Downstream Position Research Articles

Response of the temporal turbulent boundary layer to decaying free-stream turbulence

The turbulent boundary layer developing under a turbulence-laden free stream is numerically investigated using the temporal boundary layer framework. This study focuses on the interaction between the fully turbulent boundary layer and decaying free-stream turbulence. Previous experiments and simulations of this physical problem have considered a spatially evolving boundary layer beset by free-stream turbulence. The state of the boundary layer at any given downstream position in fact reflects the accumulated history of the co-evolution of boundary layer and free-stream turbulence. The central aim of the present work is to isolate the effect of local free-stream disturbances existing at the same time as the ‘downstream’ boundary layer. The temporal framework used here helps expose when and how disturbances directly above the boundary layer actively impart change upon it. The bulk of our simulations were completed by seeding the free stream above boundary layers that were ‘pre-grown’ to a desired thickness with homogeneous isotropic turbulence from a precursor simulation. Moreover, this strategy allowed us to test various combinations of the turbulence intensity and large-eddy length scale of the free-stream turbulence with respect to the corresponding scales of the boundary layer. The relative large-eddy turnover time scale between the free-stream turbulence and the boundary layer emerges as an important parameter in predicting if the free-stream turbulence and boundary layer interaction will be ‘strong’ or ‘weak’ before the free-stream turbulence eventually fades to a negligible level. If the large-eddy turnover time scale of the free-stream turbulence is much smaller than that of the boundary layer, the interaction will be ‘weak’, as the free-stream disturbances will markedly decay before the boundary layer is able be altered significantly as a result of the free-stream disturbances. For a ‘strong’ interaction, the injected free-stream turbulence causes increased spreading of the boundary layer away from the wall, permitting large incursions of free-stream fluid deep within it.

Glutamine Transporter as a Target of mTOR Signaling Modulating Longevity

Mice that express reduced levels of the c‐Myc gene (Myc+/− heterozygotes) are long‐lived. Myc hypomorphic mice display reduced rates of protein translation and decreased activity of the mammalian target of rapamycin (mTOR) complex 1 (mTORC1). Given the prominent effect of mTOR on aging, lower mTORC1 activity could contribute to the exceptional longevity and enhanced healthspan of Myc+/− animals. However, given the downstream position of MYC in these signaling cascades, the mechanism through which mTORC1 activity is downregulated in Myc+/− mice is not understood. We have found that the high‐affinity glutamine transporter SLC1A5, which is critical for activation of mTORC1 activity by amino acids, is a transcriptional target of MYC. Myc+/− cells display decreased Slc1a5 gene expression that leads to lower glutamine uptake and consequently reduced mTORC1 activity. Decreased mTORC1 activity in turn mediates an elevation of fatty acid oxidation (FAO) by indirectly upregulating the expression of carnitine palmitoyltransferase 1a (Cpt1a) that mediates the rate‐limiting step of β‐oxidation. Increased FAO has been noted in a number of long‐lived mouse models. Taken together, our results show that transcriptional feedback loops regulated by MYC modulate upstream signaling pathways such as mTOR and impact FAO on an organismal level.Support or Funding InformationSupported by NIH grant R37 AG016694 to J.M.S.

Jet disintegration in supercritical environments

A N2 jet was injected into quiescent ambient N2. The jet temperature was measured by four T-type thermocouples: one inside the injector and three at downstream positions (0.9d, 10.6d, and 28.1d, respectively; here, d is the inner diameter of the jet). The density was also measured downstream to 15d using two-dimensional Raman scattering with a pulse stretcher. Normally, our observations were consistent with expectations according to classical mixing theory; however, within a certain injection temperature range, there was no constant density region inside the jet core, and the jet temperature was measured to decrease. To explain this behavior of the jet, we considered three effects: classical mixing, thermal disintegration, and relaxation from high to low pressures. The absence of jet potential core can be explained by both thermal disintegration and relaxation, while the decrease of the temperature could be explained only by relaxation.

