Lateral Ejection Research Articles

Computation of aluminum droplet ejection and flight in microgravity

Persistent and frequent space explorations are limited by real-time parts supply and it is significant to achieve space manufacture, such as the droplet-based printing. In order to study the microgravity environment effect on droplet-based printing, this paper proposed an effective method to research the effect of space station environmental g-jitter (according to NASA experimental signal) on droplet ejection and flight process. The heat transfer, transient gravity acceleration and Marangoni effect are studied based on the improved model. The results show that the g-jitter is in the order of 10−3 magnitude and the effect on aluminum droplet ejection could be ignored when nozzle diameter (dn) is smaller than 0.1 mm and so do ground case. Combined with the ground microgravity simulation of SnPb alloy lateral ejection experiments, it can be obtained that the ejected single droplet is characterized by capillary number (Ca≤0.002), the droplet flight trajectory is dependent on the Froude number (Fr) and the laminar-turbulence transition exists during the droplet flight process. The relationship formulation between the deviation along gravity direction and the deposition distance is introduced to control and adjust the droplet flight trajectory. Moreover, the temperature effect on material property, such as surface tension and so on, has effect on the droplet breakup length. The g-jitter field enhances the Marangoni effect resulting in the deviation of droplet trajectory. In microgravity field, the computational droplet oscillation period is well coincidence with theoretical equation. Improved KIC-SST based model is available for simulating droplet-based printing in microgravity.

Dynamic mechanism of three-dimensional mixed-size grain/bed collision on non-flat bed using discrete element method

The impact of particles on slope bed is not only one of the main processes of eolian saltation, but also lead to the sand surface damage and provide sufficient materials for the sediment supply process in desert rivers. In order to reveal the mechanism of excessive sediment supply in desert rivers, it is necessary to study the grain-bed impact process, which plays an important role on the wind erosion. In this study, based on the discrete element method (DEM) and previous researches, a three-dimensional numerical simulation is carried out to study the influence of the incident angle, incident angle, and lateral incident angle on grain-bed collision under different bed surfaces. Finally, by fitting the simulation data, we give the three-dimensional splash function of ejection velocity, ejection angle, and lateral ejection angle as well as lateral ejection velocity with the change of impact velocity, impact angle, and lateral impact angle on different bed surface. This study will enhance our understanding of the processes of eolian sand movement and will provide useful information about the mechanisms that drive sediment replenishment to desert rivers.

The influence of lateral ejection on the thermal performance of matrix cooling channel

Matrix is applied as an internal cooling scheme for gas turbine blades or vanes. This paper focuses on the Influence of lateral ejection on the cooling performance of matrix channel. The purpose is to improve the internal heat transfer and thermal performance of matrix channel with proper configurations of ejection holes. A validated computational method is used to obtain flow and heat transfer results of a typical matrix channel. The influence of location, dimension and outflow orientation of the ejection holes are discussed in detail. A channel with the absence of straight flow exit is also included for comparison. The result implies that the location of ejection is the most important factor that influences the cooling performance, holes in the downstream part of sidewall turning are better than those in the upstream part. More improvement can be achieved with smaller holes and positive outflow orientation. The blockage of the straight flow exit must be avoided because heat transfer deteriorates due to uneven distribution of coolant mass flow. The effect of reduction of internal coolant mass flow can be compensated by the increased turbulence with well-designed lateral ejection.

Experimental research in rotating wedge-shaped cooling channel with multiple non-equant holes lateral inlet

The heat transfer in a novel smooth wedge-shaped cooling channel with lateral ejection of turbine blade trailing edge is experimentally investigated in both non-rotating and rotating cases. Beside the conventional inlet at the bottom of the channel, an extra coolant injection from 8 lateral non-equant holes is introduced to improve the overall heat transfer. The total mass flow rate ratio (lateral mass flow rate/total mass flow rate) varies from 0 to 1.0. The major inlet Reynolds number and rotation number respectively vary from 10000 to 20000 and from 0 to 1.16. Experimental results show that the lateral inlet decreases local bulk temperature and increases local heat transfer at the middle and the top of the static channel. In rotating cases, the lateral inlet notably improves the heat transfer at the high-radius half channel and compensates the negative effects induced by the rotation. Both intensity and uniformity of heat transfer inside the channel are enhanced while flow resistance decreases with proper mass flow rate ratio of coolant from two inlets. The most satisfactory total mass flow rate ratio is around 2/3. This new structural style of cooling channel has huge potential and provides new direction of heat transfer of turbine blade trailing edge.

