Turbulent Properties of Triple Elliptic Free Jets With Various Nozzle Orientation

An experimental investigation of nozzle orientation effects on turbulent characteristics of elliptic triple free jets was carried out for three nozzle configurations. The first configuration had each nozzle oriented along the minor plane (3_Minor), the next had two nozzles oriented along the minor plane and one along the major plane (Min_Maj_Min) and the last configuration had one nozzle oriented along the minor plane and two along the major plane (Maj_Min_Maj). The experiments were conducted using modified contoured nozzles with a sharp linear contraction for a nozzle spacing ratio of 4.1d, a nozzle equivalent diameter of 9 mm, and Reynolds number of 10,000. Nozzle orientation effects on the mean velocity, turbulent intensity, and Reynolds shear stress were discussed. The velocity decay, jet spread, merging point (MP), combined point (CP), and potential core length were used to characterize the effects of nozzle orientation on the mixing performance. The 3_Minor configuration had shorter potential core length and closer MP location which are indicative of a faster mixing in the converging region. The early merging of 3_Minor led to higher levels of streamwise turbulent intensity. One-dimensional plots revealed that jets approached self-similarity at a faster rate in the major axis. The orientation of the middle jet was found to be a key factor in determining transverse diffusion of the Reynolds shear stress in the plane of observation. Two-point correlations were used to provide insight into the effects of nozzle orientation on the spatial coherence of the large-scale turbulence structure and integral length scale.

Experimental Investigation of Nozzle Orientation Effects on Mixing Characteristics of Elliptic Triple Free Jets

An experimental investigation of nozzle orientation effects on turbulent characteristics of elliptic triple free jets was carried out for three nozzle configurations. The first configuration had all three nozzles oriented along the minor plane (3_Minor), the next had two nozzles oriented along the minor plane and one along the major plane (2_Minor_1_Major) and the last configuration had one nozzle oriented along the minor plane and two along the major plane (1_Minor_2_Major). The experiments were conducted using modified contoured nozzles with a sharp linear contraction for a nozzle-to-nozzle distance of 4.1, a nozzle equivalent diameter of 9 mm and a Reynolds number of 10,000. The effects of nozzle orientation on the mean velocity, turbulence intensity and Reynolds shear stress were discussed. The velocity decay, jet spread, merging point, combined point and potential core length were used to characterize the effects of nozzle orientation on the mixing performance. The results show that the 3_Minor configuration had shorter potential core length and closer merging point location which are indicative of a faster mixing in the converging region. Two-point correlation, skewness and flatness factors were used to provide insight into the effects of nozzle orientation on turbulence structure and higher order turbulence statistics.

The Effects of Nozzle Orientation on Mixing Characteristics of Elliptic Twin Free Jets

The effects of nozzle orientation on the mixing and turbulent characteristics of elliptical free twin jets were studied experimentally. The experiments were conducted using modified contoured nozzles with a sharp linear contraction. The centers of the nozzle pair had a separation ratio of 5.5. Four nozzle configurations were tested, one twin jet orientated along the minor plane (Twin_Minor), one twin jet orientated along the major plane (Twin_Major), one single jet orientated along the minor plane (Single_Minor) and one single jet orientated along the major plane (Single_Major). In each case, the Reynolds number based on the maximum jet velocity and the equivalent diameter was 10,000. A planar particle image velocimetry system was used to measure the velocity field in the jet symmetry plane. It was observed that the velocity decay rate is not sensitive to nozzle orientation. However, close to the jet exit the spread rate was highest in the minor plane. In addition, contour plots of Reynolds shear stress and turbulence intensities revealed significant differences between the minor and major plane. Velocity profiles showed little variation close to the jet exit, while further downstream the variations between the velocity profiles were more pronounced between the major and minor planes.

Stockeystrobusgen. nov. (Cupressaceae), and the evolutionary diversification of sequoioid conifer seed cones

An anatomically preserved seed cone from Late Cretaceous (Santonian–Coniacian) sediments of the Yezo Group on the Japanese Island of Hokkaido documents additional diversity among sequoioid conifers, and reveals previously unknown mechanisms for pollination and post-pollination seed enclosure in the conifer family Cupressaceae. The cylindrical seed cone of Stockeystrobus interdigitata gen. et sp. nov., consists of a central axis bearing helically arranged bract–scale complexes. Individual complexes are tightly packed and peltate in form, with completely fused bracts and scales. Peltate heads of adjacent complexes are attached to each other by elongated interdigitating epidermal trichomes. Each complex bears 6–8 inverted seeds on the adaxial surface of the inside of the peltate bract–scale complex head. Seeds occur in a single row, are roughly disk shaped, with broad wings in the major plane of symmetry. The nucellus is attached to the seed integument at the chalaza and free distally, with a convoluted apex. This cone reveals greater diversity of sequoioid reproductive biology than is represented among living species, and demonstrates that completely enclosed cones with well protected seeds were produced by Late Cretaceous fossil conifers of the Cupressaceae.

Conformational study on sterically hindered bis(arylimino)-isoindolines

Single crystal X-ray crystallographic analyses of three bis(arylimino)isoindoline ligands (bai's) with terminal thiazolyl (bti) and pyridyl groups (bpi) and differing degrees of sterical encumbrance are reported and discussed in the context of conformation, conjugation, and coordination properties. 4-Mebti 2 forms yellow plates from CH 2 Cl 2/pentane at -20 °C in P21/c with Z = 4, 6-Mebpi 3 crystallizes as yellow blocks from CH 2 Cl 2/n-hexane at -20 °C in P21/c with Z = 8 (two independant molecules), and 4-tBubti 4 is obtained from CHCl 3/n-hexane at ambient temperature as yellow plates in P21 with Z = 2. The latter compound forms pseudomerohedrically twinned crystals and was treated accordingly in the structure solution and refinement. The resulting molecular structures provide insight into the stepwise increase of sterical hindrance from 2 over 3 to 4 which results in a rotational displacement of one of the terminal heterocycles from the major plane. The ease of this rotation process proves a low degree of conjugation in bis(arylimino)isoindolines and stands in contrast with the formation of a helically distorted structure for a related, though strongly conjugated, t-butyl terminated tripyrrin 1.

Limitations on the accuracy possible in astrometric observations of the satellites of the major plane

Astrometric accuracy has two components; the accuracy with which an image can be centred on a CCD or photographic plate and the accuracy with which two image centres can be mapped on to standard co-ordinates. Photographic plates cover a sufficient area of sky that several standard stars can be measured with the satellite images and the mapping to standard coordinates can be done in one operation. CCDs have much smaller areas and the number of stars with sufficiently accurate positions may not be sufficient. The surface densities of the best available catalogues are shown in Table I.