Circulation Distribution Research Articles

Hydrodynamic simulation of coastal reservoir in response to flow control: a numerical study of the Saemangeum reservoir

Coastal reservoirs (CRs) are important water resources worldwide, but environmental problems can arise due to limited material mixing caused by the blocked propagation of tidal waves. The Saemangeum Reservoir is a large brackish reservoir in South Korea; owing to its complex fluctuation characteristics, accurate reproduction of its three-dimensional (3D) circulation and material distribution characteristics remains a challenge. Here, we aimed to improve the reproducibility of the Delft3D model through long-term precision monitoring and analyze problems occurring in CRs. The model reproduced the hydraulic flow and stratification phenomena in CRs. The Richardson number ( R i ) was higher than 100, and the Stratification Index ( SI ) was higher than 1 due to the density difference between the surface and bottom layers. The stratification strength of the Saemangeum Reservoir was, therefore, considered high. Moreover, a two-layer circulation occurred due to the strength of the eddy and the horizontal gradient of salinity. When the sluice gate was expanded, the area and number of days where hypoxia occurred decreased. It would also mitigate the retention of materials caused by the eddy and improve circulation. The findings of this study can be used as foundational data for solving and managing hydraulic problems within CRs.

Ionic co-aggregates based intravenous drug delivery: Evaluation on kinetics and distribution of the drug payloads and nanocarriers

Surfactants are crucial in formulating poorly soluble drugs but lead to serious side effects due to PEG chains. Novel supra-amphiphiles consisting of fatty acids and choline are developed, which spontaneously form ionic co-aggregates (ICAs) in water and exhibit strong solubilizing capacity. Paclitaxel (PTX) is adopted as a model drug here to evaluate the feasibility of choline oleate-based ICAs in the intravenous delivery of poorly soluble drugs by comparing the kinetics and distribution of payloads and nanocarriers. Choline oleate presents a maximum 10-fold enhancement in solubilizing capacity to PTX than Cremophor EL (CreEL), enabling a one-tenth use level in the formulation. Aggregation-caused quenching probes are utilized to evaluate the kinetics and biodistribution of ICAs or CreEL-based micelles (MCs). A huge gap is found between the pharmacokinetic and particokinetic curves of either nanocarrier, indicating fast leakage. ICAs lead to faster PTX leakage in blood circulation but higher PTX distribution to organs than MCs. MCs present a longer circulation in blood but a slower distribution to organs than ICAs. ICAs do not arise adverse reactions in rats following repeated injections, while MCs cause pathological changes in varying degrees. In conclusion, choline oleate-based ICAs provide an alternative to surfactants in formulating poorly soluble drugs.

Inflammatory stimulus-responsive polymersomes reprogramming glucose metabolism mitigates rheumatoid arthritis

Inflammation-resident cells within arthritic sites undergo a metabolic shift towards glycolysis, which greatly aggravates rheumatoid arthritis (RA). Reprogramming glucose metabolism can suppress abnormal proliferation and activation of inflammation-related cells without affecting normal cells, holding potential for RA therapy. Single 2-deoxy-d-glucose (2-DG, glycolysis inhibitor) treatment often cause elevated ROS, which is detrimental to RA remission. The rational combination of glycolysis inhibition with anti-inflammatory intervention might cooperatively achieve favorable RA therapy. To improve drug bioavailability and exert synergetic effect, stable co-encapsulation of drugs in long circulation and timely drug release in inflamed milieu is highly desirable. Herein, we designed a stimulus-responsive hyaluronic acid-triglycerol monostearate polymersomes (HTDD) co-delivering 2-DG and dexamethasone (Dex) to arthritic sites. After intravenous injection, HTDD polymersomes facilitated prolonged circulation and preferential distribution in inflamed sites, where overexpressed matrix metalloproteinases and acidic pH triggered drug release. Results indicated 2-DG can inhibit the excessive cell proliferation and activation, and improve Dex bioavailability by reducing Dex efflux. Dex can suppress inflammatory signaling and prevent 2-DG-induced oxidative stress. Thus, the combinational strategy ultimately mitigated RA by inhibiting glycolysis and hindering inflammatory signaling. Our study demonstrated the great potential in RA therapy by reprogramming glucose metabolism in arthritic sites.

