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