Cyclic Flow Research Articles

Breaking of Gauge Symmetry in Lattice Gauge Theories.

We study perturbations that break gauge symmetries in lattice gauge theories. As a paradigmatic model, we consider the three-dimensional Abelian-Higgs (AH) model with an N-component scalar field and a noncompact gauge field, which is invariant under U(1) gauge and SU(N) transformations. We consider gauge-symmetry breaking perturbations that are quadratic in the gauge field, such as a photon mass term and determine their effect on the critical behavior of the gauge-invariant model, focusing mainly on the continuous transitions associated with the charged fixed point of the AH field theory. We discuss their relevance and compute the (gauge-dependent) exponents that parametrize the departure from the critical behavior (continuum limit) of the gauge-invariant model. We also address the critical behavior of lattice AH models with broken gauge symmetry, showing an effective enlargement of the global symmetry, from U(N) to O(2N), which reflects a peculiar cyclic renormalization-group flow in the space of the lattice AH parameters and of the photon mass.

Undrained Cyclic Response and Resistance of Saturated Calcareous Sand considering Initial Static Shear Effect

Sand elements in the natural or manmade field have often undergone initial static shear stresses before suffering cyclic loading. To explore the effect of static shear stress, a series of undrained cyclic triaxial tests were performed on dense and loose calcareous sand under different initial and cyclic shear stresses. The triaxial test results are used to describe the effect of static shear stress on the cyclic response of the calcareous sand with different relative density. Cyclic mobility, flow deformation, and residual deformation accumulation are the three main failure modes under varying static and cyclic shear stress levels. The cyclic resistance of dense sand is greater than that of loose sand, but the initial static stress has different effects on the cyclic resistance of the two kinds of sand. The dense sand owns a higher cyclic resistance with SSR increasing, while for the loose sand, 0.12 is the critical SSR corresponding to the lowest value of the cyclic resistance. The dense sand has more fast accumulation of dissipated energy, compared with loose sand. Additionally, an exponential relationship is established between static shear stress, relative density, and normalized energy density.

Flow regime characterization of a silicon-based vaporizing liquid microthruster

The present work discusses an experimental investigation of the flow into a silicon-based vaporizing liquid microthruster equipped with sensing capabilities and low-power on-channel secondary heaters. The sensing capabilities (resistance temperature detectors and capacitive void fraction sensors) are used to investigate the flow instability and to evaluate its performances. The device has a sandwich structure composed of a silicon substrate and a glass substrate. This last one allows optical access into the device. The main heating of the propellant is provided using a platinum resistive heater placed on the bottom of the silicon layer. By varying the electrical power supplied to the main heater at fixed mass flow rate, three flow regimes have been observed and investigated: fully liquid flow, two-phase flow, and fully vaporized flow. Their dynamics have been captured through high-speed micro-flow visualizations under rough vacuum conditions (about 29 kPa). Furthermore, the expansion of the exhaust vapor plume exiting from the micronozzle has been analyzed via Schlieren visualizations. Results highlighted the occurrence of a cyclic flow behavior during the two-phase flow regime. In contrast, the flow exhibits the presence of both liquid and vapor phases at the micronozzle exit. Once the fully vaporized flow regime is established, the two-phase flow dynamics into the inlet chamber become more stable with complete filling and more uniform distribution of the flow at the microchannels entrance. Schlieren imaging captured the increase of the exhaust plume spreading half-angle when moving from ambient condition towards rough vacuum.

Updating the steady-state model of C4 photosynthesis.

C4 plants play a key role in world agriculture. For example, C4 crops such as maize and sorghum are major contributors to food production in both developed and developing countries, and the C4 grasses sugarcane, miscanthus, and switchgrass are major plant sources of bioenergy. In the challenge to manipulate and enhance C4 photosynthesis, steady-state models of leaf photosynthesis provide an important tool for gas exchange analysis and thought experiments that can explore photosynthetic pathway changes. Here a previous C4 photosynthetic model developed by von Caemmerer and Furbank has been updated with new kinetic parameterization and temperature dependencies added. The parameterization was derived from experiments on the C4 monocot, Setaria viridis, which for the first time provides a cohesive parameterization. Mesophyll conductance and its temperature dependence have also been included, as this is an important step in the quantitative correlation between the initial slope of the CO2 response curve of CO2 assimilation and in vitro phosphoenolpyruvate carboxylase activity. Furthermore, the equations for chloroplast electron transport have been updated to include cyclic electron transport flow, and equations have been added to calculate the electron transport rate from measured CO2 assimilation rates.

