The transitional characteristics of plane turbulent jets have been investigated in the present study. Hot wire measurements have been performed for a jet issuing from a rectangular nozzle of aspect ratio 20, for Reynolds number varying in the range 250⩽Re⩽6250. In this range, the characteristics of flow development are found to be Reynolds number dependent, in contrast to the fully developed turbulent jets which show features independent of initial conditions such as inlet Re. For low Re jets, the jet spread is significantly influenced by the low frequency oscillations caused by shear layer instability. Large sized vortices are formed in the shear layers at the fundamental frequency of the instability, which lead to subharmonic low frequency oscillations due to vortex pairing and merger, at larger axial distances. Consequently, the far field flow structure of a low Re jet is dominated by large size vortices which give rise to a higher level of flow intermittency, larger entrainment of ambient fluid, and faster jet decay, as compared to high Re jets. Also, in the absence of finer scales and broader spectrum of eddies, the mean flow field achieves self-similar structure much ahead of the fluctuating components and fully developed turbulent flow characteristics are not observed, even in the far field. In high Re jets, on the other hand, the vortex break-up processes also simultaneously occur along with vortex pairing and merger. Therefore, energy transfers to a broad spectrum of scales and finer scales are observed even in the near field of the jet. Although the achievement of self-similarity for the mean field is slightly faster than that for the fluctuating components, turbulence also attains a fully developed state at about a nondimensional axial distance of 20. The associated probability density functions of the fluctuating components evolve into Gaussian profiles, implying isotropic turbulence. Due to the dominance of finer scales, the overall entrainment level is less and decay is slower for a high Re jet.

Double deviation (failure to satisfactorily recover from a service failure) is a common phenomenon that has recently attracted significant research interest, but the academic literature lacks a study mapping and synthesizing the field. This article undertakes filling this gap by systematically reviewing the double deviation literature. The review classifies the literature into causes, consequences, moderators, and double service recovery and identifies research themes and future research directions within them. Key current research themes are ineffective recovery remedies and cognitive appraisal criteria as causes; emotivational goals, revengeful and reparative behaviours as consequences; firm-customer relationship-based variables as moderators; and unique tactics of double service recovery. Reassessing the scope of double deviation, uncovering customers' discrete emotions during double deviation and ascertaining the commercial viability of double service recovery are some recommendations for future research.

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It is well known that initial conditions significantly affect the flow field and the evolution characteristics of the jets. In the present study, experiments on twin pipe jets were performed to understand the effect of developing length on the twin-jet characteristics. The developing length was varied in the range of 4< L/ D<9, and hot-wire data were acquired up to a downstream distance of 40 D. Twin jets combine at farther downstream axial distance with an increase in the developing length due to delayed mixing brought about by relatively less intense vortex action. The range of the energy-containing eddies decreases, resulting in a decrease in the spread rates of the twin jet.

Jet flows are encountered in a variety of industrial applications. Although from the points of view of manufacturing with ease and small spatial requirement it is convenient to use short slit nozzles, most of the available studies deal with turbulent jets issuing from contoured nozzles. In the present work, experiments have been conducted in the moderate Reynolds number range of 250–6250 for a slit jet. Mixing characteristics of slit jets seem to be quite different from those of jets emerging out of contoured nozzles. This is primarily due to the differences in the decay characteristics and the large scale eddy structures generated in the near field, which are functions of the initial momentum thickness. It is evident that, in the range of 250⩽Re⩽6250, the overall spreading characteristics of the slit jet flow have stronger Reynolds number dependence than those of contoured nozzle jets. In particular, the slit jets exhibit slower mean velocity decay rates and slower half-width growth rates. Normalized power spectra and probability distribution functions are used to assess the spatial evolution and the Reynolds number dependence of jet turbulence. It is seen that the fluctuating components of velocity attain isotropic conditions at a smaller axial distance from the nozzle exit than that required for mean velocity components to become self-similar.