Large Jet Research Articles

Design of adaptive transonic laminar airfoils using the [formula omitted] transition model

This paper examines the design of adaptive laminar airfoils in the transonic flow regime using the γ-Re˜θt model as a transition prediction method. A robust solution procedure for the transition model is described and a grid convergence study is presented. Predictions from the model are then compared to an extensive set of experimental results containing transition measurements on a morphing airfoil. It is shown that the sensitivity of the γ-Re˜θt transition model with respect to shape variations allows its use in a design framework. Using a multi-point optimization strategy, the model is then used to design transonic airfoils suitable for a range of flow conditions. The potential improvement in drag associated with the implementation of adaptive airfoil technology is then carefully quantified using single-point optimization with the multi-point designed airfoil as a reference. Structural design constraints are taken into account to obtain a realistic estimate of possible drag reduction through airfoil morphing using current wing construction technology. Airfoil drag improvements of up to 4.6% are obtained through morphing of the section of upper surface located between the wing spars with respect to the baseline multi-point design in flow conditions typical of large business jet operation.

An NARR-Derived Climatology of Southerly and Northerly Low-Level Jets over North America and Coastal Environs

AbstractThe North American Regional Reanalysis (NARR) was used to develop an expanded, long-term (1979–2009) climatology of meridional (southerly and northerly) low-level jets over North America and surrounding coastal environs. NARR has greater spatial coverage and finer temporal (3 hourly) and horizontal (32 km) resolutions than do routine rawinsonde wind measurements. The NARR climatology focuses on jet frequency and average speed and elevation by month and 3-hourly time step. To evaluate the plausibility of the climatology, jet characteristics were compared with those obtained from prior climatological analyses, case studies, field campaigns, and numerical simulations. Strong agreement was found with many of the previously documented characteristics of well-known jets, including the northerly Pacific coast jet and southerly Great Plains jet. The NARR climatology provides additional insights into the spatial extent and seasonal shifts of large jet frequencies and into diurnal fluctuations in frequency, speed, and elevation. Weaker and/or less spatially extensive jets are also well depicted in the NARR climatology, including the southerly Gulf of California jet, summertime southerly jets and autumn northerly jets off the mid-Atlantic coast, and northerly jets in the high plains. Furthermore, several new areas of relatively frequent jet occurrence, most of which align with shallow thermal gradients, are seen in the NARR climatology. The NARR climatology supplements and enhances our understanding of North American low-level jets and points to the need for additional research on both the climatological characteristics of these jets and on the processes contributing to their formation.

모래자갈과 암반의 복합지층에 시공한 저심도 터널의 사례연구

모래와 자갈이 암반 위에 퇴적된 지층에서 터널의 윗부분이 지하수가 많은 모래자갈층을 통과하는 상황에서 터널을 시공하였다. 지상의 일부 곡선구간에 빌딩들도 있는 저심도 터널을 안전하게 시공하기 위하여 강도가 작고 지하수가 많은 터널천정부의 모래자갈이 터널 내로 낙하하는 유사현상(sand flow)을 예방해야 하였다. 이를 위하여 대구경강관다단그라우팅이나 제트그라우팅으로 터널주변 충적층을 굴착 전에 미리 보강한 후 터널을 시공하였다. 이와 같이 터널을 보강한 효과와 지상빌딩의 안전을 시공 중 계측을 통하여 확인하였다. The tunnel is excavated through the alluvial layer composed of sand and gravel with groundwater deposited on rock. A portion of upper part of the tunnel is located in the alluvial layer and there are several buildings just above the curved section of the tunnel. It is necessary to prevent from sand-flowing into the tunnel due to low strength of the alluvial, high groundwater level and shallow depth of the tunnel from the ground surface. For this, the alluvial around the tunnel is pre-reinforced by umbrella arch method with multi-stage grouting through large diameter steel pipes or jet grouting before excavating the tunnel. The effect of the pre-reinforcement of the tunnel and the safety of the buildings are monitored by measurement of ground deformation occurred during tunnelling.

