THE INFLUENCE OF SINGLY CHARGED IONS ON THE TRANSLATIONAL MOTION OF MOLECULES IN EXTREMELY DILUTE AMIDE SOLUTIONS

The type of short range solvation of Li+, Na+ K+, Rb+, Cs+, NH4+, Cl– , Br–, I–, ClO4– ions has been determined and analyzed in formamide (FA), N-methylformamide (MFA), N-dimethylformamide (DMF) at 298.15 K. In order to determine the type of ion solvation we used familiar-variable quantitative parameter (– ri), where is the translational displacement length of ion, ri is its structural radius. It was found that the difference (– ri) is equal to the coefficient of attraction friction (CAF) of ions normalized to the solvent viscosity and hydrodynamic coefficient. The sign of the CAF is determined by the sign of the algebraic sum of its ion-molecular and intermolecular components. In amide solutions the studied cations are cosmotropes (positively solvated ((– ri) > 0), structure-making ions) and anions are chaotropes (negatively solvated ((– ri) < 0 ), structure-breaking ions). In the amide series, regardless of the sign (– ri), the near-solvation enhances, which can be explained by the weakening of the specific interaction between the solvent molecules. The decrease of and respectively (– ri) with increasing cation radius in a given solvent is the result of weakening of its coordinating force due to the decrease of charge density in the series Li+–Na+–K+–Rb+–Cs+. The increase of (and (– ri), correspondingly) for the ions studied in the series FA- MFA-DMF can be explained by the weakening of intermolecular interactions in this series, which leads to the strengthening of solvation. It was found that for the halide ions in the series FA-MFA-DMF the regular growth of parameter is explained by the weakening of the solvent structure. It was shown that Li+ ion with the lowest diffusion coefficient among cations and the highest value forms kinetically stable complexes in amide solutions.

The Hydrodynamic Coefficient Analysis and Motion Control of the Lingyun Moveable Lander

A moveable lander has the advantages of low cost and strong controllability and is gradually becoming an effective autonomous ocean observation platform. In this study, the hydrodynamic property of the Lingyun moveable lander, which has completed experiments in the Mariana Trench in 2020, is analyzed with the semiempirical method and computational fluid dynamic (CFD) method. We calculate the inertial hydrodynamic coefficients and viscous hydrodynamic coefficients of the lander. The results show that the CFD can provide the hydrodynamic property for the moveable lander’s design. The dynamic equations and kinematic equations are completely constructed combined with the hydrodynamic coefficients. Subsequently, this paper utilized the PID control method and S control method to control the motions of the lander. The simulation results show that the methods accurately follow the preplanned path.

The standing biomass of saltmarshes as a key variable for estimating their wave energy damping capacity

&lt;p&gt;The estimation of wave energy dissipation produced by saltmarshes has traditionally been obtained in terms of a drag or friction force. The estimation of these forces is made taking into account the characteristics of the saltmarsh (i.e. biomechanical properties, morphology, density) and a hydrodynamic coefficient (i.e. the drag or friction coefficient). The characterization of a vegetated ecosystem by measuring leaf traits, the biomechanical properties of the plants and the number of individuals per unit area involves a lot of effort and is case-specific. In addition, hydrodynamic coefficients are selected on the basis of simplified geometry parameterizations or on calibrations performed in ad hoc studies and accurate estimates rely on their validation under real conditions.&lt;/p&gt;&lt;p&gt;Although for a very limited number of species, previous studies have shown that wave damping positively correlates with standing biomass. Therefore, standing biomass can be a unique variable that defines the wave energy attenuation capacity of the ecosystem. In addition, this variable has already been already characterized for many ecosystems by means of traditional plant harvesting or more recently using aerial images. Then, to further explore its relationship with the induced flow energy attenuation, a new set of experiments is proposed using real vegetation, with contrasting morphology and biomechanical properties, and subjected to different incident flow conditions. The experiments are carried out considering four species of vegetation, with contrasting biomechanical properties and morphology, and including two densities per species. Three water depths, wave heights from 0.08 to 0.18 m and wave periods from 1.5 to 4 s are tested. Capacitive free surface gauges and Acoustic Doppler Velocimeters (ADVs) are used to measure wave damping plant capacity along the meadow.&lt;/p&gt;&lt;p&gt;A direct relationship between the standing biomass of the meadow and plant induced wave attenuation is found for the eight vegetated conditions. In addition, a single relationship is obtained for the resultant wave damping and the eight standing biomass values. This relationship provides the basis for the use of standing biomass as a key parameter to estimate the coastal protection service provided by different saltmarsh species using a single variable that can be easily quantified from the field.&lt;/p&gt;

