Field Of Hydrodynamics Research Articles

On POD analysis of PIV measurements applied to mixing in a stirred vessel with a shear thinning fluid

P.O.D. technique is applied to 2D P.I.V. data in the field of hydrodynamics in a mixing tank with a Rushton turbine and a shear thinning fluid. Classical eigen-value spectrum is presented and phase portrait of P.O.D. coefficients are plotted and analyzed in terms of trailing vortices. A spectrum of dissipation rate of kinetic energy is introduced and discussed. Length scales associated to each P.O.D. modes are proposed.

Application of method of fundamental solutions in solving potential flow problems for ship motion prediction

A novel panel-free approach based on the method of fundamental solutions (MFS) is proposed to solve the potential flow for predicting ship motion responses in the frequency domain according to strip theory. Compared with the conventional boundary element method (BEM), MFS is a desingularized, panel-free and integration-free approach. As a result, it is mathematically simple and easy for programming. The velocity potential is described by radial basis function (RBF) approximations and any degree of continuity of the velocity potential gradient can be obtained. Desingularization is achieved through collating singularities on a pseudo boundary outside the real fluid domain. Practical implementation and numerical characteristics of the MFS for solving the potential flow problem concerning ship hydrodynamics are elaborated through the computation of a 2D rectangular section. Then, the current method is further integrated with frequency domain strip theory to predict the heave and pitch responses of a containership and a very large crude carrier (VLCC) in regular head waves. The results of both ships agree well with the 3D frequency domain panel method and experimental data. Thus, the correctness and usefulness of the proposed approach are proved. We hope that this paper will serve as a motivation for other researchers to apply the MFS to various challenging problems in the field of ship hydrodynamics.

Physics-Based Learning Models for Ship Hydrodynamics

We present the concepts of physics-based learning models (PBLM) and their relevance and application to the field of ship hydrodynamics. The utility of physics-based learning is motivated by contrasting generic learning models for regression predictions, which do not presume any knowledge of the system other than the training data provided with methods such as semi-empirical models, which incorporate physical insights along with data-fitting. PBLM provides a framework wherein intermediate models, which capture (some) physical aspects of the problem, are incorporated into modern generic learning tools to substantially improve the predictions of the latter, minimizing the reliance on costly experimental measurements or high-resolution high-fidelity numerical solutions. To illustrate the versatility and efficacy of PBLM, we present three wave-ship interaction problemsat speed waterline profiles;ship motions in head seas; andthree-dimensional breaking bow waves. PBLM is shown to be robust and produce error rates at or below the uncertainty in the generated data at a small fraction of the expense of high-resolution numerical predictions.

Physics-Based Learning Models for Ship Hydrodynamics

We present the concepts of physics-based learning models (PBLM) and their relevance and application to the field of ship hydrodynamics. The utility of physics-based learning is motivated by contrasting generic learning models for regression predictions, which do not presume any knowledge of the system other than the training data provided with methods such as semi-empirical models, which incorporate physical insights along with data-fitting. PBLM provides a framework wherein intermediate models, which capture (some) physical aspects of the problem, are incorporated into modern generic learning tools to substantially improve the predictions of the latter, minimizing the reliance on costly experimental measurements or high-resolution high-fidelity numerical solutions. To illustrate the versatility and efficacy of PBLM, we present three wave-ship interaction problems: 1) at speed waterline profiles; 2) ship motions in head seas; and 3) three-dimensional breaking bow waves. PBLM is shown to be robust and produce error rates at or below the uncertainty in the generated data at a small fraction of the expense of high-resolution numerical predictions.

Influence of a postural change of the swimmer's head in hydrodynamic performances using 3D CFD

This study deals with recent researches undertaken by the authors in the field of hydrodynamics of human swimming. The aim of this numerical study was to investigate the flow around the entire swimmer's body. The results presented in this article focus on the combination of a 3D computational fluid dynamics code and the use of the k–ω turbulence model, in the range of Reynolds numbers representative of a swimming level varying from national to international competition. Emphasis is placed on the influence of a postural change of the swimmer's head in hydrodynamic performances, which is directly related to the reduction of overall drag. These results confirm and complete those, less accurate, of a preliminary 2D study recently published by the authors and allow the authors to optimise the swimmer's head position in underwater swimming.

