Large eddy simulation of round jets with mild temperature difference

Understanding the behaviour of hot jets is crucial for various engineering and environmental applications. The present work studies the influence of heat transfer on the dynamics of horizontal round hot jets through Large Eddy Simulations (LES). Our focus lies on trajectory development, large-scale coherent structures, and turbulent kinetic budget analysis in the near-field and intermediate-field regions. LES of two horizontal round hot jets with Reynolds numbers (3934 and 5100) and corresponding Froude numbers (32.98 and 17.07) were carried out using buoyantPimpleFoam solver in OpenFOAM, and the simulation on an isothermal jet was also performed as a baseline for comparison. The results reveal that the jet core temperature decays faster in the streamwise direction but more slowly in the radial direction, indicating a wider temperature spread than velocity, and the maximum difference between the temperature and velocity spread is about 0.5D. Moreover, the energy associated with the large-scale coherent structure decreases with increasing initial jet temperature. The energy of the first two modes of snapshot Proper Orthogonal Decomposition (POD) and extended POD dropped by 12% and 14%, respectively. The coherent motion with the greatest correlation between the temperature and velocity fluctuations is identified as four pairs of Q1 and Q3 events, which are Reynolds shear stress dominant events. Furthermore, compared with the isothermal jet, the turbulent kinetic energy budgets of the hot jets indicate that the diffusion and generation terms are both reduced by approximately 50%, suggesting a transfer of more kinetic energy into potential energy rather than turbulence. The finding highlights the potential of heightened temperatures to mitigate instabilities associated with large-scale motions in hot jets. This study fills the gap on a comprehensive analysis of heat transfer effects on jet dynamics, and quantitative insights into the large-scale coherent structures are provided, contributing to a better understanding of hot jet behaviour

Improved Insulin Resistance and Lipid Metabolism by Cinnamon Extract through Activation of Peroxisome Proliferator-Activated Receptors

Peroxisome proliferator-activated receptors (PPARs) are transcriptional factors involved in the regulation of insulin resistance and adipogenesis. Cinnamon, a widely used spice in food preparation and traditional antidiabetic remedy, is found to activate PPARγ and α, resulting in improved insulin resistance, reduced fasted glucose, FFA, LDL-c, and AST levels in high-caloric diet-induced obesity (DIO) and db/db mice in its water extract form. In vitro studies demonstrate that cinnamon increases the expression of peroxisome proliferator-activated receptors γ and α (PPARγ/α) and their target genes such as LPL, CD36, GLUT4, and ACO in 3T3-L1 adipocyte. The transactivities of both full length and ligand-binding domain (LBD) of PPARγ and PPARα are activated by cinnamon as evidenced by reporter gene assays. These data suggest that cinnamon in its water extract form can act as a dual activator of PPARγ and α, and may be an alternative to PPARγ activator in managing obesity-related diabetes and hyperlipidemia

Research on the thermal stress characteristics of self-cooled brake discs of belt conveyors

Equipped with rib groove structure, the self-cooled brakes disc enjoys an excellent heat dispersion and are applied in the belt conveyors with good effect. According to Hooke’s Law, the steady-state thermo-mechanical coupling expression of the brake disc under two-dimensional conditions is deduced, and the solving method of the displacement differential equation is given. Based on the ABAQUS, thermo-mechanical coupling finite element model for self-cooled disc brakes is established and for the structure and load characteristics of the brake discs, three different azimuth paths are defined and the transient thermal stress variations under different paths are obtained. Through the thermal cycling tests of self-cooling brake disc samples at 300 °C, 400 °C, and 500 °C under the condition of heat and water-cooling for 800 times respectively and analyzing the metallographic structure with electron probe microscope, the results have showed that a large amount of graphitized tissue can be precipitated under the high circulating temperature and heating cracks can induced

Rapid, Scalable Assembly of Stereochemically Rich, Mono- and Bicyclic Acyl Sultams

