摘要:

This paper describes shock‐tube studies of the optical index of refraction of ionized argon in which observed optical effects have been related to the ionization of the shocked argon. The plasma dispersion formula has been applied to the measured refractivities to determine values of equilibrium electron concentrations on the order of 1017cm−3. Good agreement is found between experimental and calculated values of the degree of ionization. The ionization relaxation process is strikingly portrayed in the interferograms and may be studied in some detail. Some questions concerning proposed kinetics for the relaxation behind strong shock waves in monatomic gases are discussed.

ISSN:0031-9171    

DOI:10.1063/1.1705907

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The dissociation of oxygen has been observed behind shock waves at Mach numbers of 8 to 10, over a temperature range of 3000–5000°K. Photographs of the shocks were made using a Mach‐Zehnder interferometer and a spark light source of effective duration 0.1 &mgr;sec. The velocity of the shock was measured using thin‐film resistance thermometers to detect its passage. From this velocity and the state of the gas ahead of the shock, one can calculate the state of the gas behind the shock, both in the reaction zone and at equilibrium, from the interferometrically observed density ratios. Up to 12% equilibrium dissociation was obtained, following reaction zones of the order of 1 cm in length. The following rate constant, obtained from classical collision theory for the principal reactionO2+O2&rlhar2;kD2O+O2,fitted the data well:kD= 7.4 × 1011PT½(59 380/T)3exp (−59 380/T) cc mole−1sec−1, where 59 380 is the known dissociation energy of oxygen, expressed in degrees Kelvin. The quantityP, the ``collision efficiency,'' was adjusted to fit the data, and was found to be 0.07. The data are consistent with the results of several other investigators who used different methods. The recombination rate constant calculated from the dissociation rate constant is 8.4 × 1014cc2mole−2sec−1at 3500°, and is approximately proportional toT−2.

ISSN:0031-9171    

DOI:10.1063/1.1705908

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

In the Mach reflection of weak shock waves, there has been a wide difference between theory and experiment for the shock wave angles at the triple point. Using the electric tank analogy in the hodograph to obtain the shock patterns it is found that the shock waves are so strongly curved near the intersection that the triple point angles cannot be observed in the laboratory. However, it is shown that the visible shock patterns are apparently inconsistent with the hodograph boundaries specified by the existing triple point theory. The effect of shock wave thickness on the boundary conditions at the triple point is then examined. It is shown that at the intersection there must be a non‐Rankine‐Hugoniot shock wave zone separating the three R‐H shock waves. It follows that for weak shock waves where the shock curvatures → ∞ at the triple point, the simple boundary conditions of equal pressure and direction are invalid for a real fluid. A semiquantitative description is then given of a real fluid model which is consistent with the experimental data and with the Navier‐Stokes equations. The examination of this model reveals the formidable difficulties in the way of obtaining a detailed mathematical description of a triple shock wave intersection in a real fluid. The question of the solution for the limiting case as &mgr; → 0 is also discussed.

ISSN:0031-9171    

DOI:10.1063/1.1705909

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

An electron beam densitometer has been used to investigate the behavior of a conventional 1⅛‐in. i.d. shock tube operating at initial pressures of the order of 1 mm Hg. These experiments show that such a shock tube does not perform as predicted by simple theory. Most of the experiments were performed in argon with shock Mach numbers ranging between 1.2 and 7.0. The most striking observation was that for a given shock velocity,Ms= 1.6, the distance between the shock wave and contact surface as observed at the densitometer was proportional to initial pressure and independent of expansion chamber length over a tenfold range of tube length. At an initial pressure of 0.5 mm Hg the time interval between the arrival of the shock and the contact surface varied between 600 &mgr;sec atMs= 1.2 and 20 &mgr;sec atMs= 7.0. The diaphragm pressure ratio (Ar ‐ Ar) required to produce a shock of velocityMs= 1.6 varied from 200 at an initial pressure of 0.25 mm Hg to 20 at an initial pressure of 50 mm Hg. For a given diaphragm pressure ratio the shock velocity decreased with distance in a highly nonlinear manner. The density behind the shock wave was observed to increase significantly before the arrival of the contact surface under all conditions. This surprising shock‐tube behavior is believed to be related to severe laminar boundary layer development behind the shock wave at low initial pressures.

ISSN:0031-9171    

DOI:10.1063/1.1705910

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The blast wave from the detonation of a spherical charge of TNT is described based on results of a numerical calculation. The equations of motion and the equations of state for TNT and for air are described. The pressures, densities, temperatures, and velocities are detailed as functions of time and radius. Space‐time relations and energy and impulse histories are shown. A second shock is seen to originate as an imploding shock following the inward rarefaction into the explosion product gases and a series of subsequent minor shocks are seen to appear in a similar manner, moving out in the negative phase behind the main shock.

ISSN:0031-9171    

DOI:10.1063/1.1705911

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Experiments were performed to secure evidence of the mechanism during the early stages of a wire explosion. High‐speed (0.3 &mgr;sec) photographs were taken, using a second exploding wire to back‐light the first. The results showed no surface irregularities (unduloids) as frequently postulated for the liquid phase of exploding wires. Instead, the evidence points to a condition of extreme super‐heating of the liquid, followed by sudden explosive vaporization (``transplosion''). Stria in the ensuing vapor cloud were found to develop after the explosion is complete.

ISSN:0031-9171    

DOI:10.1063/1.1705912

出版商:AIP    

年代:1959

数据来源: AIP

ISSN:0031-9171    

DOI:10.1063/1.1705913

出版商:AIP    

年代:1959

数据来源: AIP

ISSN:0031-9171    

DOI:10.1063/1.1705914

出版商:AIP    

年代:1959

数据来源: AIP

ISSN:0031-9171    

DOI:10.1063/1.1705915

出版商:AIP    

年代:1959

数据来源: AIP