Available Models In Literature Research Articles

Improved Drift Flux Void Fraction Model for Horizontal Gas-liquid Intermittent Flow

Drift Flux model is widely used in literature to predict void fraction in two-phase gas-liquid flow. Drift flux model has been used for all flow regimes. The distribution parameter implemented in the model is very crucial for the accuracy of the model. A new distribution parameter was developed in this paper as a function of two dimensionless parameters and flow regime (slug or plug). The new model showed a superior predicted void fraction accuracy over all available models in literature. In this paper, the influence of the flow regimes was implemented in the formulation of the drift flux model distribution parameter for the first time in literature. The drift velocity was found to be negligible in the horizontal configuration. The proposed model was validated using unbiased data from literature from different sources and for a wide range of liquid viscosity from water up to high viscosity oil (600 cP) and pipe diameter from 19 mm up to 152 mm. The mean relative absolute error of the proposed model using all data bank is around 16% while the least error model available in literature is around 19%. Moreover, the most recent models of Rassame and Hibiki (2018) and Kong et al. (2018b) give 33% and 50%, respectively.

Analytical and numerical calculation of the detachment of particle structures from fibers

Not much research has been done on the detachment of deposit structures from fibers in gas flow. This study presents two approaches to determine the fluid velocities uc required for detachment. The first is an analytical model based on the imbalance of drag and adhesive forces. With the help of available models in literature two curves for uc as a function of deposit diameter were calculated. The two curves represent the different conditions present in a deposited structure, consisting of a mixture of reactive and inert matter, before and after reaction. It approximates the structure by one sphere, that consists of two identical half spheres, of which one detaches due to drag. The second approach is a CFD model, in which the deposited particle structure is represented through an immersed boundary method (IBM). It calculates adhesive forces based on the van der Waals force between two half-spaces, while drag is directly evaluated from flow properties at the structure’s surface. To be comparable with the analytical approach, it also approximates the deposit with two half spheres. The models are capable of describing detachment velocity behavior as a function of deposit structure size and porosity as reported in literature.Copyright © 2021 American Association for Aerosol Research

The effect of Stefan flow on Nusselt number and drag coefficient of spherical particles in non-isothermal gas flow

A Stefan flow can be generated during a phase change or reactions of a particle immersed in a fluid. This study investigates the effect of Stefan flow on the exchange of momentum (drag coefficient (CD)) and heat transfer (Nusselt number (Nu)) between the particle and bulk-fluid. Fully resolved simulations were carried out for a flow near a spherical particle immersed in a uniform bulk flow. The immersed boundary method is used for implementing fluid-solid interactions and the particle is considered as a static boundary with fixed boundary conditions. In a non-isothermal flow, the changes in thermophysical properties at the boundary layer played a role in the variation of CD and Nu by a Stefan flow further. The previously developed model for the drag coefficient of a spherical particle in a uniform isothermal flow was modified for a uniform non-isothermal flow. The model is developed based on physical interpretation. A new model is developed for the Nusselt number for a spherical particle with a uniform Stefan flow combining available models in literature. The models are validated for Stefan Reynolds number −8⩽Resf,p⩽25 and particle Reynolds number of 2⩽Ref⩽30 in gas flow (i.e. Pr≈0.7).

Permeate Flux Control in SMBR System by Using Neural Network Internal Model Control

This paper presents a design of a data-driven-based neural network internal model control for a submerged membrane bioreactor (SMBR) with hollow fiber for microfiltration. The experiment design is performed for measurement of physical parameters from an actuator input (permeate pump voltage), which gives the information (outputs) of permeate flux and trans-membrane pressure (TMP). The palm oil mill effluent is used as an influent preparation to depict fouling phenomenon in the membrane filtration process. From the experiment, membrane fouling potential is observed from flux decline pattern, with a rapid increment of TMP (above 200 mbar). Membrane fouling is a complex process and the available models in literature are not designed for control system (filtration performance). Therefore, this work proposes an aeration fouling control strategy to measure the filtration performance. The artificial neural networks (Feed-Forward Neural Network—FFNN, Radial Basis Function Neural Network—RBFNN and Nonlinear Autoregressive Exogenous Neural Network—NARXNN) are used to model dynamic behaviour of flux and TMP. In this case, only flux is used in closed loop control application, whereby the TMP effect is used for monitoring. The simulation results show that reliable prediction of membrane fouling potential is obtained. It can be observed that almost all the artificial neural network (ANN) models have similar shape with the actual data set, with the highest accuracy of more than 90% for both RBFNN and NARXN. The RBFNN is preferable due to simple structure of the network. In the control system, the RBFNN IMC depicts the highest closed loop performance with only 3.75 s (settling time) for setpoint changes when compared with other controllers. In addition, it showed fast performance in disturbance rejection with less overshoot. In conclusion, among the different neural network tested configurations the one based on radial basis function provides the best performance with respect to prediction as well as control performance.

