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Model-based analysis of biocatalytic processes and performance of microbioreactors with integrated optical sensors
摘要： Design and development of scale-down approaches, such as microbioreactor (μBR) technologies with integrated sensors, are an adequate solution for rapid, high-throughput and cost-effective screening of valuable reactions and/or production strains, with considerably reduced use of reagents and generation of waste. A significant challenge in the successful and widespread application of μBRs in biotechnology remains the lack of appropriate software and automated data interpretation of μBR experiments. Here, it is demonstrated how mathematical models can be used as helpful tools, not only to exploit the capabilities of microfluidic platforms, but also to reveal the critical experimental conditions when monitoring cascade enzymatic reactions. A simplified presented platform was evaluated via computational fluid dynamics (CFD) simulations. Remarkably, expected that the mechanistic models will significantly contribute to the further promotion of μBRs mechanism, kinetics and limiting factors. The effect of fluid flow and enzyme adsorption inside the oxygen sensor spots. The proposed model allowed an easy and rapid identification of the reaction experimental and microbioreactor designs.
关键词： Enzymatic biocatalysis,Bioprocess Modeling,Microbioreactor,Mechanistic modeling,Oxygen Monitoring,Computational Fluid Dynamics
更新于2025-09-12 10:27:22
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Computational Investigation of Melt Pool Process Dynamics and Pore Formation in Laser Powder Bed Fusion
摘要： In the laser powder bed fusion additive manufacturing process, the presence of porosity may result in cracks and significantly affects the part performance. A comprehensive understanding of the melt pool process dynamics and porosity evolution can help to improve build quality. In this study, a novel multi-physics computational fluid dynamics (CFD) model has been applied to investigate the fluid dynamics in melt pools and resultant pore defects. To accurately capture the melting and solidification process, major process physics, such as the surface tension, evaporation as well as laser multi-reflection, have been considered in the model. A discrete element method is utilized to model the generation of powder spreading upon build plate by additional numerical simulations. Multiple single track experiments have been performed to obtain the melt pool shape and cross-sectional dimension information. The predicted melt pool dimensions were found to have a reasonable agreement with experimental measurements, e.g., the errors are in the range of 1.3 to 10.6% for melt pool width, while they are between 1.4 and 15.9% for melt depth. Pores are captured by both CFD simulation and x-ray computed tomography measurement for the case with a laser power of 350 W and laser speed of 100 mm/s. The formation of keyholes maybe related to the melt pool front wall angle, and it is found that the front wall angle increases with the increase in laser line energy density. In addition, a larger laser power or smaller scanning speed can help to generate keyhole-induced pores; they also contribute to produce larger sized pores.
关键词： additive manufacturing,melt pool,computational fluid dynamics (CFD),stainless steel,discrete element method (DEM),keyhole
更新于2025-09-12 10:27:22
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Criteria of pressure and thermal damage during laser irradiation of port wine stains: Which is dominant to vascular lesions?
摘要： Port wine stains (PWSs) are congenital dermal vessel proliferations mainly treated with laser therapy. The complete removal of the vessel lesions is rarely achieved because of a lack of discriminatory analysis of the two competitive laser damages to blood vessels, namely, pressure damage and thermal damage. Unlike complete vessel constriction, which is caused by thermal damage that can be measured by temperature-related integral X, vessel rupture results from pressure damage, which has been seldom studied. In this study, the rupture potential index based on wall pressure (RPIP) was calculated as the ratio of locally acting pressure to the pressure threshold. RPIP > 1 and X > 103 were adopted as benchmarks to judge pressure damage (vessel rupture) and thermal damage (complete vessel constriction), respectively. A computational fluid dynamics simulation was carried out to provide the temperature and pressure field in the PWS vessel model during irradiation by 595 nm pulsed dye laser (PDL) or 1064 nm Nd:YAG laser. Numerical results showed that for the 595 nm laser, vessels constantly underwent rupture. The area of high RPIP determined the degree of rupture by predicting the large and multiple rupture locations of the vessel. By contrast, for the 1064 nm laser, complete constriction was the main damage type. To a single vessel of 100 lm diameter, the optimized laser parameters were E = 10 J/cm2 with tp = 6 ms for 595 nm PDL and E = 180 J/cm2 with tp = 6 ms 1064 nm for Nd:YAG laser.
