The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Carlos Guedes Soares - One of the best experts on this subject based on the ideXlab platform.
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A Numerical Method for Calculation of Ship–Ship Hydrodynamics Interaction in Shallow Water Accounting for Sinkage and Trim
Journal of Offshore Mechanics and Arctic Engineering, 2020Co-Authors: Huilong Ren, Xueqian Zhou, Serge Sutulo, Carlos Guedes SoaresAbstract:Abstract Sinkage and trim, which often occur to ships moving in shallow water, do not only have an effect on the ship–ship Hydrodynamic Interaction forces but also increase the risk of grounding. Potential flow-based online calculation of ship–ship Hydrodynamic Interaction forces without accounting for dynamic sinkage and trim is able to capture the Hydrodynamic Interaction effects with fair accuracy; however, there are still discrepancies in many cases, especially in the case of shallow water. An algorithm based on the potential theory has been devised for real-time simulation of the Hydrodynamic Interaction between two ships in shallow water accounting for sinkage and trim. The shallow water condition is modeled using the mirror image method. The sinkage and trim are solved iteratively based on the principle of Hydrodynamic balance, where a mesh trimming procedure is carried out when the waterline is changed. Simulations are performed with and without accounting for the sinkage and trim, and comparison with experimental results shows a fair agreement.
Masaoki Takahashi - One of the best experts on this subject based on the ideXlab platform.
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Hydrodynamic Interaction Model for Two Droplets under Large Step Shear Strains
Nihon Reoroji Gakkaishi, 2009Co-Authors: Kenzo Okamoto, Masayuki Yamaguchi, Masaoki TakahashiAbstract:A Hydrodynamic Interaction model is presented to predict the behaviors of two droplets in a medium after application of large step shear strains. The model expresses the droplets by arrays of rigid spheres. Because of retraction rate e in time differentials for the rigid spheres, they move toward the center of mass of them in each array and this motion of the rigid spheres generates flow field in the medium similar to the field caused by recovery of droplets owing to the interfacial tension. The Interaction between the rigid spheres is calculated using the Hydrodynamic Interaction tensor. The model predicts that the distance between the droplets in deformation direction decreases with increasing time and that the shape of the droplets becomes sigmoidal. In addition, the model calculation shows change in the distance in the deformation direction is independent of initial distance between the droplets providing that the initial distance is less than a certain value. These three predictions agree with the experimental results and strongly indicate that the origin of the Interaction between the droplets is the Hydrodynamic Interaction.
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Hydrodynamic Interaction and coalescence of two droplets under large step shear strains
Polymer, 2008Co-Authors: Kenzo Okamoto, Shigenori Iwatsuki, Masaru Ishikawa, Masaoki TakahashiAbstract:We observed change in distance between two droplets in each step after application of large multi-step shear strains. Experiments were performed using a sliding plate apparatus. Large step shear strains were applied to two polyisobutylene droplets in poly(dimethyl siloxane) matrix in the same plane between the plates. The distance between the two droplets decreases with increasing the total shear strain, which is given by the product of the step strain magnitude and the number of application of the step strains. The two droplets coalesce when the distance becomes less than the diameter of the droplets. The slope for plots of the distance versus the total strain is independent of the step strain magnitude. This indicates that the effect per unit strain on the distance is the same, irrespective of the strain magnitude. It is suggested that a stronger Hydrodynamic Interaction between the droplets is the main cause for the droplet approach.
Olga I Vinogradova - One of the best experts on this subject based on the ideXlab platform.
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Hydrodynamic Interaction with super hydrophobic surfaces
Soft Matter, 2010Co-Authors: Aleksey V Belyaev, Olga I VinogradovaAbstract:Patterned surfaces with large effective slip lengths, such as super-hydrophobic surfaces containing trapped gas bubbles, have the potential to reduce Hydrodynamic drag. Based on lubrication theory, we analyze an approach of a hydrophilic disk to such a surface. The drag force is predicted analytically and formulated in terms of a correction function to the Reynolds equation, which is shown to be the harmonic mean of corrections expressed through effective slip lengths in the two principal (fastest and slowest) orthogonal directions. The reduction of drag is especially pronounced for a thin (compared to texture characteristic length) gap. It is not really sensitive to the pattern geometry, but depends strongly on the fraction of the gas phase and local slip length at the gas area.
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Hydrodynamic Interaction with super hydrophobic surfaces
arXiv: Fluid Dynamics, 2010Co-Authors: Aleksey V Belyaev, Olga I VinogradovaAbstract:Patterned surfaces with large effective slip lengths, such as super-hydrophobic surfaces containing trapped gas bubbles, have the potential to reduce Hydrodynamic drag. Based on lubrication theory, we analyze an approach of a hydrophilic disk to such a surface. The drag force is predicted analytically and formulated in terms of a correction function to the Reynolds equation, which is shown to be the harmonic mean of corrections expressed through effective slip lengths in the two principal (fastest and slowest) orthogonal directions. The reduction of drag is especially pronounced for a thin (compared to texture period) gap. It is not really sensitive to the pattern geometry, but depends strongly on the fraction of the gas phase and local slip length at the gas area.
Garcia J De La Torre - One of the best experts on this subject based on the ideXlab platform.