Real drive cycles analysis by ordered power methodology applied to fuel consumption, CO2, NOx and PM emissions estimation

In this work three fuel consumption and exhaust emission models, ADVISOR, VT-MICRO and the European Environmental Agency Emission factors, have been used to obtain fuel consumption (FC) and exhaust emissions. These models have been used at micro-scale, using the two signal treatment methods presented. The manuscript presents: 1) a methodology to collect data in real urban driving cycles, 2) an estimation of FC and tailpipe emissions using some available models in literature, and 3) a novel analysis of the results based on delivered wheel power. The results include Fuel Consumption (FC), CO2, NOx and PM10 emissions, which are derived from the three simulators. In the first part of the paper we present a new procedure for incomplete drive cycle data treatment, which is necessary for real drive cycle acquisition in high density cities. Then the models are used to obtain second by second FC and exhaust emissions. Finally, a new methodology named Cycle Analysis by Ordered Power (CAbOP) is presented and used to compare the results. This method consists in the re-ordering of time dependant data, considering the wheel mechanical power domain instead of the standard time domain. This new strategy allows the 5 situations in drive cycles to be clearly visualized: hard breaking zone, slowdowns, idle or stop zone, sustained speed zone and acceleration zone. The complete methodology is applied in two real drive cycles surveyed in Barcelona (Spain) and the results are compared with a standardized WLTC urban cycle.

Modeling and design of a class of hybrid bistable symmetric laminates with cantilever boundary configuration

Multistable laminates have been widely analyzed in the recent past for their potential in morphing applications. However, all the analytical models developed up until now have taken into account only the free-free boundary condition. In this work two objectives are met: (a) an analytical model is developed, which extends the previously available models in literature to account for the cantilever boundary condition for a special class of hybrid bistable symmetric laminates (HBSL); (b) the previously proposed HBSL is modified by replacing the aluminum layers with bi-direction glass-epoxy prepregs in the layup. It is observed that the modified layup has a curvature similar to the previously proposed HBSL while maintaining bistability. The analytical model developed here successfully captures the equilibrium shapes and the snap-through behavior for this special class of laminates which is validated against the results obtained using ABAQUS® and experiments. The developed model is then subsequently used to study the design space and bistability characteristics of the HBSL and the proposed modified layup (m-HBSL) in the cantilever boundary condition.

Long‐term data of reinforced concrete beams subjected to high sustained loads and simplified prediction method

In 1967–1985, a research campaign comprising a unique set of long‐term experimental data on concrete beams was conducted in joint collaboration with four Belgian research institutes to determine the influence of creep and shrinkage on the long‐term behavior of reinforced concrete members. The main aim of the research campaign was the determination of the long‐term behavior of cracking and deformations subjected to permanent loads considering the influence of the magnitude of the loads and various reinforcement ratios.The objective of this article is twofold: to provide an overview of the measured data of the reinforced beams of the research campaign, which has never been published before, and to propose a simplified calculation method based on available models in literature that can predict the available measurement data. A simplified calculation model is proposed, which accounts for nonlinear creep strains due to high stresses, shrinkage, aging, and cracking in reinforced concrete beams. This numerical method is based on a cross‐sectional analysis formulated using the layered Euler‐Bernoulli beam theory, allowing fast and accurate predictions of strains, stresses, and deflections as a function of time based on fib Model Code 2010 and EN1992‐1‐1. The measurements of the beams subjected to high permanent loads during a time period of 4 years are compared to the results evaluated with the proposed simplified calculation model. The results show that the proposed simplified calculation method based on the current models of EN1992‐1‐1 and fib Model Code 2010 can predict the long‐term behavior of reinforced concrete beams subjected to high loads in good agreement with the measurements.