Structure and performance tests of a magnetocaloric cooling device with linear motion of the magnetic field source

This paper presents results of a research work aimed at designing, building and carrying out performance tests with a cooling device model utilizing linear motion of the magnetic field source and cyclic flow of a coolant through regenerator. The device incorporates two identical regenerators from 34 gadolinium plates each and a magnetic field source of 1 T. The working liquid was mixture of water and glycol with the specific heat of about 4000 J/kgK. The magnetic field source was introduced with maximum flux density of 1 T. The maximum temperature span measured on the heat exchangers was 10.3 K. Original solutions of the mechanical drives have been applied so as to achieve suitable synchronization and operating frequency of the model.

Modelling Rock Fracture Induced By Hydraulic Pulses

Soft cyclic hydraulic fracturing has become an effective technology used in subsurface energy extraction which utilises cyclic hydraulic flow pressure to fracture rock. This new technique induces fatigue of rock to reduce the breakdown pressure and potentially the associated risk of seismicity. To control the fracturing process and achieve desirable fracture networks for enhanced permeability, the rock response under cyclic hydraulic stimulation needs to be understood. However, the mechanism for cyclic stimulation-induced fatigue of rock is rather unclear and to date there is no implementation of fatigue degradation in modelling the rock response under hydraulic cyclic loading. This makes accurate prediction of rock fracture under cyclic hydraulic pressure impossible. This paper develops a numerical method to model rock fracture induced by hydraulic pulses with consideration of rock fatigue. The fatigue degradation is based on S–N curves (S for cyclic stress and N for cycles to failure) and implemented into the constitutive relationship for fracture of rock using in-house FORTRAN scripts and ABAQUS solver. The cohesive crack model is used to simulate discrete crack propagation in the rock which is coupled with hydraulic flow and pore pressure capability. The developed numerical model is validated via experimental results of pulsating hydraulic fracturing of the rock. The effects of flow rate and frequency of cyclic injection on borehole pressure development are investigated. A new loading strategy for pulsating hydraulic fracturing is proposed. It has been found that hydraulic pulses can reduce the breakdown pressure of rock by 10–18% upon 10–4000 cycles. Using the new loading strategy, a slow and steady rock fracture process is obtained while the failure pressure is reduced.

SIMULATION OF AIR HEAT TRANSFER IN CIRCULAR PIPES WITH TRIANGULAR AND SQUARE TURBULENCE STIMULATORS FOR HIGH REYNOLDS CRITERIA UP TO ONE MILLION