Japanese Tools & Techniques of Production Management

The research script links through the implementation of measuring lean manufacturing and its efficiency in Japanese vehicle business. Case study is done on Japanese vehicle business on the execution of lean manufacturing concerning the Japanese method to the Supply Chain organization method to furnish. Kaizen system generates surroundings and directorial customs which encourage the labour force to obtain improved organization’s goods and inner process, also in the phase of affluence missing any external danger. The KANBAN structure is a manufacture as well as record control system in which the downstream position obtains sufficient mechanism as compulsory and the upstream place make just sufficient to all-inclusive what has been used. Theory of Transaction Cost (TCT) has arriving fresh awareness meant for it’s utilize in building choice designed for the speculation within inter-firm’s associations.

The Influence of Alliance Ambidexterity on Innovation Performance and the Moderating Role of Firm Age

It has been argued that ambidexterity can be achieved by establishing strategic alliances with partners that occupy a downstream or upstream position in the innovation value chain (i.e., alliance ambidexterity), hence reconciling the tensions between exploration and exploitation. However, empirical tests confirming that this partnering strategy improves innovation performance are still scant. Therefore, in this paper, we aim at covering this gap by empirically analyzing the relationship between alliance ambidexterity and innovation performance. Furthermore, since firm age affects firms' commitment toward explorative and exploitative activities, we also examine the moderating effect of firm age on the abovementioned relationship. Results are based on a sample of 1017 biotechnology companies that have established, at least, one strategic alliance over the period 1982-2011. In detail, using a random-effects negative binomial regression, we find that alliance ambidexterity positively influences innovation performance, and firm age exerts a negative moderating effect.

Downstream Compensator: Innovative Systems, Modeling Analysis and Energy Optimization

The Energy optimization is becoming fundamental in the Fluid Power world. University and industries are working hard to promote innovative and efficient ideas to optimize components that are the main cause of energy dissipation of ICE and recently Electric Off-Road vehicles. A new hydraulic layout based on the concept of “Downstream compensation” is introduced and then validated using real test data. Three architectures of this innovative Directional Control Valve are presented in this paper. The first idea of layout includes a compensator controlled by two pressure signals taken before and after the main spool of the hydraulic circuit. Thanks to its controlled stroke, this compensator diverts to a highpressure accumulator part of flow that otherwise would be delivered to the tank. Moreover, two different layouts able to satisfy the Flow Sharing characteristic were developed. In any configuration, the compensator, thanks to its downstream position, allows to control the return flow, realizing a remarkable energy recovery from the overrunning loads and the simultaneous use of multiple actuators at different pressure levels.For all the analyzed hydraulic circuit, lumped parameter models were realized, using a commercial software. These models, validated with experimental tests, have allowed to calculate the energy recovery achieved by the system. Moreover, an optimization of the most important system’s parameters and components were realized to improve the system efficiency. In every tested configuration, this compensator ensures great advantages for both the energy recovery and the economic point of view. Finally, an outlook is drawn of the reuse of recovered flow through the application of an electrohydraulic motor.

Study on the Rotordynamic Performance of a Novel Anti-stagnation Labyrinth Seal

A novel structure of anti-stagnation labyrinth seal was proposed in this paper. An opposed jet suppressing the circumferential flow was generated in seal cavities with pressure-driven micro-nozzles on adjacent seal teeth. The theoretical identification approach for rotordynamic coefficients based on the infinitesimal theory was applied to predict rotordynamic coefficients of annular gas seals. The effects of the layout of anti-stagnation nozzles, inlet pressure and rotational speed on rotordynamic characteristics were investigated using a computational fluid dynamics (CFD) method. Compared with that of the traditional labyrinth seal, the new seal possesses better stability with a 200% increase in the effective damping coefficients at high whirling frequency. Compared with those in the middle and downstream position, nozzles installed in the upstream of the seal can effectively improve the dynamic stability of the system. The anti-stagnation labyrinth seal shows better stability performance for higher inlet pressure and rotational speed. The leakage flow rate of the anti-stagnation labyrinth seal is slightly higher (an increase of less than 4%) than that of the original labyrinth seal.

