Hydrodynamic interactions between multi-body aquaculture platforms and nearshore random wave dynamics: A physical experiment

This paper presents new laboratory data on long-wave (surf-beat) forcing by the random breaking of shorter gravity water waves on a plane beach. The data include incident and outgoing wave amplitudes, together with shoreline oscillation amplitudes at long-wave frequencies, from which the correlation between forced long waves and short-wave groups is examined. A detailed analysis of the cross-shore structure of the long-wave motion is presented, and the observations are critically compared with existing theories for two-dimensional surf-beat generation. The surf beat shows a strong dependency on normalized surf-zone width, consistent with long-wave forcing by a time-varying breakpoint, with little evidence of the release and reflection of incident bound long waves for the random-wave simulations considered. The seaward-propagating long waves show a positive correlation with incident short-wave groups and are linearly dependent on short-wave amplitude. The phase relationship between the incident bound long waves and radiated free long waves is also consistent with breakpoint forcing. In combination with previous work, the present data suggest that the breakpoint variability may be the dominant forcing mechanism during conditions with steep incident short waves.

Hydrodynamic interactions significantly alter the dynamics of actin networks and result in a length scale dependent loss modulus

Future nearshore wave energy converter (WEC) arrays will influence coastal wave and sediment dynamics, yet there are limited numerical methodologies to quantify their possible impacts. A novel coupled WEC-Wave numerical method was developed to quantify these possible influences on the nearshore coastal wave climate. The power performance of an Oscillating Surge Wave Energy Converter (OSWEC) array was simulated to quantify the wave energy dissipation due to the array. The OSWEC’s effect on the local wave climate was quantified by a novel coupling of two numerical models, WEC–Sim and XBeach. WEC–Sim characterizes the power extraction and wave energy transmission across the OSWEC, while XBeach captures the change in wave dynamics due to the WEC and propagates the waves to shore. This novel methodology provides the ability to directly quantify the impact of the effect of a WEC array on the local wave climate. Three case studies were analyzed to quantify the impact of a single WEC on breaking conditions and to quantify the impact of number of WECs and the array spacing on the local nearshore wave climate. Results indicate that when the WEC is placed 1100 m offshore, one WEC will cause a 1% reduction in wave height at the break point (Hsbp). As the WEC is placed further offshore, the change in Hsbp will become even smaller. Although the change in wave height from one WEC is small, WEC arrays magnify the cross–shore extent, area of influence and the magnitude of influence based on the spacing and number of WECs. For arrays with 10 or 15 WECs, the cross–shore extent was on average 200–300 m longer when the WECs were placed one to two WEC widths apart, compared with being spaced three or four widths apart. When the spacing was one WEC width apart (18 m), there was a 30% greater spatial impact on the nearshore region than arrays spaced three or four widths apart. The trend for the average transmission coefficient is within 5% for a 5, 10 or 15 WEC array, with a cumulative average of 78% transmission across all conditions.

In the present paper, the hydrodynamic interactions between bubbles and the gas supply system to a needle were experimentally investigated. In experimental investigations in one of the needles, the air volume flow rate was constant, and in the neighbouring needle, it was changed. In the paper, the methods of data analysis: wavelet decomposition, and FFT were used. It was shown that the hydrodynamic interaction becomes stronger with the increase in air volume flow rate supply to the needle. The occurrence of hydrodynamic interaction modifies bubble growth time slightly, but it significantly modifies the bubble waiting time. In the case when the liquid penetration into the needle is repeatable, then the percentage disturbances in bubble growth time and bubble waiting time are close to each other. Moreover, it can be concluded that synchronized or alternative bubble departures from twin neighbouring needles (occurring due to hydrodynamic interaction) are possible by modifying the bubble waiting time. The modification of hydrodynamic interaction between bubbles, the bubbles themselves, and gas supply systems can be used to control the bubble departure process.

