Parametric study of near-wake structure of spherical and cylindrical bodies in the laboratory

Oran, W. A.; Stone, N. H.; Samir, Uri

doi:10.1016/0032-0633(74)90071-3

Cited by 15 publications

(18 citation statements)

References 8 publications

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“…The experimental facility is described elsewhere. 6 Of particular interest was the pressure range of from ~10~6 to ~10~5 Torr which comprises the nominal operating pressure of most plasma wind tunnels.…”

Section: Resultsmentioning

confidence: 99%

“…In this Note, we will examine the influence of slow ions on both the ion and electron current distribution and the electron temperature in the wake of a body in a streaming plasma. The measurements were made in the Plasma Wind Tunnel Facility at NASA/MSFC, 6 which is being used to partially simulate the wake structure of a satellite in the ionosphere.…”

Section: Aiaa Journalmentioning

confidence: 99%

“…The decision as to the acceptable accuracy of the last initial guess is based upon satisfaction of Eq. (6). It should be noted that the iterative scheme does not require the inversion of the stiffness matrix (K' 1 ).…”

mentioning

confidence: 98%

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Slow ions in plasma wind tunnels

1976

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Fig. 2 Convergence modes l/$ 2 A n+/ I = X / 1 / 6 2 A n I. simultaneous satisfaction of two criteria is recommended for terminating the iteration cycles. One criteria is that the change in deflections between two iterations (6 2 A (W) ), as measured by E nt be sufficiently small. The other criteria is that the change in strain energy (6(7) between two iterations be sufficiently small as compared to the strain energy (U) to assure that the stress changes are not of any engineering significance.i.e. E n 1.0 result in nondecreasing values of 6 2 A W , indicating that Eqs. (2e) or (5b) should not be utilized for major increases of stiffness or an unstable structure. The increase of stiffness can be handled by an arbitrary magnification of the original stiffness (K 2 =fJiK I ), so as to result in X 72 =X /7 //i< 1.0.The algorithm assumes that the linear damaged structure has adequate strength to withstand the resulting calculated stresses, which are a known linear transformation of the displacements. If this is not justified, then the linear structure can be reanalyzed with a "pseudo load" (equal to the load ca...

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Section: Resultsmentioning

confidence: 99%

Section: Aiaa Journalmentioning

confidence: 99%

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Slow ions in plasma wind tunnels

1976

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“…Henderson and Samir (1967) measured the current depletion in the wake with respect to the ram and Samir et al (1979 studied the asymmetry in the current distribution in the wake. Oran et al (1974) observed the increasing of the density in the near-wake region. Although study of the ion collection in the electron-filled wake of a spacecraft was performed during the Charge Hazard and Wake studies' flight experiment onboard shuttles ST-60, ST-69 (Enloe et al, 1997;Davis et al, 1999), the experiment was motivated by a high charging (up to kilovolts) of the low-Earthorbiting (LEO) spacecraft in the auroral regions which are populated with the energetic electrons.…”

Section: Introductionmentioning

confidence: 83%

The spherical segmented Langmuir probe in a flowing thermal plasma: numerical model of the current collection

Seran¹,

Berthelier²,

Saouri³

et al. 2005

Ann. Geophys.

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Abstract. The segmented Langmuir probe (SLP) has been recently proposed by one of the authors (Lebreton, 2002) as an instrument to derive the bulk velocity of terrestrial or planetary plasmas, in addition to the electron density and temperature that are routinely measured by Langmuir probes. It is part of the scientific payload on the DEMETER microsatellite developed by CNES. The basic concept of this probe is to measure the current distribution over the surface using independent collectors under the form of small spherical caps and to use the angular anisotropy of these currents to obtain the plasma bulk velocity in the probe reference frame. In order to determine the SLP capabilities, we have developed a numerical PIC (Particles In Cell) model which provides a tool to compute the distribution of the current collected by a spherical probe. Our model is based on the simultaneous determination of the charge densities in the probe sheath and on the probe surface, from which the potential distribution in the sheath region can be obtained. This method is well adapted to the SLP problem and has some advantages since it provides a natural control of the charge neutrality inside the simulation box, allows independent mesh sizes in the sheath and on the probe surface, and can be applied to complex surfaces. We present in this paper initial results obtained for plasma conditions corresponding to a Debye length equal to the probe radius. These plasma conditions are observed along the Demeter orbit. The model results are found to be in very good agreement with those published by Laframboise (1966) for a spherical probe in a thermal nonflowing plasma. This demonstrates the adequacy of the computation method and of the adjustable numerical parameters (size of the numerical box and mesh, time step, number of macro-particles, etc.) for the considered plasma-probe configuration. We also present the results obtained in the case of plasma flowing with mesothermal conditions reproducing the case of measurements onboard a low altitude spacecraft. Finally, we briefly discuss the capabilities of the SLP to deCorrespondence to: E. Séran (seran@cetp.ipsl.fr) duce the plasma bulk velocity under similar conditions and present the first onboard measurements.

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“…It is well known that a charged particle or macroobject, immersed in a flowing plasma, creates a perturbed region (a wake) behind itself. [1][2][3][4][5][6][7][8][9][10][11] Wakefield potential is often invoked to explain a vertical alignment of dust particles levitating in the plasma sheath of capacitive radio-frequency (RF) discharge. In such a plasma, ions have a directed velocity relative to stationary dust particles 12 which in turn acquire a significant negative charge (10 3 -10 4 elementary charges) due to the higher electron mobility.…”

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confidence: 99%

Solution of the inverse Langevin problem for open dissipative systems with anisotropic interparticle interaction

et al. 2015

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Solution of the inverse Langevin problem is presented for open dissipative systems with anisotropic interparticle interaction. Possibility of applying this solution for experimental determining the anisotropic interaction forces between dust particles in complex plasmas with ion flow is considered. For this purpose, we have tested the method on the results of numerical simulation of chain structures of particles with quasidipole-dipole interaction, similar to the one occurring due to effects of ion focusing in gas discharges. Influence of charge spatial inhomogeneity and fluctuations on the results of recovery is also discussed. V C 2015 AIP Publishing LLC.

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Parametric study of near-wake structure of spherical and cylindrical bodies in the laboratory

Cited by 15 publications

References 8 publications

Slow ions in plasma wind tunnels

Slow ions in plasma wind tunnels

The spherical segmented Langmuir probe in a flowing thermal plasma: numerical model of the current collection

Solution of the inverse Langevin problem for open dissipative systems with anisotropic interparticle interaction

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