Journal articles on the topic 'Coupling between hydrodynamic modes'
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JIA, LAI-BING, FANG LI, XIE-ZHEN YIN, and XIE-YUAN YIN. "Coupling modes between two flapping filaments." Journal of Fluid Mechanics 581 (May 22, 2007): 199–220. http://dx.doi.org/10.1017/s0022112007005563.
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The flapping coupling between two filaments is studied theoretically and experimentally in this paper. A temporal linear instability analysis is carried out based on a simplified hydrodynamic model. The dispersion relationship between the eigen-frequency ω and wavenumber k is expressed by a quartic equation. Two special cases of flapping coupling, i.e. two identical filaments having the same length and two filaments having different lengths, are studied in detail. In the case of two identical filaments, the theoretical analysis predicts four coupling modes, i.e. the stretched-straight mode, the antisymmetrical in-phase mode, the symmetrical out-of-phase mode and the indefinite mode. The theory also predicts the existence of an eigenfrequency jump during transition between the in-phase and out-of-phase modes, which has been observed in previous experiments and numerical simulations. In the case of two filaments having different lengths, four modes similar to those in the former case are identified theoretically. The distribution of coupling modes for both the cases is shown in two planes. One is a dimensionless plane of S vs. U, where S is the density ratio of solid filament to fluid and U2 is the ratio of fluid kinetic energy to solid elastic potential energy. The other is a dimensional plane of the half-distance (h) between two filaments vs. the filament length (L). Relevant experiments are carried out in a soap-film tunnel and the stable and unstable modes are observed. Theory and experiment are compared in detail. It should be noted that the model used in our analysis is a very simplified one that can provide intuitional analytical results of the coupling modes as well as their qualitative distributions. The factors neglected in our model, such as vortex shedding, viscous and nonlinear effects, do not allow the model to predict results precisely consistent with the experiments. Moreover, the Strouhal numbers of the flapping filaments are found to be generally around a fixed value in the experiments for both cases, implying that the filaments try to maintain a lower potential energy state.
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Puhl, A., V. Altares, and G. Nicolis. "Imperfect turbulent mixing in chemical reactors: Coupling between chemical and hydrodynamic modes." Physical Review A 37, no. 8 (April 1, 1988): 3039–45. http://dx.doi.org/10.1103/physreva.37.3039.
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Guo, Hanliang, Yi Man, Kirsty Y. Wan, and Eva Kanso. "Intracellular coupling modulates biflagellar synchrony." Journal of The Royal Society Interface 18, no. 174 (January 2021): 20200660. http://dx.doi.org/10.1098/rsif.2020.0660.
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Beating flagella exhibit a variety of synchronization modes. This synchrony has long been attributed to hydrodynamic coupling between the flagella. However, recent work with flagellated algae indicates that a mechanism internal to the cell, through the contractile fibres connecting the flagella basal bodies, must be at play to actively modulate flagellar synchrony. Exactly how basal coupling mediates flagellar coordination remains unclear. Here, we examine the role of basal coupling in the synchronization of the model biflagellate Chlamydomonas reinhardtii using a series of mathematical models of decreasing levels of complexity. We report that basal coupling is sufficient to achieve inphase, antiphase and bistable synchrony, even in the absence of hydrodynamic coupling and flagellar compliance. These modes can be reached by modulating the activity level of the individual flagella or the strength of the basal coupling. We observe a slip mode when allowing for differential flagellar activity, just as in experiments with live cells. We introduce a dimensionless ratio of flagellar activity to basal coupling that is predictive of the mode of synchrony. This ratio allows us to query biological parameters which are not yet directly measurable experimentally. Our work shows a concrete route for cells to actively control the synchronization of their flagella.
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Balescu, R., H. Bessenrodt, P. K. Shukla, and K. H. Spatschek. "Instability and saturation of drift-convective modes in an inhomogeneous plasma." Journal of Plasma Physics 37, no. 2 (April 1987): 163–73. http://dx.doi.org/10.1017/s0022377800012083.
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It is found that the inclusion of the electron inertia effect (parallel to an external magnetic field) can provide a linear coupling between the electrostatic drift and the convective modes in a non-uniform plasma. This coupling leads to new branches of rapidly growing modes, which are calculated in the kinetic as well as in the hydrodynamic regimes. To study the saturation of the linear unstable modes, we account for the mode coupling and derive a set of model nonlinear fluid equations. A perturbation technique is employed to obtain a nonlinear evolution equation. In the steady state, the latter yields the saturated electric potential. It is argued that the enhanced low-frequency fluctuations can cause anomalous particle transport in a magnetoplasma.
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Híjar, Humberto, Rene Halver, and Godehard Sutmann. "Spontaneous Fluctuations in Mesoscopic Simulations of Nematic Liquid Crystals." Fluctuation and Noise Letters 18, no. 03 (July 16, 2019): 1950011. http://dx.doi.org/10.1142/s0219477519500111.
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We analyzed hydrodynamic fluctuations in nematic liquid crystals simulated by Multi-particle Collision Dynamics. Velocity effects on orientation were incorporated by allowing mesoscopic velocity gradients to exert torques on nematic particles. Backflow was included through an explicit application of angular momentum conservation during the collision events. We measured the spectra of hydrodynamic fluctuations and compared them with those derived from a linearized hydrodynamic scheme. Numerical results were found to reproduce the expected coupling between hydrodynamic modes, thus showing that the implementation simulates proper nematodynamic effects at the mesoscopic level.
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Hoch, Jannis M., Arjen V. Haag, Arthur van Dam, Hessel C. Winsemius, Ludovicus P. H. van Beek, and Marc F. P. Bierkens. "Assessing the impact of hydrodynamics on large-scale flood wave propagation – a case study for the Amazon Basin." Hydrology and Earth System Sciences 21, no. 1 (January 9, 2017): 117–32. http://dx.doi.org/10.5194/hess-21-117-2017.
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Abstract. Large-scale flood events often show spatial correlation in neighbouring basins, and thus can affect adjacent basins simultaneously, as well as result in superposition of different flood peaks. Such flood events therefore need to be addressed with large-scale modelling approaches to capture these processes. Many approaches currently in place are based on either a hydrologic or a hydrodynamic model. However, the resulting lack of interaction between hydrology and hydrodynamics, for instance, by implementing groundwater infiltration on inundated floodplains, can hamper modelled inundation and discharge results where such interactions are important. In this study, the global hydrologic model PCR-GLOBWB at 30 arcmin spatial resolution was one-directionally and spatially coupled with the hydrodynamic model Delft 3D Flexible Mesh (FM) for the Amazon River basin at a grid-by-grid basis and at a daily time step. The use of a flexible unstructured mesh allows for fine-scale representation of channels and floodplains, while preserving a coarser spatial resolution for less flood-prone areas, thus not unnecessarily increasing computational costs. In addition, we assessed the difference between a 1-D channel/2-D floodplain and a 2-D schematization in Delft 3D FM. Validating modelled discharge results shows that coupling PCR-GLOBWB to a hydrodynamic routing scheme generally increases model performance compared to using a hydrodynamic or hydrologic model only for all validation parameters applied. Closer examination shows that the 1-D/2-D schematization outperforms 2-D for r2 and root mean square error (RMSE) whilst having a lower Kling–Gupta efficiency (KGE). We also found that spatial coupling has the significant advantage of a better representation of inundation at smaller streams throughout the model domain. A validation of simulated inundation extent revealed that only those set-ups incorporating 1-D channels are capable of representing inundations for reaches below the spatial resolution of the 2-D mesh. Implementing 1-D channels is therefore particularly of advantage for large-scale inundation models, as they are often built upon remotely sensed surface elevation data which often enclose a strong vertical bias, hampering downstream connectivity. Since only a one-directional coupling approach was tested, and therefore important feedback processes are not incorporated, simulated discharge and inundation extent for both coupled set-ups is generally overpredicted. Hence, it will be the subsequent step to extend it to a two-directional coupling scheme to obtain a closed feedback loop between hydrologic and hydrodynamic processes. The current findings demonstrating the potential of one-directionally and spatially coupled models to obtain improved discharge estimates form an important step towards a large-scale inundation model with a full dynamic coupling between hydrology and hydrodynamics.
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Ciracì, Cristian, Radoslaw Jurga, Muhammad Khalid, and Fabio Della Sala. "Plasmonic quantum effects on single-emitter strong coupling." Nanophotonics 8, no. 10 (August 14, 2019): 1821–33. http://dx.doi.org/10.1515/nanoph-2019-0199.