Physics‐Based Learning Models for Ship Hydrodynamics

We present the concepts of physics-based learning models (PBLM) and their relevance and application to the field of ship hydrodynamics. The utility of physics-based learning is motivated by contrasting generic learning models for regression predictions, which do not presume any knowledge of the system other than the training data provided with methods such as semi-empirical models, which incorporate physical insights along with data-fitting. PBLM provides a framework wherein intermediate models, which capture (some) physical aspects of the problem, are incorporated into modern generic learning tools to substantially improve the predictions of the latter, minimizing the reliance on costly experimental measurements or high-resolution highfidelity numerical solutions. To illustrate the versatility and efficacy of PBLM, we present three wave-ship interaction problems: 1) at speed waterline profiles; 2) ship motions in head seas; and 3) three-dimensional breaking bow waves. PBLM is shown to be robust and produce error rates at or below the uncertainty in the generated data at a small fraction of the expense of high-resolution numerical predictions

Flow in heavy-ion collisions—theory perspective

I review recent developments in the field of relativistic hydrodynamics and its application to the bulk dynamics in heavy-ion collisions at the Relativistic Heavy-Ion Collider (RHIC) and the Large Hadron Collider (LHC). In particular, I report on progress in going beyond second order relativistic viscous hydrodynamics for conformal fluids, including temperature-dependent shear viscosity to entropy density ratios, as well as coupling hydrodynamic calculations to microscopic hadronic rescattering models. I describe event-by-event hydrodynamic simulations and their ability to compute higher harmonic flow coefficients. Combined comparisons of all harmonics to recent experimental data from both the RHIC and the LHC will potentially allow us to determine the desired details of the initial state and the medium properties of the quark–gluon plasma produced in heavy-ion collisions.

Computational Fluid Dynamics Modeling Studies on Bacterial Flagellar Motion

The study of bacterial flagellar swimming motion remains an interesting and challenging research subject in the fields of hydrodynamics and bio-locomotion. This swimming motion is characterized by very low Reynolds numbers, which is unique and time reversible. In particular, the effect of rotation of helical flagella of bacterium on swimming motion requires detailed multi-disciplinary analysis. Clear understanding of such swimming motion will not only be beneficial for biologists but also to engineers interested in developing nanorobots mimicking bacterial swimming. In this paper, computational fluid dynamics (CFD) simulation of a three dimensional single flagellated bacteria has been developed and the fluid flow around the flagellum is investigated. CFD-based modeling studies were conducted to find the variables that affect the forward thrust experienced by the swimming bacterium. It is found that the propulsive force increases with increase in rotational velocity of flagellum and viscosity of surrounding fluid. It is also deduced from the study that the forward force depends on the geometry of helical flagella (directly proportional to square of the helical radius and inversely proportional to pitch).

Heat transfer and hydrodynamics in the fields of mass forces

A brief review of the investigations in the field of heat transfer and hydrodynamics in the fields of mass forces carried out at the Institute of Applied Thermal Physics of the National Academy of Sciences of Ukraine is presented. The review is devoted to swirling flows, near convex and concave surfaces, in surface-vortex systems of various configurations.

콴다 효과를 이용한 혼-타의 양력성능 개선에 관한 연구

The Coanda effect is noticeable when a jet stream is applied tangential to a curved surface since then the jet stream remains attached to the surface beyond the point where flow separates otherwise and results in augmentation of circulation and lift. Numerous experimental and numerical studies have been performed in various fields of aerodynamics to exploit the Coanda effect and many of them found to be useful. It can be speculated that the Coanda effect may have practical application to the field of marine hydrodynamics as well since various control surfaces are being used to control behaviors of ships and offshore structures. In the present study, the Coanda effect has been applied to a horn type rudder and a series of numerical computations and model experiments are performed to find the practical applicability. The results indicate that the Coanda jet increases the lift coefficient of the rudder as much as 52% at the momentum coefficient <TEX>$C_j$</TEX> = 0.1 and the rudder angle <TEX>${\alpha}=10^{\circ}$</TEX>.

Mathematical Aspects of Hydrodynamics

The workshop was devoted to discussions of recent developments and possible future directions of research in the field of mathematical hydrodynamics. Many of the leading experts in the theory of PDE’s arising in fluid dynamics participated in this event. The topics included: Regularity, uniqueness and well-posedness problems for the NavierStokes equations Stability of Navier-Stokes solutions Open problems concerning the steady-state Navier-Stokes solutions Statistical approach to 2d hydrodynamics Inviscid limits of Navier-Stokes solutions Anomalous weak solutions of Euler’s equation Finding physically reasonable classes of weak solutions of Euler’s equations Local well-posedness of Euler’s equations in optimal spaces Stability of solutions of Euler’s equations Water waves Model equations Geometric approach to hydromechanical equations Selected compressible flow problems Mathematics

The history of the Stribeck curve and ball bearing steels: The role of Adolf Martens

The historical development on the discoveries of lubrication regimes for lubricated sliding contacts has been reviewed from the very beginning. It was found that the functional relationship between the coefficient of friction and the product of sliding speed and viscosity divided by the normal load well known as the Stribeck curve has been experimentally explored much earlier by Adolf Martens in 1888 long before Richard Stribeck did his pioneering measurements in 1902. However, basic work in this field of experimental hydrodynamics was done and results were published even earlier than that back in 1854 by Gustave A. Hirn, in 1879 by Robert H. Thurston and in 1883 by Beauchamp Tower.