A combined model to simulate the powder densification and shape changes during hot isostatic pressing

Under high temperature and pressure during Hot Isostatic Pressing (HIP), various deformation and sinter mechanisms such as plastic yielding, power law creep, and diffusion occur. They contribute either simultaneously or consecutively to the densification process depending on temperature and pressure levels. Some published works have shown that neither the pure plastic model nor the pure viscoplastic model sufficiently models the densification process during HIP, therefore a combined model which includes both a time independent plasticity and a rate dependent plasticity (creep) should be used. An innovative aspect of this work in comparison with available models in literature is the accommodation for model inaccuracies in the initial creep stage. The densification model incorporates the initial creep mechanism which occurs for a short time with a higher rate as compared to the steady stage creep rate. In this study, a combined model which consists of the influence of plasticity, primary creep, and secondary creep mechanisms is used. The authors believe that this approach can improve the quality of “near-net-shape” simulation.Innovative Aspects: The proposed model is more robust and predicts the final shape of HIP-ed components better which will support the production of Selective Net Shape or Net Shape HIP components. The reported results are of importance for companies producing big and complex shaped components through powder-HIP.

Implementing radial basis function neural network for prediction of surfactant retention in petroleum production and processing industries

ABSTRACTChemical flooding is an effective way to gain higher oil recovery as part of a tertiary oil recovery scheme. There are several variables contribute in surfactant retention in petroleum production including type of rock, pH, chemical structure of surfactant, salinity of formation water, acidity of oil, mobility, microemulsion viscosity, and cosolvent concentration. Although different theoretical studies on the mechanisms of surfactant retention are reported in the literature there is little research on the development of an accurate and effective model for prediction of surfactant retention in petroleum production. In this study, radial basis function was developed based on experimental dynamic surfactant retention data. The experimental data include a wide range of conditions. Results of the modeling study showed that the developed model is very accurate and robust in prediction of actual surfactant retention data. In addition, the comparison between the proposed model in this study and available models in literature showed the superiority of this model.

Development of Nusselt number correlation using dimensional analysis for plate heat exchanger with a carboxymethyl cellulose solution

Versatile applications of plate heat exchangers (PHE's) in various industrial processes signify their command over other types of heat exchangers. The objective of this work was to derive Nusselt number correlations using dimensional analysis in terms of all the parameters to determine the heat transfer coefficients in a PHE for various concentrations of carboxymethyl cellulose (CMC) solution and it was also compared with the available models in literature. The heat transfer coefficient increases with increase in concentration of CMC from 0.1 to 0.6 %w/w and also increases with increase in mass flow rates of both cold and hot fluids from 0.016 to 0.099 kg/s. The Nusselt number correlation developed using dimensional analysis has predicted the Nusselt number for the given PHE with a RMS deviation of 14.61.

Influence of bound water layer on the viscosity of oxide nanopowder suspensions

Abstract Nanopowder suspensions exhibit much higher viscosities compared to micron size powders. The current viscosity models greatly underestimate the viscosity of nanopowder suspensions and hence are inaccurate. Recently, it was shown that a bound water layer around the particles is partially responsible for the high viscosities of alumina nanopowder suspensions. In the present study, the existence and effect of the bound water layer on suspension viscosity has been validated for other oxide systems such as zirconia, yttria stabilized zirconia and titania. The water melting events were studied by low-temperature differential scanning calorimetry (LT-DSC) to investigate the nature of the bound water and how it varied by different oxide systems. Onset of the bound water for these oxides varied from −1 to −7 °C. The variation in melting behavior of bound water was related to the presence of charged species in solution and gel-like hydroxide formation. The bound water content was estimated and incorporated into a modified Krieger–Dougherty (K–D) equation. The modified equation was employed to interpret the experimental data. Intrinsic viscosity values were estimated as 11.6, 6.6, 5.1 and 3.1 at a shear rate of 50 s −1 for alumina, titania, zirconia and YSZ, respectively. Increasing shear rate predicted lower intrinsic viscosity values. Modified K–D equation could predict the suspension viscosity much better than the other available models in literature while distinguishing the differences between oxide systems.