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AbstractCoupling between electromagnetic cavity fields and fluorescent molecules or quantum emitters can be strongly enhanced by reducing the cavity mode volume. Plasmonic structures allow light confinement down to volumes that are only a few cubic nanometers. At such length scales, nonlocal and quantum tunneling effects are expected to influence the emitter interaction with the surface plasmon modes, which unavoidably requires going beyond classical models to accurately describe the electron response at the metal surface. In this context, the quantum hydrodynamic theory (QHT) has emerged as an efficient tool to probe nonlocal and quantum effects in metallic nanostructures. Here, we apply state-of-the-art QHT to investigate the quantum effects on strong coupling of a dipole emitter placed at nanometer distances from metallic particles. A comparison with conventional local response approximation (LRA) and Thomas-Fermi hydrodynamic theory results shows the importance of quantum effects on the plasmon-emitter coupling. The QHT predicts qualitative deviation from LRA in the weak coupling regime that leads to quantitative differences in the strong coupling regime. In nano-gap systems, the inclusion of quantum broadening leads to the existence of an optimal gap size for Rabi splitting that minimizes the requirements on the emitter oscillator strength.
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Tran, N., N. Y. Sergiienko, B. S. Cazzolato, M. H. Ghayesh, and M. Arjomandi. "Design considerations for a three-tethered point absorber wave energy converter with nonlinear coupling between hydrodynamic modes." Ocean Engineering 254 (June 2022): 111351. http://dx.doi.org/10.1016/j.oceaneng.2022.111351.
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Zhang, Qinghe, Chao Ji, Jinfeng Zhang, and Yuefeng Wu. "DEVELOPMENT OF A THREE DIMENSIONAL NUMERICAL MODEL OF SEDIMENT TRANSPORT AND MORPHOLOGICAL EVOLUTION ON SANDY BEACH." Coastal Engineering Proceedings, no. 36v (December 28, 2020): 41. http://dx.doi.org/10.9753/icce.v36v.sediment.41.
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In recent years, sandy coasts are suffering from erosion. It is of great importance to evaluate the state of coasts and assure the achievement of coastal protection measures. Therefore, a three-dimensional numerical model of sandy beach response was developed based on unstructured grids and with capability of describing nearshore hydrodynamics and sediment transports. A three-dimensional hydrodynamic model was first developed based on a coupled wave-current model system that included the Simulating Waves Nearshore (SWAN) wave model and the Finite Volume Community Ocean Model (FVCOM) circulation model. Information exchange between the two models used Model-Coupling Toolkit (MCT) software following Chen et al. (2018). The new three-dimensional radiation stress including the bottom slope effects was employed (Ji et al. 2017). Based on the hydrodynamic model, a numerical model of sediment transport and morphological evolution on sandy beach was developed.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/BVVn1kfViH0
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Fahr, H. J. "The charge-exchange induced coupling between plasma-gas counterflows in the heliosheath." Annales Geophysicae 21, no. 6 (June 30, 2003): 1289–94. http://dx.doi.org/10.5194/angeo-21-1289-2003.
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Abstract. Many hydrodynamic models have been presented which give similar views of the interaction of the solar wind plasma bubble with the counterstreaming partially ionized interstellar medium. In the more recent of these models it is taken into account that the solar and interstellar hydrodynamic flows of neutral atoms and protons are coupled by mass-, momentum-, and energy-exchange terms due to charge exchange processes. We shall reinvestigate the theoretical basis of this coupling here by use of a simplified description of the heliospheric interface and describe the main physics of the H-atom penetration through the more or less standing well-known plasma wall ahead of the heliopause. Thereby we can show that the type of charge exchange coupling terms used in up-to-now hydrodynamic treatments unavoidably leads to an O-type critical point at the sonic point of the H-atom flow, thus not allowing for a continuation of the integration of the hydrodynamic set of differential equations. The remedy for this problem is given by a more accurate formulation of the momentum exchange term for quasi-and sub-sonic H-atom flows. With a refined momentum exchange term derived from basic kinetic Boltzmann principles, we instead arrive at a characteristic equation with an X-type critical point, allowing for a continuous solution from supersonic to subsonic flow conditions. This necessitates that the often treated problem of the propagation of inter-stellar H-atoms through the heliosheath has to be solved using these newly derived, differently effective plasma – gas friction forces. Substantially different results are to be expected from this context for the filtration efficiency of the heliospheric interface.Key words. Interplanetary physics (heliopause and solar wind termination; interstellar gas) – Ionosphere (plasma temperature and density)
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Guo, Hanliang, Lisa Fauci, Michael Shelley, and Eva Kanso. "Bistability in the synchronization of actuated microfilaments." Journal of Fluid Mechanics 836 (December 11, 2017): 304–23. http://dx.doi.org/10.1017/jfm.2017.816.
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Cilia and flagella are essential building blocks for biological fluid transport and locomotion at the micrometre scale. They often beat in synchrony and may transition between different synchronization modes in the same cell type. Here, we investigate the behaviour of elastic microfilaments, protruding from a surface and driven at their base by a configuration-dependent torque. We consider full hydrodynamic interactions among and within filaments and no slip at the surface. Isolated filaments exhibit periodic deformations, with increasing waviness and frequency as the magnitude of the driving torque increases. Two nearby but independently driven filaments synchronize their beating in-phase or anti-phase. This synchrony arises autonomously via the interplay between hydrodynamic coupling and filament elasticity. Importantly, in-phase and anti-phase synchronization modes are bistable and coexist for a range of driving torques and separation distances. These findings are consistent with experimental observations of in-phase and anti-phase synchronization in pairs of cilia and flagella and could have important implications on understanding the biophysical mechanisms underlying transitions between multiple synchronization modes.
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De Wit, A. "Chemo-Hydrodynamic Patterns and Instabilities." Annual Review of Fluid Mechanics 52, no. 1 (January 5, 2020): 531–55. http://dx.doi.org/10.1146/annurev-fluid-010719-060349.
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By modifying a physical property of a solution like its density or viscosity, chemical reactions can modify and even trigger convective flows. These flows in turn affect the spatiotemporal distribution of the chemical species. A nontrivial coupling between reactions and flows then occurs. We present simple model systems of this chemo-hydrodynamic coupling. In particular, we illustrate the possibility of chemical reactions controlling or triggering viscous fingering, Rayleigh–Taylor, double-diffusive, and convective dissolution instabilities. We discuss laboratory experiments performed to study these phenomena and compare the experimental results to theoretical predictions. In each case we contrast the chemo-hydrodynamic patterns and instabilities with those that develop in nonreactive systems and unify the different dynamics in terms of the common features of the related spatial mobility profiles.
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Liu, Yujie, Rory Claydon, Marco Polin, and Douglas R. Brumley. "Transitions in synchronization states of model cilia through basal-connection coupling." Journal of The Royal Society Interface 15, no. 147 (October 2018): 20180450. http://dx.doi.org/10.1098/rsif.2018.0450.
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Despite evidence for a hydrodynamic origin of flagellar synchronization between different eukaryotic cells, recent experiments have shown that in single multi-flagellated organisms, coordination hinges instead on direct basal body connections. The mechanism by which these connections lead to coordination, however, is currently not understood. Here, we focus on the model biflagellate Chlamydomonas reinhardtii , and propose a minimal model for the synchronization of its two flagella as a result of both hydrodynamic and direct mechanical coupling. A spectrum of different types of coordination can be selected, depending on small changes in the stiffness of intracellular couplings. These include prolonged in-phase and anti-phase synchronization, as well as a range of multi-stable states induced by spontaneous symmetry breaking of the system. Linking synchrony to intracellular stiffness could lead to the use of flagellar dynamics as a probe for the mechanical state of the cell.
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Chomba, Innocent C., Kawawa E. Banda, Hessel C. Winsemius, Makungu Eunice, Henry M. Sichingabula, and Imasiku A. Nyambe. "Integrated Hydrologic-Hydrodynamic Inundation Modeling in a Groundwater Dependent Tropical Floodplain." Journal of Human, Earth, and Future 3, no. 2 (June 1, 2022): 237–46. http://dx.doi.org/10.28991/hef-2022-03-02-09.
