1,031 research outputs found
System-based maneuvering simulation of a ship navigating in the confined waterway
The system-based maneuvering simulations were conducted to investigate the ship
navigating in the confined waterway. The confinement effect was included using the model of
Vantorre [1]. The maneuvering model was validated using the turning circle and zigzag tests, and
the confinement model was verified using the experimental data of Norrbin [2]. The good agreement
proved the validity of our method. Using this method, the influences of the ship-bank distance and
the propeller rate of turn were studied and concluded. Small ship-bank distance
and large propulsion were proved to enhance the confinement effect
Influence of the draft to ship dynamics in the virtual tank based on openFOAM
A virtual tank is built based on OpenFOAM. The mesh is created using the
’blockMesh’ and the ’snappyHexMesh’ utilities successively. The ’interDyMfoam’ solver is used to
solve the flow fields. The results are compared with the experimental data of the Tokyo 2005 CFD
workshop, which show good agreement. The cases with seven different drafts are further simulated.
It is found that a small draft can make the ship unstable and weaken the effect of
the bulbous bow
Dynamic estimation of bank-propeller interaction effect on ship maneuvering using CFD method coupled to 6DOF algorithm
This paper presents a numerical investigation of ship maneuvering under the
combined effect of the bank and propeller. The incompressible turbulent flow with free
surface around the self-propelled hull form is simulated using a commercial CFD
software (Fluent). In order to estimate the dynamic effect of bank and propeller, the CFD model
with the dynamic mesh setting is coupled to the 6DOF module to compute the ship motion due to
hydrodynamic forces. The numerical simulations are carried using the equivalent experiment
conditions. The validation of the CFD model is performed by comparing the numerical results
to the experimental data
Numerical prediction of ship resistance and squat in confined waters
Accurate prediction of hydrodynamic forces opposing a ship displacement in
restricted waterways is necessary in order to improve energy efficiency of inland transport.
When a ship moves in restricted waterways, a significant increase in ship squat (combination
of sinkage and trim) and resistance occurs compared to a movement in open waters.
In this paper, a 3D numerical model based on fluid-structure coupling is presented and
used to investigate the effect of limited water depth and channel width on ship resistance
and squat
Transport and percolation in a low-density high-mobility two-dimensional hole system
We present a study of the temperature and density dependence of the
resistivity of an extremely high quality two-dimensional hole system grown on
the (100) surface of GaAs. For high densities in the metallic regime (p\agt 4
\times 10^{9} cm), the nonmonotonic temperature dependence ( mK) of the resistivity is consistent with temperature dependent
screening of residual impurities. At a fixed temperature of = 50 mK, the
conductivity vs. density data indicates an inhomogeneity driven
percolation-type transition to an insulating state at a critical density of
cm.Comment: accepted for publication in PR
Fabrication methods for a quantum cascade photonic crystal surface emitting laser
Conventional quantum cascade (QC) lasers are intrinsically edge-emitting devices with mode confinement achieved via a standard mesa stripe configuration. Surface emission in edge emitting QC lasers has therefore necessitated redirecting the waveguided laser emission using a second order grating. This paper describes the methods used to fabricate a 2D photonic crystal (PC) structure with or without a central defect superimposed on an electrically pumped QC laser structure with the goal of achieving direct surface emission. A successful systematic study of PC hole radius and spacing was performed using e-beam lithography. This PC method offers the promise of a number of interesting applications, including miniaturization and integration of QC lasers
Acoustic phonon scattering in a low density, high mobility AlGaN/GaN field effect transistor
We report on the temperature dependence of the mobility, , of the
two-dimensional electron gas in a variable density AlGaN/GaN field effect
transistor, with carrier densities ranging from 0.4 cm to
3.0 cm and a peak mobility of 80,000 cm/Vs. Between
20 K and 50 K we observe a linear dependence T
indicating that acoustic phonon scattering dominates the temperature dependence
of the mobility, with being a monotonically increasing function of
decreasing 2D electron density. This behavior is contrary to predictions of
scattering in a degenerate electron gas, but consistent with calculations which
account for thermal broadening and the temperature dependence of the electron
screening. Our data imply a deformation potential D = 12-15 eV.Comment: 3 pages, 2 figures, RevTeX. Submitted to Appl Phys Let
Fabrication technologies for quantum cascade photonic-crystal microlasers
In this paper we describe the technological and fabrication methods necessary to incorporate both photonic and electronic-band engineering in order to create novel surface-emitting quantum cascade microcavity laser sources. This technology offers the promise of several innovative applications such as the miniaturization of QC lasers, and multi-wavelength two-dimensional laser arrays for spectroscopy, gas-sensing and imaging. This approach is not limited to light-emitting devices, and may be efficiently applied to the development of mid- and far-infrared normal-incidence detectors
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