Mechanics of Collapse of WTC Towers Clarified by Recent Column Buckling Tests of Korol and Sivakumaran

The previously formulated model of the gravity-driven collapse of the twin towers of the World Trade Center (WTC) on September 11, 2011 was shown to match all the existing observations, including the video record of the crush-down motion of the top part of tower during the first few seconds, the seismically recorded duration of collapse, the size distribution of particles caused by impact comminution of concrete floor slabs, the loud booms due to near-sonic lateral ejection velocity of air and dust, and precedence of the crush-down collapse mode before the crush-up. Nevertheless, different degrees of ductility, fracturing and end support flexibility of WTC columns could lead to an equally good match of these observations and remained uncertain, due to lack of test data. Recently, Korol and Sivakumaran reported valuable experiments that allow clarifying this uncertainty. They revealed that, under the simplifying assumptions of rigid end supports and unlimited ductility (or no fracturing) of unheated columns, the energy dissipation of the WTC columns would have been at maximum 3.5-times as large as that calculated by the plastic hinge mechanism normally considered for small-deflection buckling. This increase would still allow close match of all the aforementioned observations except for the first two seconds of the video. The proper conclusion from Korol and Sivakumaran’s tests, based on close matching of the video record, is that the fracturing of unheated columns and the flexibility of their end restraints must have significantly reduced the energy dissipation in columns calculated under the assumptions of no fracture and no end restraint flexibility.

Exploration of splash function and lateral velocity based on three-dimensional mixed-size grain/bed collision

Based on the discrete element method, the three dimensional mixed-size grain/bed collision process has been investigated in this paper. By considering the influence of lateral impact angle on the mean ejection velocity and ejection number, we obtain that the mean lateral ejection velocity increases with the lateral impact angle at large mean diameter cases and also increases with the impact velocity, while decreases with impact angle. The simulation results indicate that although the lateral impact affects the mean ejection velocity, its effect on the mean ejection number is very limited. Moreover, the mean lateral ejection velocity is influenced by the impact angular velocity. Based on these studies, a more comprehensive three dimensional mixed-size splash function is given. It is of great significance to the particle motion based on turbulence in aeolian sand landform.

Comparative proximal features of the main Plinian deposits (Campanian Ignimbrite and Pomici di Base) of Campi Flegrei and Vesuvius

The proximal Plinian fall deposits of the Campanian Ignimbrite (CI; 38ky, Fedele et al., 2008) and Pomici di Base (PdB; 18ky, Bertagnini et al., 1998) have been investigated in order to understand the contribution of each part of the plume to the proximal sedimentation. Following Houghton et al. (2004b) we consider three main transport regimes: jet phase (producing facies Fb), buoyant region of the plume (producing facies Fa) and direct lateral ejection (producing facies Fc).As well documented in medial locations (Sparks et al., 1992, 1997; Ernst et al., 1996), transport regimes can develop different facies even in proximal locations according to the dynamics of the eruptive column. Our proximal deposits show stratification and diffuse bedding allowing us to introduce two new facies: stratified Fa (sFa) and diffuse bedded Fb (dbFb). These facies retain the transport regime previously proposed for Fa (buoyant plume) and Fb (jet phase) but their lithological features are influenced by near-vent depositional conditions.Lithology and sedimentological data (grain-size, componentry, maximum clasts) suggest that most of the sedimentation occurred mainly from the buoyant plume with simultaneous contribution from the other two different dynamic regimes. Coarse clasts falling from the lower margins of the plume strongly affected the sedimentation of the CI proximal fall deposit with a minor contribution from lithic clasts ballistically emplaced and partial collapses of the plume forming pyroclastic density currents. In contrast, the PdB proximal fall deposit was strongly affected by coarse clasts emplaced directly from the vent through parabolic trajectories, with very little contribution of material emplaced from the lower part of the plume. These differences can be attributed to different vent/conduit processes acting during the eruptions.