Prediction of steady hydrodynamic performance of pump jet propulsion based on free wake vortex model

Due to mutual interference between various components, the transitional motion of fluid particles in the flow field of pump jet propulsion becomes more complex and variable. Additionally, the vortex structure at the wake can undergo severe contraction and deformation. To further improve the accuracy of predicting the hydrodynamic performance of pump jet propulsion, this paper proposes a time-varying, space-varying, and induced velocity-varying free wake numerical calculation model based on potential flow theory. A set of hydrodynamic performance prediction methods that consider the interference of the free wake model is also established. Furthermore, a velocity smoothing model based on time reversal is constructed based on the distribution pattern of numerical singularity points during the induced velocity calculation process, which enhances the robustness of the calculation program. By comparing and analyzing the numerical calculation results with experimental results, including pressure, circulation distribution, and hydrodynamic performance, the accuracy of the free wake model proposed in this paper is verified. The results also demonstrate that the free wake model proposed in this paper can effectively improve the prediction accuracy of the hydrodynamic performance of the pump jet propulsion.

How does the blade element momentum method see swept or prebent blades?

The blade element momentum (BEM) method is among the mostly used engineering aerodynamic models for wind turbine rotors. Even though the BEM method is strictly only applicable to straight blades forming a planar rotor, it is in practice used for load calculation and design optimization of blades with relatively large sweep, prebend or coning. The present work aims to answer the question: How does the BEM method see swept or prebent blades? The blade element part of the method can be adapted for swept or prebent blades by projecting the velocity and loads between the 2-D airfoil section and the 3-D blade geometry under the cross-flow principle. However, momentum theory considers the 3-D wake and the induction of a planar actuator disc with straight blades. There could be significant differences between the results calculated from different implementations of the BEM method, while the details of the implementations are often omitted in the literature. In the present work, a consistent implementation including the definition of airfoil section alignments and the coordinate systems is provided. It is shown that for a given circulation distribution, the BEM method will predict approximately the same local aerodynamic loads for non-straight blades as if the blades were straight and the rotor was planar. This means using the BEM method to perform aerodynamic optimization of modern rotors with curved blades and/or rotors that are not planar can only have little meaningful result. In order to model the impact of the wake geometry on the induction, more advanced models that take into account the wake geometry on the induction are necessary.

On One Tip Vortex Core Circulation Distribution Model in the Near-Field Region of a Wing

On One Tip Vortex Core Circulation Distribution Model in the Near-Field Region of a Wing

On the role of induced power in turbine wake scaling: bridging 100-m to 0.1-m rotors

A wake scaling methodology is proposed in which turbine power is separated into its induced and profile power components. It is shown that preserving induced power as a function of thrust coefficient in conjunction with the radial circulation distribution are sufficient conditions for wake scaling. This work demonstrates the primary role of induced power in scaling turbine wakes over three orders of magnitude from full-scale down to model-scale rotors. The extended theory is verified using blade-element momentum theory (BEMT) and large-eddy simulation (LES), and an example set of model-scale turbine wake experiments is proposed for known wind tunnel facilities around the world.