关键词： Port wine stains,Vessel rupture,Vessel constriction,Computational fluid dynamics,Laser treatment
更新于2025-09-11 14:15:04
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Fine-scale features on the sea surface in SAR satellite imagery – Part 2: Numerical modeling
摘要： With the advent of the new generation of synthetic aperture radar (SAR) satellites, it has become possible to resolve fine-scale features on the sea surface on the scale of meters. The proper identification of sea surface signatures in SAR imagery can be challenging, since some features may be due to atmospheric distortions (gravity waves, squall lines) or anthropogenic influences (slicks), and may not be related to dynamic processes in the upper ocean. In order to improve our understanding of the nature of fine-scale features on the sea surface and their signature in SAR, we have conducted high-resolution numerical simulations combining a three-dimensional non-hydrostatic computational fluid dynamics model with a radar imaging model. The surface velocity field from the hydrodynamic model is used as input to the radar imaging model. The combined approach reproduces the sea surface signatures in SAR of ship wakes, low-density plumes, and internal waves in a stratified environment. The numerical results are consistent with observations reported in a companion paper on in situ measurements during SAR satellite overpasses. Ocean surface and internal waves are also known to produce a measurable signal in the ocean magnetic field. This paper explores the use of computational fluid dynamics to investigate the magnetic signatures of oceanic processes. This potentially provides a link between SAR signatures of transient ocean dynamics and magnetic field fluctuations in the ocean. We suggest that combining SAR imagery with data from ocean magnetometers may be useful as an additional maritime sensing method. The new approach presented in this work can be extended to other dynamic processes in the upper ocean, including fronts and eddies, and can be a valuable tool for the interpretation of SAR images of the ocean surface.
关键词： SAR,radar imaging,sea surface,magnetic signatures,numerical modeling,computational fluid dynamics
更新于2025-09-10 09:29:36
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STUDY OF AN ANNULAR PHOTOREACTOR WITH TANGENTIAL INLET AND OUTLET.II. THE UV/H <sub/>2</sub> O <sub/>2</sub> REACTIVE FLOW
摘要： The concentration profiles of species involved in the degradation of phenol by an advanced oxidation processes (AOP) are modeled using a CFD tool, in an annular reactor whose fluid dynamics was the object of a previous study. The reactive flow was fully described together with the kinetic model, which encompasses large kinetic constants, such as 101 0 L mol-1 s-1, and the radiation field. Phenol degradation can be simulated b y using relaxation factors of 1012 kg m-3 s-1 at least. The hydroxyl radical concentration profile, depends on the radiation field, performed by the discrete ordinate (DO) and the discrete transfer (DT) methods. Phenol can be completely degraded along the reactor. A centrifugal effect was observed, with higher concentration of degradation products along the inner wall at the reactor outlet.
关键词： Fluence rate,Advanced oxidation process,Computational fluid dynamics,Phenol degradation,Degradation kinetics,Parameter estimation,Modeling
更新于2025-09-10 09:29:36
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[IEEE 2018 9th International Conference on Mechanical and Aerospace Engineering (ICMAE) - Budapest (2018.7.10-2018.7.13)] 2018 9th International Conference on Mechanical and Aerospace Engineering (ICMAE) - Numerical Study of Wind Loads on A Solar Panel at Different Inclination Angles
摘要： A numerical analysis using Computational Fluid Dynamics methodology was carried out to study the effect of the different inclination angles on wind loads of solar panel. The wind flow is simulated as turbulent, incompressible flow with a free stream velocity of 10 m/s and a wind direction of 1800 and the inclination angles is chosen as 250, 300 and 350. The finite-volume-method is employed to solve the governing equations, coupled with the k─ε turbulence model with standard-wall treatment. The results indicate that pressure magnitudes on the panel were increased with the inclination angle. The maximum lift and drag force is appeared for the 350 inclination.