Subnational Hydropolitics: Conflict, Cooperation, and Institution-Building in Shared River Basins. By Moore, Scott M. 2018. New York: Oxford University Press.

<i>Subnational Hydropolitics: Conflict, Cooperation, and Institution-Building in Shared River Basins</i>. By Moore, Scott M. 2018. New York: Oxford University Press.

The Global Production Chain Embedding and Chinese Firms’ Outward Foreign Direct Investment

In the last few years, one of the fundamental changes in international trade is the emergence of global value chains（GVCs）, and the increasingly fragmentation of production. Under this background, Chinese firms’ going global” for foreign direct investment（FDI）might mean going global” for embedding GVCs. However, few researches investigate firms’ FDI behaviors from the perspective of GVCs, especially from the impact of embedding in GVCs on FDI decision-making and location choice.This paper uses industrial enterprise data compiled by China’s National Bureau of Statistics, import and export trade data collected by China’s General Administration of Customs, FDI data from Ministry of Commerce and WIOD data. We calculate upstreamness initiated by Antras, et al.（2012）and Chor, et al.（2014）, which measures the position of Chinese manufacturing firms in GVCs. We also examine how this position determines the decision of outward foreign direct investment（OFDI）. We find that firms at both ends of GVCs are more likely to invest overseas. That is to say, firms with upstream import embedding position and downstream export embedding position are more likely to invest abroad. These results are robust when using alternative measures, considering the endogeneity and the rare event issues. Furthermore, we also find that firms’ different investment motivations and regional choices are followed in light of firms’ GVC position.This paper contributes to the existing literature in two aspects: First, we take a further step to investigate Chinese firms’ going out” reasons from a new perspective such as GVCs; Second, different from the existing researches focusing on calculating the added-value of exports at the national or industry level, this paper measures the embedding position of global production chains at the firm level. It empirically analyzes the different characteristics of firms with different production chain embedding locations in their OFDI, and further discusses the impact of trade-based specialization in GVCs on global production networks such as OFDI motivations and OFDI location selections, based on the heterogeneity of OFDI.Our research, to a certain extent, reveals the inherent logic of Chinese firms participating in global trade and global production networks, helps the government make more targeted going out” policies under the B&R” initiative, provides differentiated policy support to firms with different GVC divisions when going out”, and gives better guidance to firms on FDI.

Performance enhancement of wind energy harvester utilizing wake flow induced by double upstream flat-plates

Small-scale wind energy harvesting system is being considered to provide green long-term electric power to unattended sensor network nodes which are widely used in urban and natural environments. This paper proposes that placing a double-plate structure upstream of the bluff body in the wind energy harvesting system can significantly improve the output performance. At a certain wind speed, two wake flow zones with low-pressure are formed behind two upstream side-by-side plates, which induced the bluff body at the downstream intermediate position to deviate to both sides. Even at a low wind speed, the vibration of bluff body can still occur because the pressure fluctuation of the wake zone disturb the static equilibrium. Placing the double plates upstream of a wind energy harvester with a cylinder can change the vibration response from VIV (vortex-induced vibration) to galloping. Moreover, when the ratios of the horizontal and vertical distances to the windward width of the cylinder are 1 and 0.5, respectively, the cut-in wind speed is as low as 1.5 m/s. For the galloping-based wind energy harvester with a square prism, after the double plates are placed upstream, the cut-in wind speed decreases from 3.5 m/s to 1 m/s and the output voltage increases from 1 V to 12 V at 1.5 m/s. The increase of voltage caused by the addition of double plates to the upstream of six different bluff bodies indicates the good adaptability of this structure. The higher voltage output capability by this method at low wind speed significantly expands the application scope of wind energy harvesters.