Numerical and experimental study of mechanisms responsible for turbulent secondary flows in boundary layer flows over spanwise heterogeneous roughness

We study the dynamics of turbulent boundary layer flow over a heterogeneous topography composed of roughness patches exhibiting relatively high and low correlation in the streamwise and spanwise directions, respectively (i.e. the roughness appears as streamwise-aligned ‘strips’). It has been reported that such roughness induces a spanwise-wall normal mean secondary flow in the form of mean streamwise vorticity associated with counter-rotating boundary-layer-scale circulations. Here, we demonstrate that this mean secondary flow is Prandtl’s secondary flow of the second kind, both driven and sustained by spatial gradients in the Reynolds-stress components, which cause a subsequent imbalance between production and dissipation of turbulent kinetic energy that necessitates secondary advective velocities. In reaching this conclusion, we study (i) secondary circulations due to spatial gradients of turbulent kinetic energy, and (ii) the production budgets of mean streamwise vorticity by gradients of the Reynolds stresses. We attribute the secondary flow phenomena to extreme peaks of surface stress on the relatively high-roughness regions and associated elevated turbulence production in the fluid immediately above. An optimized state is attained by entrainment of fluid exhibiting the lowest turbulent stresses – from above – and subsequent lateral ejection in order to preserve conservation of mass.

Optimization of ejection angles of double-jet film-cooling holes using RBNN model

The effects of the ejection and lateral ejection angles of double-jet film-cooling holes on the film-cooling effectiveness was evaluated, and the shape of the double-jet film-cooling holes was optimized using three-dimensional Reynolds-averaged Navier–Stokes equations with a shear stress transport turbulence model and a radial basis neural network surrogate model. The numerical results for the film-cooling effectiveness were validated by a comparison with experimental data. To optimize the double jet film-cooling holes, the spatially-averaged, film-cooling effectiveness was considered as the objective function. Latin hypercube sampling was performed to determine the design points in the design space. A radial basis neural network model was constructed using the objective function values calculated at the design points. The optimal point was obtained from the constructed surrogate using sequential quadratic programming. The cooling performance of the double-jet film-cooling holes was improved considerably by optimization compared to the reference geometry. The constructed surrogate model was found to be sufficiently reliable.

Clinical efficacy of Gossypium herbaceum L. seeds in perceived insufficient milk (PIM) supply: A randomized single-blind placebo-controlled study

To evaluate the efficacy of Gossypium herbaceum L. in perceived insufficient milk (PIM) supply. In this single-blind, placebo-controlled, randomized clinical trial, test group (n = 30), received kernel of Gossypium herbaceum, 10 g (powder filled in the capsules) orally in three divided doses for 1 month, whereas the placebo group (n = 15), received wheat flour. The primary outcome measures were reduction in volume of supplementary feeds, and weight gain of the baby. The secondary outcome measures were improvement in subjective satisfaction of the mothers regarding the well being and happiness of babies, feeling fullness in the breast, contra lateral ejection of the milk, and mother’s observation in increase of breast milk. These parameters were rated on a graded scale ranging from 1 to 5 (1 denoting unsatisfactory and 5 representing highly satisfactory). The data was analyzed by using Student’s t test, Chi-square or Fisher exact test to find the significance (P < 0.05) of the study parameters. In the test group, 21(70 %), 7(23.33 %) and 2(6.67 %) mothers had complete relactation, partial relactation and no response correspondingly, whereas in the control group 4(26.67 %) mothers had complete relactation, and 11(73.33 %) mothers had no response. The volume of supplementary feeds to the infant in the test group was significantly reduced to 40 ± 75.88 ml after treatment from the baseline of the test group (291.66 ± 70.50 ml; P < 0.001) and placebo (226.66 ± 149.84 ml; P < 0.008). The secondary outcome measures of the test group were significant statistically. This herb is efficacious, safe and cost effective in augmenting lactation in PIM supply.

Analysis and Optimization of Double-Jet Film-Cooling Holes

A parametric analysis and optimization of double-jet film-cooling holes was performed using three-dimensional Reynolds averaged Navier–Stokes equations with the shear stress transport turbulence model. The numerical results for film-cooling effectiveness were validated in comparison with experimental data. The lateral and streamwise distances between the centers of the holes, along with two lateral ejection angles, were chosen as the design variables. The effects of these four variables on the film-cooling effectiveness were evaluated. For optimization of double-jet film-cooling holes, film-cooling effectiveness was considered as the objective function. Latin hypercube sampling was used to determine the design points. A weighted average surrogate model was constructed using the objective function values calculated at the design points. Sequential quadratic programming was used to search for the optimal point from the constructed surrogate. The cooling performance of double-jet film-cooling holes was improved considerably by optimization in comparison with the reference geometry.