关键词： computational fluid dynamics,wind loads,inclination angle,solar panel
更新于2025-09-10 09:29:36
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Development and characterization of a continuous solar-collector-reactor for wastewater treatment by photo-Fenton process
摘要： Design, hydrodynamic modeling and performance characterization of a low cost, non-concentrating type solar-collector-reactor has been presented in this article. The reactor comprises of interconnected parallel channels, which are open at the top to receive sunlight. Because of its modular structure, the reactor can be easily scaled up to any required size. The hydrodynamic features of the reactor were investigated using computational fluid dynamic simulation along with the standard residence time distribution analysis. Primary performance characterization study was conducted in solar photo-Fenton remediation of two model pollutants, namely Trypan blue dye and Dichlorvos pesticide. Under optimum parametric conditions of pH, FeSO4-H2O2 dosage ratio and inlet concentration, the primary pollutants were recorded to degrade by more than 94%, which clearly marks the efficacy of the proposed design. In addition to the simulated wastewater, the reactor performance was also tested in treatment of effluent obtained from jute dyeing unit, where 58% COD reduction was achieved.
关键词： Solar photo-Fenton,Computational fluid dynamics (CFD),Open channel flow,Continuous reactor
更新于2025-09-09 09:28:46
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Numerical Demonstration of In-Tube Liquid-Column Migration Driven by Photoisomerization
摘要： Droplet manipulation by light-induced isomerization was numerically demonstrated and investigated regarding the driving mechanism. Such a non-invasive manipulation of a droplet in a microchannel can be realized, for example, by the use of watery solution of photoresponsive surfactant that exhibits the isomerization. Due to variable fluid properties between the cis and trans isomers, one-side light irradiation on a liquid column in a tube would lead to some kind of imbalance between the two ends of the liquid column and then drive droplet migration. The present numerical simulations of air–liquid two-phase flow and its scalar transport of the isomer, considering the variable static contact angle, agreed quantitatively with the experimental results in terms of the migration speed. This fact supports the contention that the droplet migration is more likely to be driven by an imbalance in the wettability, or the contact angle. The migration speed was found to be less dependent on the liquid-column length, but proportional to the tube diameter.
关键词： photochemical reaction,non-invasive control,wettability,surface tension,microfluidics,computational fluid dynamics,lab-on-a-chip,droplet manipulation,two-phase flow,photoresponsible surfactant
更新于2025-09-09 09:28:46
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Numerical and Experimental Study of the Spatial Stress Distribution on the Cornea Surface During a Non-Contact Tonometry Examination
摘要： The determination of biomechanical properties of the cornea by a non-contact tonometry (NCT) examination requires a precise knowledge of the air puff generated in the device, which is applied to the cornea surface. In this study, a method is proposed to identify the resulting stress profile on the surface, which may be used to numerically solve an inverse problem to obtain the material properties. This method is based on an experimental characterization of the air puff created by the Corvis ST in combination with computational fluid dynamic (CFD) simulations, which are adjusted to the experimental data. The identified nozzle inlet pressure of approximately 25 kPa (188.5 mmHg) is then used for a numerical influence study of the interaction between the air puff and the cornea deformation. Therefore, eleven cornea deformation states based on measurements are implemented in the CFD model. A more realistic model is also analyzed by the geometrical reproduction of the human face, which is used for a further influence study. The outcomes showed a dependence between the cornea deformation and the pressure as well as the shear stress distribution. However, quantitatively, the shear stress component can be considered of minor importance being approximately one hundred times smaller than the pressure. The examination with consideration of the human face demonstrates that the pressure and shear stress distributions are not rotationally symmetric in measurements on real humans, which indicates the requirement to include more complex stress distributions on the eye. We present the detailed stress distribution on the cornea during a non-contact tonometry examination, which is made accessible for further investigations in the future by analytical nonlinear functions.
关键词： Corneal biomechanics,Non-contact tonometry,Shear force distribution,Air puff characterization,Computational fluid dynamics,Pressure distribution
更新于2025-09-04 15:30:14