Hydrodynamic forces on a ship moving with constant rudder angle: A theoretical treatment of rudder angle test

2021 ◽  
pp. 435-447
Author(s):  
H. Yasukawa ◽  
Y. Yoshimura ◽  
K. Nakatake
Keyword(s):  
Hydrodynamic Forces ◽  
Theoretical Treatment ◽  
Rudder Angle

Tilting-Pad Journal Bearings With Electronic Radial Oil Injection

1998 ◽  
Vol 120 (3) ◽  
pp. 583-594 ◽  
Author(s):  
I. F. Santos ◽  
F. H. Russo
Keyword(s):  
Hydrodynamic Lubrication ◽  
Hydrodynamic Forces ◽  
Journal Bearings ◽  
Theoretical Treatment ◽  
Bearing Surface ◽  
Static Behavior ◽  
Tilting Pad ◽  
Surface Active ◽  
Oil Injection ◽  
Tilting Pad Journal Bearings

This paper gives a theoretical treatment of the problem of journal bearings modeling connected to electronic oil injection into the bearing gap. The feasibility of influencing the static behavior of hydrodynamic forces by means of such oil injection is investigated. The lubricant is injected into the bearing gap by two mechanisms of lubrication: the conventional hydrodynamic lubrication and through orifices distributed along the bearing surface (active lubrication in the radial direction). By controlling the pressure of the oil injection, it is possible to get large variations in the active hydrodynamic forces; such effects could be useful for reducing vibrations in rotating machines.

Contrasts of planar defects in reflection electron microscopy

1993 ◽  
Vol 51 ◽  
pp. 1004-1005
Author(s):  
Feng Tsai ◽  
J. M. Cowley
Keyword(s):  
Electron Microscopy ◽  
Surface Defects ◽  
Practical Importance ◽  
Theoretical Treatment ◽  
Crystal Surfaces ◽  
Planar Defects ◽  
Surface Steps ◽  
Surface Reconstructions ◽  
Domain Boundaries ◽  
Reflection Electron Microscopy

Reflection electron microscopy (REM) has been used to study surface defects such as surface steps, dislocations emerging on crystal surfaces, and surface reconstructions. However, only a few REM studies have been reported about the planar defects emerging on surfaces. The interaction of planar defects with surfaces may be of considerable practical importance but so far there seems to be only one relatively simple theoretical treatment of the REM contrast and very little experimental evidence to support its predications. Recently, intersections of both 90° and 180° ferroelectric domain boundaries with BaTiO3 crystal surfaces have been investigated by Tsai and Cowley with REM.The REM observations of several planar defects, such as stacking faults and domain boundaries have been continued by the present authors. All REM observations are performed on a JEM-2000FX transmission electron microscope. The sample preparations may be seen somewhere else. In REM, the incident electron beam strikes the surface of a crystal with a small glancing angle.

FURTHER CONSIDERATIONS ON THE CALCULATIONS OF SECRETION RATES. A CORRECTION

1961 ◽  
Vol 38 (3) ◽  
pp. 469-472 ◽  
Author(s):  
K. R. Laumas ◽  
J. F. Tait ◽  
S. A. S. Tait
Keyword(s):  
Steady State ◽  
Compartmental Model ◽  
Single Injection ◽  
Previous Treatment ◽  
Urinary Metabolite ◽  
Theoretical Treatment ◽  
Basic Equations ◽  
Special Circumstances ◽  
Secretion Rates

ABSTRACT Reconsideration of the question of the validity of the calculations of the secretion rates from the specificity activity of a urinary metabolite after the single injection of a radioactive hormone has led us to conclude that the basic equations used in a previous theoretical treatment are not generally applicable to the nonisotopic steady state if the radioactive steroid and hormone are introduced into the same compartment. If this is so, in a two compartmental model with metabolism occurring in both pools, it is now shown that the calculation (S = R — τ) is rigorously valid if certain precautions are taken. This is in contrast to the previous treatment which concluded (in certain special circumstances) that the calculation might not be correct. However, if the hormone is secreted in both compartments and the radioactive steroid is injected into only one, then the calculation (S = R — τ) may not be correct in certain circumstances as was previously concluded (Laumas et al. 1961).

Application of remote sensing technology to the relation of submarine pipelines and coastal morphology

1995 ◽  
Vol 32 (2) ◽  
pp. 77-83
Author(s):  
Y. Yüksel ◽  
D. Maktav ◽  
S. Kapdasli
Keyword(s):  
Remote Sensing ◽  
Sediment Transport ◽  
Surf Zone ◽  
Hydrodynamic Forces ◽  
Construction Site ◽  
Coastal Morphology ◽  
Remote Sensing Technology ◽  
Sensing Technology ◽  
Sea Bed

Submarine pipelines must be designed to resist wave and current induced hydrodynamic forces especially in and near the surf zone. They are buried as protection against forces in the surf zone, however this procedure is not always feasible particularly on a movable sea bed. For this reason the characteristics of the sediment transport on the construction site of beaches should be investigated. In this investigation, the application of the remote sensing method is introduced in order to determine and observe the coastal morphology, so that submarine pipelines may be protected against undesirable seabed movement.

scholarly journals Capsule Migration and Deformation in a Converging Micro-Capillary