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steady state behavior of dilute polymers in elongational flow dependence of the critical elongational rate on chain length Hydrodynamic Interaction and excluded volume
Journal of Rheology, 1999Co-Authors: J Hernandez G Cifre, Garcia J De La TorreAbstract:The steady-state properties of flexible polymer chains in solutions undergoing elongational flow have been studied using Brownian dynamics simulation. The coil–stretch transition is observed when the elongational rate, e exceeds a certain critical value ec. In this work, we describe in detail the simulation procedure and how to extract polymer dimensions, solution viscosity, and birefringence from the trajectories. Preliminary simulations involving no Hydrodynamic Interaction (HI) are used to check the simulation procedures by comparing their results with theoretical predictions for such an (unphysical) case. Afterwards, simulations with fluctuating nonaveraged HI are carried out to provide results comparable with experiments. After simulations with and without intramolecular potential, we arrive at a most important conclusion: the chain length dependence of ec is the same in theta conditions as in good solvent conditions. Combining ec with other solution properties such as the longest relaxation time, the intrinsic viscosity, and the radius of gyration, dimensionless compound quantities can be formulated. From our simulation results, we obtain numerical values for such quantities, which include the HI effect, and which are therefore useful for analyzing experimental data.The steady-state properties of flexible polymer chains in solutions undergoing elongational flow have been studied using Brownian dynamics simulation. The coil–stretch transition is observed when the elongational rate, e exceeds a certain critical value ec. In this work, we describe in detail the simulation procedure and how to extract polymer dimensions, solution viscosity, and birefringence from the trajectories. Preliminary simulations involving no Hydrodynamic Interaction (HI) are used to check the simulation procedures by comparing their results with theoretical predictions for such an (unphysical) case. Afterwards, simulations with fluctuating nonaveraged HI are carried out to provide results comparable with experiments. After simulations with and without intramolecular potential, we arrive at a most important conclusion: the chain length dependence of ec is the same in theta conditions as in good solvent conditions. Combining ec with other solution properties such as the longest relaxation time...
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gaussian chains with excluded volume and Hydrodynamic Interaction shear rate dependence of radius of gyration intrinsic viscosity and flow birefringence
Polymer, 1996Co-Authors: K D Knudsen, Garcia J De La Torre, Arnljot ElgsaeterAbstract:The effect of excluded volume (EV) and Hydrodynamic Interaction (HI) on a dilute solution of flexible polymer chains situated in a shear field has been studied by means of a Brownian dynamics simulation. The polymer was modelled as a Gaussian chain, accounting for the excluded volume effect by means of an exponentially decaying repulsive potential. The Hydrodynamic Interaction was included by means of the Rotne-Prager-Yamakawa tensor. The parameters studied were the mean square radius of gyration, the intrinsic viscosity, and the differential polarizability and extinction angle that are parameters relevant in flow birefringence studies. The EV-effect is seen to be most important at low shear rate. This is followed by an intermediate region where EV falls off and HI still has considerable effect, ending up with a chain that is so stretched out that neither EV nor HI has influence on conformational or Hydrodynamical properties, giving parameter values in accordance with theory for the no-EV, no-HI case.
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shear rate dependence of the intrinsic viscosity of bead and spring chains Hydrodynamic Interaction and excluded volume effects
Polymer, 1991Co-Authors: J Lopez J Cascales, Garcia J De La TorreAbstract:Abstract The shear-rate dependence of the intrinsic viscosity of the bead-and-spring (or Rouse) model for polymer chains with rigorous inclusion of Hydrodynamic Interaction (HI) and excluded volume (EV) is studied, for chains of varying length, using the Brownian dynamics simulation technique. The simulation results describe a transition from the zero-shear-rate viscosity, which depends strongly on HI and EV, to the region of very high shear rate, where the simulated viscosity is found to be that corresponding to the absence of HI and EV. As the latter is larger than the former when the chain is long enough, a shear-thickening behaviour is predicted for long bead-and-spring chains. The dumbbell model, which is the shortest chain, gives the wrong, opposite, prediction.
Huilong Ren - One of the best experts on this subject based on the ideXlab platform.
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A Numerical Method for Calculation of Ship–Ship Hydrodynamics Interaction in Shallow Water Accounting for Sinkage and Trim
Journal of Offshore Mechanics and Arctic Engineering, 2020Co-Authors: Huilong Ren, Xueqian Zhou, Serge Sutulo, Carlos Guedes SoaresAbstract:Abstract Sinkage and trim, which often occur to ships moving in shallow water, do not only have an effect on the ship–ship Hydrodynamic Interaction forces but also increase the risk of grounding. Potential flow-based online calculation of ship–ship Hydrodynamic Interaction forces without accounting for dynamic sinkage and trim is able to capture the Hydrodynamic Interaction effects with fair accuracy; however, there are still discrepancies in many cases, especially in the case of shallow water. An algorithm based on the potential theory has been devised for real-time simulation of the Hydrodynamic Interaction between two ships in shallow water accounting for sinkage and trim. The shallow water condition is modeled using the mirror image method. The sinkage and trim are solved iteratively based on the principle of Hydrodynamic balance, where a mesh trimming procedure is carried out when the waterline is changed. Simulations are performed with and without accounting for the sinkage and trim, and comparison with experimental results shows a fair agreement.