A Computational Study of the Inertial Collapse of Gas Bubbles Near a Rigid Surface

Cavitation research is essential to a variety of applications ranging from naval hydrodynamics to medicine and energy sciences. Vapor cavities can grow from sub-micron-sized nuclei to millimeter-sized bubbles, and collapse violently in an inertial fashion. This implosion, which concentrates energy into a small volume, can produce high pressures and temperatures, generate strong shock waves, and even emit visible light. One of the main consequences of cavitation is structural damage to neighboring surfaces due to bubble collapse. The propagation of shock and rarefaction waves in a multiphase medium results in a complicated multiscale and multiphysics problem. Laboratory experiments of such flows are challenging due to the wide range of spatial and temporal scales, difficult optical access, and limitations of measurement devices. To better understand these flows, we use highly resolved numerical simulations of the inertial collapse of individual vapor bubbles near a rigid surface. For this purpose, we developed a novel numerical multiphase model combined with high-performance computing techniques to perform accurate and efficient simulations of the three-dimensional compressible Navier-Stokes equations for a binary, gas-liquid system. We present the detailed dynamics of the Rayleigh collapse of a single vapor bubble near a rigid wall for different geometrical configurations and driving pressures. We explain that the presence of a rigid boundary breaks the symmetry of the collapse and hinders the energy concentration. As a result, a liquid re-entrant jet directed toward the wall forms, ultimately giving rise to lower pressure and temperatures produced upon collapse. We characterize the collapse non-sphericity, and show that this quantity, which strongly depends on the initial stand-off distance of the bubble from the wall, significantly affects the overall dynamics. We further show that bubbles initially close to the wall or attached to the surface are responsible not only for the high pressure loads along the wall, but also the elevated temperatures on the solid surface. In fact, for certain soft materials, instantaneous temperatures greater than the melting point may be achieved on the surface, thus confirming that thermal damage is a potential threat to such materials exposed to cavitating flows. Furthermore, the development of scalings for important collapse properties (jet velocity, shock pressure, wall pressures/temperatures), in terms of the initial stand-off distance and driving pressure, not only illustrates universality of non-spherical bubble dynamics but also provides means to predict these phenomena. Since real flows involve many bubbles, we also investigate the inertial collapse of a pair of vapor bubbles near a rigid surface. We explain that the presence of a second bubble in the vicinity of the original (primary) bubble leads to far more complicated dynamics and completely changes the single-bubble scalings. Strong interactions between the bubbles and the boundary drastically increase the collapse non-sphericity and amplify/hinder the pressures and temperatures produced by the collapse. Our simulations show that the re-entrant jets in both bubbles form at distorted angles, and for certain configurations, ``double jetting'', occurs, in which two jets penetrate the primary bubble. The results indicate that bubble-bubble interactions and their effects on collapse dynamics near a wall are non-negligible. Furthermore, given the complexity of even this simple problem and the large number of parameters, the value of extending such high-resolution simulations to develop scalings for the collapse of many bubbles is debatable at the present time; it may be worth considering alternative modeling approaches.PHDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/144079/1/alahyari_1.pd

Comparison of Different Levels of Vitamin Premix on Meat Lipid Oxidation in Floor and Battery Cage Broiler Raising Systems

A total of 1260 male broiler chicks (Ross 308) were allocated to 7 treatment groups (different levels and access time to vitamin premix (VP)) at 29 to 42 days of age, in floor system (Experiment 1) and battery cage system (Experiment 2). The oxidative stability was evaluated by thiobarbituric acid reactive substances (TBARS) on the thigh yield that were storage for 180 days in -20˚C. Results of experiment 1 showed that VP reduction and withdrawal from 29 d of age did not impair body weight, feed intake and feed conversion ratio during the final period of treatments (29-42d).Results of experiment 2 showed that there were no significant differences in the birds’ performance with reduction or withdrawal of VP from diets in 29-35 days among the experimental groups, but in 36-42 days of age, the performance of the group of birds fed with diet without VP (T1) was significantly lower than other groups. The results of experiment 2 showed that the performance of birds fed with diet without VP was significantly lower than other treatments in 36-42 days of age. The results of TBARS values in experiment 1 for thigh meat samples of birds slaughtered at 42 days of age showed that TBARS values of treatments without VP were significantly higher than other treatments. However in experiment 2, TBARS values of treatments without VP and with 33% VP were significantly higher than other treatments for birds slaughtered at 42 days of age. Finally, the results of this study demonstrate firstly that it is not possible to withdraw but it can be possible to reduce VP in finisher broiler's diets without negative effects on performance and meat quality during the time of freezing in both methods of rearing. Secondly, it is possible to reduce the VP levels in diet of broilers reared in floor system more than battery cage system

