Generation of realistic nonwoven and foam filter geometry and mesh for filtration simulation using open-source tools

Recovery of liquid aerosols (mists) from industrial processes is typically accomplished through coalescence filtration, employing highly porous nonwoven (fibrous), knitted or foam media which are regarded to potentially provide high collection efficiencies. Highly resolved pore-scale computational fluid dynamics (CFD) analysis of mist filtration processes is increasingly becoming an important tool for design and optimization of such filter media. A key to efficient application-specific optimization of filter media is the ability to generate CFD-suitable virtual filter geometries with controllable geometric parameters including solidity, fibre diameters, morphology, etc. - yet, a review of the literature suggests that the current designs are heavily reliant on computed tomography (CT) scans of available filter media for accurate representation of the pore-scale structures in a computational simulation. In the present study, a novel methodology is presented for generating realistic virtual nonwoven (fibrous) and foam filter geometries with parametric customizability, using open-source tools including Python, OpenFOAM libraries, Gmsh and Blender. Further, a methodology for the generation of a computational mesh suitable for multiphase CFD at the pore-scale is delineated for the two types of filter media generated using the present technique, viz: nonwoven and foam, using open-source tools available within the OpenFOAM framework. The proposed methodology for the generation of virtual filter media and computational mesh is validated by qualitative comparison against with images from electron-microscopy (SEM) scans of real filters as well as comparison of the single-phase pressure drops predicted from CFD simulations using the generated fibrous and foam media with different solidities, fibre (or strand of foam) diameters, filter thicknesses, against the literature. The excellent agreement between the predicted pressure drops and the literature and its consistency over the several different geometric conditions considered for comparison reaffirms the validity of the proposed methodology for efficient virtual filter media development, which can eventually lead to enhanced parametric optimization capabilities and reduced design costs and lead times

Influence of filter domain size on the simulation of gas-liquid filtration in nonwoven and foam media

The process of coalescence mist filtration in liquid- or gas-liquid systems is strongly controlled by the dynamics of the multi-component fluid transport at the pore- or fibrescales and its interactions with the filter media. However, current designs of mist filters are largely based on empirical data or on single-fibre filtration theory, primarily because of the complexity and difficulty in making accurate measurements at such (small) length scales. Current advancements in high performance computing provide a unique possibility to understand the dynamics of such flows using highly resolved droplet and interface capturing computational fluid dynamics (CFD) simulations - which can provide vital data for application-specific optimization of filter media. However it is important that the spatio-temporal resolutions required to accurately numerical model the fluid dynamics of micro or nano-fibre filtration processes at full size of the filters may typically demand simulations to be run with several hundred million (to over a billion) computational cells and long run-times. Hence, for reduced design lead times as well as computational cost, it is desirable to keep the size of the filter domain to a minimum, while ensuring that the largest fluid structures and scales are captured in the simulations. A review of the (limited) literature on CFD simulations of the mist-filtration process reveals that the size of the filtration domain have been predominantly chosen rather arbitrarily based on the a set multiple of the Brinkman screening length or by the computing power available - and no reported studies are yet available that address conditions of high levels of fluid saturation that involve large fluid structures. In the present study, a series of systematic computational simulations using successively larger domain sizes are carried out to identify the relationship between the characteristics of the two phase flow (such as saturation, thickness of liquid layer, pressure drop, etc.) and the size of the filter domains considered. Two vastly different types of filter media, nonwoven and foam, with similar properties such as packing density, fibre (or element of foam) diameters are chosen to additionally infer the influence of filter structures at the pore-scales to the domain size. The transient simulations are carried out using the interface capturing volume-of-fluid (VOF) solver available within the open-source CFD framework OpenFOAM

Simulating transport in and entrainment form nonwoven fibrous, knitted, and opne-cell foam filters