Turbulent vortex pair at equilibrium and its interaction with the ground at

A turbulent two-vortex system (T-2VS) is obtained by inserting analytical model wake vortices into very weak homogeneous isotropic turbulence (HIT) and by evolving them in time using large-eddy simulation until a turbulent state at statistical equilibrium is reached. The T-2VS is characterised as follows: circulation distribution of the vortices; energy of the mean and fluctuating fields; energy dissipation rate. It is also verified that essentially the same T-2VS is obtained when varying the initial model or initial HIT perturbation. A wall-resolved simulation of the T-2VS further interacting with a smooth ground is then performed at $Re_\varGamma = 2 \times 10^5$ ; this is $10 \times$ higher than in previous works, which allows us to better capture the high Reynolds number behaviour. The high release height of the T-2VS also ensures a physically correct approach to the ground. The results are compared with the literature and also to what is obtained for the case of non-turbulent vortices interacting with the same ground at the same Reynolds number. The flow topologies are discussed, and significant differences are highlighted regarding the separation of the boundary layer generated at the ground, and the way this secondary vorticity interacts with the primary vortices and makes them decay. The vortex trajectories are also measured, together with their circulation distribution and global circulation evolution, and the differences are discussed.

Inverse aerodynamic design for distributed propulsion wing with expected circulation distribution

Distributed Propulsion Wing (DPW) technology offers significant advantages in terms of flight energy savings, but the strong aerodynamic coupling between the propulsive internal flow and aerodynamic external flow brings significant design challenges. As the primary DPW profile design is of great significance, this paper proposes a hybrid method to solve the inverse problem mainly based on the formula relationship between the required aerodynamic loads and the profile shape, which is more direct and instructive compared with traditional parametric iterative methods. The aerodynamic characteristics are described by the circulation distribution in the Fourier series form, then the mean camber line of the profile is solved through the re-derived airfoil theory considering disk’s influence. Further CFD correction methods are also proposed. To validate the effectiveness and feasibility of the proposed hybrid inverse method, several DPW profile design tests are then conducted. Finally, the relationship between 2D and realistic 3D unit shape is also researched. The results show that the proposed inverse design method has great accuracy and convergence speed in the design tests, and shows good robustness against changes of the design parameters. The 2D profile shape and the actual 3D shape of DPW unit can establish an aerodynamic-propulsion equivalent relationship based on the same internal mass fluxes.

Numerical simulations of bio-inspired approaches to enhance underwater swimming efficiency

The present study discusses the numerical simulation results of swimming similar to manta rays. The complex three-dimensional kinematics of manta rays were implemented to unravel the intricacies of its propulsion mechanisms by using the discrete vortex method (DVM). The DVM replaces the requirement for a structured grid across the computational domain with a collection of vortex elements. This method simplifies grid generation, especially for intricate geometries, resulting in time and effort savings in meshing complex shapes. By modeling the pectoral fins with discrete panels and utilizing vortex rings to represent circulation and wake, the study accurately computes the pressure distribution, circulation distribution, lift coefficient, and thrust coefficient of the manta ray. This study focuses on the modulation of aerodynamic performance by altering the span length and the length change ratio during the downstroke and upstroke motion (SV). The manta ray's three-dimensional vortex configurations comprise a combination of vortex rings, vortex contrails, and horseshoe vortices. Analysis of the three-dimensional vortex structure indicates the presence of multiple vortex rings and horseshoe vortex rings at higher SV values, while adequate formation of horseshoe vortices is not observed at lower SV values. In terms of propulsive performance, both lift and thrust increase with SV, while the propulsive efficiency demonstrates its peak at SV = 1.75. The analysis reveals that at higher SV values, the net thrust generated primarily originates from the tip of the fins. Moreover, the study illustrates a significant enhancement in propulsive efficiency, particularly in association with optimal Strouhal numbers ranging between 0.3 and 0.4. The key findings of this study may be used in efficient design of agile autonomous underwater vehicles for marine exploration and surveillance applications.