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The rapid development of free and open-access hydrological models and coupling framework tools continues to present more opportunities for coupled model development for improved assessment of floodplain hydrology. In this study, we set up an Upper Zambezi hydrological model and a fully spatially hydrological-hydrodynamic coupled model for the Barotse Floodplain using GLOFRIM (GLObally applicable computational FRamework for Integrated hydrological–hydrodynamic Modelling). The hydrological and hydrodynamic models used are WFLOW and LISFLOOD-FP, respectively. The simulated flows generated by the wflow model for the upstream gauge stations before the Barotse Floodplain were quite similar and closely matched the observed flow as indicated by the evaluation statistics; Chavuma, nse = 0.738; kge = 0.738; pbias = 2.561 and RSR = 0.511; Watopa, nse = 0.684; kge = 0.816; pbias = 10.577 and RSR = 0.557; and Lukulu, nse = 0.736; kge = 0.795; pbias = 10.437 and RSR = 0.509. However, even though the wflow hydrological model was able to simulate the upstream hydrology very well, the results at the floodplain outlet gauge stations did not quite match the observed monthly flows at Senanga gauge station as indicated by the evaluation statistics: nse = 0.132; kge = 0.509; pbias = 37.740 and RSR = 0.9233. This is mainly because the representation of both floodplain channel hydrodynamics and vertical hydrological processes is necessary to correctly capture floodplain dynamics. Thus, the need for an approach that saves as a basis for developing fully spatially distributed coupled hydrodynamic and hydraulic models’ assessments for groundwater dependent tropical floodplains such as the Barotse floodplain, in closing the gap between hydrology and hydrodynamics in floodplain assessments. A fully coupled model has the potential to be used in implementing adaptive wetland management strategies for water resources allocation, environmental flow (eflows), flood control, land use and climate change impact assessments. Doi: 10.28991/HEF-2022-03-02-09 Full Text: PDF
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Mandre, Shreyas, and L. Mahadevan. "A generalized theory of viscous and inviscid flutter." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 466, no. 2113 (October 7, 2009): 141–56. http://dx.doi.org/10.1098/rspa.2009.0328.
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We present a unified theory of flutter in inviscid and viscous flows interacting with flexible structures based on the phenomenon of 1 : 1 resonance. We show this by treating four extreme cases corresponding to viscous and inviscid flows in confined and unconfined flows. To see the common mechanism clearly, we consider the limit when the frequencies of the first few elastic modes are closely clustered and small relative to the convective fluid time scale. This separation of time scales slaves the hydrodynamic force to the instantaneous elastic displacement and allows us to calculate explicitly the dependence of the critical flow speed for flutter on the various problem parameters. We show that the origin of the instability lies in the coincidence of the real frequencies of the first two modes at a critical flow speed beyond which the frequencies become complex, thus making the system unstable to oscillations. This critical flow speed depends on the difference between the frequencies of the first few modes and the nature of the hydrodynamic coupling between them. Our generalized framework applies to a range of elastohydrodynamic systems and further extends the Benjamin–Landahl classification of fluid–elastic instabilities.
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Ren, Nianxin, Hongbo Wu, Kun Liu, Daocheng Zhou, and Jinping Ou. "Hydrodynamic Analysis of a Modular Floating Structure with Tension-Leg Platforms and Wave Energy Converters." Journal of Marine Science and Engineering 9, no. 4 (April 14, 2021): 424. http://dx.doi.org/10.3390/jmse9040424.
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This work presents a modular floating structure, which consists of five inner tension-leg platforms and two outermost wave energy converters (denoted as MTLPW). The hydrodynamic interaction effect and the mechanical coupling effect between the five inner tension-leg platforms (TLP) and the two outermost wave energy converters (WEC) are taken into consideration. The effects of the connection modes and power take-off (PTO) parameters of the WECs on the hydrodynamic performance of the MTLPW system are investigated under both operational and extreme sea conditions. The results indicate that the hydrodynamic responses of the MTLPW system are sensitive to the connection type of the outermost WECs. The extreme responses of the bending moment of connectors depend on the number of continuously fixed modules. By properly utilizing hinge-type connectors to optimize the connection mode for the MTLPW system, the effect of more inner TLP modules on the hydrodynamic responses of the MTLPW system can be limited to be acceptable. Therefore, the MTLPW system can be potentially expanded to a large degree.
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Wang, Zi Jian, Li Ming Wu, and Sheng Xie Xiao. "Vibration Response Analysis on Deep-Water Piers under Earthquake and Wave Coupling Motivation." Applied Mechanics and Materials 548-549 (April 2014): 1607–12. http://dx.doi.org/10.4028/www.scientific.net/amm.548-549.1607.
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Taking a typical cylindrical solid pier as example, this paper utilizes the way of additional mass to consider the influences of hydrodynamic pressure on piers. It establishes dynamic response comparative analysis of single pier model under different earthquakes’ motivation taking ANSYS finite element software as computing platform. This draws conclusion that hydrodynamic pressure keeps characteristics of changing the seismic response of piers in which pier top displacement and pier bottom internal force are increased. Also it acquires the conclusion that weight and cycle of structure are related to the effect of hydrodynamic pressure. Through analyzing continuous beam bridge and continuous rigid-frame bridge, it is verified that there exists close relationship between effect of hydrodynamic pressure and inherent cycle of structure in which the higher inherent cycle becomes, the lower influence hydrodynamic pressure keeps on structure.
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Hamilton, Evelyn, and Pietro Cicuta. "Changes in geometrical aspects of a simple model of cilia synchronization control the dynamical state, a possible mechanism for switching of swimming gaits in microswimmers." PLOS ONE 16, no. 4 (April 8, 2021): e0249060. http://dx.doi.org/10.1371/journal.pone.0249060.
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Active oscillators, with purely hydrodynamic coupling, are useful simple models to understand various aspects of motile cilia synchronization. Motile cilia are used by microorganisms to swim and to control the flow fields in their surroundings; the patterns observed in cilia carpets can be remarkably complex, and can be changed over time by the organism. It is often not known to what extent the coupling between cilia is due to just hydrodynamic forces, and neither is it known if it is biological or physical triggers that can change the dynamical collective state. Here we treat this question from a very simplified point of view. We describe three possible mechanisms that enable a switch in the dynamical state, in a simple scenario of a chain of oscillators. We find that shape-change provides the most consistent strategy to control collective dynamics, but also imposing small changes in frequency produces some unique stable states. Demonstrating these effects in the abstract minimal model proves that these could be possible explanations for gait switching seen in ciliated micro organisms like Paramecium and others. Microorganisms with many cilia could in principle be taking advantage of hydrodynamic coupling, to switch their swimming gait through either a shape change that manifests in decreased coupling between groups of cilia, or alterations to the beat style of a small subset of the cilia.
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VILLAIN, L., and S. BONAZZOLA. "NUMERICAL TIME EVOLUTION OF INERTIAL MODES IN SLOWLY ROTATING NEUTRON STARS." International Journal of Modern Physics A 17, no. 20 (August 10, 2002): 2780. http://dx.doi.org/10.1142/s0217751x02012077.
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A numerical and linear study of modes driven toward instability by PN radiation-reaction force (current quadrupole) in slowly rotating neutron stars was presented. It consists in a time evolution using spectral methods in spherical coordinates for spatial operators. Whatever the noisy initial data, there exists a hydrodynamic instability. Yet, depending on the background, the symmetric properties of the mode may change. Thus, in a rigid rotating Newtonian star, the expected and purely axial r-mode1 is growing. But, when the Newtonian background is assumed to be differentially rotating or when the evolution is done in the framework of general relativity with Cowling approximation (frozen spacetime), a coupling between axial and polar modes appears. Then, the mode driven to instability no longer belongs to one of these subclasses. Preliminary results were presented, showing the common features and main differences between Newtonian and relativistic cases2.
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Fairbairn, Callum W., and Gordon I. Ogilvie. "Non-linear dynamics of hydrodynamic tori as a model of oscillations and bending waves in astrophysical discs." Monthly Notices of the Royal Astronomical Society 505, no. 4 (May 29, 2021): 4906–19. http://dx.doi.org/10.1093/mnras/stab1554.