Experimental study on hydrodynamic interaction between dam-break waves and circular pier

采用布朗动力学模拟方法,研究了流体动力学作用对稀溶液中悬浮粒子聚集过程的影响.模拟中忽略了一个粒子同时与多个粒子碰撞聚集的可能,引入了前人有关两粒子间流体动力学作用影响的研究成果.模拟结果证实了流体动力学的作用在比较大的幅度上减缓了粒子的聚集过程,是导致粒子聚集速率的实验值低于Smoluchowski理论值的重要原因之一.另外,在分别加入和排除重力作用,以及考虑和忽略粒子间流体动力学作用在内的各种...

The behaviour of sheared colloidal suspensions with full hydrodynamic interactions (HIs) is numerically studied. To this end, we use the hybrid stochastic rotation dynamics-molecular dynamics (SRD-MD) method. The shear viscosity of colloidal suspensions is computed for different volume fractions, both for dilute and concentrated cases. We verify that HIs help in the collisions and the streaming of colloidal particles, thereby increasing the overall shear viscosity of the suspension. Our results show a good agreement with known experimental, theoretical, and numerical studies. This work demonstrates the ability of SRD-MD to successfully simulate transport coefficients that require correct modelling of HIs.

This paper numerically and experimentally investigates the hydrodynamic interaction between two semi-submersible type VLFS modules in the frequency domain. Model tests were conducted to investigate the relationship between interactions and wave headings. Numerical studies were performed by solving the radiation-diffraction problem and were validated against the experimental results. Motion Response Amplitude Operators (RAOs) were obtained from numerical and experimental studies. The dependency of the hydrodynamic interaction effect on wave headings is clarified. The influence of different wave periods on the motion responses of two-module VLFS and wave elevations in the gap is studied. The results indicate that the hydrodynamic interactions of the two modules are directly related to the wave headings and the periods of the incident wave. The shielding effect plays an important role in short wave, and the influence decreases with the increase of the incident wavelength. The numerical results based on the diffraction-radiation code can give a relatively good estimation to the responses in short wave while for long wave, it would over-predict the response.

The effect of hydrodynamic interactions in a grafted polymer brush under shear flow is examined. It is shown that the hydrodynamic interactions in a strained brush cause an increase in the brush thickness due to an asymmetry in the pair distribution of monomers. The predictions are in qualitative agreement with some recent experiments. I. Introduction The equilibrium properties and phase transitions of polymer brushes have been widely studied.' A brush consists of polymer molecules end-grafted onto a solid surface such that the distance between the points of attachment, d, is small compared to the radius of gyration of a single polymer molecule in a solvent or a melt. Due to the proximity of the grafting points, the polymers are highly stretched and the thickness of the brush is large compared to the radius of gyration of a polymer insolution. This thickness is determined by a balance between the elastic tension along the chain and the osmotic pressure due to the excluded-volume interactions between the monomers. Alexander and de Gennes2a used scaling arguments to show that the brush thickness varies as Nd-2/3; this scaling law has been subsequently verified by more detailed theoretical calculations* and e~periments.~ Thus, the brush thickness is proportional to the number of monomers N, in contrast to the iW2 and iW5 depend- encies of the radius of gyration of a polymer in a melt and a solvent, respectively. Rabin and Alexandera were the first to study the effect of a shear flow at the surface of a polymer brush. They treated the brush as a collection of closely packed concentration blobs, each having a diameter equal to the distance between grafting points. The effect of the shear flow was approximated by a force actingat the free surface of the brush. This force causes an elongation and tilt of the polymers in the direction of the flow, but the theory predicts that the thickness of the layer is unaltered by the force at the surface. However, experimental studies by Klein et aL7 using a surface force measurement apparatus showed that there is an increase of up to 20 76 in the brush thickness due to a shear flow. Barrats subsequently revisited the Rabin and Alexander calculation and showed that the theory is capable of predicting an increase in the brush thickness. This is caused by a decrease in the osmotic compressibility due to the force acting at the free surface. In this paper, we analyze the effect of hydrodynamic interactions in a polymer brush when a shear flow is applied at the surface. We find that the interactions cause a net upward force on the polymers, which could lead to an increase in the brush thickness. The change in the brush thickness is calculated as a function of the shear velocity, and the theoretical predictions are compared with the experimentally observed increase in the brush thickness.

