Turbulence and Cavitation Suppression by Quaternary Ammonium Salt Additives

We identify the physical mechanism through which newly developed quaternary ammonium salt (QAS) deposit control additives (DCAs) affect the rheological properties of cavitating turbulent flows, resulting in an increase in the volumetric efficiency of clean injectors fuelled with diesel or biodiesel fuels. Quaternary ammonium surfactants with appropriate counterions can be very effective in reducing the turbulent drag in aqueous solutions, however, less is known about the effect of such surfactants in oil-based solvents or in cavitating flow conditions. Small-angle neutron scattering (SANS) investigations show that in traditional DCA fuel compositions only reverse spherical micelles form, whereas reverse cylindrical micelles are detected by blending the fuel with the QAS additive. Moreover, experiments utilising X-ray micro computed tomography (micro-CT) in nozzle replicas, quantify that in cavitation regions the liquid fraction is increased in the presence of the QAS additive. Furthermore, high-flux X-ray phase contrast imaging (XPCI) measurements identify a flow stabilization effect in the region of vortex cavitation by the QAS additive. The effect of the formation of cylindrical micelles is reproduced with computational fluid dynamics (CFD) simulations by including viscoelastic characteristics for the flow. It is demonstrated that viscoelasticity can reduce turbulence and suppress cavitation, and subsequently increase the injector’s volumetric efficiency

Life table parameters and digestive enzymes activity of Helicoverpa armigera (Lep.: Noctuidae) on different tomato cultivars

The tomato fruit borer, Helicoverpa armigera (Hübner), is a destructive insect pest of many host crops in Iran and worldwide. The effect of different tomato cultivars (SUN 6108 f1, Rio grande UG, Korral, CH falat, Hed rio grande and Cal JN3) was studied on life table parameters of H. armigera under laboratory (25 ± 1 °C, 65 ± 5% RH and a photoperiod of 16: 8 (L: D) hours), and on the activity of some digestive enzymes of its sixth larval instars under field conditions. The larval period was longest on Hed rio grande (35.500 ± 1.340 days) and shortest on Korral (24.290 ± 0.688 days). The intrinsic rate of increase (rm) ranged from 0.094 ± 0.003 to 0.159 ± 0.002 (day-1), which was lowest on Rio grande UG and highest on Korral. The larvae reared on the leaves of SUN 6108 f1 showed the highest amylolytic activity (0.062 ± 0.00004 mU mg-1), whereas the lowest activity was in the larvae fed on the leaves of Cal JN3 (0.027 ± 0.00004 mU mg-1) and Korral (0.027 ± 0.0001 mU mg-1). The amylolytic activity of larvae fed on the fruits of tomato cultivars was highest on Cal JN3 (0.047 ± 0.0001 mU mg-1). Also, the highest general proteolytic activity of H. armigera was in the larvae reared on the leaves of Hed rio grande (3.235 ± 0.004 U mg-1) and fruits of Rio grande UG (2.757 ± 0.135 U mg-1). It could be concluded that Rio grande UG is unsuitable host for the growth and development of H. armigera

Impact of KOH etching on nanostructure fabricated by local anodic oxidation method

In this letter, we investigate the impact of potassium hydroxide (KOH) etching procedure on Silicon nanostructure fabricated by Atomic force microscopy on P-type Silicon-on-insulator. An electrochemical process, as the local anodic oxidation followed by two wet chemical etching steps, KOH etching for silicon removal and hydrofluoric etching for oxide removal, were implemented to fabricate the silicon nanostructures. The effect of the pure KOH concentrations (10% to 30% wt) on the quality of the surface is studied. The influence of etching immersing time in etching of nanostructure and SOI surface are considered as well. Impact of different KOH concentrations mixed with 10% IPA with reaction temperature on etch rate is investigated. The KOH etching process is elaborately optimized by 30%wt. KOH + 10%vol. IPA in appropriate time and temperature. The angle of the walls in etch pit for extracted nanowire reveals some deviation from the standard anisotropic etching

Performance of turbulence and cavitation models in prediction of incipient and developed cavitation

