1,424 research outputs found
Burning rate control of solid propellants Patent
Pressurized gas injection for burning rate control of solid propellant
Effective mass in quantum effects of radiation pressure
We study the quantum effects of radiation pressure in a high-finesse cavity
with a mirror coated on a mechanical resonator. We show that the optomechanical
coupling can be described by an effective susceptibility which takes into
account every acoustic modes of the resonator and their coupling to the light.
At low frequency this effective response is similar to a harmonic response with
an effective mass smaller than the total mass of the mirror. For a plano-convex
resonator the effective mass is related to the light spot size and becomes very
small for small optical waists, thus enhancing the quantum effects of
optomechanical coupling.Comment: 11 pages, 4 figures, RevTe
Quantum limits of cold damping with optomechanical coupling
Thermal noise of a mirror can be reduced by cold damping. The displacement is
measured with a high-finesse cavity and controlled with the radiation pressure
of a modulated light beam. We establish the general quantum limits of noise in
cold damping mechanisms and we show that the optomechanical system allows to
reach these limits. Displacement noise can be arbitrarily reduced in a narrow
frequency band. In a wide-band analysis we show that thermal fluctuations are
reduced as with classical damping whereas quantum zero-point fluctuations are
left unchanged. The only limit of cold damping is then due to zero-point energy
of the mirrorComment: 10 pages, 3 figures, RevTe
Analysis of radiation patterns of interaction tones generated by inlet rods in the JT15D engine
Interaction tones were intentionally generated by circumferential arrays of equally spaced rods that protrude radially from the inlet wall near the face of the 28-blade fan. Arrays of 28 and 41 rods, selected to give specific far field radiation properties, were tested. The expected properties were readily apparent in the measured radiation patterns. A more detailed analysis of the test data showed both the precision and limitations of the applied acoustic theory. Rods protruding 23 percent of the radius predominantly generated only lowest radial order modes, as expected. Measured and predicted radiation patterns were generally in good agreement. The agreement, however, depended on a significant degree of implied refraction due to inlet velocity gradients. Refraction, if present, would impact static-flight noise comparisons
An analysis of the viscous flow through a compact radial turbine by the average passage approach
A steady, three-dimensional viscous average passage computer code is used to analyze the flow through a compact radial turbine rotor. The code models the flow as spatially periodic from blade passage to blade passage. Results from the code using varying computational models are compared with each other and with experimental data. These results include blade surface velocities and pressures, exit vorticity and entropy contour plots, shroud pressures, and spanwise exit total temperature, total pressure, and swirl distributions. The three computational models used are inviscid, viscous with no blade clearance, and viscous with blade clearance. It is found that modeling viscous effects improves correlation with experimental data, while modeling hub and tip clearances further improves some comparisons. Experimental results such as a local maximum of exit swirl, reduced exit total pressures at the walls, and exit total temperature magnitudes are explained by interpretation of the flow physics and computed secondary flows. Trends in the computed blade loading diagrams are similarly explained
Effects of Simulated Flight on Fan Noise Suppression
Attenuation properties of three treated fan inlets were evaluated. Tunnel flow simulated the inflow clean-up effect on source noise observed in flight and allowed observation of the blade passage frequency tone cut-off phenomenon. Acoustic data consisted of isolated inlet noise measured in the far field at two fixed positions and with traverses at four frequencies. Attenuation and source noise properties with and without flight simulation are compared and discussed. Averaged attenuation properties showed relative agreement of the inlets with their design intent, however, tunnel flow significantly affected the attenuation spectra
Optical phase-space reconstruction of mirror position at the attometer level
We describe an experiment in which the quadratures of the position of an
harmonically-bound mirror are observed at the attometer level. We have studied
the Brownian motion of the mirror, both in the free regime and in the
cold-damped regime when an external viscous force is applied by radiation
pressure. We have also studied the thermal-noise squeezing when the external
force is parametrically modulated. We have observed both the 50% theoretical
limit of squeezing at low gain and the parametric oscillation of the mirror for
a large gain.Comment: 10 pages, 11 figure
Acoustic Signatures of a Model Fan in the NASA-Lewis Anechoic Wind Tunnel
One-third octave band and narrowband spectra and continuous directivity patterns radiated from an inlet are presented over ranges of fan operating conditions, tunnel velocity, and angle of attack. Tunnel flow markedly reduced the unsteadiness and level of the blade passage tone, revealed the cutoff design feature of the blade passage tone, and exposed a lobular directivity pattern for the second harmonic tone. The full effects of tunnel flow are shown to be complete above a tunnel velocity of 20 meters/second. The acoustic signatures are also shown to be strongly affected by fan rotational speed, fan blade loading, and inlet angle of attack
Probing optomechanical correlations between two optical beams down to the quantum level
Quantum effects of radiation pressure are expected to limit the sensitivity
of second-generation gravitational-wave interferometers. Though ubiquitous,
such effects are so weak that they haven't been experimentally demonstrated
yet. Using a high-finesse optical cavity and a classical intensity noise, we
have demonstrated radiation-pressure induced correlations between two optical
beams sent into the same moving mirror cavity. Our scheme can be extended down
to the quantum level and has applications both in high-sensitivity measurements
and in quantum optics
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