Defining Protein Pattern Differences Among Molecular Subtypes of Diffuse Gliomas Using Mass Spectrometry*[S

Molecular characterization of diffuse gliomas has thus far largely focused on genomic and transcriptomic interrogations. Here, we utilized mass spectrometry and overlay protein-level information onto genomically defined cohorts of diffuse gliomas to improve our downstream molecular understanding of these lethal malignancies. Bulk and macrodissected tissues were utilized to quantitate 5,496 unique proteins over three glioma cohorts subclassified largely based on their IDH and 1p19q codeletion status (IDH wild type (IDHwt), n = 7; IDH mutated (IDHmt), 1p19q non-codeleted, n = 7; IDH mutated, 1p19q-codeleted, n = 10). Clustering analysis highlighted proteome and systems-level pathway differences in gliomas according to IDH and 1p19q-codeletion status, including 287 differentially abundant proteins in macrodissection-enriched tumor specimens. IDHwt tumors were enriched for proteins involved in invasiveness and epithelial to mesenchymal transition (EMT), while IDHmt gliomas had increased abundances of proteins involved in mRNA splicing. Finally, these abundance changes were compared with IDH-matched GBM stem-like cells (GSCs) to better pinpoint protein patterns enriched in putative cellular drivers of gliomas. Using this integrative approach, we outline specific proteins involved in chloride transport (e.g. chloride intracellular channel 1, CLIC1) and EMT (e.g. procollagen-lysine, 2-oxoglutarate 5-dioxygenase 3, PLOD3, and serpin peptidase inhibitor clade H member 1, SERPINH1) that showed concordant IDH-status-dependent abundance differences in both primary tissue and purified GSC cultures. Given the downstream position proteins occupy in driving biology and phenotype, understanding the proteomic patterns operational in distinct glioma subtypes could help propose more specific, personalized, and effective targets for the management of patients with these aggressive malignancies.

$\boldsymbol{E}\times\boldsymbol{B}$ Drift of Electrons in a Radial Electric Field and Longitudinal Magnetic Field

To examine the effect of the radial electric field on the electron rotational motion under ${E}\times {B}$ field, particularly $E_{r} \times B_{z}$ geometry, for a plasma with magnetized electrons and nonmagnetized ions flowing through a uniform magnetic channel, an experimental study is conducted by applying a steady-state plasma flow along the uniform longitudinal magnetic field $B_{z}$ . The argon plasma flow is generated by atmospheric-pressure dc arc discharge, followed by a continuous expansion into a rarefied gas-wind tunnel with a uniform magnetic field 0.15 T. Inside one of the magnets which is situated at rather a downstream position, a ring electrode is set to apply the radial electric field $E_{r}$ . An up–down probe is employed for the analysis of the electron azimuthal rotational motion. The value of the radial electric field applied in the plasma is about ~150 V/m. The probe measurement indicates the ${E}\times {B}$ rotation of electrons, particularly when the radially inward electric field is externally applied, whose order is about ~1000 m/s. The inward electric field results in the electron rotational motion in the same direction as the diamagnetic current. On the other hand, when the outward electric field is applied, the electron rotational motion is not observed. The order of the observed electron drift velocity is consistent with the theoretical value. ${E}\times {B}$ rotation velocity is found to be almost equal to that by the electron diamagnetic current. Even without the external electric field, the observed electron saturation current indicates that there is a rotational motion of electrons, which is considered to be due to the electron diamagnetic current.