The aim of this article is to assess the impact of turbulence and cavitation models on the prediction of diesel injector nozzle flow. Two nozzles are examined, an enlarged one, operating at incipient cavitation, and an industrial injector tip, operating at developed cavitation. The turbulence model employed includes the re-normalization group k–ε, realizable k–ε and k–ω shear stress transport Reynolds-averaged Navier–Stokes models; linear pressure–strain Reynolds stress model and the wall adapting local eddy viscosity large eddy simulation model. The results indicate that all Reynolds-averaged Navier–Stokes and the Reynolds stress turbulence models have failed to predict cavitation inception due to their limitation to resolve adequately the low pressure existing inside vortex cores, which is responsible for cavitation development in this particular flow configuration. Moreover, Reynolds-averaged Navier–Stokes models failed to predict unsteady cavitation phenomena in the industrial injector. However, the wall adapting local eddy viscosity large eddy simulation model was able to predict incipient and developed cavitation, while also capturing the shear layer instability, vortex shedding and cavitating vortex formation. Furthermore, the performance of two cavitation methodologies is discussed within the large eddy simulation framework. In particular, a barotropic model and a mixture model based on the asymptotic Rayleigh–Plesset equation of bubble dynamics have been tested. The results indicate that although the solved equations and phase change formulation are different in these models, the predicted cavitation and flow field were very similar at incipient cavitation conditions. At developed cavitation conditions, standard cavitation models may predict unrealistically high liquid tension, so modifications may be essential. It is also concluded that accurate turbulence representation is crucial for cavitation in nozzle flows

Illustrating the effect of viscoelastic additives on cavitation and turbulence with X-ray imaging

The effect of viscoelastic additives on the topology and dynamics of the two-phase flow arising within an axisymmetric orifice with a flow path constriction along its main axis has been investigated employing high-flux synchrotron radiation. X-ray Phase Contrast Imaging (XPCI) has been conducted to visualise the cavitating flow of different types of diesel fuel within the orifice. An additised blend containing Quaternary Ammonium Salt (QAS) additives with a concentration of 500 ppm has been comparatively examined against a pure (base) diesel compound. A high-flux, 12 keV X-ray beam has been utilised to obtain time resolved radiographs depicting the vapour extent within the orifice from two views (side and top) with reference to its main axis. Different test cases have been examined for both fuel types and for a range of flow conditions characterised by Reynolds number of 35500 and cavitation numbers (CN) lying in the range 3.0–7.7. It has been established that the behaviour of viscoelastic micelles in the regions of shear flow is not consistent depending on the cavitation regimes encountered. Namely, viscoelastic effects enhance vortical (string) cavitation, whereas hinder cloud cavitation. Furthermore, the use of additised fuel has been demonstrated to suppress the level of turbulence within the orifice

Properties of an acid-tolerant, persistent Cheddar cheese isolate, Lacticaseibacillus paracasei GCRL163

The distinctive flavours in hard cheeses are attributed largely to the activity of nonstarter lactic acid bacteria (NSLAB) which dominate the cheese matrix during maturation after lactose is consumed. Understanding how different strains of NSLAB survive, compete, and scavenge available nutrients is fundamental to selecting strains as potential adjunct starters which may influence product traits. Three Lacticaseibacillus paracasei isolates which dominated at different stages over 63-week maturation periods of Australian Cheddar cheeses had the same molecular biotype. They shared many phenotypic traits, including salt tolerance, optimum growth temperature, growth on N-acetylglucosamine and N-acetylgalactosamine plus delayed growth on D-ribose, carbon sources likely present in cheese due to bacterial autolysis. However, strains 124 and 163 (later named GCRL163) survived longer at low pH and grew on D-tagatose and D-mannitol, differentiating this phenotype from strain 122. When cultured on growth-limiting lactose (0.2%, wt/vol) in the presence of high concentrations of L-leucine and other amino acids, GCRL163 produced, and subsequently consumed lactate, forming acetic and formic acids, and demonstrated temporal accumulation of intermediates in pyruvate metabolism in long-term cultures. Strain GCRL163 grew in Tween 80-tryptone broths, a trait not shared by all L. casei-group dairy isolates screened in this study. Including citrate in this medium stimulated growth of GCRL163 above citrate alone, suggesting cometabolism of citrate and Tween 80. Proteomic analysis of cytosolic proteins indicated that growth in Tween 80 produced a higher stress state and increased relative abundance of three cell envelope proteinases (CEPs) (including PrtP and Dumpy), amongst over 230 differentially expressed proteins

Effect of cube texture on local softening of friction stir welded joints for nanostructured AA2024 processed by accumulative roll bonding