Analytical Comparisons of Standardized Nasal Cavity

Human nasal cavities are unique and distinct when compared to each other. This causes difficulties in comparing the available information as there are no clear guidelines or standard procedures to adhere with. The creation of a standardized model is important to represent a certain population and will be beneficial for related fields of research. A standardized healthy female Malaysian nasal cavity was used as an initial step towards generalizing the bigger population. This is the first essential step towards solving inter-individual differences caused by geometrical variations among humans and the lack of universality from previous researches. In this study, critical comparisons were carried out to evaluate the standardized model with eight different models from previous works. This paper focuses on several aspects for comparisons such as cross sectional areas of the complete model, half model (right nasal cavity) and pressure drops obtained from computational analysis. The results show obvious differences as individual models used were obtained from different populations. This provides a new opportunity for a better understanding of the standardized model which will be a vital addition to the available models in literature.

Evaluation of Nd: YAG Laser Welding Efficiencies for 304L Stainless Steel

The laser material interaction, controlling of process parameters and their effect on melting, solidification and process efficiency are critical to understand the behavior of the weld joints. This paper aims to study the effect of welding speed on different process efficiencies in 304L Stainless Steel. The bead on 304L austenitic stainless steel plate is created by varying welding speed. A novel semi-empirical method based on weld pool volume measured from experimental results is used to predict the melting efficiency of Nd: YAG laser welding process. The dimensionless parameter models are used to estimate various types of measurable controlling parameters. These parameters have good agreement with the various available models in literature.

Prediction of tar and particulate in biomass gasification using adaptive neuro fuzzy inference system

Biomass is an important primary source of renewable energy source. Producer gas, a derivative of Biomass, comprises of tar and particulate content which is harmful and critical parameter for IC engine application, which influences the design of filter. Numerous researchers have developed various types of filter for gas cleaning system in order to reduce the tar content and particulate in producer gas. In this work, an experimental investigation has been carried out on the newly developed hybrid compact filter using two different feeds such as rice husk and wood. The experimental results obtained were used to justify the newly developed system with adaptive neuro-fuzzy inference system(ANFIS). The data has been collected taken from an experimental database of a 20 kW open core downdraft TNAU(Tamil Nadu Agricultural University)-modified gasifier with compact hybrid filter system. A comparison between the predictions of ANFIS model with other available model in literature is presented. The ANFIS results reveal that the model delivers the tar and particulate content with an accuracy of 99.98%. The test results prove the possibility to develop and evaluate an ANFIS based model to predict tar content and particulate for any filter design under varying input conditions.

Modeling of indoor radon concentration from radon exhalation rates of building materials and validation through measurements

Building materials are the second major source of indoor radon after soil. The contribution of building materials towards indoor radon depends upon the radium content and exhalation rates and can be used as a primary index for radon levels in the dwellings. The radon flux data from the building materials was used for calculation of the indoor radon concentrations and doses by many researchers using one and two dimensional model suggested by various researchers. In addition to radium content, the radon wall flux from a surface strongly depends upon the radon diffusion length (L) and thickness of the wall (2d). In the present work the indoor radon concentrations from the measured radon exhalation rate of building materials calculated using different models available in literature and validation of models was made through measurement. The variation in the predicted radon flux from different models was compared with d/L value for wall and roofs of different dwellings. The results showed that the radon concentrations predicted by models agree with experimental value. The applicability of different model with d/L ratio was discussed. The work aims to select a more appropriate and general model among available models in literature for the prediction of indoor radon.

Surface Potential of Methyl Isobutyl Carbinol Adsorption Layer at the Air/Water Interface

The surface potential (ΔV) and surface tension (γ) of MIBC (methyl isobutyl carbinol) were measured on the subphase of pure water and electrolyte solutions (NaCl at 0.02 and 2 M). In contrast to ionic surfactants, it was found that surface potential gradually increased with MIBC concentration. The ΔV curves were strongly influenced by the presence of NaCl. The available model in literature, in which surface potential is linearly proportional to surface excess, failed to describe the experimental data. Consequently, a new model, employing a partial charge of alcohol adsorption layer, was proposed. The new model predicted the experimental data consistently for MIBC in different NaCl solutions. However, the model required additional information for ionic impurity to predict adsorption in the absence of electrolyte. Such inclusion of impurities is, however, unnecessary for industrial applications. The modeling results successfully quantify the influence of electrolytes on surface potential of MIBC, which is critical for froth stability.

