Downstream Expansion Research Articles

Characteristics of cylindrical cavities in a compressible turbulent flow

The characteristics of flow over rectangular cavities have been well documented. However, few studies have considered cylindrical cavity flows. For compressible cylindrical cavity flows, the type of cavity flowfield is dependent on the diameter-to-depth ratio (D/H), which is similar to the length-to-depth ratio for a rectangular cavity flow. For an open-type cavity flow (D/H≤6.14), there is a slight upstream influence and uniform static pressure distributions are observed inside the cavity; a small adverse pressure gradient ahead of the rear face and a downstream expansion. The leading- and rear-edge expansions are more significant for transitional- (D/H=8.60–21.00) and closed-type (D/H=43.00) cavities. The amplitude of surface pressure fluctuations increases toward the rear face, for all of the test cases, whereas an additional peak near the middle of cavity floor is observed for a closed-type cavity. Notably, the effect of freestream Mach number is pronounced only on the amplitude of peak pressure fluctuations near the rear wall. Similarities between a cylindrical cavity and a rectangular cavity for a compressible flow are also highlighted in this study.

The acoustics of short circular holes opening to confined and unconfined spaces

The sound generated or absorbed by short circular holes with a mean flow passing through them is relevant in many practical applications. Analytical models for their acoustic response often ignore the fact that such holes open to a confined or finite space either side, or account for this effect simply by adding an end mass inertial correction. The vortex–sound interaction within a short hole has been recently shown to strongly affect the acoustic response at low frequencies (D. Yang, A.S. Morgans, J. Sound Vib. 384 (2016) 294–311 [19]). The present study considers a semi-analytical model based on Green's function method to investigate how the expansion ratios either side of a short hole affect the vortex–sound interaction within it. After accounting for expansions to confined spaces using a cylinder Green's function method, the model is substantially simplified by applying a half-space Green's function for expansions to large spaces. The effect of both the up- and downstream expansion ratios on the acoustics of the hole is investigated. These hole models are then incorporated into a Helmholtz resonator model, allowing a systematic investigation into the effect of neck-to-cavity expansion ratio and neck length. Both of these are found to affect the resonator damping.

The Effect of Yaw Angle on a Compressible Rectangular Cavity Flow

Experiments are performed to determine the characteristics of a compressible flow over yawed rectangular cavities for Mach numbers of 0.64, 0.70, and 0.83. The cavity’s length-to-depth ratio varies from 4.43 to 21.50 and the length-to-width ratio is unity. The yaw angle is 0°–45°. The upstream compression and downstream expansion near the front and rear corners of a cavity decrease when the value of the yaw angle increases. The amplitude of the fluctuating pressure is a maximum for an open cavity with a yaw angle of 15°. An increase in the yaw angle results in a reduction in the pressure fluctuations for both open and transitional cavities. In the span-wise direction, variations in the mean and fluctuating pressure are less significant than those in the chord-wise direction. The oscillating frequency of resonance varies slightly with the yaw angle, but the amplitudes for the power spectral density are significantly reduced when the yaw angle is larger than 30°. For lower Mach numbers, the lower mode plays an important role in self-sustained oscillations for an open cavity when there is an increase in the yaw angle.

Sheathless and high throughput sorting of paramagnetic microparticles in a magneto-hydrodynamic microfluidic device.

Sorting of microorganisms and particles from a mixture is critical for numerous biotechnological and medical applications. Several sorting methods such as pinched flow fractionation (PFF), optical sorting, dielectrophoresis, acoustic separation, magnetophoresis and deterministic lateral displacement (DLD) have been reported in literature. But most of these methods lack ideal characteristics of a sorter such as ability to process at high throughput, simple design, non-complicated fabrication method, sheathless operation and high purity in separation. In this paper, we have introduced a novel sorting technique by integrating focusing of magnetic particles in a narrow microchannel with their hydrodynamic separation at a downstream expansion channel which meets majority of the aforementioned characteristics. To achieve this, the sheathless focusing of paramagnetic microparticles in the narrow microchannel and their deflection at the expansion channel were first studied at various flow rates (0.5-5 ml h-1). Then, a mixture of 5 and 11 μm paramagnetic particles was introduced into the device and their separation was examined quantitatively. It was found that the magnetic particles were focused along the wall of channel, however their centers were positioned on two distinct streamlines owing to difference in their sizes. Hence, these two particles were found separated from each other as they flew into the expansion region. This technique of size based separation of paramagnetic particles works at a high throughput of 107 particles per hour and offers more than 98% purity in sorting.

