Influence of the state of the inlet endwall boundary layer on the interaction between pressure surface separation and endwall flows

This paper describes the effect of the state of the inlet boundary layer (laminar or turbulent) on the structure of the endwall flow on two different profiles of low-pressure (LP) turbine blades (solid thin and hollow thick). At present the state of the endwall boundary layer at the inlet of a real LP turbine is not known. The intention of this paper is to show that, for different designs of LP turbine, the state of the inlet boundary layer affects the performance of the blade in very different ways. The testing was completed at low speed in a linear cascade using area traversing, flow visualization and static pressure measurements. The paper shows that, for a laminar inlet boundary layer, the two profiles have a similar loss distribution and structure of endwall flow. However, for a turbulent inlet boundary layer the two profiles are shown to differ significantly in both the total loss and endwall flow structure. The pressure side separation bubble on the solid thin profile is shown to interact with the passage vortex, causing a higher endwall loss than that measured on the hollow thick profile.

The effect of wake passing on a flow separation in a low pressure turbine cascade

This paper describes an investigation into the effect that passing wakes have on a separation bubble that exists on the pressure surface and near the leading edge of a low pressure turbine blade. Previous experimental studies have shown that the behaviour of this separation is strongly incidence dependent and that it responds to its disturbance environment. The results presented in this paper examine the effect of wake passing in greater detail. Two dimensional, Reynolds averaged, numerical predictions are first used to examine qualitatively the unsteady interaction between the wakes and the separation bubble. The separation is predicted to consist of spanwise vortices whose development is in phase with the wake passing. However, comparison with experiments shows that the numerical predictions exaggerate the coherence of these vortices and also overpredict the time-averaged length of the separation. Nonetheless, experiments strongly suggest that the predicted phase locking of the vortices in the separation onto the wake passing is physical.

The effect of boundary layer trips on intake separation in crosswinds

The flow typical of that occurring over the windward lip of an aero engine intake operating in a crosswind has been reproduced on a 2D lip. The uncontrolled boundary layer undergoes a laminar separation at the leading edge of the lip. It has been shown that a minimum size of boundary layer trip, positioned upstream of the separation location, is required to enable the flow to remain attached around the leading edge. A turbulent separation then occurs in the diffuser. Larger diameter trips promote earlier diffuser separation. Copyright © 2008 by the American Institute of Aeronautics and Astronautics, Inc.

Species identification of family Lutjanidae and separation of populations of John’s snapper (Lutjanus johnii) in Persian Gulf and Oman Sea based on otolith shape analysis

The anatomical and morphometric (shape indices, contour descriptors and otolith weight) characterizations of sagittal otoliths were investigated in 13 species of Lutjanus spp. inhabiting the Persian Gulf. This is the first study that compares the efficiency of three different image analysis techniques for discriminating species based on the shape of the outer otolith contour, including elliptical Fourier descriptors (EFD), fast Fourier transform (FFT) and wavelet transform (WT). Sagittal otoliths of snappers are morphologically similar with some small specific variations. The use of otolith contour based on wavelets (WT) provided the best results in comparison with the two other methods based on Fourier descriptors, but only the combination of the all three methods (EFD, FFT and WT) was useful to obtain a robust classification of species. The species prediction improved when otolith weight was included. In relation to the shape indices, only the aspect ratio provided a clear grouping of species. Also, another study was carried on to test the possibility of application of shape analysis and comparing otolith contour of otoliths of Lutjanus johnii from Persian Gulf and Oman Sea to identify potential stocks. The results showed the otoliths have differences in contour shape and can be contribute to two different stocks.

Unsteady Effects of Shock Wave Induced Separation

The aim of this series is to publish promptly and in detailed form new material from the field of Numerical Fluid Mechanics and Multidisciplinary Design ...

Separation and purification of ovulation-inducing factors in the seminal plasma of the Bactrian camel (Camelus bactrianus)

Ovulation in the Bactrian camel depends upon ovulation-inducing factors in the seminal plasma. The present study was conducted to isolate and purify the bioactive fractions from the seminal plasma of these camels. The seminal plasma was fractionated by anion-exchange chromatography, and six fractions were obtained. The bioactive potential of each fraction was estimated from its effect on rat pituitary tissue cultured in vitro and by the effect of an intramuscular injection of the fraction into female camels in vivo. Both the third fraction (F3) and the fifth fraction (F5) stimulated the release of LH in vitro and in vivo. In addition, female camels ovulated within 48 h after intramuscular injection of F3. However, neither F3 nor F5 had any significant effect on the secretion of FSH, either in vitro or in vivo. When F3 was further fractionated into four subfractions, the third subfraction (F3-3) still stimulated the in vitro release of LH, but not of FSH. An attempt to further purify the ovulation-inducing factors in F3-3 failed owing to the similarity of the molecular characters.

Corner separation effects for normal shock wave/turbulent boundary layer interactions in rectangular channels

Experiments are conducted to examine the mechanisms behind the coupling between corner separation and separation away from the corner when holding a high-Machnumber M∞ = 1.5 normal shock in a rectangular channel. The ensuing shock wave interaction with the boundary layer on the wind tunnel floor and in the corners was studied using laser Doppler anemometry, Pitot probe traverses, pressure sensitive paint and flow visualization. The primary mechanism explaining the link between the corner separation size and the other areas of separation appears to be the generation of compression waves at the corner, which act to smear the adverse pressure gradient imposed upon other parts of the flow. Experimental results indicate that the alteration of the -region, which occurs in the supersonic portion of the shock wave/boundary layer interaction (SBLI), is more important than the generation of any blockage in the subsonic region downstream of the shock wave. © Copyright 2012 Cambridge University Press.