Processes ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 452
Author(s):  
Yiyang Wang ◽  
Panagiotis Dimitrakopoulos
Keyword(s):  
Viscosity Ratio ◽  
Hydrodynamic Forces ◽  
Straight Channel ◽  
Lateral Migration ◽  
Computational Investigation ◽  
Physiological Processes ◽  
Lower Viscosity ◽  
Elastic Capsules ◽  
Interfacial Deformation ◽  
Capsule Size

The lateral migration of elastic capsules towards a microchannel centerline plays a major role in industrial and physiological processes. Via our computational investigation, we show that a constriction connecting two straight microchannels facilitates the lateral capsule migration considerably, which is relatively slow in straight channels. Our work reveals that the significant cross-streamline migration inside the constriction is dominated by the strong hydrodynamic forces due to the capsule size. However, in the downstream straight channel, the increased interfacial deformation at higher capillary numbers or a lower viscosity ratio and lower membrane hardness results in increased lateral cross-streamline migration. Thus, our work highlights the different migration mechanisms occurring over curved and straight streamlines.

The economics of escalation

2021 ◽  
Vol 33 (1) ◽  
pp. 106-140
Author(s):  
Fabio D’Orlando ◽  
Sharon Ricciotti
Keyword(s):  
Human Nature ◽  
Budget Constraint ◽  
Theoretical Treatment ◽  
Jel Codes ◽  
Innate Behavior ◽  
Hedonic Adaptation ◽  
The Past ◽  
Subjective Scale ◽  
The Subject ◽  
Positional Effects

Escalation is a key characteristic of many consumption behaviors that has not received theoretical attention. This paper aims to propose both a definition and a theoretical treatment of escalation in consumption. We define escalation as a subject’s attempt to obtain “more” or engage in consumption behaviors that are “more intense” on a measurable, quantitative or qualitative, objective or subjective, scale (more difficult ski slopes, stronger drugs, harder sex, better restaurants etc.), even if the subject preferred less intense consumption behaviors in the past. Further, this evolution in behavior also occurs if the budget constraint does not change. We will find endogenous and exogenous theoretical microfoundations for escalation in models of hedonic adaptation, desire for novelty, acquisition of consumption skills, rising aspirations, positional effects, and envy. However, we will also discuss the possibility that the tendency to escalate is a specific innate behavior inherent to human nature. Finally, we will propose a preliminary theoretical formalization of such behavior and indicate the possible implications of taking escalation into adequate consideration. JEL codes: B52, D11, D90, D91, I31

Machine learning–based reduced-order modeling of hydrodynamic forces using pressure mode decomposition

2021 ◽  
pp. 095441002199986
Author(s):  
Hassan F Ahmed ◽  
Hamayun Farooq ◽  
Imran Akhtar ◽  
Zafar Bangash
Keyword(s):  
Machine Learning ◽  
Short Term Memory ◽  
Stokes Equations ◽  
Decomposition Analysis ◽  
Hydrodynamic Forces ◽  
Reduced Order Modeling ◽  
Navier Stokes ◽  
Reduced Order ◽  
Mode Decomposition ◽  
Lift And Drag

In this article, we introduce a machine learning–based reduced-order modeling (ML-ROM) framework through the integration of proper orthogonal decomposition (POD) and deep neural networks (DNNs), in addition to long short-term memory (LSTM) networks. The DNN is utilized to upscale POD temporal coefficients and their respective spatial modes to account for the dynamics represented by the truncated modes. In the second part of the algorithm, temporal evolution of the POD coefficients is obtained by recursively predicting their future states using an LSTM network. The proposed model (ML-ROM) is tested for flow past a circular cylinder characterized by the Navier–Stokes equations. We perform pressure mode decomposition analysis on the flow data using both POD and ML-ROM to predict hydrodynamic forces and demonstrate the accuracy of the proposed strategy for modeling lift and drag coefficients.

scholarly journals Hydrodynamic Forces Exerting on an Oscillating Cylinder under Translational Motion in Water Covered by Compressed Ice

Water ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 822
Author(s):  
Yury Stepanyants ◽  
Izolda Sturova
Keyword(s):  
Lift Force ◽  
Wave Motion ◽  
Translational Motion ◽  
Added Mass ◽  
Hydrodynamic Forces ◽  
Wave Resistance ◽  
Translational Velocity ◽  
Damping Coefficients ◽  
Incompressible Ideal Fluid ◽  
Theoretical Results

This paper presents the calculation of the hydrodynamic forces exerted on an oscillating circular cylinder when it moves perpendicular to its axis in infinitely deep water covered by compressed ice. The cylinder can oscillate both horizontally and vertically in the course of its translational motion. In the linear approximation, a solution is found for the steady wave motion generated by the cylinder within the hydrodynamic set of equations for the incompressible ideal fluid. It is shown that, depending on the rate of ice compression, both normal and anomalous dispersion can occur in the system. In the latter case, the group velocity can be opposite to the phase velocity in a certain range of wavenumbers. The dependences of the hydrodynamic loads exerted on the cylinder (the added mass, damping coefficients, wave resistance and lift force) on the translational velocity and frequency of oscillation were studied. It was shown that there is a possibility of the appearance of negative values for the damping coefficients at the relatively big cylinder velocity; then, the wave resistance decreases with the increase in cylinder velocity. The theoretical results were underpinned by the numerical calculations for the real parameters of ice and cylinder motion.

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