이중분사 막냉각 홀의 측면 분사각 및 홀 사이의 거리가 막냉각 효율에 미치는 영향

In the present work, a parametric study on double-jet film-cooling has been carried out to enhance the film-cooling effectiveness using three-dimensional Reynolds-averaged Navier-Stokes analysis. The shear stress transport turbulence model is used as the turbulence closure. The lateral ejection angles and the lateral and streamwise distance between the centers of the cooling holes are chosen as the geometric parameters. The spatially averaged film-cooling effectiveness averaged over an area of 8 hole diameters in width and 30 hole diameters in streamwise length is used to evaluate the performance of film-cooling. The parameter of the lateral distance has the largest impact on the film cooling effectiveness compared to the others. On the other hand, the parameter of streamwise distance gives the least influence on the film cooling effectiveness.

Local Heat Transfer Distribution in a Rectangular Pin Channel With and Without Vortex Generators

Short pin fins are used to enhance heat transfer rates by increasing the level of turbulence in the trailing edge of gas turbine blades. Experiments are conducted to investigate the local Nusselt number distributions in a staggered pin-fin array using the infrared thermal imaging technique. The pin fins are arranged in a rectangular channel with an aspect ratio of 9. The pins have streamwise pitch-to-diameter (XS/D) and spanwise pitch-to-diameter (XT/D) ratios of 2 with a pin height-to-diameter (H/D) ratio of 2. Ejection holes of 5-mm diameter with a pitch of 12.7 mm are used to study the effects of lateral ejection. Both one-wall and two-wall heating situations are studied for straight-flow and lateral-ejection cases. It is found that the local Nusselt numbers are highest below the horseshoe vortices just upstream of the individual pin fins. For the straight-flow case, the Nusselt numbers for the two-wall heating case are observed to be 15–20% higher than those of the one-wall heating case. Lateral ejection causes a decrease of about 1–10% for the one-wall heating case, while there is an increase of about 10% for the two-wall heating case. Experiments are also carried out with vortex generators between individual pin fins. Vortex generators cause an increase in heat transfer by about 50% compared to the straight-flow cases.

Double-Jet Ejection of Cooling Air for Improved Film Cooling

Film cooling in gas turbines leads to aerodynamic mixing losses and reduced temperatures of the gas flow. Improvements of the gas turbine thermal efficiency can be achieved by reducing the cooling fluid amount and by establishing a more equal distribution of the cooling fluid along the surface. It is well known that vortex systems in the cooling jets are the origin of reduced film-cooling effectiveness. For the streamwise ejection case, kidney vortices result in a liftoff of the cooling jets; for the lateral ejection case, usually only one dominating vortex remains, leading to hot gas flow underneath the jet from one side. Based on the results of numerical analyses, a new cooling technology has been introduced by the authors, which reaches high film-cooling effectiveness as a result of a well-designed cooling hole arrangement for interaction of two neighboring cooling jets (double-jet film cooling (DJFC)). The results show that configurations exist, where an improved film-cooling effectiveness can be reached because an anti-kidney vortex pair is established in the double-jet. The paper aims at the following major contributions: (1) to introduce the DJFC as an alternative film-cooling technology to conventional film-cooling design; (2) to explain the major phenomena, which leads to the improvement of the film-cooling effectiveness by application of the DJFC; and (3) to prove basic applicability of the DJFC to a realistic blade cooling configuration and present the first test results under machine operating conditions.