Objective . Conduct mathematical modeling of tornado zone structure systems between cyclic flow turbulence stimulators with the surface arrangement of triangular and square cross-sections based on multiblock computational techniques, based on solutions of the factorialized finite- volume procedure of the Reynolds equations (closed through the Menter shear stress transport model) and energy equations (on a multiscale intersecting structured grid) at high Reynolds criteria Re=10 6 with an exhaustive analysis of the relevant current lines. Methods. The calculations were carried out on a mathematical foundation based on the solution of the factorized finite-volume procedure of the Reynolds equations, which are closed using the low-Reynolds Menter shear stress transport model, and the energy equations on a multiscale intersecting structured grid (factorized finite-volume procedure). Results . Mathematical simulations of the heat exchange process in straight and round horizontal pipes with turbulence stimulators with d/D=0.95...0.90 and t/D=0.25...1.00 of triangular and square transverse profiles with large Reynolds numbers (Re=10 6 ) on a foundation with multiblock computing technologies, which are based on solutions of factorized and finite-volume Reynolds equations and energy equations, were conducted. It was found that the relative intensification of heat transfer [(Nu/Nu GL )| Re=106 ]/[(Nu/Nu GL )| Re=105 ] in round pipes with square air turbulence stimulators for large Reynolds numbers (Re=10 6 ), which may be relevant in the channels used in heat exchangers, could be higher with a large-scale increment of hydraulic resistance than for slightly smaller numbers (Re=10 5 ), for relatively high flow turbulence stimulators d/D=0.90 for the entire range under consideration for the parameter of the relative step between them t/D=0.25...1.00 a little more than 3%; for triangular turbulence stimulators, the crosssection profiles have similar values. For lower square turbulence stimulators with d/D=0.95, this increase in relative heat transfer for large Reynolds numbers (Re=10 6 ) compared to smaller numbers (Re=10 5 ) does not exceed 6%; for triangular cross-section turbulence stimulators, similar indicators are slightly more than 4%. Conclusion. The calculated results based on the developed model can optimize the intensification by turbulence stimulators and control the processes of heat transfer intensification. It is shown that for higher square turbulence stimulators and higher Reynolds numbers, a limited increase in the relative Nusselt criterion Nu/Nu GL is accompanied by a significant increase in the relative hydro resistance due to the very significant influence of return currents, which can flow directly on the turbulence stimulator to the greater extent, the higher the Reynolds number; for triangular turbulence stimulators, the above trend persists and even deepens.

Cyclic flow behavior of anisotropically consolidated sand with a small amount of fines

In practical engineering, the sand deposits or fills usually contains fine particles and their stress condition is generally anisotropic. This paper reports on an experimental study on the cyclic flow and liquefaction behavior of anisotropically consolidated sand with a small amount of fines. The results indicate that anisotropic consolidation can either reduce or enhance the soil's resistance to cyclic failure, depending on the (extensional) static stress level, which is closely related to the flow deformation type behavior. The responses are further compared to those of sand without fines at the same relative density condition. It is found that the addition of fines has an inhibiting effect on the cyclic flow deformation of the soil mixture, resulting in a higher and more rapid increase in cyclic resistance when the extensional static stress becomes larger. Furthermore, a particle-scale interpretation is presented to provide a better understanding of the distinct macro-observations associated with fines.

Pore-scale modelling and sensitivity analyses of hydrogen-brine multiphase flow in geological porous media

Underground hydrogen storage (UHS) in initially brine-saturated deep porous rocks is a promising large-scale energy storage technology, due to hydrogen’s high specific energy capacity and the high volumetric capacity of aquifers. Appropriate selection of a feasible and safe storage site vitally depends on understanding hydrogen transport characteristics in the subsurface. Unfortunately there exist no robust experimental analyses in the literature to properly characterise this complex process. As such, in this work, we present a systematic pore-scale modelling study to quantify the crucial reservoir-scale functions of relative permeability and capillary pressure and their dependencies on fluid and reservoir rock conditions. To conduct a conclusive study, in the absence of sufficient experimental data, a rigorous sensitivity analysis has been performed to quantify the impacts of uncertain fluid and rock properties on these upscaled functions. The parameters are varied around a base-case, which is obtained through matching to the existing experimental study. Moreover, cyclic hysteretic multiphase flow is also studied, which is a relevant aspect for cyclic hydrogen-brine energy storage projects. The present study applies pore-scale analysis to predict the flow of hydrogen in storage formations, and to quantify the sensitivity to the micro-scale characteristics of contact angle (i.e., wettability) and porous rock structure.

Deterioration behavior of gypsum breccia in surrounding rock under the combined action of cyclic wetting-drying and flow rates

The cyclic wetting-drying (W-D) phenomenon, which is a part of weathering processes, plays a vitally important role in affecting rock materials’ properties. In this paper, the gypsum breccia, an environmentally sensitive rock, was taken as the research object, which has the characteristics of high solubility. The deterioration behavior of gypsum breccia under W-D cycles with different flow rates was investigated. A one-dimensional water saturation test was conducted to study the coupling mechanism of water saturation-dissolution of gypsum breccia. A series of W-D cycle tests with different flow rates (0, 10, and 20 l/h) for gypsum breccia were conducted to reveal its deterioration behavior. Furthermore, the influence of these effects on the stability of the tunnel was discussed. The results show that gypsum breccia has a coupling behavior of water saturation and dissolution in the water environment. The effect of W-D cycles is the primary reason for the formation of visible cracks in gypsum breccia, while the flowing water will wash away the loose particles caused by the action of W-D cycles and accelerate the development of visible cracks and dissolution in gypsum breccia. The combination of these two actions gradually deteriorates the self-stability of the surrounding rock, which eventually leads to lining damage due to overload. The study can provide references for the engineering design of tunnels in gypsum breccia.