Influence of Rotor Inflow, Tip Loss, and Aerodynamics Modeling on the Maximum Thrust Computation in Hover

Comprehensive rotorcraft simulation codes are the workhorses for designing and simulating helicopters and their rotors under steady and unsteady operating conditions. These codes are also used to predict helicopters’ limits as they approach rotor stall conditions. This paper focuses on the prediction of maximum rotor thrust when hovering (due to stall limits) and the thrust and power characteristics when the collective control angle is further increased. The aerodynamic factors that may significantly affect the results are as follows: steady vs. unsteady aerodynamics, steady vs. dynamic stall, blade tip losses, curvature flow, yaw angle, inflow model, and blade-vortex interaction. The inflow model and tip losses are found to be the most important factors. For real-world applications vortex-based inflow models are considered the best choice, as they reflect the blade circulation distribution within the inflow distribution. Because the focus is on the impact of aerodynamic modeling on rotor stall, the blade design and its flexibility are intentionally not considered.

Research on Black Start Control technology of Energy Storage Power Station Based on VSG All Vanadium Flow Battery

To reduce the losses caused by large-scale power outages in the power system, a stable control technology for the black start process of a 100 megawatt all vanadium flow battery energy storage power station is proposed. Firstly, a model is constructed for the liquid flow battery energy storage power station, and in order to improve the system capacity, four unit level power stations are processed in parallel. Secondly, based on the energy storage of all vanadium flow batteries, the traditional voltage and frequency stability control technology has been improved to address the characteristics of low inertia and damping in power electronic interfaces. The improved VSG strategy has been applied to the overall control of a hundred megawatt level flow battery energy storage power station, solving the voltage and frequency instability problems caused by load shocks and fluctuations. Finally, stable control of multiple parallel machines during the self starting process of the liquid flow battery energy storage power station was achieved, avoiding the occurrence of multiple machine circulation and uneven power distribution problems during the self starting process.

Haze Optical Depth in Exoplanet Atmospheres Varies with Rotation Rate: Implications for Observations

Transmission spectroscopy supports the presence of uncharacterized, light-scattering and -absorbing hazes in the atmospheres of many exoplanets. The complexity of factors influencing the formation, 3D transport, radiative impact, and removal of hazes makes it challenging to match theoretical models to the existing data. Our study simplifies these factors to focus on the interaction between planetary general circulation and haze distribution at the planetary limb. We use an intermediate-complexity general circulation model, ExoPlaSim, to simulate idealized organic haze particles as radiatively active tracers in the atmospheres of tidally locked terrestrial planets for 32 rotation rates. We find three distinct 3D spatial haze distributions, corresponding to three circulation regimes, each with a different haze profile at the limb. All regimes display significant terminator asymmetry. In our parameter space, super-Earth-sized planets with rotation periods greater than 13 days have the lowest haze optical depths at the terminator, supporting the choice of slower rotators as observing targets.

Activable Photodynamic DNA Probe with an "AND" Logic Gate for Precision Skin Cancer Therapy.

Photodynamic therapy (PDT) has emerged as a promising approach for squamous cell carcinoma treatment but hindered by tumor hypoxia, acquired resistance, phototoxicity, and so on. To address these issues, we developed a smart strategy utilizing activable photosensitizers delivered by an aptamer-functionalized DNA probe (ADP). The ADP incorporated an AS1411 aptamer for tumor targeting and a linear antisense oligonucleotide (ASO) for recognition of Survivin mRNA. In the absence of the target, PDT remained quenched, thereby avoiding phototoxicity during circulation and nonselective distribution. With the aid of the aptamer, ADP achieved selective targeting of tumors. Upon internalization, ADP targeted recognized Survivin mRNA, triggering PDT activation, and releasing ASO to down-regulate Survivin expression and reverse tumor resistance. Consequently, the activable photosensitizers exhibited an "AND" logic gate, combining tumor-targeting delivery and tumor-related gene activation, thus enhancing its specificity. Additionally, the incorporation of hemin into the ADP provided catalase activity, converting tumor-abundant H2O2 into O2, thereby ameliorating tumor hypoxia. The resulting functionalized G-quadruplex/hemin-DNA probe complex demonstrated targeted delivery and activation, minimized side effects, and enhanced PDT efficacy in both xenograft tumor-bearing mice and patient-derived xenograft models. This study offers a unique and promising platform for efficient and safe PDT, thus holding great potential for future clinical translation and improved cancer therapy.