Mafic, Large‐Volume, Pyroclastic Density Current Deposits from Phreatomagmatic Eruptions in the Ferrar Large Igneous Province, Antarctica

Mafic volcaniclastic deposits are increasingly recognized as important components of continental flood basalt provinces, but the mode of origin of these deposits and the possible environmental influence of the eruptions that formed them remain poorly constrained. The Mawson Formation (Ferrar large igneous province, Jurassic) contains the best‐known examples of large‐scale, mafic, primary pyroclastic deposits from any flood basalt province worldwide. At southern Allan Hills, in contrast with other sites, the Mawson Formation consists predominantly of subhorizontal, laterally continuous, meter‐thick layers that fall into four facies: (1) poorly sorted, coarse lapilli‐tuff or tuff‐breccia beds; (2) tuff or fine lapilli‐tuff beds; (3) block‐rich layers; and (4) accretionary lapilli‐bearing beds. We interpret the first facies as deposits of high‐concentration pyroclastic density currents (PDCs) resulting from the collapse of phreatomagmatic eruption plumes, some from a source probably several kilometers away in Coombs Hills. The finer‐grained layers were probably deposited by dilute PDCs, whereas block‐rich layers originated from local sources predominantly by lateral ejection and ballistic fall. Dilute, moist turbulent currents were also likely responsible for the generation and deposition of large (up to 4.5 cm) rim‐type accretionary lapilli. Emplacement of meters‐thick basaltic PDC deposits over areas of at least 100–200 km2 is suggested, with individual deposit volumes on the order of a cubic kilometer. Prelava pyroclastic eruptions of the Ferrar mafic magmas were explosive, produced significant eruption clouds, and distributed their products over substantial areas.

Complex proximal deposition during the Plinian eruptions of 1912 at Novarupta, Alaska

Proximal (<3 km) deposits from episodes II and III of the 60-h-long Novarupta 1912 eruption exhibit a very complex stratigraphy, the result of at least four transport regimes and diverse depositional mechanisms. They contrast with the relatively simple stratigraphy (and inferred emplacement mechanisms) for the previously documented, better known, medial–distal fall deposits and the Valley of Ten Thousand Smokes ignimbrite. The proximal products include alternations and mixtures of both locally and regionally dispersed fall ejecta, and numerous thin complex deposits of pyroclastic density currents (PDCs) with no regional analogs. The locally dispersed component of the fall deposits forms sector-confined wedges of material whose thicknesses halve radially from and concentrically about the vent over distances of 100–300 m (cf. several kilometers for the medial–distal fall deposits). This locally dispersed fall material (and many of the associated PDC deposits) is rich in andesitic and banded pumices and richer in shallow-derived wall-rock lithics in comparison with the coeval medial fall units of almost entirely dacitic composition. There are no marked contrasts in grain size in the near-vent deposits, however, between locally and widely dispersed beds, and all samples of the proximal fall deposits plot as a simple continuation of grain size trends for medial–distal samples. Associated PDC deposits form a spectrum of facies from fines-poor, avalanched beds through thin-bedded, landscape-mantling beds to channelized lobes of pumice-block-rich ignimbrite. The origins of the Novarupta near-vent deposits are considered within a spectrum of four transport regimes: (1) sustained buoyant plume, (2) fountaining with co-current flow, (3) fountaining with counter-current flow, and (4) direct lateral ejection. The Novarupta deposits suggest a model where buoyant, stable, regime-1 plumes characterized most of episodes II and III, but were accompanied by transient and variable partitioning of clasts into the other three regimes. Only one short period of vent blockage and cessation of the Plinian plume occurred, separating episodes II and III, which was followed by a single PDC interpreted as an overpressured "blast" involving direct lateral ejection. In contrast, regimes 2 and 3 were reflected by spasmodic sedimentation from the margins of the jet and perhaps lower plume, which were being strongly affected by short-lived instabilities. These instabilities in turn are inferred to be associated with heterogeneities in the mixture of gas and pyroclasts emerging from the vent. Of the parameters that control explosive eruptive behavior, only such sudden and asymmetrical changes in the particle concentration could operate on time scales sufficiently short to explain the rapid changes in the proximal 1912 products.

Microseismicity and tectonics in the Granada Basin (Spain)

A microseismic experiment carried out in 1994 in the Granada Basin (Spain) permitted the precise recording of more than 80 local earthquakes. The dense distribution of the local network, with 40 to 50 instrumental records for each event, enabled us to have well-controlled hypocenters, and also 10 reliable focal mechanisms. The above observations are interpreted together with topographic data, neotectonics, and sub-surface information. Microtectonic observations in Sierra Elvira, Padul and Zafarraya gave a set of fault planes and striae, which were interpreted in terms of the recent regional stress tensor. The actual stress tensor obtained from the microseismic campaign data gives a regime in radial extension, with σ 1 vertical and σ 3 oriented NS to NNE. Microtectonic information is coherent with these orientations, but closer to 3-axial extension. A set of 64 mechanisms obtained from the permanent Andalusian network favors a NS orientation for σ 3. This results are interpreted in terms of the general model implying the lateral ejection of the Betic ranges towards the Atlantic.