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ABSTRACT Understanding oscillations and waves in astrophysical fluid bodies helps to elucidate their observed variability and the underlying physical mechanisms. Indeed, global oscillations and bending modes of accretion discs or tori may be relevant to quasi-periodicity and warped structures around compact objects. While most studies rely on linear theory, observationally significant, non-linear dynamics is still poorly understood, especially in Keplerian discs for which resonances typically demand a separate treatment. In this work, we introduce a novel analytical model which exactly solves the ideal, compressible fluid equations for a non-self-gravitating elliptical cylinder within a local shearing sheet. The aspect ratio of the ring is an adjustable parameter, allowing a continuum of models ranging from a torus of circular cross-section to a thin ring. We restrict attention to flow fields which are a linear function of the coordinates, capturing the lowest order global motions and reducing the dynamics to a set of coupled ordinary differential equations (ODEs). This system acts as a framework for exploring a rich range of hydrodynamic phenomena in both the large amplitude and Keplerian regimes. We demonstrate the connection between tilting tori and warped discs within this model, showing that the linear modes of the ring correspond to oppositely precessing global bending modes. These are further confirmed within a numerical grid based simulation. Crucially, the ODE system developed here allows for a more tractable investigation of non-linear dynamics. This will be demonstrated in a subsequent paper which evidences mode coupling between warping and vertical motions in thin tilted rings.
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Jordan, Peter, Vincent Jaunet, Aaron Towne, André V. G. Cavalieri, Tim Colonius, Oliver Schmidt, and Anurag Agarwal. "Jet–flap interaction tones." Journal of Fluid Mechanics 853 (August 23, 2018): 333–58. http://dx.doi.org/10.1017/jfm.2018.566.
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Motivated by the problem of jet–flap interaction noise, we study the tonal dynamics that occurs when an isothermal turbulent jet grazes a sharp edge. We perform hydrodynamic and acoustic pressure measurements to characterise the tones as a function of Mach number and streamwise edge position. The observed distribution of spectral peaks cannot be explained using the usual edge-tone model, in which resonance is underpinned by coupling between downstream-travelling Kelvin–Helmholtz wavepackets and upstream-travelling sound waves. We show, rather, that the strongest tones are due to coupling between Kelvin–Helmholtz wavepackets and a family of trapped, upstream-travelling acoustic modes in the potential core, recently studied by Towneet al. (J. Fluid Mech.vol. 825, 2017) and Schmidtet al. (J. Fluid Mech.vol. 825, 2017). We also study the band-limited nature of the resonance, showing the high-frequency cutoff to be due to the frequency dependence of the upstream-travelling waves. Specifically, at high Mach number, these modes become evanescent above a certain frequency, whereas at low Mach number they become progressively trapped with increasing frequency, which inhibits their reflection in the nozzle plane.
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Giorgi, Giuseppe, Josh Davidson, Giuseppe Habib, Giovanni Bracco, Giuliana Mattiazzo, and Tamás Kalmár-Nagy. "Nonlinear Dynamic and Kinematic Model of a Spar-Buoy: Parametric Resonance and Yaw Numerical Instability." Journal of Marine Science and Engineering 8, no. 7 (July 9, 2020): 504. http://dx.doi.org/10.3390/jmse8070504.
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Mathematical models are essential for the design and control of offshore systems, to simulate the fluid–structure interactions and predict the motions and the structural loads. In the development and derivation of the models, simplifying assumptions are normally required, usually implying linear kinematics and hydrodynamics. However, while the assumption of linear, small amplitude motion fits traditional offshore problems, in normal operational conditions (it is desirable to stabilize ships, boats, and offshore platforms), large motion and potential dynamic instability may arise (e.g., harsh sea conditions). Furthermore, such nonlinearities are particularly evident in wave energy converters, as large motions are expected (and desired) to enhance power extraction. The inadequacy of linear models has led to an increasing number of publications and codes implementing nonlinear hydrodynamics. However, nonlinear kinematics has received very little attention, as few models yet consider six degrees of freedom and large rotations. This paper implements a nonlinear hydrodynamic and kinematic model for an archetypal floating structure, commonplace in offshore applications: an axisymmetric spar-buoy. The influence of nonlinear dynamics and kinematics causing coupling between modes of motion are demonstrated. The nonlinear dynamics are shown to cause parametric resonance in the roll and pitch degrees of freedom, while the nonlinear kinematics are shown to potentially cause numerical instability in the yaw degree of freedom. A case study example is presented to highlight the nonlinear dynamic and kinematic effects, and the importance of including a nominal restoring term in the yaw DoF presented.
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Li, Xin, and Ming Xiao Xie. "Numerical Modeling of the Tidal Current Movement of the Baima Port, China." Applied Mechanics and Materials 675-677 (October 2014): 806–10. http://dx.doi.org/10.4028/www.scientific.net/amm.675-677.806.
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The Sanduao Bay is the bay with many of islands where the coastline is very winding with complex hydrodynamics and sediment transportation. Using a 2-D wave-current coupling hydrodynamic model of the Mike21 software package, the hydrodynamics condition on the Pingang Operation Area of Baima Port in the Sanduao Bay is simulatated. The results show that the current field in the berth is smooth that is beneficial to maintenance of water depth and reduction of siltation in berth. And the velocity in reclamation and dredging area is reduced less than 0.05m/s. the reclamation near the coastline and dredging in the berth make the velocity varied and the varying range is between 0.3m/s and 0.4m/s.
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Zhao, Enjin, Lin Mu, and Bing Shi. "Numerical Study of the Influence of Tidal Current on Submarine Pipeline Based on the SIFOM–FVCOM Coupling Model." Water 10, no. 12 (December 10, 2018): 1814. http://dx.doi.org/10.3390/w10121814.
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The interaction between coastal ocean flows and the submarine pipeline involved with distinct physical phenomena occurring at a vast range of spatial and temporal scales has always been an important research subject. In this article, the hydrodynamic forces on the submarine pipeline and the characteristics of tidal flows around the pipeline are studied depending on a high-fidelity multi-physics modeling system (SIFOM–FVCOM), which is an integration of the Solver for Incompressible Flow on the Overset Meshes (SIFOM) and the Finite Volume Coastal Ocean Model (FVCOM). The interactions between coastal ocean flows and the submarine pipeline are numerically simulated in a channel flume, the results of which show that the hydrodynamic forces on the pipeline increase with the increase of tidal amplitude and the decrease of water depth. Additionally, when scour happens under the pipeline, the numerical simulation of the suspended pipeline is also carried out, showing that the maximum horizontal hydrodynamic forces on the pipeline reduce and the vertical hydrodynamic forces grow with the increase of the scour depth. According to the results of the simulations in this study, an empirical formula for estimating the hydrodynamic forces on the submarine pipeline caused by coastal ocean flows is given, which might be useful in engineering problems. The results of the study also reveal the basic features of flow structures around the submarine pipeline and its hydrodynamic forces caused by tidal flows, which contributes to the design of submarine pipelines.
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Kubyshkina, Daria, Aline A. Vidotto, Luca Fossati, and Eoin Farrell. "Coupling thermal evolution of planets and hydrodynamic atmospheric escape in mesa." Monthly Notices of the Royal Astronomical Society 499, no. 1 (September 15, 2020): 77–88. http://dx.doi.org/10.1093/mnras/staa2815.
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ABSTRACT The long-term evolution of hydrogen-dominated atmospheres of sub-Neptune-like planets is mostly controlled to by two factors: a slow dissipation of the gravitational energy acquired at the formation (known as thermal evolution) and atmospheric mass-loss. Here, we use mesa to self-consistently couple the thermal evolution model of lower atmospheres with a realistic hydrodynamical atmospheric evaporation prescription. To outline the main features of such coupling, we simulate planets with a range of core masses (5–20 M⊕) and initial atmospheric mass fractions (0.5–30 per cent), orbiting a solar-like star at 0.1 au. In addition to our computed evolutionary tracks, we also study the stability of planetary atmospheres, showing that the atmospheres of light planets can be completely removed within 1 Gyr and that compact atmospheres have a better survival rate. From a detailed comparison between our results and the output of the previous-generation models, we show that coupling between thermal evolution and atmospheric evaporation considerably affects the thermal state of atmospheres for low-mass planets and, consequently, changes the relationship between atmospheric mass fraction and planetary parameters. We, therefore, conclude that self-consistent consideration of the thermal evolution and atmospheric evaporation is of crucial importance for evolutionary modelling and a better characterization of planetary atmospheres. From our simulations, we derive an analytical expression between planetary radius and atmospheric mass fraction at different ages. In particular, we find that, for a given observed planetary radius, the predicted atmospheric mass fraction changes as age0.11.
