pressure drop and heat transfer coefficient are considered in a shell and tube heat exchanger with single segmental baffles and staggered tube layout. The effects of number of baffles are considered 4, 6, 8, 10, 12, and 14 and baffle spacing are considered 366.67, 220,157.14, 122.22, 100, and 84.61 respectively with 38% baffle cut are investigated to study the effect of pressure drop and heat transfer coefficient.Shell and tube heat exchanger with single segmental baffles is designed with same input parameters using Kern’s theoretical method and Bell-Delaware method. From the CFD simulation results, heat transfer coefficient and pressure drop values for varying tube layout are provided.Variation of number of baffles with shell side pressure drop heat transfer coefficient are shown. It is discussed that for both methods (analytical calculation and CFD result) pressure drops will be increases with increases number of baffles. K- Standard turbulence model with second order discretization and fine mesh is selected for CFD simulation considered.The result are shown highly sensitive to tube layout orientation selection, it is observed for this heat exchanger geometry 30 tube layout and 14 baffle arrangement gives slightly better results. Keywords : CFD Ansys simulation, Heat transfer coefficient, Pressure drop DOI: 10.7176/IEL/10-3-03 Publication date: November 30 th 2020

Numerical Simulation and Design Optimization of Baffle Perforations for Better Noise Reduction

An increasing vehicle population always pressurizes to focus on environmental concerns for reduced noise level and harmful emissions. Even though many qualitatively optimized exhaust systems are developed during last two decades, still researchers focus on noise reduction and emission control. Abundant research and development activities are carried out to get a reasonable back pressure drop along with a significant noise reduction in the muffler. The development in computational coding leads to a realistic prediction of flow and acoustic characteristics inside the muffle. Hence the present research work focuses on computational simulation of muffler with single and multi-chambers separated by baffles along with porous pipes. The present work analyses a conventional single baffle muffler configuration and compares the flow behaviour with multi chambers separated by multiple baffle configurations. The shape of the baffle holes is also optimised to get better acoustic performance based on the transmission losses. The flow behaviour and its details are studied inside the muffler to identify the possibility of design improvements. Among the muffler configurations with single and multiple chambers, the overall pressure losses are calculated and compared to get an optimized design with reasonable sound attenuation.

Multiple Fano resonances in metal–insulator–metal waveguide with umbrella resonator coupled with metal baffle for refractive index sensing**Project supported by the National Natural Science Foundation of China (Grant Nos. 61367005 and 61865008) and the Natural Science Foundation of Gansu Province, China (Grant No. 17JR5RA078).

A single baffle metal–insulator–metal (MIM) waveguide coupled with a semi-circular cavity and a cross-shaped cavity is proposed based on the multiple Fano resonance characteristics of surface plasmon polaritons (SPPs) subwavelength structure. The isolated state formed by two resonators interferes with the wider continuous state mode formed by the metal baffle, forming Fano resonance that can independently be tuned into five different modes. The formation mechanism of Fano resonance is analyzed based on the multimode interference coupled mode theory (MICMT). The finite element method (FEM) and MICMT are used to simulate the transmission spectra of this structure and analyze the influence of structural parameters on the refractive index sensing characteristics. And the transmission responses calculated by the FEM simulation are consistent with the MICMT theoretical results very well. The results show that the figure of merit (FOM) can reach 193 and the ultra-high sensitivity is 1600 nm/RIU after the structure parameters have been optimized, and can provide theoretical basis for designing the high sensitive refractive index sensors based on SPPs waveguide for high-density photonic integration with excellent performance in the near future.

Sound insulation properties of two-layer baffles used in vibroacoustic protection

The subject of the research presented in the article was the modelling of acoustic properties of two-layer baffles, used in vibroacoustic protection. Baffles of this type are used, among others, in the construction of walls of the sound insulating enclosures of machines and devices. The heterogeneous single baffles that were analysed were panels made of two sound insulation layers, solid rubber and a steel plate. A sound insulation calculation model for heterogeneous single two-layer baffles used in vibroacoustic protection has been proposed. The model has been verified in relation to the laboratory tests of rubber-steel baffles of various thickness. The results of calculations were also compared with the spectral characteristics of sound insulation obtained with the use of the mass law and commercial software. Using the proposed calculation model, simulation tests of the sound insulation effectiveness of rubber-steel and rubber-aluminium baffles were performed.

Application of Statistical Energy Analysis Method for modelling sound insulation of baffles

The article presents the model of sound insulation of single homo-geneous baffles based on the Statistical Method of Energy Analysis. The determined frequency characteristics of airborne sound insulation of the baffles obtained from the calculation model with the results of experimental tests were compared. Calculations using the Statistical Method of Energy Analysis and laboratory tests were performed for plates made of plexiglass and acrylic.

Calculation models for analysing the sound insulating properties of homogeneous single baffles used in vibroacoustic protection

The article presents the results of laboratory tests and calculations, using selected theoretical models, regarding the airborne sound insulation of five homogeneous single baffles. The analysed materials of various thickness, such as steel, aluminium, PVC, acrylic and plexiglass, are used in the construction of walls in vibroacoustic protection as sound absorbing and insulating enclosures or acoustic barriers. Based on the analysis of the obtained results, a new calculation model of sound insulation for single homogeneous baffles used in passive noise control methods was proposed. A comparative analysis of computational models for these materials showed that the proposed model is the most accurate among traditional theoretical ones, both in terms of the frequency characteristic and the single-number index of sound insulation. Verification of the new model was carried out with reference to the results of experimental tests, results obtained using commercial software and experimental results from another testing laboratory of building partitions, concerning several glass plates, which may also be used as elements of vibroacoustic protection.

Slosh-induced hydrodynamic force in a water tank with multiple baffles

This study uses laboratory experiments and a Large Eddy Simulation (LES) model to investigate the sloshing phenomenon in a rectangular water tank with multiple bottom-mounted baffles. The kinematic motion of the water surface was solved by the Volume of Fluid (VOF) method. The simulation results were verified by the measured wave heights in a water tank installed on a shaking table. The numerical model was employed to systematically determine the effects of the spacing and height of the baffles on the sloshing phenomenon. The simulation results indicate that the natural frequency of the tank was altered by the multiple baffles and was related to the effective water depth above the baffles. The diminishing effect of multiple baffles on the hydrodynamic force is better than that of a single baffle. In addition, the sloshing force on the sidewalls of the tank can be characterized by the excitation amplitude, frequency, and water depth. While the sloshing height and hydrodynamic force decrease as the baffle number or baffle height increase, the effect of baffles on the sloshing lessens when the relative baffle height hb/hw ≥ 0.75.