摘要:

A confined electric arc for the determination of gas transport properties is developed to the point that the resultant properties are found within a few percent. The measurements include the arc electrical gradient characteristic, the flow pressure drop, the radiative heat transfer, the spectral temperature distribution, and microwave resonance characteristics. Values of the electrical and thermal conductivity of equilibrium argon are tabulated for the temperature range from 7500 to 13 750°K. Helium in the confined arc at atmospheric pressure up to 400 A is shown not to be in thermodynamic equilibrium and hence its equilibrium properties cannot be determined by use of this experimental arrangement.

ISSN:0031-9171    

DOI:10.1063/1.1762255

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Volumetric radiative loss measurements, correlated with temperature in the range of 10 000 to 26 000°K, have been made on an argon plasma. Pressures of 0.5, 1.0, and 2.0 atm have been used. The 1.0‐atm measurements have been corrected for both absorption and ultraviolet emission and the results agree with those of Emmons in the common temperature range. The 6965 Ar I line has also been studied yielding lineshifts, halfwidths, absorption and emission coefficients. The line shift and halfwidth results are below theoretical predictions. Transition probabilities determined from both emission and absorption studies are found to be in reasonable agreement.

ISSN:0031-9171    

DOI:10.1063/1.1762256

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The jump equations for an oblique ionizing shock wave are examined in detail. A qualitative description of the shock structure helps to eliminate one of the four possible solutions and to limit the electric currents which the remaining shock solutions can carry. The criterion of evolutionarity is applied to ionizing shock waves to obtain necessary conditions for the existence of unique solutions. A shock structure restriction is proven which allows one to define a unique solution for every shock speed. Using these results, the Chapman‐Jouguet mode of electromagnetic shock tube operation is justified in the weak‐ionizing shock‐wave limit. Oblique, normal and transverse ionizing shocks in hydrogen, including the effects of ionization and dissociation, are compared. The temperature, thermalization efficiency, heating time, conversion ratio of magnetic to thermal energies and the specific impulse obtained by such shocks are used as measures of comparison. The transverse type of shock is shown to be the most effective one for producing a hot plasma sample. Results of several recent experiments are compared to the theoretical predictions, and the accuracy of the shock model and conclusions drawn from it are criticized briefly.

ISSN:0031-9171    

DOI:10.1063/1.1762257

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The plasma created by the output of a 2 to 10 JQ‐switched ruby laser focused into air, argon, helium and hydrogen at pressures from 15 to 1000 psi has been photographically recorded during and after the laser heating pulse. The growth of the luminous plasma front during laser irradiation was in accordance with a prediction based on a radiatively supported detonation‐wave model in which a Gaussian pulse shape was used for the instantaneous energy addition. With hydrogen at atmospheric pressure an appreciable fraction of the laser energy was transmitted. Consequently, the detonation‐wave model had to include only partial absorption of the incident laser beam. This was done by using the inverse bremsstrahlung absorption coefficient and a constant depth of energy addition. The shock wave created by this sudden energy addition was observed by using a Schlieren system. The growth of the shock wave was not in accordance with that predicted by spherical‐blast‐wave theory. The shock‐wave position from the initial point of breakdown varied as time from breakdown to the (0.20 ± 20%) power independent of gas species or operating condition.

ISSN:0031-9171    

DOI:10.1063/1.1762258

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The kink mode of a planar highly conducting liquid jet traveling through a perpendicular electric field is unstable, in the sense that perturbations grow spatially. Control of this growing wave is shown by means of an electronic feedback system which measures the disturbance and applies a controlling force proportional to the measured disturbance. In a practical case, the feedback must be implemented by a finite number of stations in which the disturbance at some point within the station is sampled and a feedback force proportional to this disturbance is applied throughout the section. The response of a single station indicates that if the feedback gain exceeds a certain critical value, the sampled feedback system becomes temporally unstable. To study the spatial stability of a collection of these stations a new stability criterion has been formulated. This criterion indicates that while the sampled feedback may induce spatial instability at certain frequencies, it is possible to stabilize the system studied under certain operating conditions for all frequencies. Various experiments on a water jet confirm the existence of the feedback‐induced temporal instability, and show that it is possible to stabilize a spatially unstable system by using sampled feedback.

ISSN:0031-9171    

DOI:10.1063/1.1762259

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

If a temperature gradient is imposed on a slightly conducting liquid, a gradient in natural electrical conductivity generally results. It is shown that if the liquid is then subjected to a wave of electric field traveling perpendicular to the temperature and conductivity gradients, charges are induced in the liquid bulk. These charges relax to form a traveling wave which interacts with the imposed field to pump the liquid. The sign of the conductivity gradient determines whether the liquid is pumped in the same direction or a direction opposite to that of the traveling wave. Equations are given for the velocity profile in plane flow, showing the effect of fluid properties as well as of the frequency, wavelength, and potential of the traveling wave. Experiments support the significance of the theory. Observations of a type of bulk Rayleigh‐Taylor instability are discussed.

ISSN:0031-9171    

DOI:10.1063/1.1762260

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Schwarzschild's criterion states that a fluid layer in hydrostatic equilibrium in a gravitational field will become unstable if the rate of change of pressure with density exceeds the corresponding adiabatic derivative. The validity of the criterion is discussed. The initial‐value problem for the hydrodynamic perturbation equations for adiabatic motion is reduced to a time‐independent problem. The latter is solved by a systematic classification of the possible motions. The method uses the theory of symmetric, semibounded operators. The distinction between thermodynamic and general gravitational equilibrium follows naturally. In particular, it is proved that the density in a gravitating body cannot increase outwards.

ISSN:0031-9171    

DOI:10.1063/1.1762261

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A theory has previously been developed of the effects of diffusion on interfacial instabilities at the liquid‐liquid interface between two solvents when they are mutually immiscible and when a third species, the solute, is diffusing across the interface. The theory is extended to consider the effects of system inhomogeneities. These are expected to be large in the neighborhood of the interface, and the analysis shows their significance in changing the criterion for the onset of instability. An experiment is suggested which would test some consequences of the theory.

ISSN:0031-9171    

DOI:10.1063/1.1762262

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The Couette flow of a rarefied gas between two concentric cylinders is analyzed numerically for an inverse Knudsen number ranging from 0 to 10 and different gap‐to‐radius ratios. The model of the Boltzmann equation proposed by Bhatnagar, Gross, and Krook is linearized and the transport integro‐differential equation reduced to a purely integral one, which is solved numerically. The resulting drag coefficients for the outer cylinder are in a good agreement with available experimental data.

ISSN:0031-9171    

DOI:10.1063/1.1762263

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A numerical study is made of hypersonic flow past the leading edge of a flat plate. The full time‐dependent Navier‐Stokes equations are solved using the particle‐in‐cell and fluid‐in‐cell computing methods. The effects of several plate boundary conditions are investigated for two free‐stream Mach numbers. These conditions include velocity slip and temperature jump at the plate surface. Solutions reveal the existence of an appreciable boundary layer pressure gradient near the leading edge. Comparisons are made with both experiment and analytical theory for a cooled plate in Mach 25 flow. These comparisons show good agreement between the calculations and experiment in the magnitude of the surface pressures.

ISSN:0031-9171    

DOI:10.1063/1.1762264

出版商:AIP    

年代:1967

数据来源: AIP