High-throughput photocontrol of water drop generation, fusion, and mixing in a dual flow-focusing microfluidic device

We describe the first method to control, in a single microfluidic device, the generation, fusion, and mixing of pico- to nanoliter water-in-oil drops using a straightforward LED light stimulus. This is achieved by implementing a photosensitive surfactant in the water phases of a novel dual flow-focusing microfluidic configuration. UV illumination at 365 nm enables dynamic switch of the flow behavior between a stable dual jet regime (−UV) and a stable dual drop regime (+UV), thus allowing us to generate on-demand two distinct populations of water drops. These drops are fused and mixed downstream inside expansion chambers, offering both a dynamic control by light stimulation and a controllable degree of fusion and mixing by the positions of chambers. The mixing inside the fused drops is found to be much faster than diffusion due to the chaotic advection inside the moving drops.

Cancer stemness and progression: mitochondria on the stage

Cancer stemness and progression: mitochondria on the stage

Does stream structure affect dispersal by water? A case study of the invasive tree Ailanthus altissima in Spain

Riparian zones are highly susceptible to invasion by alien plants. For both invasive and non-invasive plants, water has been proved to be an important vector for seed dispersal, connecting distant populations and, therefore, contributing to the downstream expansion of invaders. However, the effect of intrinsic factors of watercourses, such as habitat quality, on the invaders’ dispersal ability is largely unknown. We compared the dispersal ability of Ailanthus altissima fruits through a release experiment in two contrasting 100 m-long stretches of a nearnatural and a degraded reach of the same river. One hundred fruits were released in the centre of the channel and allowed to float during 90 minutes. Results showed that fruit retention was five times lower in the degraded reach, suggesting that the loss of complexity in the fluvial habitat structure may increase dispersal distances of A. altissima fruits in headwater streams of similar characteristics. The lack of potential depositional zones, such as pools, meanders, or biological structures in the degraded reach increased the water dispersal success of A. altissima fruits. Among the studied retentive structures, macrophytes were found to be the main natural barrier to limit dispersal of A. altissima fruits. Velocities of dispersed fruits were highly variable within each reach but did not depend on the habitat quality. This study provides reasons to consider the heterogeneity and complexity of riparian and fluvial habitat to control the dispersion of fruits of the invasive tree A. altissima.

An experimental and computational assessment of blockage effects on wind turbine wake development

ABSTRACTAn experiment was conducted to evaluate the initial wake expansion in scaled wind turbine tests as a means to guide future wake interference studies. Five scaled wind turbine rotors with different diameters were designed for testing in a closed‐loop water channel to evaluate the effects of blockage on the initial wake expansion behind a wind turbine. The initial wake expansion was assessed by using quantitative dye visualization to identify the propagation of tip vortices downstream of the rotor. The thrust coefficient developed by the scaled models was recorded using a six‐component balance and was correlated to the downstream wake expansion. The rotors used in the experiment were operated at a tip speed ratio of 6, a Reynolds number based on the tip speed and tip chord of approximately 23,000 and resulted in blockage values that ranged from 6% to 25%. Dye visualization indicated that the initial wake expansion downstream of a rotor was narrowed and that tip vortex pairing behaviour was modified because of increasing blockage. Blockage effects were significant and resulted in a wake that was more than 50% narrower when blockage was 25% compared with the observed expansion with 10% blockage. A computational simulation was conducted with the Generalized Unsteady Vortex Particle (GENUVP) discrete vortex method code using the rotor in freestream conditions and was compared with the experiments. The magnitude of the wake expansion in the freestream computations was similar to the wake expansion in the experiment when blockage was less than 10%. Copyright © 2013 John Wiley & Sons, Ltd.

Effect of the downstream transition region of a flow measurement flume of rectangular compound cross section on flow properties

In this study, the effect of the downstream expansion region of a flow measurement flume of rectangular compound cross section on some of the flow properties; such as the discharge coefficient, Cd, the approach velocity coefficient, Cv and the modular limit, ML were investigated. For this reason, extensive laboratory tests were conducted with nine models of different downstream transitions. The aforementioned hydraulic quantities were then related with the relevant parameters to obtain sets of curves from which one could decide which kind of downstream transition type would produce the highest modular limit. It was found that model type A yielded the highest modular limit with a downstream slope of about 1/7.