Using E-waste in asphalt mixtures – a laboratory investigation

Incorporating electronic waste (E-waste) in a new asphalt mixture is a subjected connected to the recycling process of PCB (Printed Circuit Boards), in which PCB waste is turned into a powder. The aim of the paper is to present the performance of the new asphalt pavement obtained by using PCB waste to substitute lime filler in a share of 100%. First, laboratory analyses are performed to determine the composition of PCB. Then, the feasibility of using PCB waste in the asphalt pavement industry is analysed in a series of laboratory investigations conducted on asphalt concrete BA16 rul 50/70 (AC16) that is a standard asphalt mixture in Romania. The following tests are performed on the new material: cyclic compression-dynamic flow, rutting test, and Marshall Stability and flow. The conclusion after the first experimental stage of this research is that the mixture containing PCB is softer than the control/witness mixture containing lime filler. Further investigations regarding the use of E-waste in road asphalt pavements will be conducted to find a way to reduce the use of new raw materials in the road construction industry.

Wavefunctions in dS/CFT revisited: principal series and double-trace deformations

We study wavefunctions of heavy scalars on de Sitter spacetime and their implications to dS/CFT correspondence. In contrast to light fields in the complementary series, heavy fields in the principal series oscillate outside the cosmological horizon. As a consequence, the quadratic term in the wavefunction does not follow a simple scaling and so it is hard to identify it with a conformal two-point function. In this paper, we demonstrate that it should be interpreted as a two-point function on a cyclic RG flow which is obtained by double-trace deformations of the dual CFT. This is analogous to the situation in nonrelativistic AdS/CFT with a bulk scalar whose mass squared is below the Breitenlohner-Freedman (BF) bound. We also provide a new dS/CFT dictionary relating de Sitter two-point functions and conformal two-point functions in the would-be dual CFT.

Energy-Based Modeling of the Feedback Control of Biomolecular Systems With Cyclic Flow Modulation

Energy-based modelling brings engineering insight to the understanding of biomolecular systems. It is shown how well-established control engineering concepts, such as loop-gain, arise from energy feedback loops and are therefore amenable to control engineering insight. In particular, a novel method is introduced to allow the transfer function based approach of classical linear control to be utilised in the analysis of feedback systems modelled by network thermodynamics and thus amalgamate energy-based modelling with control systems analysis. The approach is illustrated using a class of metabolic cycles with activation and inhibition leading to the concept of Cyclic Flow Modulation.

Advanced electrochemical detection of nitrogenous bases, synthetic oligonucleotides, and single-stranded DNA through flow injection analysis and catalytic oxidation on Prussian Blue

The effect of Prussian Blue (PB, ferric hexacyanoferrate) on oxidation of free nucleobases, synthetic oligonucleotides, single- and double-stranded DNA (ssDNA and dsDNA) was evaluated by cyclic voltammetry (CV) and flow injection analysis (FIA) on carbon screen printed electrodes, both bare (SPE) and PB modified (SPE/PB). It has been found that electrocatalytic oxidation of nucleobases, namely guanine, adenine, thymine, and cytosine, or nucleobase residues takes place via electrochemically generated Berlin Green (BG), fully oxidized form of PB. The constant potential FIA allowed one to register electrooxidation of all DNA nitrogenous bases at 0.95 V and three nitrogenous bases (except for cytosine) at 0.70 V on SPE and SPE/PB. The modification of electrode surface with PB resulted in a shift of oxidation potential to less positive values and enhanced (up to 8 times) detection sensitivity for DNA nucleobases. The pronounced catalytic effect of electrogenerated BG on their oxidation has also been observed for synthetic oligonucleotides and degraded ssDNA of natural origin. By fractionating ssDNA, it has been found that the main contributor to the total oxidation signal is the fraction of lowest molecular weight (< 3 kDa). At the same time, no oxidation signal was observed for large molecular weight native dsDNA in the potential range from 0 to 1 V on bare SPE and SPE/PB in both CV and FIA measurement modes. Therefore, the advanced electrochemical detection by FIA with SPE/PB was achieved for all nucleobases, synthetic oligonucleotides, and ssDNA of natural origin. Moreover, the obtained results expand the contemporary understanding of DNA electrochemistry.

