Study of nonequilibrium two-phase flow of a gas-particle mixture Technical note no. 2

Two-phase nonequilibrium flow of particle suspensions in gaseous mediu

A theoretical and flight test study of pressure fluctuations under a turbulent boundary layer. Part 2: Flight test study

The study of pressure fluctuations under a turbulent boundary layer was undertaken with the objective of extending previous work to lower frequencies. Wind tunnel and flight test measurements are invalid at low frequencies because of extraneous acoustic noises and free stream turbulence. A glider was instrumented and used as a test bed to carry microphones into a smooth flow free of acoustic noise. Hodgson had previously measured the spectrum of boundary layer noise on a glider wing. These tests showed a drop off at low frequencies that could not be reproduced in any other facility. The measurements were made on the forward fuselage of a glider where the boundary layer could develop naturally and have some length in a zero pressure gradient before the measurements were made. Two different sets of measurements were made

The effect of a row of Helmholtz resonators on the turbulence in a boundary layer

Detailed acoustic measurements were made of the resonator's response as the free stream speed was varied from 30 mph to 155 mph. The average sound pressure level (SPL) and peak frequency response clearly show the existence of strong tuning between the boundary layer and the resonator for the Helmholtz (f sub 0) mode as well as for the first standing wave (f sub 1) mode. The narrow speed range for tuning and the gap between the strong tuning for the Helmholtz mode and the first standing wave mode is evident. The frequency at which the peak SPL response occurred at each speed is given. The peak response for the Helmholtz mode occurred at a free stream velocity of 26 m/s (at which RE sub theta = 6,560) with a resonant frequency of 570 Hz and a sound pressure level of 141 dB. The peak response for the first standing wave occurs at the maximum wind tunnel speed of 70 m/s (at which Re sub theta = 14,900) Hz with a resonant frequency of 1,890 Hz and a sound pressure level of 154 dB. At resonance the microphones do not maintain a constant SPL, but rather the latter fluctuates in a seemingly random fashion. The values presented here are time averaged rms values. Of interest was the occurrence of phase locking between adjacent resonators witha phase lag of 180 deg. This report covers the period from 5 May to 30 September on the subject project

Bubble-Driven Inertial Micropump

The fundamental action of the bubble-driven inertial micropump is investigated. The pump has no moving parts and consists of a thermal resistor placed asymmetrically within a straight channel connecting two reservoirs. Using numerical simulations, the net flow is studied as a function of channel geometry, resistor location, vapor bubble strength, fluid viscosity, and surface tension. Two major regimes of behavior are identified: axial and non-axial. In the axial regime, the drive bubble either remains inside the channel or continues to grow axially when it reaches the reservoir. In the non-axial regime the bubble grows out of the channel and in all three dimensions while inside the reservoir. The net flow in the axial regime is parabolic with respect to the hydraulic diameter of the channel cross-section but in the non-axial regime it is not. From numerical modeling, it is determined that the net flow is maximal when the axial regime crosses over to the non-axial regime. To elucidate the basic physical principles of the pump, a phenomenological one-dimensional model is developed and solved. A linear array of micropumps has been built using silicon-SU8 fabrication technology, and semi-continuous pumping across a 2 mm-wide channel has been demonstrated experimentally. Measured variation of the net flow with fluid viscosity is in excellent agreement with simulation results.Comment: 18 pages, 18 figures, single colum

A bilateral shear layer between two parallel Couette flows

We consider a shear layer of a kind not previously studied to our knowledge. Contrary to the classical free shear layer, the width of the shear zone does not vary in the streamwise direction but rather exhibits a lateral variation. Based on some simplifying assumptions, an analytic solution has been derived for the new shear layer. These assumptions have been justified by a comparison with numerical solutions of the full Navier-Stokes equations, which accord with the analytical solution to better than 1% in the entire domain. An explicit formula is found for the width of the shear zone as a function of wall-normal coordinate. This width is independent of wall velocities in the laminar regime. Preliminary results for a co-current laminar-turbulent shear layer in the same geometry are also presented. Shear-layer instabilities were then developed and resulted in an unsteady mixing zone at the interface between the two co-current streams.Comment: 6 pages, 7 figures. Accepted for publication in Phys. Rev.

