4,946 research outputs found
Combined pressure and temperature distortion effects on internal flow of a turbofan engine
An additional data base for improving and verifying a computer simulation developed by an engine manufacturer was obtained. The multisegment parallel compressor simulation was designed to predict the effects of steady-state circumferential inlet total-pressure and total-temperature distortions on the flows into and through a turbofan compression system. It also predicts the degree of distortion that will result in surge of the compressor. The effect of combined 180 deg square-wave distortion patterns of total pressure and total temperature in various relative positions is reported. The observed effects of the combined distortion on a unitary bypass ratio turbofan engine are presented in terms of total and static pressure profiles and total temperature profiles at stations ahead of the inlet guide vanes as well as through the fan-compressor system. These observed profiles are compared with those predicted by the complex multisegment model. The effects of relative position of the two components comprising the combined distortion on the degree resulting in surge are discussed. Certain relative positions required less combined distortion than either a temperature or pressure distortion by itself
Truth and Probability
Contains two other essays as well: Further Considerations & Last Papers: Probability and Partial Belief.
Performance and stall limits of a YTF30-P-1 turbofan engine with uniform inlet flow
Performance and stall limits of YTF30-P-1 turbofan engine with uniform compressor inlet flo
Relativistic models of magnetars: the twisted-torus magnetic field configuration
We find general relativistic solutions of equilibrium magnetic field
configurations in magnetars, extending previous results of Colaiuda et al.
(2008). Our method is based on the solution of the relativistic Grad-Shafranov
equation, to which Maxwell's equations can be reduced in some limit. We obtain
equilibrium solutions with the toroidal magnetic field component confined into
a finite region inside the star, and the poloidal component extending to the
exterior. These so-called twisted-torus configurations have been found to be
the final outcome of dynamical simulations in the framework of Newtonian
gravity, and appear to be more stable than other configurations. The solutions
include higher order multipoles, which are coupled to the dominant dipolar
field. We use arguments of minimal energy to constrain the ratio of the
toroidal to the poloidal field.Comment: 13 pages, 12 figures. Minor changes to match the version published on
MNRA
Hall drift of axisymmetric magnetic fields in solid neutron-star matter
Hall drift, i. e., transport of magnetic flux by the moving electrons giving
rise to the electrical current, may be the dominant effect causing the
evolution of the magnetic field in the solid crust of neutron stars. It is a
nonlinear process that, despite a number of efforts, is still not fully
understood. We use the Hall induction equation in axial symmetry to obtain some
general properties of nonevolving fields, as well as analyzing the evolution of
purely toroidal fields, their poloidal perturbations, and current-free, purely
poloidal fields. We also analyze energy conservation in Hall instabilities and
write down a variational principle for Hall equilibria. We show that the
evolution of any toroidal magnetic field can be described by Burgers' equation,
as previously found in plane-parallel geometry. It leads to sharp current
sheets that dissipate on the Hall time scale, yielding a stationary field
configuration that depends on a single, suitably defined coordinate. This
field, however, is unstable to poloidal perturbations, which grow as their
field lines are stretched by the background electron flow, as in instabilities
earlier found numerically. On the other hand, current-free poloidal
configurations are stable and could represent a long-lived crustal field
supported by currents in the fluid stellar core.Comment: 8 pages, 5 figure panels; new version with very small correction;
accepted by Astronomy & Astrophysic
Herfried Hoinkes: pioneer of degree-day methods to calculate glacier mass-balance from air temperature
Structure and deformations of strongly magnetized neutron stars with twisted torus configurations
We construct general relativistic models of stationary, strongly magnetized
neutron stars. The magnetic field configuration, obtained by solving the
relativistic Grad-Shafranov equation, is a generalization of the twisted torus
model recently proposed in the literature; the stellar deformations induced by
the magnetic field are computed by solving the perturbed Einstein's equations;
stellar matter is modeled using realistic equations of state. We find that in
these configurations the poloidal field dominates over the toroidal field and
that, if the magnetic field is sufficiently strong during the first phases of
the stellar life, it can produce large deformations.Comment: 10 pages, 5 figures. Minor changes to match the version published on
MNRA
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