Research on Propeller Modeling and Fluid-Solid Coupling Analysis

Taking the AU5-50 propeller as an example, the detailed process of propeller modeling with atlas method and PropCad is compared. By comparing the auxiliary profiles used for modeling, it is pointed out that the blade model established by PropCad has more complete features and is not restricted by the propeller type. Besides, to verify the credibility of the PropCad modeling method, simulation analysis is carried out. First, the hybrid mesh and boundary layer mesh are divide for the flow field by integrated computer engineering and manufacturing (ICEM). Second, grid independence is verified utilizing a multiple reference frame (MRF) model. In the verifying process, three widely used turbulence models are analyzed and compared under advance ratio 0.7, and the results show that the hydrodynamic coefficient error calculated by the shear stress transport (SST) k-ω model is the smallest. Third, the computational fluid dynamics (CFD) calculation model is determined. The hydrodynamic performance of the propeller at different advance ratios is analyzed, and the CFD calculation results are in good agreement with the open water test data. Finally, the fluid-solid coupling analysis of the propeller is performed, and it is verified that the stress field of the propeller meets the material strength requirement. Therefore, it is proved to be feasible to conduct propeller modeling with PropCad.

Numerical Study on the Tandem Submerged Hydrofoils Using RANS Solver

This paper is presented on the tandem two-dimensional hydrofoils with profiles NACA4412 in single-phase and two-phase flow domains for different submergence depths and different distances in a various angle of attack (AoA). Also, supercavitation is studied at σ = 0.34 by the Zwart cavitation model. Reynolds-averaged Navier–Stokes (RANS) with the shear stress transport (SST) K-ω is employed as a turbulence model in transient analysis of Ansys FLUENT software. The numerical results show that, by increasing depth, the drag coefficient increases for both hydrofoils 1 and 2 as well as the lift coefficient. The drag coefficient of hydrofoil 2 is bigger than hydrofoil 1 for all depths; moreover, it was found that the flow pressure behind the hydrofoil 1 had affected the upper and the lower surface of the hydrofoil 2 at each distance or AoA. These effects are observed in the hydrofoil 2 lift coefficient as well as the flow separation. However, the maximum lift-to-drag ratio is observed at AoA = 8 ° and 3.5c distance. Also, single-phase results reveal that the value of pressure and the hydrodynamic coefficient are very different from the two-phase flow results, due to the elimination of the free surface. So, a two-phase flow domain is recommended for increasing the accuracy of results. In addition, the investigation of supercavitation shows a growth in cavity occurrence on the surface by raising AoA.

Magnetic Coupling for a 10 kW Tidal Current Turbine: Design and Small Scale Experiments

This paper presents a coupling design that improves water tightness of a marine current turbine (MCT). The coupling is numerically analyzed and incorporated into the design of an MCT from a previous study. The performance of the MCT with the magnetic coupling is compared to the previous results in small scale turbine experiments. The results show that the new design is water tight and has lower mechanical losses when compared with previous results. The new turbine has increased maximum power output (from 116 W to 122 W) and hydrodynamic coefficient of power (Previously 0.45 to 0.46). Using these results, the coupling design is scaled for a 10 kW MCT and further analyzed by finite element analysis. The results obtained show that the magnetic coupling is capable of withstanding the combined weight of the hub and blade assembly. The results in this study will be used for developing a prototype for deployment in real seas.

Time Domain Analysis of Single Module Movement of Deep Sea Rights Enforcement Platform

Due to its large size, deep sea rights enforcement platform cannot be closed in the dock, so it needs to be dragged to the pre-installed position for module to module connection. Based on the ANSYS AQWA software, a single module finite element model of the platform is established to solve the security problem of the far-reaching maritime rights enforcement platform in the sea. The hydrodynamic coefficient and the transfer function of the motion response are calculated in the frequency domain, and the response spectrum analysis is carried out. It is worth noting that the single module is a trapezoidal asymmetric structure, so the shape influence on the calculation results will be focused on. The results show that the motion response of the single module is greatly influenced by the wave cycle and the wave direction, because the single module of the platform is a trapezoid asymmetric structure, and the hydrodynamic coefficients are different under different incident waves. Through comparison and parameter analysis, the rationality of the single module design and the good motion performance under the actual sea condition are verified.

Study on determination method of hydrodynamic coefficient of Marine pile foundation

The irregular waves are simulated by using standard spectrum. Instantaneous value method, Fourier analysis method, least square method and "harbour hydrological code" are used to determine the moment force of coefficient CM and drag coefficient CD. Then CM and CD that linearized by Borgman L.E. equation are substituted into Morison equation. The time history curve of the wave force on the pile is calculated and compared with the measured wave force data under the action of irregular wave to analyze the advantages and disadvantages of several methods to determine CM and CD. The results show that the comparison between CM and CD determined by Fourier analysis and least square method is practical.