Numerical and experimental investigations on dynamic response of twin-barge floatover system in standby phase

Cilia-driven motility and fluid transport are ubiquitous in nature and essential for many biological processes, including swimming of eukaryotic unicellular organisms, mucus transport in airway apparatus or fluid flow in the brain. The-biflagellated micro-swimmer Chlamydomonas reinhardtii is a model organism to study the dynamics of flagellar synchronization. Hydrodynamic interactions, intracellular mechanical coupling or cell body rocking is believed to play a crucial role in the synchronization of flagellar beating in green algae. Here, we use freely swimming intact flagellar apparatus isolated from a wall-less strain of Chlamydomonas to investigate wave dynamics. Our analysis on phase coordinates shows that when the frequency difference between the flagella is high (10–41% of the mean), neither mechanical coupling via basal body nor hydrodynamics interactions are strong enough to synchronize two flagella, indicating that the beating frequency is perhaps controlled internally by the cell. We also examined the validity of resistive force theory for a flagellar apparatus swimming freely in the vicinity of a substrate and found quantitative agreement between the experimental data and simulations with a drag anisotropy of ratio 2. Finally, using a simplified wave form, we investigated the influence of phase and frequency differences, intrinsic curvature and wave amplitude on the swimming trajectory of flagellar apparatus. Our analysis shows that by controlling the phase or frequency differences between two flagella, steering can occur.

ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTHow Many Stages in the Coil-to-Globule Transition of Linear Homopolymer Chains in a Dilute Solution?Xiaodong Ye, Yijie Lu, Lei Shen, Yanwei Ding, Shilin Liu, Guangzhao Zhang, and Chi WuView Author Information The Hefei National Laboratory for Physical Sciences at Microscale and the Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, China, and Department of Chemistry, The Chinese University of Hong Kong, Shatin N.T., Hong Kong Cite this: Macromolecules 2007, 40, 14, 4750–4752Publication Date (Web):June 19, 2007Publication History Received22 January 2007Revised27 May 2007Published online19 June 2007Published inissue 1 July 2007https://doi.org/10.1021/ma070167dCopyright © 2007 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views883Altmetric-Citations66LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (97 KB) Get e-AlertsSUBJECTS:Fluorescence,Kinetics,Lasers,Scattering,Thermoresponsive polymers Get e-Alerts

Slurry of activated carbon particles mixed with an aqueous electrolyte solution has been used as “flowable electrode” in a few recent electrochemical systems, e.g., electrochemical flow capacitors (EFCs) for energy storage, and flow-electrode capacitive deionization (FCDI) for water treatment. In these applications, the porous carbon particles with very large specific surface area adsorb ions from the electrolyte and meanwhile store electrical charges when a voltage source is added in the charging process. Under the flow condition, the motion of the particles and their mutual contact form a dynamically varying electrical network for the charge transport through the bulk material. We introduce a novel particle-based computational model using the Stokesian dynamics to simulate the hydrodynamic interaction of the carbon particles and the charge transport. An analogous electrical circuit model is developed by approximating the particles with many interconnected resistor-capacitor units, and the circuit’s topology is temporally changing depending on the instantaneous particle configuration. The Stokesian model and the circuit model are solved simultaneously to study how the hydrodynamic interaction and cluster formation affect the charge transport process of the slurry. The presence of the stationary current collector can be included to incorporate the near-wall effects on particle mobility. In the simulation, we vary the particle concentration as well as the ratio of the particle charging time to the hydrodynamic interaction time. The results shows that the charge transport in the carbon slurry is enhanced by increasing the concentration of the particles and faster particle charging. In addition, cluster formation of the particles plays an important role for the electronic transport process. After scaling, the transient electrical current from the present study generally agrees with that from previous experimental and modeling studies.