Magnetic field suppression characteristics in interaction process between shock wave and light gas cylinder

Based on ideal compressible magnetohydrodynamics (MHD) equations, the interface instabilities induced by the interaction between planar shock wave and the light gas (Helium) cylinder under the influence of the magnetic fields with different directions are investigated numerically by using the CTU(corner transport upwind)+CT (constrained transport) algorithm. The numerical results elucidate the evolution of flow field characteristics and wave structures with and without magnetic field. Moreover, we examine the influence of the magnetic field direction on a characteristic scales (including the length, height and width of the central axis of gas cylinder), as well as the volume compressibility. Then, the mechanism of the magnetic field direction affecting the interface instability is studied in depth by integrating the analyses of the circulation, energy, velocity and magnetic force distribution within the flow field. The core of this study, is to explore the suppression mechanism of interface instability by magnetic field force. The results show that the magnetic pressure plays a crucial role in driving vorticity away from the interface, thereby reducing its deposition on the density interface. Simultaneously, it adheres to the divided vortex layer, thereby effectively isolating the influence of Richtmyer-Meshkov instability on the interface. On the other hand, the magnetic tension adheres to the separated vortex layer, and its direction is opposite to that of the vorticity generated by the shear of interface velocity. This action effectively suppresses the Kelvin-Helmholtz instability and the rolling-up of vortices on the density interface. Additionally, under the control of a longitudinal magnetic field, the direction of magnetic tension is opposite to the direction of the central jet, effectively suppressing the development of Rayleigh-Taylor instability.

Perencanaan Taman Wisata Alam Danau Tamblingan Buleleng, Bali

Planning for Tamblingan Lake Natural Park Buleleng, Bali. The Tamblingan lake's natural tourist park has a potential of attractions that are aided by both its unique and strategic location. This makes the Tamblingan natural park a highly prospecting area that is able to attract tourists and plan the park's natural parks. The study intended to set up a zoning plan for lake tamblingan natural tourist park. The method in this study used survey method. By the stage of planning starting from the preparation stage, inventory, analysis, synthesis, concept, and planning. This research has a site plan. The attractive, environmentally insightful concept of tourism is based on the potential resources of landscapes and attractions and tourist attractions to preserve the landscape's resources and sustainability. The end result of the study was the landscape plans for the natural park areas of Tamblingan lakes involving the distribution of space, circulation, activity, and facilities.

The impact of the COVID-19 pandemic on the circulation, seasonal distribution, and research of other respiratory pathogens in Turkey

IntroductionRespiratory infections are one of the world's most common infectious diseases. Following the species, numbers, and seasonal distribution of acute respiratory agents is important for the protection of public health. Our study aimed to determine the effect of the COVID-19 pandemic on the circulation and seasonal distribution of non-SARS-CoV-2 respiratory tract agents and research on non-SARS-CoV-2 agents. MethodsThe results of the Multiplex PCR respiratory panel of 3702 nasopharyngeal swab samples sent between January 2018 and December 2021 were evaluated retrospectively. Scientific articles on acute respiratory infections between 2010 and 2021 from Turkey were analyzed in Scopus for bibliometric analysis. Results1.382 pathogens were detected. During the pandemic, the number of non-SARS-CoV-2 pathogens was found to be statistically significantly lower than before the pandemic. It was determined that while the most frequent agent before the pandemic was the Adenovirus, the most frequent agent was the RSV-A during the pandemic. Our network analysis of keywords indicated that academic interest in 2020-21 was directed toward COVID-19, which coincides with the pandemic period. ConclusionsOur study determined the fact that the incidence, species, and seasonal distribution of non-SARS-COV-2 respiratory agents changed after the onset of the pandemic. Increasing the identification and following-up of these pathogens in health organizations and also presenting these data to literature and sharing with academics is important. We are of the opinion that the results of our study shall shed light on the epidemiology of changing respiratory infections and the prevention and following-up of future health problems.

