Quasi-isentrope

Chhabildas, L.C. and L.M. Barker (1988), Dynamic Quasi-Isentropic Compression of Tungsten, in Shock Waves in Condensed Matter (edited by S.C. Schmidt and N.C. Holmes), Elsevier Science, New York, pp. 111-114. 

That this is not always the case should be expected. In fact, if it was not for heterogeneous localization of some flow phenomena, it would be very diflicult to initiate secondary explosives, or to effect shock-induced chemical reactions in solids. Heterogeneous shear deformation in metals has also been invoked as an explanation for a reduction in shear strength in shock compression as compared to quasi-isentropic loading. We present here a brief discussion of some aspects of heterogeneous deformation in shock-loaded solids. 

Keywords fullerite, conductivity, shock waves, manganin gauges, quasi-isentropic compression... 

In the first part of present work specific conductivity of fullerene C60 crystals has been measured under smooth quasi-isentropic loading conditions up to 15 GPa at initial temperatures T=293 K and 77 K. We have registered the sharp increase of conductivity more than 6 orders of magnitude in a range of pressure from 0 to 15 GPa, Fig. 1. Value of conductivity regains initial properties after dynamic load is removed. The results received testified about sharply decreasing of band-gap of C6o under compression. However the experimental temperature dependence of... 

The purpose of the second part of the present research is measurement of conductivity of fullerene C6o crystals under high pressures more than at the former experiments to find out metallization C(, is possible. In the latest experiments we used a mode of multi-step quasi-isentropic compression of fullerene crystals by series of consecutive flat shock waves which enables us to reach much higher... 

The result of typical experiment of measurement of conductivity of C6o under multi-step quasi-isentropic compression up to final pressure 30 Gpa is presented on Fig. 2 as time dependences of sample conductivity and pressure, measured with help of manganin-foil pressure sensor. It is visible as we can see that at the beginning conductivity of a sample sharply increases and then starts to decrease smoothly despite of proceeding increase of pressure. As against to range 0-15 GPa... 

If A is the effective cross-sectional area of the quasi-one-dimensional flow and is the stagnation temperature, then for an ideal gas with constant specific heats [122] in variable-area, isentropic flow. 

Figure 3.10. Global distribution of the potential vorticity on the 850 K isentropic surface during a wintertime planetary wave event. The shaded region over the Pacific ocean with a weak gradient is characterized by nonlinear wave dissipation and strong quasi-horizontal mixing. This region is referred to as the surf zone . Wind vectors are also indicated and provide information about large-scale transport. Courtesy of A. O Neill, University of Reading, UK.

Rather than being an infinitely thin surface, the tropopause should be regarded as a highly dynamic layer over which the mixing ratios of chemical compounds (such as water vapor or ozone) change rapidly from their tropospheric to their stratospheric values. This layer behaves as a quasi-material entity in the tropics, it nearly coincides with the isentropic surface of 380 K. In the extratropics, it corresponds to the iso-surface of 2-4 potential vorticity units, and includes a mixture of air with tropospheric and stratospheric characteristics (e.g., tracer mixing ratios). 

In summary, for a prescribed nozzle profile A(x) and inlet conditions, the area-Mach relation Eq. 3 and isentropic flow relations Eqs. 4,5 and 6 are sufficient to completely determine the nozzle flow field under the quasi-ID model. 

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