Assessment of Geochemical Limitations to Utilizing CO2 as a Cushion Gas in Compressed Energy Storage Systems.

Compressed energy storage (CES) of air, CO2, or H2 in porous formations is a promising means of energy storage to abate the intermittency of renewable energy production. During operation, gas is injected during times of excess energy production and extracted during excess demands to drive turbines. Storage in saline aquifers using CO2 as a cushion or working gas has numerous advantages over typical air storage in caverns. However, interactions between CO2 and saline aquifers may result in potential operational limitations and have not been considered. This work utilizes reactive transport simulations to evaluate the geochemical reactions that occur during injection and extraction operational cycles for CES in a porous formation using CO2 as a cushion gas. Simulation results are compared with similar simulations considering an injection-only flow regime of geologic CO2 storage. Once injected, CO2 creates conditions favorable for dissolution of carbonate and aluminosilicate minerals. However, the dissolution extent is limited in the cyclic flow regime where significantly smaller dissolution occurs after the first cycle such that CO2 is a viable choice of cushion gas. In the injection-only flow regime, larger extents of dissolution occur as the fluid continues to be undersaturated with respect to formation minerals throughout the study period and porosity increased uniformly from 24.84% to 33.6% throughout the simulation domain. For the cyclic flow conditions, porosity increases nonuniformly to 31.1% and 25.8% closest and furthest from the injection well, respectively.

Cyclic tangential flow filtration system for isolation of extracellular vesicles.

Size-based filtration techniques have been developed for high-throughput isolation of extracellular vesicles (EVs). Conventional direct filtration systems have limitations in that large particles generally not only block the pores of the membrane but also damage the particles because of the high fluid pressure. Here, we propose a cyclic tangential flow filtration (TFF) system that includes two membranes with pore sizes of 200 and 30 nm, connected to a peristaltic pump that feeds the stream flowing to the membrane for continuous circulation. The cyclic TFF system is better able to isolate the specific 30–200 nm size range in one step through dual cyclic filtration compared with direct filtration (DF) and single cyclic TFF (scTFF). We further introduced a buffer-exchange process to the dcTFF system after filtration to remove contaminants for more efficient purification. As a result of comparative evaluation of dcTFF and ExoQuick, EVs isolated by dcTFF had more abundant exosome markers and active EVs. The cyclic TFF system not only has great potential to separate EVs with high selectivity and separation efficiency in small volumes of samples but can also be used in clinical applications, including medical diagnostic procedures.

Fabrication and Stabilization of Oxidized Carbon Black Nanoparticle Dispersion in Aqueous Solution for Photothermal Conversion Enhancement.

This study aims to explore oxidized carbon black nanoparticles (OCB-NPs) capped with an inorganic surfactant dispersed in water, as a carbon black water-based nanofluid, on photothermal conversion enhancement. We used ultraviolet–visible (UV–vis) absorption spectroscopy and zeta potential analyzers to identify the optimal concentration of sodium hexametaphosphate (SHMP) as an inorganic surfactant for OCB-NPs in order to determine the maximum value of UV–vis light absorption and absolute zeta potential. Then, the concentrations of 0.025–0.1 wt % OCB water-based nanofluid with SHMP were formulated by an ultrasonic bath for the examination of rheological behavior, thermal conductivity, and heating rate. The results indicated that the heating rate improvement of the water-based nanofluid involving 0.1 wt % OCB-capped with SHMP after irradiation by UV–vis light with wavelengths ranging from 220 to 380 nm, which is included in the solar spectrum, and an intensity of 205 W/m2 increased by approximately 66%, compared to the base fluid in the cyclic flow system. Furthermore, after a 1 month storage period, the dispersion stabilization of water-based nanofluid including 0.1 wt % OCB-capped with SHMP reached 98%, as estimated by the UV–vis spectrophotometer.