A retrospective investigation into the occurrence and human exposure to polychlorinated naphthalenes (PCNs), dibenzo-p-dioxins and furans (PCDD/Fs) and PCBs through cod liver products (1972–2017)

A retrospective analysis of a number of historical medicinal grade cod-liver oil samples produced in Northern Europe revealed relatively high contamination levels of PCNs, PCDD/Fs and PCBs. The total toxic equivalence (TEQ) associated with PCDD/Fs, dl-PCBs and PCNs was in the range 95 to 427 pg g-1 for Baltic cod-liver oils and from 70 to 148 pg g-1 for oils sourced from the North Atlantic. The corresponding range for canned cod liver products (Baltic Sea) sampled in 2017 ranged from 52 to 104 pg g-1 fat (33 to 34 pg g-1 ww). The contribution from PCBs to the overall TEQ toxicity was around 3 to 6-fold higher than from PCDD/Fs and ranged from 24 to 318 pg TEQ g-1ww. The estimated summed TEQ intakes of PCDD/Fs, dl-PCBs and dl-PCNs resulting from the consumption of the daily recommended doses was highest for the Baltic cod-liver oils ranging from 16 to 293 pg kg-1 body mass (bm) day-1 for an adult, 20 to 183 pg kg-1 bm day-1 for a teenager and 15 to 131 pg kg-1 bm day-1 for a child. The contribution to daily adult TEQ intake from PCNs alone, although relatively small is estimated to contribute up to 5-fold above the recent EFSA proposed TWI of 2 pg kg-1 bm. The results indicate that although currently produced fish oils may undergo rigorous purification procedures and show low contaminant levels, cod livers sourced from the Baltic and consumed locally, continue to contribute substantially to the dietary intake of these contaminants

Relationship of Physical Performance with Body Composition and Bone Mineral Density in Individuals over 60 Years of Age: A Systematic Review

The purpose of this review was to examine the relationship between physical performance and body composition measurements, including fat/muscle mass and bone mineral density (BMD) in individuals ≥60 years of age. Various measurements used to assess body composition, BMD, and physical performance (PP) were discussed as well. Medline/PubMed, CINAHL, and SCIE were used to identify articles. After limiting the search for age and kind of physical performance measures, 33 articles were evaluated. Higher fat mass was associated with poorer physical performance while higher muscle mass was a predictor of better physical performance, especially in the lower extremities. Additionally, evidence showed that higher muscle fat infiltration was a determinant of poorer physical performance. BMD was shown to be a good predictor of physical performance although the relationship was stronger in women than in men. Developing standardized methods for PP measurements could help in further investigation and conclusions of its relationship with body composition

Poorer Integration of Local Orientation Information Occurs in Students With High Schizotypal Personality Traits

Contour integration is impaired in schizophrenia patients, even at the first episode, but little is known about visual integration abilities prior to illness onset. To examine this issue, we compared undergraduate students high and low in schizotypal personality traits, reflecting putative liability to psychosis, on two psychophysical tasks assessing local and global stages of the integration process. The Radial Frequency Jittered Orientation Tolerance (RFJOT) task measures tolerance to orientation noise at the local signal level, when judging global stimulus orientation, whilst the Radial Frequency Integration Task (RFIT) measures the ability to globally integrate the local signals that have been extracted during shape discrimination. Positive schizotypy was assessed with the Perceptual Aberration (PAb) scale from the Wisconsin Schizotypy Scales-Brief. On the RFJOT task, the High PAb group (n = 55) tolerated statistically significantly less noise (d = −0.494) and had a lower proportion of correct responses (d = −0.461) than the Low PAb group (n = 77). For the RFIT there was no statistically significant difference in integration abilities between the High and Low PAb groups. High and Low PAb groups also differed on other positive and disorganized (but not negative) schizotypy traits, hence poorer performance on the RFJOT may not be solely related to unusual perceptual experiences. These findings suggest that difficulties with local noise tolerance but not global integration occur in healthy young adults with high levels of schizotypal personality traits, and may be worth investigating as a marker of risk for schizophrenia