A one-pot, sequential protocol is reported that involves complementary ambiphile pairing (CAP) of a vinyl sulfonamide with a variety of unprotected amino acids via aza-Michael addition and subsequent intramolecular amidation. The method generates diverse, sp3-rich mono- and bicyclic acyl sultams in a highly scalable manner. Modular pairing of stereochemically rich building blocks allows quick access to all possible isomers. Extension to include one-pot, sequential 3-, 4- and 5-multicomponent protocols is also discussed

Prediction of a High Temperature Bonding Condition at the Interface for the Hot-Rolled Stainless Steel Clad Plate on Rolling

The stainless steel-carbon steel clad plate was investigated using the theoretical analysis of various factors influencing the high-temperature interfacial bonding during its rolling. Phenomenological prediction analysis model of interfacial bonding strength at high temperature which considers the vacuum depth, rolling temperature, and rolling reduction, was established. The specific thermal simulation experiment was designed, the bonding strength of carbon steel and stainless steel at 1000~1200°C and compression degree of 10~30% was measured by a Gleeble 3500 thermal simulator, as a result, the interfacial bonding ratio was obtained. The results show that the bonding ratio is 0.5-0.65 at the experimental temperature and compression degree. The numerical simulation method was used to analyze the influence of the compression degree of the first pass for a 2000×1500×100 mm stainless steel clad plate under the interfacial bonding condition. The simulation results show that the optimum compression degree of the first pass is 15-20% at the rolling temperature of 1200°C.Листовая углеродистая сталь, плакированная нержавеющей сталью, исследована с помощью теоретического анализа различных факторов, влияющих на высокотемпературное межповерхностное сцепление при ее прокатке, феноменологической модели прогнозного анализа прочности межповерхностного сцепления при высокой температуре, которая учитывает глубину разрежения, температуру прокатки и обжатие при прокатке. Подготовлен специальный эксперимент с моделированием температурного режима, прочность сцепления углеродистой и нержавеющей сталей при 1000–1200°С и степени обжатия 10~30% измерена с помощью моделирующего устройства с регулируемым температурным режимом Gleeble 3500, получена относительная прочность межповерхностного сцепления. Показано, что при температуре и степени обжатия, принятых в эксперименте, относительная прочность сцепления составляет 0.50–0.65. Метод численного моделирования использован для анализа влияния степени обжатия за первый пропуск пластины плаплакированной нержавеющей сталью размером 2000×1500×100 мм на межповерхностное сцепление. Оптимальная степень обжатия за первый пропуск составляет 15–20% при температуре прокатки 1200°С

A numerical investigation of wave-supported gravity flow during cold fronts over the Atchafalaya Shelf

Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 125(9), (2020): e2019JC015269, doi:10.1029/2019JC015269Wave‐supported fluid mud (WSFM) plays an important role in sediment downslope transport on the continental shelves. In this study, we incorporated WSFM processes in the wave boundary layer (WBL) into the Community Sediment Transport Modeling System (CSTMS) on the platform of the Coupled Ocean‐Atmosphere‐Wave‐and‐Sediment Transport modeling system (COAWST). The WSFM module was introduced between the bottommost water layer and top sediment layer, which accounted for the key sediment exchange processes (e.g., resuspension, vertical settling, diffusion, and horizontal advection) at the water‐WBL and WBL‐sediment bed boundaries. To test its robustness, we adapted the updated model (CSTMS + WBL) to the Atchafalaya shelf in the northern Gulf of Mexico and successfully reproduced the sediment dynamics in March 2008, when active WSFM processes were reported. Compared with original CSTMS results, including WSFM module weakened the overall intensity of sediment resuspension, and the CSTMS + WBL model simulated a lutocline between the WBL and overlying water due to the formation of WSFM. Downslope WSFM transport resulted in offshore deposition (>4 cm), which greatly changed the net erosion/deposition pattern on the inner shelf off the Chenier Plain. WSFM flux was comparable with suspended sediment flux (SSF) off the Atchafalaya Bay, and it peaked along the Chenier Plain coast where wave activities were strong and the bathymetric slope was steep. The influence of fluvial sediment supply on sediment dynamics was limited in the Atchafalaya Bay. Sensitivity tests of free settling, flocculation, and hindered settling effects suggested that sediments were transported further offshore due to reduced settling velocity in the WBL once fluid mud was formed. Although sediment concentration in the WBL was sensitive to surface sediment critical shear stress, cohesive bed behavior was less important in WSFM dynamics when compared with strong hydrodynamic during cold fronts.Research support provided through NSF CyberSEES (Award CCF‐1856359), NASA (Award NNH17ZHA002C), Louisiana Board of Regents (award number NASA/LEQSF(2018‐20)‐Phase3‐11), Bureau of Ocean Energy Management (Cooperative Agreement Award M20AC00007), NSF Coastal SEES (Award EAR‐1427389 ), NSF (Award OCE‐20203676), and LSU Foundation Billy and Ann Harrison Endowment for Sedimentary Geology.2021-02-1