Reservoir to river passage of age‐0+ year fishes, indication of a dispersion pathway for a non‐native species

This study demonstrates passage of age-0+ year individuals of pikeperch Sander lucioperca, common bream Abramis brama and non-native tubenose goby Proterorhinus semilunaris from the Nové Mlýny Reservoir into the River Dyje (Danube River basin, Czech Republic) through the turbine of a hydropower facility. Most fishes had standard length (LS ) in the range 12-33 mm. Seasonal patterns corresponded with spawning activity, i.e. an early single spawning event for S. lucioperca, multiple spawning events for A. brama and continuous spawning with a later start and prolonged duration for P. semilunaris. Sander lucioperca, P. semilunaris and larger A. brama (>22 mm) drifted almost exclusively during the dark; smaller A. brama displayed no preference for light or dark. Proterorhinus semilunaris displayed significantly lower mortality than other species when passing through the turbine (3% compared to 18%). The passage of high numbers of P. semilunaris from the reservoir (estimated at 473 000 individuals per year), and their subsequent mass downstream drift, may have contributed to rapid population establishment along the River Dyje and the quick downstream expansion.

Iron overload can suppress IL23 expression from human monocyte-derived dendritic cells and subsequent downstream Th17 expansion

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Exogenous Calcium Induces Autophagy via Classical Autophagic Machinery and Recruits Endoplasmic Reticulum Membranes to Form Autophagosomes

Calcium plays a role in regulation of autophagy. We have reported that exogenously added calcium as the calcium phosphate precipitate (CPP) induces autophagy. Here we further show that CPP‐induced autophagy applies classical autophagic machinery including LC3 conjugation molecules Atg4, Atg5 and Atg3, and autophagosome nucleation molecules FIP200 and Beclin1; however, Atg9 is not involved. CPP does not induce mTOR inhibition, neither over‐production of radical oxygen species, and only slightly increases endoplasmic reticulum (ER) stress. CPP activates DFCP1 in a PI3k and calcium dependent manner, and increases the association of DFCP1 with autophagosomes. ER membrane, but not Golgi and mitochondria membranes, comprises part of the LC3 positive autophagsomes. These data suggests CPP works through non‐mTOR dependent mechanisms to activate downstream classical autophagosome nucleation and expansion molecules, and the growth of autophagosomes induced by CPP is closely related to ER.

Governance implications of nanomaterials companies’ inconsistent risk perceptions and safety practices

Current research on the nanotechnology industry indicates its downstream expansion at a rapid pace, while toxicological research and best practices for environmental health and safety are still being developed. Companies that use and/or produce engineered nanomaterials (ENMs) have enormous potential to influence safe-handling practices for ENMs across the product life cycle. Knowledge of both industry practices and leaders’ perceptions of risk is vital for understanding how companies will act to control potential environmental and health risks. This article reports results from a new international survey of nanomaterials companies in 14 countries. In this survey, company participants reported relatively high levels of uncertainty and/or perceived risk with regard to ENMs. However, these perspectives were not accompanied by expected risk-avoidant practices or preferences for regulatory oversight. A majority of companies indicated “lack of information” as a significant impediment to implementing nano-specific safety practices, but they also reported practices that were inconsistent with widely available guidance. Additionally, in the absence of safe-handling regulations, companies reported nano-specific health and safety programs that were narrow in scope. Taken together, these findings indicate that health and safety guidance is not reaching industry. While industry leaders’ reluctance toward regulation might be expected, their own reported unsafe practices and recognition of possible risks suggest a more top-down approach from regulators is needed to protect workers and the environment.

Range expansion dynamics of the invasive round goby (Neogobius melanostomus) in a river system

The rates of upstream and downstream range expansion of the round goby (Neogobius melanostomus) were examined in the Trent-Severn Waterway in 2009 and 2010. Relative abundance, demographics, and habitat use were also compared between areas of range expansion and a longer established area to determine how these characteristics varied along the invasion pathway. Round gobies were sampled using an angling removal method in May and August of 2009 and 2010 at 75 sites at each area of range expansion and 25 sites near the center of their range where they first became established in the waterway. Areas of range expansion had initially low abundance and low site occupancy in May 2009 relative to the longer established area. Large increases in abundance and site occupancy were observed over the first summer of occupation, but with limited range expansion. Rapid range expansion was observed during the non-reproductive season at the upstream edge of range. Individuals sampled in the expanded upstream range were small and female biased relative to other range locations. Round gobies also exhibited higher habitat selectivity for rocky substrates at range edges than in the longer established area. These characteristics of seasonal dispersal, biased demographics of dispersers, and high habitat selectivity may be important components of successful range expansion of the round goby in invaded ecosystems.