Numerical investigation on buoyancy and inclination effects on transient mixed convection in a channel with discretely heated plane symmetric contraction-expansions

In this work, transient mixed convection in a channel with discretely heated plane symmetric contraction-expansions at the mid-channel section emulating electronic components is studied numerically. The facing walls of the obstructions are isothermal, the other bounding walls of the constriction and the channel have non-adiabatic walls. The impact of changes in the cross section and their corresponding sensitivity to duct orientation on the overall flow and thermal evolution in space and time is analysed for fixed Prandtl number of Pr=7, Reynolds number in the range 100 ≤Re≤ 1000, channel inclination of 0∘≤Γ≤90∘, and different values of buoyancy strength (Richardson number). Results indicate that as the duct approaches the horizontal configuration, buoyancy strength reduces and higher threshold values of the Richardson number are required to induce instability. Also, depending on the parametric set, the flow and temperature distributions can experience an oscillatory behavior associated to variations in size of a complex vortical structure that occupies the spatial region near the partial blockage and that extends to downstream positions of the latter. Numerical predictions demonstrate how the blockage height affects the wake structure and vortex dynamics, and the effects of the Prandtl number and heat losses to the channel walls on the evolution of the flow and heat transfer response are presented and discussed in detail.

Aggressive interactions affect foraging and use of space in a drift foraging salmonid, Salvelinus malma (Salmoniformes: Salmonidae)

Abstract Although intraspecific interactions likely affect habitat choice and foraging behaviour in animals, our knowledge regarding how these factors interact is frequently limited to either lab or field studies, but not both. We observed pairs of dominant and subordinate drift-foraging Dolly Varden char (Salvelinus malma) in an Alaskan stream, and quantified intraspecific interactions and foraging behaviour. Dominant individuals had higher foraging rates, occupied slower holding velocities and were displaced shorter distances during bouts compared to subordinate individuals. Individuals initiated bouts more frequently from the downstream position, than from lateral or upstream positions. Dominant individuals were more likely to occupy the upstream position after a bout than subordinates, which ensures that dominants have the first opportunity to capture drifting prey.

Large Eddy Simulation of Flow over Wavy Cylinders with Different Twisted Angles at a Subcritical Reynolds Number

The deformation of the cylinder has been proved to greatly reduce the fluctuation of lift and the vortex-induced vibration. In this article, a new form of deformation mode for the smooth cylinder is proposed in order to reduce the vortex-induced vibrations, which can be applied to marine risers and submarine pipelines to ensure the working performance and safety of offshore platforms. Large eddy simulation (LES) is adopted to simulate the turbulent flow over wavy cylinders with three different twisted angles at a subcritical Reynolds number Re = 28,712. Comparing with the results of smooth cylinder, the maximum drag and lift reduction of wavy cylinder A3 with α = 40° can reach 17% and 84%, respectively, and the corresponding vortex formation length increases significantly, while the turbulence intensity decreases relatively. Meanwhile, the circumferential minimum pressure coefficient is greater than that of the smooth cylinder, which also provides a greater drag reduction for the cylinder. The surface separation line, turbulent kinetic energy distribution, and wake vortex structure indicate that the elongation of separated shear layer and wake shedding position is larger than that of the smooth cylinder, and the vorticity value in the near wake region decreases. A periodic vortex structure is generated along the spanwise direction, and a weaker and more stable Karman vortex street is reformed at a further downstream position, which ultimately leads to the reduction of drag and fluctuating lift of the wavy cylinder.

Natural circulation two-phase flow characteristics in a rod bundle channel under stable and rolling motion conditions

Natural circulation two-phase flow characteristics are studied under stable and rolling motion conditions in a rod bundle channel. The mass quality, flow rate and frictional pressure drop variation results with increasing heat flux are given and the effects of system pressure and inlet subcooling are analyzed. The flow rate decline is observed under high mass quality conditions since the frictional pressure drop is large enough. The flow instability characteristics for different stages with increasing heat flux are given. The main reason for the flow instability characteristics variation is that the dominant factor changes from subcooled boiling to the pressure drop oscillation. The experimental results indicate that increasing the system pressure and the inlet resistance of the test section, including moving the compressible volume to a downstream position, can delay the onset of the flow instability. The time-average flow parameters under rolling motion conditions are mainly influenced by the stable mass quality and the rolling parameters. For high stable mass quality conditions, the time-average two-phase flow parameters decrease a little compared to stable results. With the stable mass quality decreasing, the time-average mass quality gradually increases with the rolling frequency. For further lower stable mass quality conditions, the time-average values are even larger than stable values. For the frictional resistance calculation, a few correlations are evaluated and recommended. Additionally, new correlations are fitted for stable and time-average two-phase frictional pressure drop prediction in high mass quality conditions.