Evolution of retreating subduction boundaries formed during continental collision

Retreating subduction boundaries, formed where the rate of subduction exceeds the rate of overall plate convergence, appear to be commonly developed features within regions of early or incomplete continent‐continent collision. They are characterized by regional extension within the overriding plate and, at their leading edge, by thin‐skinned arcuate thrust belts that are concave towards the overriding plate. As is illustrated by examples from the Mediterranean region, the formation of retreating subduction boundaries is intimately related to the process of continental collision. During the early stages of collision, retreating subduction boundaries are commonly formed by lateral ejection from zones of crustal shortening along the main collision boundary. Retreating plate boundaries can also form before the main collision, and the associated thrust belts emplaced as precollisional accretionary assemblages. Because the driving mechanism for retreating subduction boundaries appears to be gravity acting on a dense subducted slab (slab pull), subduction usually ceases when, and only when, thick buoyant continental crust enters the subduction zone. Thus differences in the evolution and duration of retreating subduction systems can be largely attributed to the size and configuration of the deep water regions available to be subducted. In some cases, retreating subduction boundaries may “escape” into the open ocean, where they form nearly isolated, local tectonic systems. In these systems the rate of subduction is approximately compensated by the rate of upper plate extension, and migration of the system across the oceanic region may be very rapid. For example, the Horseshoe Seamounts, located about 800 km offshore in the eastern North Atlantic, may be the active expression of an east dipping, westwardly migrating retreating subduction boundary that has evolved from the Betic Cordillera‐Rif system active in Miocene time and may now be progressing across the Atlantic at approximately 50 mm/yr. An analogous situation may be represented by the Scotia Arc system, a westward dipping retreating subduction system located between the South American and Antarctic plates, which may have “escaped” into the South Atlantic ocean from a zone of crustal shortening in the Andes and is now progressing across the Atlantic at a rate of about 80 mm/yr.

Turbulent Heat Transfer and Friction in Pin Fin Channels With Lateral Flow Ejection

Experiments were conducted to study the effects of lateral flow ejection on the overall heat transfer and pressure drops for turbulent flow through pin fin channels. The two test sections of the investigation were rectangular channels with staggered arrays of six and eight streamwise rows of pins, respectively. The pin length-to-diameter ratio was one and both the streamwise and spanwise pin spacings were 2.5 times the pin diameter. Heat transfer and friction data were obtained for various ejection exit geometries, for ejection ratios between 0 and 1, and for Reynolds numbers between 6000 and 60,000. The results of the study show that, for any given ejection ratio, the overall Nusselt number increases with increasing Reynolds number. However, the overall Nusselt number is reduced by as much as 25 percent as the ejection ratio is increased from 0 to 1 over the range of Reynolds number studied. The Nu–Re–ε relationship, which is insensitive to varying the ejection exit geometry, can be correlated by the equation (Nu/Nu0) = (Nu1/Nu0)ε, where Nu0 = c0Rem and Nu1 = c1Ren are the overall Nusselt numbers in the 0 and 100 percent lateral flow ejection cases, respectively. The results also show that the overall friction factor is independent of the flow Reynolds number over the range of Reynolds number studied. However, the friction factor is strongly dependent on the ejection ratio as well as the geometries of the straight flow exit and lateral ejection flow exit.

Lateral ejection of low energy protons in high energy heavy-ion collisions.

We study the angular distributions of low energy protons for various multiplicity cuts in ${E}_{L}$=0.8 GeV/nucleon heavy nuclear collisions in terms of the nuclear cascade model. The differential cross sections for low energy protons (${E}_{c}$100 MeV, with ${E}_{c}$ being the proton energy in the center-of-mass frame) in the lateral direction move up relatively with respect to those in the forward direction as the multiplicity cut increases. For the case of La+La collisions, for example, the differential cross section becomes maximum at ${\ensuremath{\theta}}_{c}$=90\ifmmode^\circ\else\textdegree\fi{} above the multiplicity cut M60.