The effect of aqueous extract of Malva neglecta on expression of inflammatory biomarkers involved in pain in synoviocytes and THP-1 cells as a model of monocyte/macrophage and human cartilage cells in osteoarthritis

Background: Osteoarthritis (OA) is now considered as an active complex of biomechanical, biochemical and cellular processes, not a mere degenerative disorder. Considering the complications of common treatments of OA, including non-steroidal anti-inflammatory drug (NSAIDs) and corticosteroids, establishment of new treatments is crucial. This study aimed to explore the effect of Malva Neglecta extract on the main inflammatory biomarkers in OA.Materials and Methods: Aqueous extract of Malva Neglecta, ibuprofen and betamethasone were prepared to investigate their effects on inflammatory biomarkers. Synoviocytes were obtained from the healthy radiocarpal joint cartilage of an 8-month-old Holstein cow. Human monocyte/macrophage (THP-1) cells were also obtained to investigate the effect of Malva neglecta extract on inflammatory agents. Lipopolysaccharide (LPS) was used to induce production of inflammatory cytokines in both cells. Real-time PCR was used to investigate the effect of Malva Neglecta extract on expression profile of TNF-α, IL-1β, COX-2, IL-18 and iNOS. Production of NO and PGE2 was also investigated in THP-1 cells.Results: Malva Neglecta extract reduced TNF-α, IL-1β, iNOS, IL-18 and COX-2 expression in synoviocytes. Expression of all of these factors was also reduced by the extract in THP-1 cells. Moreover, production of PGE2 and NO in the LPS-induced THP-1 cells was reduced by Malva neglecta extract. Ibuprofen and betamethasone were more effective in reducing inflammatory agents than the extract.Conclusion: According to Malva’s ability to reduce the pro-inflammatory cytokines in the synoviocytes and THP-1 cells, its potential role as a supplement method to common NSAIDs and corticosteroids was confirmed

Multi-port coordination: Unlocking flexibility and hydrogen opportunities in green energy networks

\ua9 2024Seaports are responsible for consuming a large amount of energy and producing a sizeable amount of environmental emissions. However, optimal coordination and cooperation present an opportunity to transform this challenge into an opportunity by enabling flexibility in their generation and load units. This paper introduces a coordination framework for exploiting flexibility across multiple ports. The proposed method fosters cooperation between ports in achieving lower environmental emissions while leveraging flexibility to increase their revenue. This platform allows ports to participate in providing flexibility for the energy grid through the introduction of a green port-to-grid concept while optimising their cooperation. Furthermore, the proximity to offshore wind farms is considered an opportunity for the ports to investigate their role in harnessing green hydrogen. The proposed method explores the hydrogen storage capability of ports as an opportunity for increasing the techno-economic benefits, particularly through coupling them with offshore wind farms. Compared to existing literature, the proposed method enjoys a comprehensive logistics-electric model for the ports, a novel coordination framework for multi-port flexibility, and the potentials of hydrogen storage for the ports. These unique features position this paper a valuable reference for research and industry by demonstrating realistic cooperation among ports in the energy network. The simulation results confirm the effectiveness of the proposed port flexibility coordination from both environmental and economic perspectives

A novel resource allocation model based on the modularity concept for resiliency enhancement in electric distribution networks

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A stochastic multi-range robust approach for low carbon technology participation in electricity markets