An array of nine fabricated models comprised of three different shapes, with three model sizes for each shape, has been utilized in tow tank tests to investigate the hydrodynamic interaction between glacial ice masses and a transiting tanker. A generic model tanker was towed past free-floating ice mass models at various speeds and proximities. The ice masses were either spherical, pyramidal or cylindrical in shape. The influence of waves of various periods and wave heights was also investigated. Sway and surge of the ice masses in response to the tanker passage were measured as the primary indicators of the hydrodynamic interactions. Notable among the many observed behaviors was that waves tended to enhance the degree of sway. Also, in the scenarios tested the magnitude of surge speed and sway speed were <10% of the tanker speed, and would therefore not significantly reduce impact speed during collisions. The program results are intended for use primarily in the validation of IOT’s numerical simulations of bergy bit/ship collisions, but can also serve as a validation database for simulation studies by other researchers.

The trend in microfluidics and lab-on-a-chip is to miniaturize and integrate many functions in a single chip, while achieving a high functional performance. To reach fast processing and a high sensitivity at the same time, recent lab-on-a-chip approaches use high-volume preparation steps together with micro-scaled detection techniques. One of the challenges is to solve transport limitations within microfluidic processes. Using superparamagnetic particles as actuation vehicles in lab-on-a-chip systems appears to be a promising approach. However, the full control of particle motion in direction and velocity remains complicated. In this thesis we investigate the interactions between neighboring particles, surrounding fluid and nearby walls. We found that these effects highly influence the dynamics of the particle loaded fluid. First particle dynamics in open fluid volumes was studied using an experimental setup containing a sub-microliter fluid volume surrounded by four miniaturized electromagnets for particle actuation. On the basis of optical velocity measurements, the induced motion of single particles and ordered particle chains was analyzed. Experiments on single particles revealed velocities that highly vary between particles and also the average measured velocity was found to deviate from theoretical predictions, which we attributed to non-uniform magnetic particle properties. Equations for the influence of particle chain formation on magnetization and hydrodynamics have been established, and show an increasing logarithmic dependence of the velocity as function of the chain length. Experimental studies on rotating particle chains showed transient regimes for the chain shape including chain rupture events, which could be reconstructed with a mechanistic pin-joint model based on magnetic and hydrodynamic inter-particle forces. Furthermore, within spatial confinements of a microsystem, we studied the interactions between particles, fluid, and nearby walls. An experimental setup was built providing a constant magnetic force on individual particles dispersed in a microchannel. The hydrodynamic interactions appeared to generate unforeseen self-organization phenomena. Superparamagnetic particles aligned on the channel axis successively organize towards a stable poly-twin system, which could be explained by a 1-dimensional model based on the flow profile along the axis. In addition, particles traveling close to a channel wall show complex rotation transitions that result in s-shaped trajectories while focusing towards the channel center, which could be explained by self-induced fluid velocity gradients within the channel. Using micro-scaled flux guides to generate high magnetic field gradients, the particles reached amplified velocities and could be controlled in their circular pathways within the channels. On system level, the fluid driving efficiency of the observed particle configurations were evaluated with numerical simulation models. Axially aligned particles appear to be very efficient for fluid pumping through channels. The efficiency can be tuned by the particle to channel radius and the particle spacing. The off-axis counter-rotating particles appear to enhance near-surface mixing. Integrated fluid actuation by magnetic particles is demonstrated in micro pore systems, where pressure-driven techniques are ineffective for the exchange of fluids. Our experimental investigations and theoretical analyses lead to a better understanding of particle dynamics, in order to improve the functional performance of magneto-fluidic microsystems