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Lyu, Jihang, Rong Yang, and Lingcai Huang. "Structure Dynamic Response of Amphibious Aircraft Induced by Water-Taxiing." International Journal of Aerospace Engineering 2021 (November 10, 2021): 1–10. http://dx.doi.org/10.1155/2021/6104407.
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The significant dynamic response under the combined impact of aerodynamic and hydrodynamic forces could be likely to appear because of the structural flexibility, when taxiing on the water surface for amphibious aircraft. Meanwhile, the modal characteristics of the structure are also affected by the additional motion of water. These require that the influence of the structural elasticity and the coupling effect between water and structure should be considered in dynamic response analysis of water-taxiing. According to the peculiarities of the amphibious aircraft, structural dynamics model is based on the distribution of stiffness and mass, Virtual Mass Theory is utilized to solve the wet modes on the water surface, rational function approximations of unsteady aerodynamic force in time-domain are constructed by the Minimum-State Approximation Formula, and loose coupling method is employed to simulate the hydrodynamic elastic response under the encounter of amphibian with single wave and repeated waves, respectively. Analysis of dynamic characteristics during the water-taxiing of the amphibious aircraft has been achieved in this work. The results show that wet natural frequencies of the aircraft have different degrees of decline compared with the dry frequencies because of the influence of added water on the hull, and the response amplitude of dynamic loads obtained by using the wet modes have some certain extent decrease compared with the dry modes. The dynamic amplitude of different locations changes in different degree relatives to the center of gravity position, which reflects the influence of structural elasticity. Due to the excitation of single wave and repeated waves, the structural vibration amplitude will increase rapidly, but the amplitude shows a certain divergence trend under the action of repeated waves with a given oscillation frequency, which is more severe for structural strength design.
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Fernández, Gael, Vasiliki Stratigaki, and Peter Troch. "Irregular Wave Validation of a Coupling Methodology for Numerical Modelling of Near and Far Field Effects of Wave Energy Converter Arrays." Energies 12, no. 3 (February 8, 2019): 538. http://dx.doi.org/10.3390/en12030538.
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Between the Wave Energy Converters (WECs) of a farm, hydrodynamic interactions occur and have an impact on the surrounding wave field, both close to the WECs (“near field” effects) and at large distances from their location (“far field” effects). To simulate this “far field” impact in a fast and accurate way, a generic coupling methodology between hydrodynamic models has been developed by the Coastal Engineering Research Group of Ghent University in Belgium. This coupling methodology has been widely used for regular waves. However, it has not been developed yet for realistic irregular sea states. The objective of this paper is to present a validation of the novel coupling methodology for the test case of irregular waves, which is demonstrated here for coupling between the mild slope wave propagation model, MILDwave, and the ‘Boundary Element Method’-based wave–structure interaction solver, NEMOH. MILDwave is used to model WEC farm “far field” effects, while NEMOH is used to model “near field” effects. The results of the MILDwave-NEMOH coupled model are validated against numerical results from NEMOH, and against the WECwakes experimental data for a single WEC, and for WEC arrays of five and nine WECs. Root Mean Square Error (RMSE) between disturbance coefficient (Kd) values in the entire numerical domain ( R M S E K d , D ) are used for evaluating the performed validation. The R M S E K d , D between results from the MILDwave-NEMOH coupled model and NEMOH is lower than 2.0% for the performed test cases, and between the MILDwave-NEMOH coupled model and the WECwakes experimental data R M S E K d , D remains below 10%. Consequently, the efficiency is demonstrated of the coupling methodology validated here which is used to simulate WEC farm impact on the wave field under the action of irregular waves.
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Huang, Yang, and Decheng Wan. "Investigation of Interference Effects Between Wind Turbine and Spar-Type Floating Platform Under Combined Wind-Wave Excitation." Sustainability 12, no. 1 (December 27, 2019): 246. http://dx.doi.org/10.3390/su12010246.
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In order to further understand the coupled aero-hydrodynamic performance of the floating offshore wind turbine (FOWT) in realistic ocean environment, it is necessary to investigate the interference effects between the unsteady aerodynamics of the wind turbine and different degree-of-freedom (DOF) platform motions under combined wind-wave excitation. In this paper, a validated CFD analysis tool FOWT-UALM-SJTU with modified actuator line model is applied for the coupled aero-hydrodynamic simulations of a spar-type FOWT system. The aero-hydrodynamic characteristics of the FOWT with various platform motion modes and different wind turbine states are compared and analyzed to explore the influence of the interference effects between the wind turbine and the floating platform on the performance of the FOWT. The dynamic responses of local relative wind speed and local attack angle at the blade section and wind-wave forces acting on the floating platform are discussed in detail to reveal the interaction mechanism between the aerodynamic loads and different DOF platform motions. It is shown that the surge motion and the pitch motion of the floating platform both significantly alter the local attack angle, while only the platform pitch motion have significant impacts on the local relative wind speed experienced by the rotating blades. Besides, the shaft tilt and the pro-cone angle of the wind turbine and the height-dependent wind speed all contribute to the variation of the local attack angle. The coupling between the platform motions along different DOFs is obviously amplified by the aerodynamic forces derived from the wind turbine. In addition, the wake deflection phenomenon is clearly observed in the near wake region when platform pitch motion is considered. The dynamic pitch motion of the floating platform also contributes to the severe wake velocity deficit and the increased wake width.
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LI, HAI-LIANG, GUOJING ZHANG, and KAIJUN ZHANG. "ALGEBRAIC TIME DECAY FOR THE BIPOLAR QUANTUM HYDRODYNAMIC MODEL." Mathematical Models and Methods in Applied Sciences 18, no. 06 (June 2008): 859–81. http://dx.doi.org/10.1142/s0218202508002887.
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The initial value problem is considered in the present paper for the bipolar quantum hydrodynamic (QHD) model for semiconductors in ℝ3. The unique strong solution exists globally in time and tends to the asymptotical state with an algebraic decay rate as time goes to infinity is proved. And, the global solution of linearized bipolar QHD system decays in time at an algebraic decay rate from both above and below is shown. This means that in general we cannot get an exponential time-decay rate for bipolar QHD system, which is different from the case of unipolar QHD model (where global solutions tend to the equilibrium state at an exponential time-decay rate) and is mainly caused by the nonlinear coupling and cancelation between two carriers. Moreover, it is also shown that the nonlinear dispersion does not affect the long time asymptotic behavior, which by product gives rise to the algebraic time-decay rate of the solution of the bipolar hydrodynamical model in the semiclassical limit.
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SHAIKH, DASTGEER. "Dynamics of Alfvén waves in partially ionized astrophysical plasmas." Journal of Plasma Physics 76, no. 3-4 (December 18, 2009): 305–15. http://dx.doi.org/10.1017/s0022377809990493.
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AbstractWe develop a two dimensional, self-consistent, compressible fluid model to study evolution of Alfvenic modes in partially ionized astrophysical and space plasmas. The partially ionized plasma consists mainly of electrons, ions and significant neutral atoms. The nonlinear interactions amongst these species take place predominantly through direct collision or charge exchange processes. Our model uniquely describe the interaction processes between two distinctly evolving fluids. In our model, the electrons and ions are described by a single-fluid compressible magnetohydrodynamic (MHD) model and are coupled self-consistently to the neutral fluid via compressible hydrodynamic equations. Both plasma and neutral fluids are treated with different energy equations that adequately enable us to monitor non-adiabatic and thermal energy exchange processes between these two distinct fluids. Based on our self-consistent model, we find that the propagation speed of Alfvenic modes in space and astrophysical plasma is slowed down because these waves are damped predominantly due to direct collisions with the neutral atoms. Consequently, energy transfer takes place between plasma and neutral fluids. We describe the mode coupling processes that lead to the energy transfer between the plasma and neutral and corresponding spectral features.
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Acharya, Subhajit, and Biman Bagchi. "Non-Markovian rate theory on a multidimensional reaction surface: Complex interplay between enhanced configuration space and memory." Journal of Chemical Physics 156, no. 13 (April 7, 2022): 134101. http://dx.doi.org/10.1063/5.0084146.