The movement and re-entrainment of liquid droplets from three different filter media, namely fibrous, knitted, and open-cell foam was investigated numerically using computational fluid dynamics (CFD). A range of face velocities were considered which resulted in a range of oil transform rates and steady state saturation levels. It will be shown that liquid volume fraction in filters depends on velocity and time. The minimum velocity required for detachment of droplets was also identified. The main purpose of this research is to investigate the behaviour of pre saturated oil-mist filters in different geometric configuration and also different air flow conditions. In this study, all the produced filter geometries have a packing density (solidity) of 2 % with fiber/element diameter of 9 μm and overall dimensions of: 2mm (z), 0.5 mm (x), and 0.5 mm (y). In order to capture the gas-liquid interface, the Volume of Fluid (VOF) method will be applied. To perform the simulations, the open source computational fluid dynamics (CFD) toolbox, OpenFOAM is used. To verify the accuracy of computations, the calculation of clean pressure drop is compared against well-established pressure approximation in the literature. This work has examined the movement and re-entrainment of droplets in fibrous, knitted, and open-cell foam media with a range of different face velocities. It was found that by increasing in velocity and time, liquid volume fraction in the filters reduced though re-entrainment once a threshold of 2 m/s in all three cases. Furthermore, it has been shown that knitted media produced largest re-entrainment and the fibrous media the least. It is worth mentioning that other factors such as saturation, initial droplet position, temperature may play an important role in re-entrainment form filter which are not investigated in this study. It is important to note however that these results would need to be validated in real media. The large drops entrained from knitted media would be advantageous in many cases as they would readily settle under gravity

Antiviral activity of the mineralocorticoid receptor NR3C2 against Herpes simplex virus Type 1 (HSV-1) infection

Abstract Analysis of a genome-scale RNA interference screen of host factors affecting herpes simplex virus type 1 (HSV-1) revealed that the mineralocorticoid receptor (MR) inhibits HSV-1 replication. As a ligand-activated transcription factor the MR regulates sodium transport and blood pressure in the kidney in response to aldosterone, but roles have recently been elucidated for the MR in other cellular processes. Here, we show that the MR and other members of the mineralocorticoid signalling pathway including HSP90 and FKBP4, possess anti-viral activity against HSV-1 independent of their effect on sodium transport, as shown by sodium channel inhibitors. Expression of the MR is upregulated upon infection in an interferon (IFN) and viral transcriptional activator VP16-dependent fashion. Furthermore, the MR and VP16, together with the cellular co-activator Oct-1, transactivate the hormone response element (HRE) present in the MR promoter and those of its transcriptional targets. As the MR induces IFN expression, our data suggests the MR is involved in a positive feedback loop that controls HSV-1 infection

ANN multiscale model of anti-HIV Drugs activity vs AIDS prevalence in the US at county level based on information indices of molecular graphs and social networks

[Abstract] This work is aimed at describing the workflow for a methodology that combines chemoinformatics and pharmacoepidemiology methods and at reporting the first predictive model developed with this methodology. The new model is able to predict complex networks of AIDS prevalence in the US counties, taking into consideration the social determinants and activity/structure of anti-HIV drugs in preclinical assays. We trained different Artificial Neural Networks (ANNs) using as input information indices of social networks and molecular graphs. We used a Shannon information index based on the Gini coefficient to quantify the effect of income inequality in the social network. We obtained the data on AIDS prevalence and the Gini coefficient from the AIDSVu database of Emory University. We also used the Balaban information indices to quantify changes in the chemical structure of anti-HIV drugs. We obtained the data on anti-HIV drug activity and structure (SMILE codes) from the ChEMBL database. Last, we used Box-Jenkins moving average operators to quantify information about the deviations of drugs with respect to data subsets of reference (targets, organisms, experimental parameters, protocols). The best model found was a Linear Neural Network (LNN) with values of Accuracy, Specificity, and Sensitivity above 0.76 and AUROC > 0.80 in training and external validation series. This model generates a complex network of AIDS prevalence in the US at county level with respect to the preclinical activity of anti-HIV drugs in preclinical assays. To train/validate the model and predict the complex network we needed to analyze 43,249 data points including values of AIDS prevalence in 2,310 counties in the US vs ChEMBL results for 21,582 unique drugs, 9 viral or human protein targets, 4,856 protocols, and 10 possible experimental measures.Ministerio de Educación, Cultura y Deportes; AGL2011-30563-C03-0