Evaporative cooling and the Mpemba effect

The Mpemba effect is popularly summarized by the statement that “hot water can freeze faster than cold”, and has been observed experimentally since the time of Aristotle; however, there exist almost no theoretical models that predict the effect. With a view to initiating rigorous modelling activity on this topic, this paper analyzes in some depth the only available model in literature, which considers the potential role of evaporative cooling and treats the cooling water as a lumped mass. Certain omissions in the original work are highlighted and corrected, and results are obtained for a wide range of operating conditions—in particular, initial liquid temperature and cooling temperature. The implications and importance of the results of the model for experimental design are discussed, as are extensions of the model to handle more realistic 1-, 2- and 3-dimensional configurations.

Viscosity and Viscosity Estimate Model of Fluoride-Free and Titanium-Bearing Mold Fluxes

The relationship between the binary basicity (CaO/SiO 2), TiO 2, Na 2O, Li 2O, MgO, MnO, B 2O 3 and viscosity for fluoride-free and titanium-bearing mold fluxes were systematically researched. The rotating cylinder method was employed in the experiment to measure the viscosity of the slag. The results indicate that Li 2O, B 2O 3 and Na 2O play major roles in decreasing viscosity, especially Li 2O, which is the most effective flux, while MgO and MnO exert little influence on viscosity. Meanwhile, it can be concluded that with increasing TiO 2 content, the viscosity of fluoride-free and titanium-bearing mold fluxes increases at first but then falls when the amount of TiO 2 is greater than 6.0%. Based on large amounts of experimental statistics of the viscosity of fluoride-free and titanium-bearing mold fluxes, an available model in literature for predicting the mold-slag viscosity was modified. This modified model can be used to predict the viscosity of fluoride-free and titanium-bearing mold fluxes. In fact, the predicted values approximate the observed values with a ±10.6% average deviation. Compared with the classical models, the average deviation is higher and it was found that the modified model can be used to estimate the viscosity of fluoride-free and titanium-bearing mold fluxes.

Regulation of Force Dynamics in Fast Twitch Muscle

Several regulatory steps controlling skeletal muscle force generation have been experimentally demonstrated, and mathematical models have been developed to understand these mechanisms. Here, we investigated the minimal set of mechanisms required to describe both the range in peak force from twitch to tetanus and the characteristics of contraction and relaxation. Hereto, we measured calcium fluorescence using Rhod‐2 and force kinetics in murine EDL muscles at different stimulation frequencies, ranging from twitch to tetanus. Next, we tested available models in literature with a validated spatiotemporal calcium model as input. Monte Carlo simulations, covering a large parameter space, have been performed to test if the evaluated force models could describe the force dynamics.These simulations showed that calcium activation of the cross bridges sufficed to describe the increment in force from twitch to tetanus. In addition, numerical analysis indicated that extending the models with cooperative activation through strongly attached cross‐bridges was required to reproduce the dynamics of contraction and especially of relaxation. Therefore, we hypothesize that the minimal set of mechanisms to describe force dynamics in fast twitch muscle includes both activation by calcium bound to troponin and cooperative activation through strongly attached cross‐bridges.

Tracing the Void Content Development and Identification of its Effecting Parameters during in Situ Consolidation of Thermoplastic Tape Material

One of the ways to identify the quality of structures made from fibre-reinforced thermoplastic material is by examining its void content percentage. Significant improvement in mechanical properties can be achieved by minimising it. The purpose of this work was to develop a simulation tool from existing available model in literature, to trace out the void development inside the laminate during the manufacturing and identification of major influencing process parameter. The effects of consolidating force, process velocity, hot gas flow in the heating region, and repetitive passes were investigated through simulation. A series of experiments was carried out on several AS4/PEEK laminated plates manufactured by automatic tape placement process. Simulated void distribution through thickness and density were compared with measured values to trace the effecting input parameters. Thickness build-up with successive lay-ups is also monitored online and the average thickness lies in close proximity to the predicted range. Major influencing process parameters were identified.