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A theory of barrier crossing rate on a multidimensional reaction energy surface is presented. The theory is a generalization of the earlier theoretical schemes to higher dimensions, with the inclusion of non-Markovian friction along both the reactive and the nonreactive coordinates. The theory additionally includes the bilinear coupling between the reactive and the nonreactive modes at the Hamiltonian level. Under suitable conditions, we recover the rate expressions of Langer and Hynes and establish a connection with the rate treatment of Pollak. Within the phenomenology of generalized Langevin equation description, our formulation provides an improvement over the existing ones because we explicitly include both the non-Markovian effects along the reaction coordinate and the bilinear coupling at the Hamiltonian level. At intermediate-to-large friction, an increase in dimensionality by itself tends to reduce the rate, while the inclusion of the memory effects increases the rate. The theory predicts an increase in rate when off-diagonal friction terms are included. We present a model calculation to study isomerization of a stilbene-like molecule using the prescription of Hochstrasser and co-workers on a two-dimensional reaction energy surface, employing Zwanzig–Bixon hydrodynamic theory of frequency-dependent friction. The calculated rate shows a departure from the predictions of Langer’s theory and also from the two-dimensional transition state theory.
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Ollila, Santtu T. T., Tapio Ala-Nissila, and Colin Denniston. "Hydrodynamic forces on steady and oscillating porous particles." Journal of Fluid Mechanics 709 (August 20, 2012): 123–48. http://dx.doi.org/10.1017/jfm.2012.325.
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AbstractWe derive new analytical results for the hydrodynamic force exerted on a sinusoidally oscillating porous shell and a sphere of uniform density in the Stokes limit. The coupling between the spherical particle and the solvent is done using the Debye–Bueche–Brinkman (DBB) model, i.e. by a frictional force proportional to the local velocity difference between the permeable particle and the solvent. We compare our analytical results and existing dynamic theories to lattice–Boltzmann simulations of the full Navier–Stokes equations for the oscillating porous particle. We find our analytical results to agree with simulations over a broad range of porosities and frequencies.
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Kailasham, R., Rajarshi Chakrabarti, and J. Ravi Prakash. "Shear viscosity for finitely extensible chains with fluctuating internal friction and hydrodynamic interactions." Journal of Rheology 67, no. 1 (January 2023): 105–23. http://dx.doi.org/10.1122/8.0000498.
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An exact solution of coarse-grained polymer models with fluctuating internal friction and hydrodynamic interactions has not been proposed so far due to a one-to-all coupling between the connector vector velocities that precludes the formulation of the governing stochastic differential equations. A methodology for the removal of this coupling is presented, and the governing stochastic differential equations, obtained by attaching a kinetic interpretation to the Fokker–Planck equation for the system, are integrated numerically using Brownian dynamics simulations. The proposed computational route eliminates the calculation of the divergence of the diffusion tensor, which appears in models with internal friction, and is about an order of magnitude faster than the recursion-based algorithm for the decoupling of connector-vector velocities previously developed [Kailasham et al., J. Rheol. 65, 903 (2021)] for the solution of freely draining models with internal friction. The effects of the interplay of various combinations of finite extensibility, internal friction, and hydrodynamic interactions on the steady-shear-viscosity are examined. While finite extensibility leads solely to shear-thinning, both internal friction and hydrodynamic interactions result in shear-thinning followed by shear-thickening. The shear-thickening induced by internal friction effects is more pronounced than that due to hydrodynamic interactions.
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Walker, S. J. "Coupled hydrodynamic and transport models of Port Phillip Bay, a semi-enclosed bay in south-eastern Australia." Marine and Freshwater Research 50, no. 6 (1999): 469. http://dx.doi.org/10.1071/mf98071.
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Coupled hydrodynamic and transport models of Port Phillip Bay were developed as part of the Port Phillip Bay Environmental Study. Model coupling was achieved via a particle tracking method, giving great flexibility in both geometry and time step for the transport model. This technique allowed ecological (water quality) modules to be included efficiently, so that long-term management scenarios could be adequately addressed. Validation of the hydrodynamic model was done primarily against observed sea-level and current meter data. For the transport model, comparisons were made with data on salinity in the bay observed over five years. Despite some disagreement between the hydrodynamic model and observations of longer-term (non-tidal) currents, the transport model provided good simulations of salinity throughout the bay. Transport-model flushing time for the bay was about 270 days (similar to estimates obtained from salinity and radionuclide measurements), varying with model geometry and with position inside the bay. As well as providing physical forcing for ecological simulations (described elsewhere in this issue), the models identified a systematic bias in the known freshwater budget for the bay.
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Bhagavat, M., V. Prasad, and I. Kao. "Elasto-Hydrodynamic Interaction in the Free Abrasive Wafer Slicing Using a Wiresaw: Modeling and Finite Element Analysis." Journal of Tribology 122, no. 2 (July 19, 1999): 394–404. http://dx.doi.org/10.1115/1.555375.
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Free abrasive machining (FAM) process associated with the wiresaw wafer slicing involves a three body abrasion environment. During the process, the cutting action is caused by fine abrasives freely dispersed in the slurry, which get trapped between an axially moving taut wire and the ingot being sliced. In this paper a model is proposed wherein the entry of abrasives into the cutting zone is governed by elasto-hydrodynamic (EHD) interaction between the slurry and the wire. An EHD film is formed by the abrasive carrying viscous slurry, squeezed between the wire and the ingot. This phenomenon is analyzed here using the finite element method. The analysis of such an interaction involves coupling of the basic Reynold’s equation of hydrodynamics with the elasticity equation of wire. Newton–Raphson algorithm is used to formulate and solve this basic coupling. The finite element discretization of the resulting nonlinear equation is carried out using Galerkin’s method of weighted residuals. Basic hydrodynamic interaction model and the incorporation of the entry level impact pressure into the inlet boundary conditions are the two novel features introduced in this work. The analysis yields film thickness profile and pressure distribution as a function of wire speed, slurry viscosity, and slicing conditions. A perusal of results suggests that the wiresawing occurs under “floating” machining condition. The minimum film thickness is greater than the average abrasive size. This is practically very important since the wiresaw is used to slice fragile semiconductor wafers with severe requirements on the surface finish. The possible mechanism by which a floating abrasive can cause material removal is also touched upon in this work. Material removal rate has been modeled based on energy considerations. [S0742-4787(00)00702-5]
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Venditti, Claudia, Stefano Cerbelli, Giuseppe Procopio, and Alessandra Adrover. "Comparison between one- and two-way coupling approaches for estimating effective transport properties of suspended particles undergoing Brownian sieving hydrodynamic chromatography." Physics of Fluids 34, no. 4 (April 2022): 042010. http://dx.doi.org/10.1063/5.0088977.
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Simplified one-way coupling approaches are often used to model transport properties of diluted particle suspensions for predicting the performance of microcapillary hydrodynamic chromatography (MHDC). Recently, a one-way coupling approach was exploited to optimize the geometry and operating conditions of an unconventional double-channel geometry with a square cross section, where a Brownian sieving mechanism acting alongside the MHDC separation drive (BS-MHDC) is enforced to boost separation resolution. In this article, a cylindrical geometry enforcing the same BS-MHDC separation drive is thoroughly investigated by following a two-way coupling, fully three-dimensional approach, and results are compared with those obtained enforcing the one-way coupling analysis. Device geometry and operating conditions are optimized by maximizing the separation resolution. The effective velocity and dispersion coefficient of spherical, finite-sized particles of different diameters are computed, and two-phase effects are discussed in detail. Similar to the square channel device, the cylindrical double-channel geometry allows for a sizable reduction in the column length and in the analysis time (a factor above 12 for the length and a factor larger than 3 for the processing time) when compared to the standard MHDC configuration ensuring the same separation resolution. As expected, the one-way coupling approach overestimates the separation performance of both the BS-MHDC and the standard MHDC devices with respect to the two-way coupling analysis. But, surprisingly, the enhancement factor of the BS-MHDC over the standard MHDC is underestimated by the single-phase approximation as it doubles when wall/particle interactions are properly accounted for with a two-phase description.
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NAJAFI, ALI, and FAEZEH POUSANEH. "THERMOPHORESIS AND THE EFFECT OF HYDRODYNAMIC INTERACTIONS IN A LINEAR MODEL FOR COLLOIDS." International Journal of Modern Physics B 25, no. 32 (December 30, 2011): 4379–85. http://dx.doi.org/10.1142/s0217979211059292.
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Thermal diffusion or Soret effect is the directed motion of colloidal particles in temperature gradient. In this article, by assuming local thermodynamic equilibrium, the drift velocity for a molecular system composed of two connected spheres is calculated. It is shown that for this system the positive Soret coefficient is given by: ST = (3/8)(a/l)(1/T), where l is the average linear size of the system, a is the radius of spheres and T is the local temperature. To investigate the hydrodynamic coupling in a dilute suspension of diffusers, we calculate the average drift velocity for two far diffusers. It is shown that due to the hydrodynamic interaction, an overall attraction between diffusers can be achieved.