Network evolution and the embedding of complex technical solutions: The case of the Leaf House network

The purpose of this paper is to investigate the connection between network evolution and technology embedding. To this end, we performed an exploratory case study of the network surrounding an eco-sustainable technology, Leaf House, Italy's first zero-carbon emission house. We apply theories on technological development within industrial networks, with a specific focus on their resource layer and on the three settings involved in embedding an innovation: “developing”, “producing”, and “using”. Our results contribute to these theories by developing four propositions on the connections between network evolution and embedding: first, technology embedding entails both downstream network expansion and upstream restrictions. Secondly, conflicts among actors increase as technology embedding approaches the producing and using settings. Third and fourth, the more the shapes a technology can assume, and the more each of these shapes involves actors acting in different settings, the easier it is to embed it. The paper concludes with managerial implications and suggestions for further research.

Dispersal and coexistence of two non-native crayfish species (Pacifastacus leniusculusandProcambarus clarkii) in NE Portugal over a 10-year period

Key-words: Pacifastacus leniusculus, Procambarus clarkii, dispersal rate, crayfish coexistence NE Portugal is one of the most isolated and low populated regions of Western Europe. Recently, two American crayfish species reached this area: signal crayfish Pacifastacus leniusculus coming from Spain and red swamp crayfish Procambarus clarkii in its northward expansion. The dispersion of both species was followed throughout the last decade in river Macas (Douro catchment). Our results support the hypothesis of faster downstream colonisation. The mean spread rate of signal crayfish was faster for the downstream expansion, 2.8 km·yr −1 , while the upstream rate was 1.7 km·yr −1 . Exceptionally, in one period, the rate of spread reached 6.7 km·yr −1 , which was apparently caused by downstream washing in extreme conditions of flow. The mean rate of spread is higher than the observed in other studies which may also be related to the low current velocity of late spring and summer that provides favourable conditions for a fast upstream colonisation. Coexistence of signal and red swamp crayfish was detected in a large river sector. Signal crayfish strongly dominates in the upper and intermediate sectors which are the colder part of the river and in the lower sectors, species abundances are not significantly different. Winter temperature in the higher altitude reaches seems to moderate the competitive abilities of P. clarkii.

Waves and spatially localized structures in the turbulent flows of a viscous fluid: Calculation results

A direct numerical simulation was performed of intermittent and turbulent flows of viscous incompressible fluid in an infinite circular pipe. The Navier-Stokes equations were integrated at the Reynolds numbers of 1800 ≤ Re ≤ 4000 calculated from the mean velocity and a pipe diameter of D = 2R. The numerically obtained solutions belong to the class of mean streamwise periodic solutions with a very large period λmax = 16πR. The Fourier harmonic components of the velocity fluctuations corresponding to very low longitudinal wavenumbers are shown to be the most energetic. A detailed study was carried out of the structures of the calculated turbulent and intermittent flows. The accuracy and the very possibility of the approximation of the turbulent velocity field by the superposition of traveling and standing waves are analyzed. It is shown that the parameters of such a representation (wave amplitudes, phase velocities, and the position of the wave front) are strongly dependent on whether or not very low longitudinal wavenumbers are included in the mathematical model of the flow The numerical solutions at Re = 2200 and 2350 describe the intermittent type of the flow, for which the localized turbulent structures (turbulent puffs) propagate downstream while retaining their spatial dimensions. The space-time structure of the calculated turbulent puffs is compared with the available experimental data. The main statistical characteristics of the turbulence inside and outside the turbulent puff are calculated and the convective rate of the puffs downstream expansion is determined.