The role of sediment-induced light attenuation on primary production during Hurricane Gustav (2008)

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Zang, Z., Xue, Z. G., Xu, K., Bentley, S. J., Chen, Q., D'Sa, E. J., Zhang, L., & Ou, Y. The role of sediment-induced light attenuation on primary production during Hurricane Gustav (2008). Biogeosciences, 17(20), (2020): 5043-5055, doi:10.5194/bg-17-5043-2020.We introduced a sediment-induced light attenuation algorithm into a biogeochemical model of the Coupled Ocean–Atmosphere–Wave–Sediment Transport (COAWST) modeling system. A fully coupled ocean–atmospheric–sediment–biogeochemical simulation was carried out to assess the impact of sediment-induced light attenuation on primary production in the northern Gulf of Mexico during the passage of Hurricane Gustav in 2008. When compared with model results without sediment-induced light attenuation, our new model showed a better agreement with satellite data on both the magnitude of nearshore chlorophyll concentration and the spatial distribution of offshore bloom. When Hurricane Gustav approached, resuspended sediment shifted the inner shelf ecosystem from a nutrient-limited one to a light-limited one. Only 1 week after Hurricane Gustav's landfall, accumulated nutrients and a favorable optical environment induced a posthurricane algal bloom in the top 20 m of the water column, while the productivity in the lower water column was still light-limited due to slow-settling sediment. Corresponding with the elevated offshore NO3 flux (38.71 mmol N m−1 s−1) and decreased chlorophyll flux (43.10 mg m−1 s−1), the outer shelf posthurricane bloom should have resulted from the cross-shelf nutrient supply instead of the lateral dispersed chlorophyll. Sensitivity tests indicated that sediment light attenuation efficiency affected primary production when sediment concentration was moderately high. Model uncertainties due to colored dissolved organic matter and parameterization of sediment-induced light attenuation are also discussed.This research has been supported by the National Science Foundation (grant nos. CCF-1856359, EnvS-1903340, OCE-1635837 and EAR-1427389), NASA (grant no. NNH17ZHA002C), the Louisiana Board of Regents (grant no. NASA/LEQSF(2018-20)-Phase3-11) and the LSU Foundation Billy and Ann Harrison Endowment for Sedimentary Geology

Multicapillary Flow Reactor: Synthesis of 1,2,5-Thiadiazepane 1,1-Dioxide Library Utilizing One-Pot Elimination and Inter-/Intramolecular Double aza-Michael Addition Via Microwave-Assisted, Continuous-Flow Organic Synthesis (MACOS)

A microwave-assisted, continuous-flow organic synthesis (MACOS) protocol for the synthesis of functionalized 1,2,5-thiadiazepane 1,1-dioxide library, utilizing a one-pot elimination and inter-/intramolecular double aza-Michael addition strategy is reported. The optimized protocol in MACOS was utilized for scale-out and further extended for library production using a multicapillary flow reactor. A 50-member library of 1,2,5-thiadiazepane 1,1-dioxides was prepared on a 100- to 300-mg scale with overall yields between 50 and 80% and over 90 % purity determined by proton nuclear magnetic resonance (1H-NMR) spectroscopy

