63,023 research outputs found
Study for prediction of rotor/wake/fuselage interference. Part 2: Program users guide
A method was developed which permits the fully coupled calculation of fuselage and rotor airloads for typical helicopter configurations in forward flight. To do this, an iterative solution is carried out based on a conventional panel representation of the fuselage and a blade element representation of the rotor where fuselage and rotor singularity strengths are determined simultaneously at each step and the rotor wake is allowed to relax (deform) in response to changes in rotor wake loading and fuselage presence. On completion of the iteration, rotor loading and inflow, fuselage singularity strength (and, hence, pressure and velocity distributions) and rotor wake are all consistent. The results of a fully coupled calculation of the flow around representative helicopter configurations are presented. The effect of fuselage components on the rotor flow field and the overall wake structure is discussed as well as the aerodynamic interference between the different parts of the aircraft. Details of the computer program are given
Study for prediction of rotor/wake/fuselage interference, part 1
A method was developed which allows the fully coupled calculation of fuselage and rotor airloads for typical helicopter configurations in forward flight. To do this, an iterative solution is carried out based on a conventional panel representation of the fuselage and a blade element representation of the rotor where fuselage and rotor singularity strengths are determined simultaneously at each step and the rotor wake is allowed to relax (deform) in response to changes in rotor wake loading and fuselage presence. On completion of the iteration, rotor loading and inflow, fuselage singularity strength (and, hence, pressure and velocity distributions) and rotor wake are all consistent. The results of a fully coupled calculation of the flow around representative helicopter configurations are presented. The effect of fuselage components on the rotor flow field and the overall wake structure is detailed and the aerodynamic interference between the different parts of the aircraft is discussed
Coriolis effects during pitch and roll maneuvers in a piloted flight simulator
Effect of suprathreshold value of Coriolis acceleration on pilot of flight simulator - reference to perception of illusory motion and position in spac
Fast initialization of a high-fidelity quantum register using optical superlattices
We propose a method for the fast generation of a quantum register of
addressable qubits consisting of ultracold atoms stored in an optical lattice.
Starting with a half filled lattice we remove every second lattice barrier by
adiabatically switching on a superlattice potential which leads to a long
wavelength lattice in the Mott insulator state with unit filling. The larger
periodicity of the resulting lattice could make individual addressing of the
atoms via an external laser feasible. We develop a Bose-Hubbard-like model for
describing the dynamics of cold atoms in a lattice when doubling the lattice
periodicity via the addition of a superlattice potential. The dynamics of the
transition from a half filled to a commensurately filled lattice is analyzed
numerically with the help of the Time Evolving Block Decimation algorithm and
analytically using the Kibble-Zurek theory. We show that the time scale for the
whole process, i.e. creating the half filled lattice and subsequent doubling of
the lattice periodicity, is significantly faster than adiabatic direct quantum
freezing of a superfluid into a Mott insulator for large lattice periods. Our
method therefore provides a high fidelity quantum register of addressable
qubits on a fast time scale.Comment: 22 pages, 9 figures, IOP style. Revised version to appear in NJ
Nature of the spin liquid state of the Hubbard model on honeycomb lattice
Recent numerical work (Nature 464, 847 (2010)) indicates the existence of a
spin liquid phase (SL) that intervenes between the antiferromagnetic and
semimetallic phases of the half filled Hubbard model on a honeycomb lattice. To
better understand the nature of this exotic phase, we study the quantum
spin model on the honeycomb lattice, which provides an effective
description of the Mott insulating region of the Hubbard model. Employing the
variational Monte Carlo approach, we analyze the phase diagram of the model,
finding a phase transition between antiferromagnet and an unusual SL
state at , which we identify as the SL phase of the
Hubbard model. At higher we find a transition to a
dimerized state with spontaneously broken rotational symmetry.Comment: 5 pages, 6 figure
The RHMC algorithm for theories with unknown spectral bounds
The Rational Hybrid Monte Carlo (RHMC) algorithm extends the Hybrid Monte
Carlo algorithm for lattice QCD simulations to situations involving fractional
powers of the determinant of the quadratic Dirac operator. This avoids the
updating increment () dependence of observables which plagues the Hybrid
Molecular-dynamics (HMD) method. The RHMC algorithm uses rational
approximations to fractional powers of the quadratic Dirac operator. Such
approximations are only available when positive upper and lower bounds to the
operator's spectrum are known. We apply the RHMC algorithm to simulations of 2
theories for which a positive lower spectral bound is unknown: lattice QCD with
staggered quarks at finite isospin chemical potential and lattice QCD with
massless staggered quarks and chiral 4-fermion interactions (QCD). A
choice of lower bound is made in each case, and the properties of the RHMC
simulations these define are studied. Justification of our choices of lower
bounds is made by comparing measurements with those from HMD simulations, and
by comparing different choices of lower bounds.Comment: Latex(Revtex 4) 25 pages, 8 postscript figure
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