Effect of Coriolis force on a wind farm wake

The effect of the Coriolis force on the wake of a wind farm in a conventionally neutral and a stable boundary layer is investigated using large eddy simulations. We find that the average flow angle varies with the downstream position in the wind farm. In the entrance region of the wind farm, the flow blockage and wind veer create a positive gradient of the vertical flux at hub-height, which causes a counter-clockwise flow deflection in the Northern hemisphere, when observed from above. Further downstream, the vertical entrainment of air from the upper layers of the boundary layer generates a negative gradient of the vertical flux at hub-height, which results in a clockwise flow deflection in the Northern hemisphere. The deflection is more pronounced for the stable boundary layer than for the conventionally neutral boundary layer. In addition, we find that the wake deflection has a significant impact on the power production of turbines further downstream in the wind farm.

Particle migration of concentrated suspension flow in bifurcating channels

Flow of suspension in bifurcating channels has extensive applications in industrial and natural settings. A phenomenon of particular interest during the flow of concentrated suspension is shear-induced particle migration. Previous works on suspension transport in branched channels have been limited to dilute flow conditions. We have carried out experiments using the Particle Image Velocimetry (PIV) technique to study concentrated suspension transport in asymmetric T- and symmetric Y-shape channels. Numerical simulations of fluid flow and particle transport equations were also carried out for the same geometry which was used in the experiments. The migration and transport of particles in the simulations were studied using the Diffusive Flux Model. We have observed in both experiments and numerical simulations that due to the shear-induced migration phenomena the particles move towards the center of the channel, and this gives rise to the blunting of velocity profile before the junction. After the bifurcation, the peak of velocity profile moves in the direction of the outer wall, whereas, the maxima in particle concentration was observed near the inner walls. This causes asymmetry in the velocity and concentration profiles in the daughter branches. As we move towards the downstream positions the maxima in velocity and concentration profiles again shifts toward the center of the channel. The results from the experiments and simulations are observed to be in good agreement.

Radiative edge cooling experiments in Wendelstein 7-X start-up limiter campaign

Impurity seeding experiments during the start-up limiter campaign of Wendelstein 7-X provide first evidence for a localization effect of the 3D magnetic edge structure on the seeded impurities and their radiation distribution and cooling effect. Moreover, species dependencies have been seen. Nitrogen was observed to cool the entire edge plasma, with a stronger electron temperature reduction measured at the downstream position at the limiter. The radiation was limited at the periphery of the confined region. Both the temperature reduction and the radiation enhancement were directly correlated to the injection of the coolant gas. Mitigation of the limiter heat loads was also measured. Neon was observed to affect also the confined plasma with a long-lasting radiation and a cooling of the entire plasma.

Influence on film cooling effectiveness of novel holes based on cylindrical configurations

In this study, four novel film cooling hole designs, all based on cylindrical holes, are numerically evaluated, and compared with those of a simple cylindrical hole and a laterally-diffused shaped hole. Film cooling effectiveness and surrounding thermal and flow fields are documented for operation with various blowing ratios. It is shown that the two-stage cylindrical hole can improve film cooling effectiveness at higher blowing ratios. The primary hole with two secondary holes can enhance film cooling performance by creating anti-kidney vortex pairs that will weaken jet liftoff caused by the kidney vortex pair that is created by the primary hole. The tri-circular shaped hole provides better film cooling effectiveness values only near the hole, but worse at downstream positions. The two-stage structure for the tri-circular shaped hole provides better film coverage because it changes the flow structure inside the delivery channel and decreases jet penetration into the passage flow.