Copyright © 2023 The Authors. The current research provides an insight into the correlation between the crystallographic textures, microstructure, and hardness of friction stir welded joints in nanostructured AA2024 alloys processed through accumulative roll bonding (ARB). Utilizing varying rotational speeds (250, 500, 750, and 1000 rpm) at a constant traverse tool (150 mm/min) during friction stir welding (FSW), microstructural analyses reveal distinct grain structures and texture components in the nugget zone. The fully recrystallized Cube {001}⟨100⟩ texture-oriented grains appear at the rotational speed of 750 rpm. The hardness profiles of ARB-processed strips after FSW at different rotational speeds show local softening in the nugget zones. There might be a hypothesis concerning the dissolution of stable and metastable precipitates based on generated heat input, providing insights into the mechanisms influencing hardness variations. Notably, the examination of Cube {001}⟨100⟩ texture and its correlation with local softening adds a valuable dimension to the understanding of microstructural changes in FSW of nanostructured AA2024 alloys processed by accumulative roll bonding process

Foveal avascular zone and vessel density in healthy subjects: An optical coherence tomography angiography study

Purpose: To report the normal characteristics and correlations of the foveal microvascular networks using optical coherence tomography angiography (OCTA) in a healthy Iranian population. Methods: Enface 3x3 OCTA images were obtained using the RTVue Avanti spectral-domain optical coherence tomography with AngioVue software (Optovue, Fremont, CA, USA). Foveal avascular zone (FAZ) area, central foveal point thickness and inner retinal thickness at the foveal center and the vascular density of the superficial retinal capillary plexus (SCP) and deep retinal capillary plexus (DCP) in the fovea were recorded. Results: Seventy normal eyes of 70 subjects (range, 9 to 71 years) were studied. Mean FAZ area was 0.32 ± 0.11 (range, 0.13-0.67) mm2 in SCP and 0.50 ± 0.13 (range, 0.19-0.94) mm2 in DCP. Mean SCP vessel density was 29.6 ± 4.7 (range, 16.3-40.3) in the fovea. Mean DCP vessel density was 27.0 ± 5.9 (range, 15.0-45.2) in the fovea. The FAZ area at SCP level was negatively correlated to the central subfield thickness (P < 0.001). The FAZ area at DCP level correlated negatively to the central subfield thickness and was significantly associated to age (both P < 0.001). The foveal SCP vessel density significantly correlated with foveal thickness and the foveal DCP vessel density correlated significantly with central foveal subfield thickness and was inversely related to age (all P < 0.05). Conclusion: In this study, central foveal subfield thickness was a major determinant of the FAZ size and foveal vessel density. Age was a determinant for FAZ area and whole image vessel density in DCP. © 2018 Medknow Publications.All Rights Reserved

Improving strength-ductility synergy of nano/ultrafine-structured Al/Brass composite by cross accumulative roll bonding process

Copyright © 2023 The Author(s). Increasing the strength of metallic multilayered composites fabricated through accumulative roll bonding (ARB) is typically accompanied by a sacrifice in ductility. In the current work, we propose a strategy to achieve microstructural refinement and outstanding strength-ductility synergy in Al/Brass composites. Here, the aluminum matrix exhibits a bimodal grain distribution, consisting of fine equiaxed grains with an average size of ∼100 nm and ultrafine-elongated grains, in which the brass fragments were distributed uniformly. These microstructural features, introduced through cross accumulative roll bonding (CARB), provide synergistic strengthening effects. The CARB processed composite exhibits a mean misorientation angle of 43.16° and a fraction of high angle grain boundaries of 87%, compared to values of 38.02° and 79% for ARB processed specimen. The CARB processed composite demonstrates a major texture characterized by prominent Rotated Brass {110}, Rotated Goss {011}, and Rotated Cube {001} components. In contrast, the ARB processed specimen revealed strong Goss {011}, Rotated Goss {011}, Brass {011}, and S {123} components. The Copper {112} and S {123} components were nearly absent in the CARB processed composite, because both of them were unstable under the CARB regime. The CARB processed composite shows a tensile strength of 405 MPa and a remarkable elongation of 12.4% at ambient temperature, outperforming ARB processed specimen with a tensile strength of 335 MPa and elongation of 9.5%. These unique mechanical properties in the CARB processed composite are ascribed to the dislocation strengthening, bimodal grain size distribution, uniformity of the brass fragments, and quality of bonding at the interfaces.Ministry of Science and Higher Education of the Russian Federation (FENU-2023-0013).; Seoul National University, Seoul, South Korea (Brain Korea 21 (BK21) Postdoctoral Fellowship to MN).