SPEC MPI2007—an application benchmark suite for parallel systems using MPI

AbstractThe SPEC High‐Performance Group has developed the benchmark suite SPEC MPI2007 and its run rules over the last few years. The purpose of the SPEC MPI2007 benchmark and its run rules is to further the cause of fair and objective benchmarking of high‐performance computing systems. The rules help to ensure that the published results are meaningful, comparable to other results, and reproducible. MPI2007 includes 13 technical computing applications from the fields of computational fluid dynamics, molecular dynamics, electromagnetism, geophysics, ray tracing, and hydrodynamics. We describe the benchmark suite, and compare it with other benchmark suites. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Mathematical simulation of nonstationary mixing of steel in a ladle-furnace unit

Researchers can now use universal mathematical models to solve a variety of problems in various fields of hydrodynamics and heat exchange; this allows the experiment cost and time to be significantly decreased. The well-known programs of engineer analysis (ANSYS, FlowVision, EFD, SYSWELD, ProCast, etc.) are based on numerical iteration techniques that can obtain solutions to the differential equations used to describe almost all physical problems to a given accuracy. With computer simulation, researchers can significantly decrease the costs of designing new constructions and systems and solve the problems of optimization. The specific feature of the computer models is a discrete solution in a system under study: a researcher can choose the required degree of discretization of solution, increasing the number of points in the system for which properties are determined if necessary. It should be noted that it is difficult to obtain a large number of points at which the properties of the system are determined in order to construct a physical model. This problem becomes practically impossible when a real industrial unit is studied; therefore, it is necessary to estimate the process inside the system from microparameters, which is related to an increase in the number of erroneous estimates and a wrong operation of an object.

Dynamics of Charged Quantized Vortices

We study theoretically the dynamics of charged quantized vortices (CQVs). CQVs (ion-vortex complexes) have been used as an important probe in the field of quantum hydrodynamics. Recent experimental studies of quantum turbulence at very low temperatures utilize CQVs. In this work we propose the equation of motion of CQVs based on the vortex filament model. An analytical solution for a charged vortex ring shows how it expands under an electric field. Numerical simulation reveals the characteristic behavior of CQVs under an electric field.

Stellar Core Collapse: A Case Study in the Design of Numerical Algorithms for Scalable Radiation Hydrodynamics

The fields of radiation and hydrodynamics are time-honored disciplines in physics. However, it is only since the nuclear age that the importance of radiation hydrodynamics - a single field studying the interplay of radiation and material hydrodynamics together - has come into prominence. Similarly, it is only since the computer age that physically interesting problems in this field have become tractable. In this article, the authors discuss the process of building a model to study one of the fundamental problems of astrophysics: the supernova explosion of a massive star caused by the collapse of its core. An explanation for the mechanism of this explosion involves the interaction of material hydrodynamics and neutrino radiation.

Research Works Done at the Technical Thermophysics Institute of the National Academy of Sciences of Ukraine in the Field of Heat Transfer and Hydrodynamics of Surface-Vortex Systems

Research Works Done at the Technical Thermophysics Institute of the National Academy of Sciences of Ukraine in the Field of Heat Transfer and Hydrodynamics of Surface-Vortex Systems

Recent developments in the field of ship hydrodynamics at the Ship Laboratory of Helsinki University of Technology

Some recent developments in the fields of ship hydrodynamics, stability and hydroelasticity at the ship laboratory of Helsinki University of Technology are briefly described.

Working in hydrodynamics with Yogiro Hama

I present a brief overview on the motivation for performing relativistic nuclear collisions and the justification for using hydrodynamics to describe them. The contribution of Prof. Hama to the field of hydrodynamics and his efforts to form a group working on this subject are outlined.

The limits of Navier-Stokes theory and kinetic extensions for describing small-scale gaseous hydrodynamics

This paper reviews basic results and recent developments in the field of small-scale gaseous hydrodynamics which has received significant attention in connection with small-scale science and technology. We focus on the modeling challenges arising from the breakdown of the Navier-Stokes description, observed when characteristic lengthscales become of the order of, or smaller than, the molecular mean free path. We discuss both theoretical results and numerical methods development. Examples of the former include the limit of applicability of the Navier-Stokes constitutive laws, the concept of second-order slip and the appropriate form of such a model, and how to reconcile experimental measurements of slipping flows with theory. We also review a number of recently developed theoretical descriptions of canonical nanoscale flows of engineering interest. On the simulation front, we review recent progress in characterizing the accuracy of the prevalent Boltzmann simulation method known as direct simulation Monte Carlo. We also present recent variance reduction ideas which address the prohibitive cost associated with the statistical sampling of macroscopic properties in low-speed flows.