Leakage of protein into lungs of preterm ventilated rabbits is correlated with activation of clotting, complement, and polymorphonuclear leukocytes in plasma

We investigated whether leakage of protein in lungs of pre term ventilated rabbits of 28- and 29-d gestational age is correlated with activation of clotting, complement, and polymorphonuclear leukocytes (PMN) in plasma. We found signs of systemic activation of clotting, complement, and PMN in ventilated 28-d gestational age rabbits, as indicated, respectively, bf increased median plasma fibrin monomer concentrations (83 versus 40% of normal adult rabbit plasma in nonventilated 28-d gestational age rabbits, p <0.01), decreased median plasma CH50 activity (112 versus 122 U/L in nonventilated 28-d gestational age rabbits, p <0.05), and increased median plasma beta-glucuronidase concentrations (159 versus 97% of maximal activated adult rabbit plasma in nonventilated 28-d gestational age rabbits, p <0.05). We did not find signs of systemic activation in the ventilated 29-d gestational age group. Higher median total protein concentrations in alveolar wash of the ventilated 28-d gestational age rabbits (2.7 versus 1.3 mg/mL in the nonventilated rabbits, p <0.01) indicated protein leakage into the lungs, and this protein leakage was more pronounced in the lungs of ventilated 28-d gestational age rabbits than in those of ventilated 29-d gestational age rabbits (2.1 mg/ml, p <0.01). The total protein concentration in the alveolar wash of all 28-d gestational age rabbits was correlated with the concentration of fibrin monomers (p = 0.51, p = 0.035) and beta-glucuronidase (rho = 0.61, p = 0.011), and the CH50 activity (rho = -0.73; p = 0.002) in plasma. We conclude that leakage of protein in lungs of preterm ventilated rabbits of 28-d gestational age is correlated with activation of clotting, complement, and PMN in plasma. This activation process may contribute to lung injury by intravascular and intraalveolar deposition of fibrin and formation of proteinaceous edema

Effect of Contact Angle on Equilibrium Saturation during Mist Filtration in Nonwoven Fibrous and Foam Media

Coalescence filtration using knitted, foam or nonwoven fibrous media is the widely applied in the industry for separation and recovery of liquid mists that are generated in many processes, including lubricated machining, compressors and engine crankcases. The dynamics of multi-component/ phase fluid transport and its interaction with the filter surface at the pore-scale and the contact angle dynamics are expected to significantly influence performance and efficiency of filtration processes. Most mist filters currently used in the industry are hydro- or oleophillic in nature, even though it is expected that philic filters will develop higher steady state saturation levels compared to phobic media. For hydro- or oleo-phobic media, it can be expected that once steady operation is reached, the total level of saturation in the filter media will be significantly lower, thus providing advantages in lower pressure drops and better overall performance. However, phobic media may possibly result in greater levels of aerosol re-entrainment and a greater potential for clogging by (other) solid particles since parts of the filter may not be fully wetted. Yet, the literature on the influence of contact angles and its dynamics on mist filtration characteristics and transport of collected fluid in the filter (including drainage and re-entrainment) is sparse. Practical difficulties in the measurement of contact angles on micro-/nano-fibres have also been a consistent dilatory factor in accurate quantification of the wetting characteristics of filter media. Computational fluid dynamics (CFD) simulations at the pore-scale with interface capturing techniques offer a unique advantage in enabling parameters such as contact angles and other fluid properties to be precisely defined - and hence ideal for parametric characterization of the filter performance. With the aim of isolating the influence of contact angles on the transport of collected liquid in a filter medium, in the present study, CFD simulations are carried out where the filter is pre-saturated with Diethylhexyl Sebacate (DEHS) which is flushed with air (at constant flow rate). Two structurally different types filter media, nonwoven and foam, with similar properties such as fibre (or element of foam) diameter, packing density and size are used for the present study to compare the influence of contact angles across types of filters. The present simulations reveal that there can be a specific contact angle (between 60 Grad and 120 Grad) for both the types of filters (and operating conditions) considered where the saturation in the medium can drop close to zero resulting in a possibly self-cleaning mist filter