Favorable fragmentation: river reservoirs can impede downstream expansion of riparian weeds

River valleys represent biologically rich corridors characterized by natural disturbances that create moist and barren sites suitable for colonization by native riparian plants, and also by weeds. Dams and reservoirs interrupt the longitudinal corridors and we hypothesized that this could restrict downstream weed expansion. To consider this "reservoir impediment" hypothesis we assessed the occurrences and abundances of weeds along a 315-km river valley corridor that commenced with an unimpounded reach of the Snake River and extended through Brownlee, Oxbow, and Hells Canyon reservoirs and dams, and downstream along the Snake River. Sampling along 206 belt transects with 3610 quadrats revealed 16 noxious and four invasive weed species. Ten weeds were upland plants, with Canada thistle (Cirsium arvense) restricted to the upstream reaches, where field morning glory (Convolvulus arvensis) was also more common. In contrast, St. John's wort (Hypericum perforatum) was more abundant below the dams, and medusahead wildrye (Taeniatherum caput-medusae) occurred primarily along the reservoirs. All seven riparian species were abundant in the upstream zones but sparse or absent below the dams. This pattern was observed for the facultative riparian species, poison hemlock (Conium maculatum) and perennial pepperweed (Lepidium latifolium), the obligate riparian, yellow nut sedge (Cyperus esculentus), the invasive perennial, reed canary grass (Phalaris arundinacea), and three invasive riparian trees, Russian olive (Elaeagnus angustifolia), false indigo (Amorpha fruticosa), and tamarisk (Tamarix spp.). The hydrophyte purple loosestrife (Lythrum salicaria) was also restricted to the upstream zone. These longitudinal patterns indicate that the reservoirs have impeded the downstream expansion of riparian weeds, and this may especially result from the repetitive draw-down and refilling of Brownlee Reservoir that imposes a lethal combination of drought and flood stress. The dams and reservoirs may also interrupt hydrochory, the downstream flow of seeds and clonal fragments. We thus conclude that with some operational patterns, dams and reservoirs can impede the downstream expansion of riparian weeds.

Diet composition and consumption rate in round goby (Neogobius melanostomus) in its expansion phase in the Trent River, Ontario

We assessed density, gut fullness and prey composition of round goby (Neogobius melanostomus) from three areas in the Trent River (Ontario) representing areas of initial introduction and subsequent expansion. Round goby had been present at the area of original introduction since 2003, and by 2007/2008, their range had expanded upstream and downstream into the outermost reaches sampled in the study. Catch per unit angling effort in nearshore sites indicated that round goby density in the area of original introduction was more than double their density in the upstream expansion area and nearly three times the density in the downstream expansion area. Gut fullness index was lower in gobies from the area of original introduction than for those at the upstream and downstream edges of their expanded range. The most dramatic difference in diet composition was with dreissenids, where large gobies (≥70 mm) occupying the area of original introduction had almost no dreissenid biomass in their guts, whereas dreissenids were the predominant prey type in gobies occupying the two expansion areas. Post-hoc zebra mussel density in the area of original introduction was an order of magnitude lower than in the two expansion areas which, combined with the differences in stomach fullness and prey composition, suggest that local, density-related reduction of this prey type was occurring in the river.

Rituximab plus Peg-interferon-α/ribavirin compared with Peg-interferon-α/ribavirin in hepatitis C–related mixed cryoglobulinemia

AbstractTreatment of hepatitis C (HCV)–mixed cryoglobulinemia (MC) may target either the viral trigger (HCV) or the downstream B-cell clonal expansion. Prospective cohort study of 38 HCV-MC patients who received a combination of rituximab (375 mg/m2) once a week for 1 month followed by Peg-interferon-α (Peg-IFN-α; 2a, 180 µg or 2b, 1.5 µg/kg) weekly plus ribavirin (600-1200 mg) daily for 48 weeks were compared with 55 HCV-MC patients treated by Peg-IFN-α/ribavirin with the same modalities. In the whole population of HCV-MC patients (n = 93), a complete clinical response was achieved in 73.1% (68 of 93), cryoglobulin clearance in 52.7% (49 of 93), and a sustained virologic response in 59.1% (55 of 93). Compared with Peg-IFN-α/ribavirin, rituximab plus Peg-IFN-α/ribavirin–treated patients had a shorter time to clinical remission (5.4 ± 4 vs 8.4 ± 4.7 months, P = .004), better renal response rates (80.9% vs 40% of complete response, P = .040), and higher rates of cryoglobulin clearance (68.4% vs 43.6%, P = .001) and clonal VH1-69+ B-cell suppression (P < .01). Treatment was well tolerated with 11% of discontinuation resulting from antiviral therapy and no worsening of HCV RNA under rituximab. Our findings indicate that rituximab combined with Peg-IFN-α/ribavirin is well tolerated and more effective than Peg-IFN-α/ribavirin in HCV-MC.