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Herman, Agnieszka, Maciej Dojczman, and Kamila Świszcz. "High-resolution simulations of interactions between surface ocean dynamics and frazil ice." Cryosphere 14, no. 11 (November 5, 2020): 3707–29. http://dx.doi.org/10.5194/tc-14-3707-2020.
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Abstract. Frazil and grease ice forms in the ocean mixed layer (OML) during highly turbulent conditions (strong wind, large waves) accompanied by intense heat loss to the atmosphere. Three main velocity scales that shape the complex, three-dimensional (3D) OML dynamics under those conditions are the friction velocity u* at the ocean–atmosphere interface, the vertical velocity w* associated with convective motion, and the vertical velocity w*,L associated with Langmuir turbulence. The fate of buoyant particles, e.g., frazil crystals, in that dynamic environment depends primarily on their floatability, i.e., the ratio of their rising velocity wt to the characteristic vertical velocity, which is dependent on w* and w*,L. In this work, the dynamics of frazil ice is investigated numerically with the high-resolution, non-hydrostatic hydrodynamic model CROCO (Coastal and Regional Ocean COmmunity Model), extended to account for frazil transport and its interactions with surrounding water. An idealized model setup is used (a square computational domain with periodic lateral boundaries, spatially uniform atmospheric and wave forcing). The model reproduces the main features of buoyancy- and wave-forced OML circulation, including the preferential concentration of frazil particles in elongated patches at the sea surface. Two spatial patterns are identified in the distribution of frazil volume fraction at the surface: one related to individual surface convergence zones, very narrow, and oriented approximately parallel to the wind/wave direction and one in the form of wide streaks with a separation distance of a few hundred meters, oriented obliquely to the direction of the forcing. Several series of simulations are performed, differing in terms of the level of coupling between the frazil and hydrodynamic processes, from a situation when frazil has no influence on hydrodynamics (as in most models of material transport in the OML) to a situation in which frazil modifies the net density, effective viscosity, and transfer coefficients at the ocean–atmosphere interface and exerts a net drag force on the surrounding water. The role of each of those effects in shaping the bulk OML characteristics and frazil transport is assessed, and the density of the ice–water mixture is found to have the strongest influence on those characteristics.
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Cen, Wei Jun, Hui Sun, and Kun Xiong. "Dynamic Interaction between Reservoir and a High Concrete Face Rockfill Dam on Deep Alluvium Deposit." Applied Mechanics and Materials 353-356 (August 2013): 833–36. http://dx.doi.org/10.4028/www.scientific.net/amm.353-356.833.
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Potential-based fluid model and Westergaard added mass model were used to reflect the dynamic interaction of reservoir-CFRD(concrete face rockfill dam)-foundation coupling system. The deep alluvium deposit was treated as porous medium using Biot's dynamic consolidation theory. In the coupled analysis, the paper focused on hydrodynamic pressures in the reservoir zone, dynamic response and pore water pressure in the structure zone. The result shows that the dynamic response of added mass model is greater than that of potential-based fluid model. The porous medium of alluvium deposit is of great significance in performing soil liquefaction analysis and reservoir-dam-foundation system.
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Mahanty, J., and MT Michalewicz. "Interaction Potential of a Charged Particle in a Plane?Sphere Geometry." Australian Journal of Physics 40, no. 3 (1987): 413. http://dx.doi.org/10.1071/ph870413.
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The three� dimensional potential of a charged particle tunneling between a flat metal surface and a spherical metal tip is calculated within the framework of the hydrodynamic description of metallic electrons. It is demonstrated that the inclusion of coupling of surface modes in the two electrodes, even for separations as small as 10 times the screening length in either of them, contributes less than 5% of the total potential of a point charge. Hence the potential is obtained as a superposition of contributions from a planar surface and a charge neutral, conducting sphere (and can include a simple classical term for a sphere at a fixed potential). This should enable accurate determination of three� dimensional tunnel currents in scanning tunneling microscope geometry.
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Soloviev, Alexander. "Colliding poles with colliding nuclei." EPJ Web of Conferences 274 (2022): 05015. http://dx.doi.org/10.1051/epjconf/202227405015.
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In these proceedings, I will discuss collisions of poles in the complex plane as a signature of phase transitions for theories relevant to the quark gluon plasma. I will begin with an illustrative example, namely the chiral phase transition, which can be characterized by colliding poles as a function of temperature. Then, recognizing the interplay between weak and strong coupling sectors in a typical collision, I will introduce a hybrid model with a weakly broken symmetry, which has a rich quasi-hydrodynamic phenomenological description where hydrodynamic and non-hydrodynamic poles are unified by a common dispersion relation. I will show that energy is transferred initially from the soft to the hard sector before irreversibly transferring back to the soft sector at late times, and that the model reproduces many features common to dissipative systems with a weakly broken symmetry including the k-gap.
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Fuentes, Sebastián, Carlos Chávez, Fernando Brambila-Paz, and Josué Trejo-Alonso. "Hydrodynamic Border Irrigation Model: Comparison of Infiltration Equations." Water 14, no. 13 (July 1, 2022): 2111. http://dx.doi.org/10.3390/w14132111.
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The variation in moisture content between subsequent irrigations determines the use of infiltration equations that contain representative physical parameters of the soil when irrigation begins. This study analyzes the reliability of the hydrodynamic model to simulate the advanced phase in border irrigation. For the solution of the hydrodynamic model, a Lagrangian scheme in implicit finite differences is used, while for infiltration, the Kostiakov equation and the Green and Ampt equation are used and compared. The latter was solved using the Newton–Raphson method due to its implicit nature. The models were validated, and unknown parameters were optimized using experimental data available in the literature and the Levenberg–Marquardt method. The results show that it is necessary to use infiltration equations based on soil parameters, because in subsequent irrigations, the initial conditions change, modifying the advance curve in border irrigation. From the coupling of both equations, it is shown that the empirical Kostiakov equation is only representative for a specific irrigation event, while with the Green and Ampt equations, the subsequent irrigations can be modeled, and the advance/infiltration process can be observed in detail.
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Han, Weiwei, Shuyin Wu, Xue Gao, Xinyao Zong, and Jingsong Shan. "Experimental and Numerical Study on Fracture Characteristics of Interface between In Situ Engineered Cementitious Composites and Steel Deck." Advances in Materials Science and Engineering 2021 (February 6, 2021): 1–12. http://dx.doi.org/10.1155/2021/6653516.
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In this study, engineered cementitious composite (ECC) is used as the pavement of orthotropic steel deck bridge and an epoxy adhesive is used to achieve wet-bonding between the steel deck and cast-in-place ECC. To investigate the fracture properties of bimaterial interface, the double cantilever beam (DCB) and 4-point end notched flexure (4ENF) specimens were used to obtain the fracture toughness, and virtual crack closure technology (VCCT) was used to calculate the energy release rates. A mixed fracture criterion was also established based on the blister test in this study. In addition, for the phenomena of water accumulation in the interface cracks, the hydrodynamic pressure under load was evaluated with a two-way fluid-solid coupling model and the propagation mechanism of cracks at the water-bearing interface was explored. The results showed that the energy release rates at the crack front showed obvious nonuniform distribution characteristics. The blister test indicated that a mixed fracture was in good agreement with the linear fracture criterion. The fracture effect produced by the hydrodynamic pressure of the interfacial water-bearing crack was far less than the fracture toughness of the interface, which indicated that the hydrodynamic pressure could hardly destroy the interface at one time but might cause the erosion fatigue damage of the interface.
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Casas, Jérôme, Thomas Steinmann, and Gijs Krijnen. "Why do insects have such a high density of flow-sensing hairs? Insights from the hydromechanics of biomimetic MEMS sensors." Journal of The Royal Society Interface 7, no. 51 (April 28, 2010): 1487–95. http://dx.doi.org/10.1098/rsif.2010.0093.