Thermomechanical Coupling Model for a Stainless Steel-Clad Plate on Heat Treatment

Quick and correct prediction of the internal stress and deformation of stainless steel-clad plates on heat treatment is a problem of specific interest. A thermomechanical coupling model based on the engineering elastic-plastic theory is detailed. The discretization method and difference equations used simultaneously provide effective numerical calculations for the model. The generalized finite element model verifies relevant simplification conditions and efficiency of the numerical calculation logic. Heat treatment experiments of clad plates are also designed and presented, and the ability of the model to predict the stress and deformation behavior of the clad plate in the actual heat treatment process is evaluated. The calculation logic of the model is reasonable, and the prediction error of deformation and internal stress of the plate is ~15%. The model exhibits an extremely high computational efficiency and can meet the requirements of on-line analysis for heat treatment processes.Быстрое и точное прогнозирование внутреннего напряжения и кривизны деформации листов, плакированных нержавеющей сталью, при термообработке остается актуальной проблемой в этой области исследования. Рассматривается модель термомеханической связи листа, основанная на инженерной теории упругих и пластических деформаций. Для реализации эффективного численного расчета модели совместно используются метод дискретизации и разностные уравнения. Применение обобщенной конечноэлементной модели позволяет подтвердить соответствующие условия упрощения и рациональность логики численного расчета модели. Планируются и описываются эксперименты по термообработке таких плакированных листов и анализируется способность модели прогнозировать характер напряжения и деформации плакированного листа в реальном процессе термообработки. Логика расчета модели обоснована, при этом погрешность прогнозирования деформации и внутреннего давления листа составляет ~15%. Модель также имеет очень высокую вычислительную эффективность и может удовлетворять требованиям анализа в режиме он-лайн для процессов термообработки.Швидке і точне прогнозування внутрішніх напружень і кривизни деформації листів, плакованих нержавіючої сталлю, при термообробці залишається актуальною проблемою в цій області дослідження. Розглядається модель термомеханічного зв'язку листа, заснованої на інженерної теорії пружних і пластичних деформацій. Для реалізації ефективного чисельного розрахунку моделі спільно використовуються метод дискретизації і різницеві рівняння. Застосування узагальненої скінченноелементної моделі дозволяє підтвердити відповідні умови спрощення і раціональність логіки чисельного розрахунку моделі. Плануються і описуються експерименти по термообробці таких плакованих листів і аналізується здатність моделі прогнозувати характер напружень і деформації плакованного листа в реальному процесі термообробки. Логіка розрахунку моделі обгрунтована, при цьому похибка прогнозування деформації і внутрішнього тиску листа складає ~ 15%. Модель також має дуже високу обчислювальну ефективність і може задовольняти вимогам аналізу в режимі он-лайн для процесів термообробки

Synthesis of an Isoindoline-Annulated, Tricyclic Sultam Library via Microwave-Assisted, Continuous-Flow Organic Synthesis (MACOS)

A microwave-assisted, continuous-flow organic synthesis (MACOS) protocol for the synthesis of an isoindoline-annulated, tricyclic sultam library, utilizing a Heck–aza-Michael (HaM) strategy, is reported. This sequence involves a Heck reaction on vinylsulfonamides with batch microwave heating followed by a one-pot, sequential intramolecular aza-Michael cyclization/Boc-deprotection using MACOS. Subsequent cyclization with either 1,1′-carbonyldiimidazole or chloromethyl pivalate using MACOS provided an array of tricyclic sultams. This efficient three-step protocol requires only a few hours to produce the target sultams starting from simple starting materials. Using this strategy, a 38-member library of isoindoline-annulated sultams was generated in good to excellent overall yields (53–87%)