Fluid dynamics of oscillatory flow across parallel-plates in standing-wave thermoacoustic system with two different operation frequencies

Thermoacoustic system is one of the alternative technologies that provides green working principles but the lack of understanding of the complex fluid flow and energy transfer interactions within structures inside the system is leading to difficulty in accurate analysis related to the system. This study presents fluid dynamic investigation of vortex shedding and velocity profile of an oscillatory flow across a parallel-plate structure inside a standing-wave thermoacoustic system by using a two-dimensional ANSYS FLUENT CFD (computational fluid dynamics) of SST k-ω turbulence model. The model was validated using experimental data and theoretical solution. Two different operating frequencies of 14.2 Hz and 23.6 Hz were investigated with drive ratios (defined as maximum pressure amplitude to mean pressure) from 0.3% up to 3%. The results revealed that velocity profiles and boundary layers within the area of parallel-plate stack changes with time and the changes followed the cyclic travel of vortex across the structure. Two layers of vortex formed near the surface of the solid structure. These layers, known as the main and secondary vortex layers, change with the cyclic flow, and are affecting the shape of velocity profiles within the channel. The appearance of an ‘m’ shape, a ‘slug’ shape and a ‘parabolic’ shape velocity profiles are also depending on the flow amplitude (drive ratio) and flow frequency. The ‘parabolic’ velocity profile is only found for a certain moment of flow with thick boundary layer. The results indicated that fully developed flow may not be likely for cases presented in this paper. Hence care should be exercised in the use of equations during the analysis of thermoacoustic system. As the parallel-plate structure is usually an important structure of the system, a proper understanding of the dynamics of flow within this structure is crucial. These findings are expected to give better insight for future design of thermoacoustic system.

Cyclic Flow Shop Robotic Cell Scheduling Problem With Multiple Part Types

This article considers the problem of cyclic flow shop (CFS) scheduling problems in robotic cells deploying several single and dual gripper robots. In this problem, different part types are successively processed on multiple machines with different pickup criteria including free pickup, pickup within time windows, and no-waiting times. The parts are transported between the machines by the robots. We propose a novel integer programming approach that determines the optimal sequence of parts simultaneously for the sequencing of the robots’ movements and the cyclic schedule, which also results in maximizing the throughput rate. The proposed mathematical model is validated on a number of randomly generated test instances. These problem instances are constructed by varying the number of machines, part types, robots, and gripper options. This allows a detailed analysis of the model including how it scales with increasing numbers of machines, part types, robots, and grippers. An experimental evaluation shows that our proposed model is very effective for a range of small medium-sized problems. In particular, we find that differing number of robots and gripper options directly affects the cycle time and in turn, the throughput rate. Overall, our integer programming model finds good feasible solutions for up to 20 machines and 10 part types, which is comparable to real-world industrial problems.

Performance of a new model of nasal filter when challenged against PM1 aerosols

ABSTRACT Nasal filters are increasingly used in reducing personal haze exposures, but there is no retrievable evidence on its efficiency. In this study, a nasal filter testing system was designed. NaCl aerosols were generated to simulate PM1. Three different sizes of a new model of nasal filter were tested under two flow types (constant vs. cyclic) and three flow rates (15, 30, and 50 L/min). All PM1 penetration values were > 80%. Either enlarging filter size or lowering flow rate significantly reduced PM1 penetration, and PM1 penetration under cyclic flow was significantly higher compared with constant flow. To avoid mouth breathing, nasal filters could only be worn under light work-rates or rest conditions. The quality factor of nasal filters was only hundredths that of the N95 and P100 FFRs. This study reveals that there is a future need to design nasal filter materials with higher efficiency and lower flow resistance.