The Potential Role of Bering Strait in the Dynamics of Multidecadal Variability in the North Atlantic: An Idealized Model Study

Abstract Multidecadal variability on time scales between 20 and 70 years have been observed in the time series of North Atlantic SST. Many mechanisms have been proposed to explain multidecadal variabilities in the Atlantic. Generally, it is the interaction between the meridional overturning circulation (MOC) and North Atlantic surface buoyancy distribution that sustains this variability, with buoyancy anomalies either due to ocean-only processes or to air–sea interactions. In this context, the role of the Arctic Ocean, especially its freshwater flux into the North Atlantic, has been underappreciated. Bering Strait, the only oceanic pathway between the Pacific Ocean and the Arctic Ocean, has been found important in Arctic Ocean freshwater budget and in modulating the time-averaged state and long-term response of the MOC to high-latitude buoyancy forcing anomalies, via freshwater transport between the Pacific and Atlantic Oceans. In this paper, we use idealized configurations that include a Pacific-like wide basin and an Atlantic-like narrow basin. The two basins are connected both in the south and north to longitudinally periodic channels, representing the Southern Ocean and the Arctic Ocean, respectively. The Pacific-like basin is opened to the north only through a shallow and narrow strait, while the Atlantic-like basin is fully open to the north. With the goal of studying the role of Bering Strait in the multidecadal variability, we find that the freshwater transport from the Bering Strait forms a tongue structure along the western boundary of the narrow basin, which enhances the local horizontal density gradient. The western boundary region becomes unstable to large-scale baroclinic anomalies, giving rise to multidecadal variability.

Large Eddy Simulation for Empirical Modeling of the Wake of Three Urban Air Mobility Vehicles

Recent advances in urban air mobility have driven the development of many new vertical take-off and landing (VTOL) concepts. These vehicles often feature original designs departing from the conventional helicopter configuration. Due to their novelty, the characteristics of the supervortices forming in the wake of such aircraft are unknown. However, these vortices may endanger any other vehicle evolving in their close proximity, owing to potentially large induced velocities. Therefore, improved knowledge about the wakes of VTOL vehicles is needed to guarantee safe urban air mobility operations. In this work, we study the wake of three VTOL aircraft in cruise by means of large eddy simulation. We present a two-stage numerical procedure that enables the simulation of long wake ages at a limited computational cost. Our simulations reveal that the wakes of rotary vehicles (quadcopter and side-by-side helicopter) feature larger wake vortex cores than an isolated wing. Their decay is also accelerated due to self-induced turbulence generated during the wake roll-up. A tilt-wing wake, on the other hand, is moderately turbulent and has smaller vortex cores than the wing. Finally, we introduce an empirical model of the vortex circulation distribution that enables fast prediction of wake-induced velocities, within a 2% error of the simulation results on average.

Usutu Virus (<i>Flaviviridae, Orthoflavivirus</i>). Potential Danger and Possibility of Spread on the Territory of the Russian Federation

In recent decades, an increase in the number of cases of detection of the Usutu virus (Usutu, USUV, Orthoflavivirus usutuense) (family Flaviviridae, genus Orthoflavivirus) has caused great concern among medical professionals, including virologists and specialists in infectious diseases, especially since its appearance in Europe, where the pathogen caused mass birds die-off, and annually registered human cases. This review provides information about the structure of the virus and its genetic variants, geographical distribution and features of circulation in Europe and Africa, the methods and principles used to indicate and identify this pathogen, as well as the main symptoms of the disease it causes. An assessment of the environmental prerequisites for the occurrence of outbreaks of the disease caused by the Usutu virus on the territory of the Russian Federation was also carried out.