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Insects and arachnids are often quite hairy. The reasons for this high density of sensory hairs are unknown. Previous studies have predicted strong hydrodynamic coupling between densely packed airflow-sensitive hairs. Flow perturbation owing to single hairs and between tandem hairs, however, has never been experimentally measured. This paper aims to quantify the extent of flow perturbation by single and tandem hairs directly, using biomimetic microelectromechanical system (MEMS) hairs as physical models and particle image velocimetry (PIV) for flow visualization. Single and tandem MEMS hairs of varying interhair distances were subjected to oscillatory flows of varying frequency. Decreasing hair-to-hair distance markedly reduced flow velocity amplitude and increased the phase shift between the far-field flow and the flow between hairs. These effects were stronger for lower flow frequencies. We predict strong hydrodynamic coupling within whole natural hair canopies exposed to natural stimuli, depending on arthropod and hair sizes, and hair density. Thus, rather than asking why arthropods have so many hairs, it may be useful to address why hairs are packed together at such high densities, particularly given the exquisite sensitivity of a single hair.
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Buie, Cullen, and Juan Santiago. "Model and Experimental Study of Hydrodynamic Coupling between a Fuel Pump and a Direct Methanol Fuel Cell." ECS Transactions 16, no. 2 (December 18, 2019): 1525–38. http://dx.doi.org/10.1149/1.2981993.
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Takae, Kyohei, and Hajime Tanaka. "Role of hydrodynamics in liquid–liquid transition of a single-component substance." Proceedings of the National Academy of Sciences 117, no. 9 (February 12, 2020): 4471–79. http://dx.doi.org/10.1073/pnas.1911544117.
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Liquid–liquid transition (LLT) is an unconventional transition between two liquid states in a single-component system. This phenomenon has recently attracted considerable attention not only because of its counterintuitive nature but also since it is crucial for our fundamental understanding of the liquid state. However, its physical understanding has remained elusive, particularly of the critical dynamics and phase-ordering kinetics. So far, the hydrodynamic degree of freedom, which is the most intrinsic kinetic feature of liquids, has been neglected in its theoretical description. Here we develop a Ginzburg–Landau-type kinetic theory of LLT taking it into account, based on a two-order parameter model. We examine slow critical fluctuations of the nonconserved order parameter coupled to the hydrodynamic degree of freedom in equilibrium. We also study the nonequilibrium process of LLT. We show both analytically and numerically that domain growth becomes faster (slower), depending upon the density decrease (increase) upon the transition, as a consequence of hydrodynamic flow induced by the density change. The coupling between nonconserved order parameter and hydrodynamic interaction results in anomalous domain growth in both nucleation-growth–type and spinodal-decomposition–type LLT. Our study highlights the characteristic features of hydrodynamic fluctuations and phase ordering during LLT under complex interplay among conserved and nonconserved order parameters and the hydrodynamic transport intrinsic to the liquid state.
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Mesquita, Janine Brandão de Farias, and Iran Eduardo Lima Neto. "Coupling Hydrological and Hydrodynamic Models for Assessing the Impact of Water Pollution on Lake Evaporation." Sustainability 14, no. 20 (October 19, 2022): 13465. http://dx.doi.org/10.3390/su142013465.
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The present study evaluated the impact of hydrological variability on the hydrodynamics of an urban lake in Brazil, considering water quality dynamics and its effects on evaporation. The Storm Water Management Model (SWMM) was applied to the lake basin, and the two-dimensional model CE-QUAL-W2 was used to simulate the hydrodynamics and lake evaporation. The two models were coupled to carry out the integrated basin-lake modeling. Then, two water quality models were applied: a transient complete mixing model and an empirical model based on wind speed. Time series of total phosphorus (TP) were generated, and empirical correlations between TP and hydrological variables were proposed. Modeled TP and measured biochemical oxygen demand (BOD) were correlated with monthly Class A pan coefficients (K) adjusted for the lake. The K-values were negatively correlated with TP modeled by the complete mixing model (R2 = 0.76) and the empirical model (R2 = 0.52), as well as by BOD measurements (R2 = 0.85). This indicates that water pollution attenuates evaporation rates. Scenarios of lake pollution and level reduction due to evaporation were also analyzed. The results from this study are important to improve the management of lakes and reservoirs by including the impact of pollution on the water balance.
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Dzierzbicka-Głowacka, L., J. Jakacki, M. Janecki, and A. Nowicki. "Activation of the operational ecohydrodynamic model (3-D CEMBS) – the hydrodynamic part." Geoscientific Model Development Discussions 5, no. 3 (July 16, 2012): 1851–75. http://dx.doi.org/10.5194/gmdd-5-1851-2012.
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Abstract. The paper presents a description of the hydrodynamic part of the coupled ice-ocean model that also includes ecosystem predictive model for evaluation of the condition of the marine environment and the Baltic ecosystem, as well as a preliminary empirical verification of the operational hydrodynamic model based on the POP code in order to determine the consistence between the results obtained from the model and experimental results for the sea surface temperature. The current Baltic Sea model is based on the Community Earth System Model (CESM from NCAR – National Center for Atmospheric Research). CESM was adopted for the Baltic Sea as a coupled sea-ice model. It consists of the Community Ice Code (CICE model, version 4.0) and the Parallel Ocean Program (POP, version 2.1). The models are coupled through the coupler (CPL7), which is based on the Model Coupling Toolkit (MCT) routines. The current horizontal resolution is about 2 km (1/48 degrees). The ocean model has 21 vertical levels. The driver time step is 1440 s and it is also coupling the time step. The ocean model time step is about 480 s (8 min). Currently, the model is forced by fields from the European Center for Medium Weather Forecast. In the operational mode, 48-h atmospheric forecasts are used, which are supplied by the UM model of the Interdisciplinary Centre for Mathematical and Computational Modelling of the Warsaw University. The model of the marine ecosystem is the right tool for monitoring the state and bioproductivity of the marine ecosystem and forecasting the physical and ecological changes in the studied basin.
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Monteiro, Caroline Barbosa, Eduardo de Paula Kirinus, Wiliam Correa Marques, Phelype Haron Oleinik, and Juliana Costi. "Analysis of Two Oil Spills in the Southern Brazilian Shelf, in the Years of 2012 and 2014." Defect and Diffusion Forum 372 (March 2017): 70–80. http://dx.doi.org/10.4028/www.scientific.net/ddf.372.70.
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Numerical models have been widely used to simulate and predict the behavior and transport of oil spills in marine environments. Their behavior is governed by physical, chemical and biological processes which are related to the hydrocarbon properties, hydrodynamic and weather conditions, and other environmental variables. The transport and interactions of oil particles were evaluated in simulations reproducing two oil spills recorded in the northern part of the Southern Brazilian Shelf (SBS). The numerical simulations were performed using the ECOS (Easy Coupling Oil System) model coupled to the three-dimensional hydrodynamic module TELEMAC3D. The hydrodynamic model provides the variables needed by oil spill model to calculate and infer the properties and behavior of the oil slick. The results indicate that the local wind forcing is the most important factor in determining the oil fate, followed by the intensities and directions of coastal currents. Regarding the events, in 2012 the oil reached the coast after 10 hours of the leak while in 2014 it was transported towards the ocean. The simulation strategy used in this article did not prove to be appropriate for estimates of the oil risk in the region, due to the distinct susceptibility responses between the events simulated.
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Müller, Maximilian, Malte Woidt, Matthias Haupt, and Peter Horst. "Challenges of fully-coupled high-fidelity ditching simulations." MATEC Web of Conferences 233 (2018): 00020. http://dx.doi.org/10.1051/matecconf/201823300020.
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An important element of the process of aircraft certification is the demonstration of the crashworthiness of the structure in the event of an emergency landing on water, also referred to as ditching. Novel numerical simulation methods that incorporate the interaction between fluid and structure open up a promising way to model ditching in full scale. This study presents a numerical framework for the simulation of ditching on a high–fidelity level. A partitioned approach that combines a finite volume hydrodynamic fluid solver as well as an finite element structural solver is implemented using a Python-based distributed coupling environment [1]. High demands are placed both on the fluid and the structural solver. The fluid solver needs to account for hydrodynamic effects such as cavitation in order to correctly compute the ditching loads acting on the aircraft structure. In the structural model, the highly localized damage induces nonlinearities and large differences in model scale. In order to reduce the computational effort a reduced order model is used to model the failure of fuselage frames. The fluid-structure coupling requires an explicit coupling scheme. It is shown that the standard Dirichlet-Neumann approach exhibits unstable behaviour if a strong added-mass effect is present, as is the case in aircraft ditching. This indicates a need for methods other than the standard Dirichlet-Neumann approach [2].