\ua9 2024Ambitious emission reduction targets require fostering more low-carbon technologies (LCTs) in distribution networks. Projections for future energy use predict a significant implementation of these technologies in residential areas. Despite this, individually they cannot effectively participate in electricity markets. This study examines the potential participation of residential LCTs (RLCTs) in multiple electricity markets, including wholesale day-ahead, real-time, and local energy markets (LEM), through the aggregators. We propose a stochastic weighted multi-range robust model to provide a strategy for RLCT aggregators to function as both sellers and buyers in these markets, as price-makers in LEM and price-takers in wholesale markets. The proposed model accounts for the uncertainty associated with the effect of offers/bids on the market clearing price of LEM and the availability patterns of aggregated LCTs. Results of a case study using realistic data reveal that the proposed approach results in higher overall profits compared to both risk-neutral and risk-averse robust methods. Furthermore, the introduced model is resilient to forecast errors, as evidenced by a 12% decrease in profits with the proposed approach compared to a 26% decrease with a risk-neutral strategy when the forecast error was increased by 20%

A Mixed Epistemic-Aleatory Stochastic Framework for the Optimal Operation of Hybrid Fuel Stations

The fast development of technologies in the smart grids provides new opportunities such as co-optimization of multi-energy systems. One of the new concepts that can utilize multiple energy sources is a hybrid fuel station (HFS). For instance, an HFS can benefit from energy hubs, renewable energies, and natural gas sources to supply electric vehicles along with natural gas vehicles. However, the optimal operation of an HFS deals with uncertainties from different sources that do not have similar natures. Some may lack in term of historical data, and some may have very random and unpredictable behavior. In this study, we present a stochastic mathematical framework to address both types of these uncertainties according to the innate nature of each uncertain variable, namely: epistemic uncertainty variables (EUVs) and aleatory uncertainty variables (AUVs). Also, the imprecise probability approach is introduced for EUVs utilizing the copula theory in the process, and a scenario-based approach combining Monte Carlo simulation with Latin Hypercube sampling is applied for AUVs. The proposed framework is employed to address the daily operation of a novel HFS, leading to a two-stage mixed-integer linear programming problem. The proposed approach and its applicability are verified using various numerical simulations

Designing Tuneable Narrowband Bandpass Filter Utilizing Neural Network

Abstract: In this study we aim at adjusting the singleband and dualband bandpass filter designed in a ED02AH technology. The quality factor and center frequency of the filter will change by varactor diodes. Here, we use a neural network to acquire the proper biasing voltages of varactor diodes in order to obtain specific gain and quality factor

Effects of different levels of vitamin premix in finisher diets on performance, immuno - competence and meat lipid oxidation of chickens fed on corn - soybean meal

The present study was carried out to examine the effects of a vitamin premix (VP)reduction or withdrawal from finisher diet (29-43 days) on performance,immuno-competence,and characteristicsof leg bones and meat lipid oxidation of chickens fed oncorn-soybeanmeal based diet. A total of 900 male broiler chickens (Ross 308) were allocatedtofivetreatment groups(0, 33%, 66%, 100% and 133% VP), withninereplicates per treatmentgroup. At 29 and 36 days of ages, four birds from each replicate were injected with sheepredblood cells (SRBC). The cell-mediated immunity was determined via phytohemagglutinin(PHA) and 1-chloro 2-4-dinitrobenzen (DNCB)at 34 and 42 days of ages.At 33, 38 and 43days of age, 42 days of ages, and two birds of each replicate were slaughteredand boneparameters measured. The oxidative stability was evaluated by thiobarbituric acid reactivesubstances (TBARS) on the thigh samples that were stored for 90 day at-80 ̊C. The resultsshowed that reduction or withdrawal of VP from diets at different time points of the finisherperiod did not affect performance, immunocompetence and characteristics of leg bones.Results of TBARS showed thatlipid peroxidation of the treatment without VP wassignificantly higher than of the other treatments when slaughtered at 43 days of age. Finally,the results of this study demonstrated that it is not possible to reduce the VP in finisherbroilers’ diets without negative effects on meat quality during the time of freezing