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  • 1
    Electronic Resource
    Electronic Resource
    Magnetohydrodynamic scaling: From astrophysics to the laboratory : The 42nd annual meeting of the division of plasma physics of the American Physical Society and the 10th international congress on plasma physics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 1804-1816 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: During the last few years, considerable progress has been made in simulating astrophysical phenomena in laboratory experiments with high-power lasers. Astrophysical phenomena that have drawn particular interest include supernovae explosions; young supernova remnants; galactic jets; the formation of fine structures in late supernovae remnants by instabilities; and the ablation-driven evolution of molecular clouds. A question may arise as to what extent the laser experiments, which deal with targets of a spatial scale of ∼100 μm and occur at a time scale of a few nanoseconds, can reproduce phenomena occurring at spatial scales of a million or more kilometers and time scales from hours to many years. Quite remarkably, in a number of cases there exists a broad hydrodynamic similarity (sometimes called the "Euler similarity") that allows a direct scaling of laboratory results to astrophysical phenomena. A discussion is presented of the details of the Euler similarity related to the presence of shocks and to a special case of a strong drive. Constraints stemming from the possible development of small-scale turbulence are analyzed. The case of a gas with a spatially varying polytropic index is discussed. A possibility of scaled simulations of ablation front dynamics is one more topic covered in this paper. It is shown that, with some additional constraints, a simple similarity exists. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1344562
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  • 2
    Electronic Resource
    Electronic Resource
    An experimental testbed for the study of hydrodynamic issues in supernovae : The 42nd annual meeting of the division of plasma physics of the American Physical Society and the 10th international congress on plasma physics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 2446-2453 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: More than a decade after the explosion of supernova 1987A, unresolved discrepancies still remain in attempts to numerically simulate the mixing processes initiated by the passage of a very strong shock through the layered structure of the progenitor star. Numerically computed velocities of the radioactive 56Ni and 56Co, produced by shock-induced explosive burning within the silicon layer, for example, are still more than 50% too low as compared with the measured velocities. To resolve such discrepancies between observation and simulation, an experimental testbed has been designed on the Omega Laser for the study of hydrodynamic issues of importance to supernovae (SNe). In this paper, results are presented from a series of scaled laboratory experiments designed to isolate and explore several issues in the hydrodynamics of supernova explosions. The results of the experiments are compared with numerical simulations and are generally found to be in reasonable agreement. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1352594
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  • 3
    Electronic Resource
    Electronic Resource
    Flow conditioning for improved optical propagation of beams through regions bounded by surfaces of high solidity (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 1915-1922 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A flow conditioning system has been designed to maximize the thermal homogeneity in an enclosed region through which a laser beam must propagate. In the present application, such an enclosed region exists between the Nd:glass disks of a high average power solid-state laser amplifier. Experiments have been conducted on a test facility to quantify the magnitude of the beam losses due to thermal scattering. It is shown that the intensity of the incoherent light which is thermally scattered from this region can be reduced to less than 0.1% of the incident-beam intensity under apropriate flow and cooling conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348762
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  • 4
    Electronic Resource
    Electronic Resource
    Spatial resolution of gated x-ray pinhole cameras : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 792-795 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have conducted an investigation of the spatial resolution of a new gated x-ray pinhole camera (FXI). The spatial resolution, or its Fourier transform the modulation transfer function (MTF), is critical for quantitative interpretation of recent hydrodynamic instability data taken on the Nova laser. We have taken data corresponding to backlit straight edges, pinholes, and grids, both on the bench and in situ on Nova. For both the pinhole and edge data, the MTF at all wavelengths of interest can be deduced from a single image. Grids are of more limited usefulness, giving the value of the MTF only at the spatial period of the grid. These different techniques for characterizing the MTF of gated x-ray pinhole cameras will be discussed, with results specific to the FXI presented. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147743
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  • 5
    Electronic Resource
    Electronic Resource
    Optical technique for the measurement of turbulent spectra using the photorefractive properties of BaTiO3 (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 864-866 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An optical technique for obtaining two-dimensional spectra of turbulent flows is presented. A coherent beam is passed through a turbulent flow and acquires phase perturbations which are related to the density field of the flow. This phase-modulated beam is focused to obtain the Fourier transform of the incoherent, fluctuating portion of the field. The coherent portion of the field is removed by exploiting the photorefractive properties of BaTiO3 as a temporal filter. The technique is an improvement over existing methods in that it is nonintrusive, has a wide dynamic range, and requires no assumption of isotropy of the turbulence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104263
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  • 6
    Electronic Resource
    Electronic Resource
    On the use of a phased heater array for the controlled excitation of arbitrary three-dimensional perturbations in a laminar boundary layer (1986)
    Springer
    Experiments in fluids 5 (1986), S. 33-35 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Flush mounted resistive heating elements were used successfully by Liepmann, Brown and Nosenchuck (1981) to excite and control the development of two-dimensional Tollmien-Schlichting waves. Due to increased interest in the three dimensional nature of boundary-layer transition, this technique has recently been extended to provide a means for introducing arbitrary controlled three-dimensional perturbations into a laminar flow. This paper describes the design and operation of a programmable 32-element linear heater array capable of exciting a wide variety of flow disturbances hitherto unobtainable in the laboratory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00272422
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  • 7
    Electronic Resource
    Electronic Resource
    Optical technique for direct measurement of power spectra in compressible turbulence (1994)
    Springer
    Experiments in fluids 17 (1994), S. 10-15 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We present exploratory tests of a new optical method which measures directly two components of the 3-D power spectrum of the refractive-index fluctuation. The method was applied to a Mach 2 turbulent shear layer. Length scales of 0.1 mm to 1.0 mm were resolved within a shear-layer thickness ranging from 5 mm to 10 mm. At low-to-moderate wavenumbers, the spectral behavior is roughlyκ −3, while at higher wavenumbers it isκ −3.7. These spectral slopes are in agreement with prevailing theoretical predictions for anisotropic (low-wavenumber) and isotropic (high-wavenumber) turbulence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02412798
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