A theoretical study is presented for the influences of a small amount of NaCl on the ionization relaxation behind an argon shock wave progressing in a shock tube. Basic conservation equations, which are coupled with the rate equations for Ar-NaCl reactions, include the effects of wall boundary layer in a shock tube, non-Maxwellian energy distribution of electrons, and self-absorption of Na resonance line. From numerical calculations, main conclusions are obtained as follows. (1) NaCl admixture reduces the relaxation time. This effect is predominant in the region of low shock Mach number and high p₁d value (p₁ : initial pressure, d : tube diameter). (2) NaCl admixture reduces the electron temperature mainly at the early relaxation stage. This effect extends to the latter half of the relaxation as the Mach number lowers. (3) The energy distribution of free electrons is non-Maxwellian in the course of the relaxation.

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A wake behind a circular cylinder at Reynolds number 850-1700 was visualized by the smoke-wire method. The observations of the flow together with the results of quantitative measurements, such as various velocity correlation coefficients, illustrated the formation process of spoon-shaped large eddies in the region 90≤x/d≤230 attained through the deformation and rearrangement of the regular Kármán vortices. A spoon vortex was likely to pair with the counterpart on the opposite side of the wake. The large scale bulges of the turbulent and non-turbulent interface of the wake were shown to correspond to these spoon vortices.
These results indicate that some of coherent structures are organized by rearrangement and deformation of initially regular vortex in the turbulent flow.

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We attempted to measure velocity distributions along a radial direction of vortex rings using both smoke wire and hot wire anemometer at an instant when a pair of vortex rings, performing mutual slip-through at Reynolds number Γ/ν=1500, came to locate just in the same plane; the velocity distributions obtained by both methods were found to show fairly good agreement.
The experimental results agreed well with those of the potential theory when the slip-through was successfully achieved.
The characteristics of the temporal velocity variations at fixed locations during the mutual slip-through were examined and clarified experimentally and theoretically.

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Two types of unsteadiness must be considered when spectral analysis is applied to unsteady turbulence such as that found in the aorta. Firstly, the statistical properties of the turbulence itself change in time and so the definition of spectral density must be reconsidered. Secondly, the turbulent velocity fluctuations, whether they are steady or unsteady, are carried by an unsteady convective velocity which alters their properties as seen by a stationary observer.
In the present study, unsteadiness of turbulence in the latter sense is discussed by applying Taylor's hypothesis of “frozen turbulence” to turbulence with an unsteady convective velocity. If both a “frozen” pattern of turbulence and a constant convective velocity are assumed, measured frequency spectra can be easily transformed into wavenumber (spatial) spectra, usually as a trivial part of normalization. In the case of unsteady turbulence, however, the convection velocity is no longer constant and the conventional method can not be used. A new method of estimating the spatial properties of unsteady turbulence is proposed in which the temporal fluctuations of the turbulence velocity are transformed into spatial fluctuations using a non-linear transformation based upon the unsteady convective velocity. The transformed data are then Fourier analysed to yield a wavenmber spectrum directly.
The proposed method is applied to data obtained in the canine ascending aorta. Spectra calculated by the proposed method differ significantly from those obtained by the conventional method, particularly in the high wavenumber (or frequency) range. This difference is discussed as an “aliasing” phenomenon that has also been known in steady turbulence.

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The apparent viscosity of a concentrated suspension of rigid spherical particles is obtained theoretically. To take into account finite concentration of suspended particles, the “free surface spherical cell” model proposed by Happel is adopted. We define bulk quantities of a suspension as volume averages, taken over a cell volume, of the corresponding local quantities. From the relationship between the bulk stress and the bulk rate of strain the apparent viscosity is defined. It is shown that the result thus obtained can explain the experimental data at volume fractions c<0.3. Especially in contrast to the result obtained by Happel, the apparent viscosity is reduced to the well-known Einstein formula at very low concentration.

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