Mitral repair with the sole use of a semi-rigid band in a sub-population of patients with Barlow's disease: a 4-year follow-up with stress echocardiography.

Surgical treatment of Barlow's disease is usually demanding. In a sub-population of Barlow patients with bileaflets prolapse and central regurgitant jet, we performed mitral repair using only a semi-rigid annuloplasty band. Stress echocardiography follow-up was evaluated. Of a total of 350 consecutive patients with mitral prolapse, 69 had anatomical features of Barlow's disease. Of these, 40 with multiple large central jets without chordal rupture were repaired only using an annuloplasty band, and these constituted the study group. An echocardiographic study of the acute change in valvular and ventricular morphology before and after surgery was carried out. Patients were evaluated at discharge and after a mean follow-up of 4.7 ± 3.2 years by stress echocardiography. No death or reoperation occurred. Acute echocardiographic study revealed that mitral annuloplasty led to a significant migration of the leaflets towards the apex of the left ventricle. Coaptation length increased dramatically from 2.7 ± 0.8 to 11.3 ± 2.7 mm and a reduction in annular diameters and leaflet length was observed. The left ventricle was elongated (72.8 ± 6.9 vs 63.2 ± 8.1 mm) and the distance from the papillary muscle tip to the mitral annulus increased (anterior 30 ± 3.9 vs 20.3 ± 4.8 mm, posterior 29.7 ± 4.3 vs 20.8 ± 5.6 mm). At discharge, residual mitral regurgitation was mild in 1 case and trivial in 3. The results were confirmed at stress echocardiography follow-up with normal valve function at peak exercise. In patients with severe mitral regurgitation due to Barlow's disease with multiple central jet and without chordal rupture, mitral annuloplasty is effective in restoring mitral valve function owing to profound changes in mitral valve and left ventricle geometry. At follow-up, stress echocardiography confirms the results and the stability of the repair.

MAGNETIC UNTWISTING IN SOLAR JETS THAT GO INTO THE OUTER CORONA IN POLAR CORONAL HOLES

We study 14 large solar jets observed in polar coronal holes. In EUV movies from SDO/AIA, each jet appears similar to most X-ray jets and EUV jets that erupt in coronal holes, but each is exceptional in that it goes higher than most, so high that it is observed in the outer corona beyond 2.2 RSun in images from the SOHO/LASCO/C2 coronagraph. From AIA He II 304 {\AA} movies and LASCO/C2 running-difference images of these high-reaching jets, we find: (1) the front of the jet transits the corona below 2.2 RSun at a speed typically several times the sound speed; (2) each jet displays an exceptionally large amount of spin as it erupts; (3) in the outer corona, most of the jets display measureable swaying and bending of a few degrees in amplitude; in three jets the swaying is discernibly oscillatory with a period of order 1 hour. These characteristics suggest that the driver in these jets is a magnetic-untwisting wave that is basically a large-amplitude (i.e., non-linear) torsional Alfven wave that is put into the reconnected open field in the jet by interchange reconnection as the jet erupts. From the measured spinning and swaying we estimate that the magnetic-untwisting wave loses most of its energy in the inner corona below 2.2 RSun. We point out that the torsional waves observed in Type-II spicules might dissipate in the corona in the same way as the magnetic-untwisting waves in our big jets and thereby power much of the coronal heating in coronal holes.

Analysis of bolus formation in micropipette ejection systems.

The ejection of drugs from micropipettes is practiced frequently in biomedical research and clinical studies however, little is known about the dynamics of this process. The fundamentals of disperse fluid injection via a capillary into an ambient immiscible fluid have been investigated extensively. Here, we experimentally investigate the bolus formation in micropipette ejection systems, where the injection and ambient fluid are the same. We experimentally measure the temporal evolution of the bolus formation in the same fluid. There are three different bolus formation mechanisms that arise from different Re t regimes: a) a nearly spherical bolus, b) a pear-like bolus, and c) a large distortion or axial jet. We examine the scaled dimensions of the bolus, R b/D t, L b/D t, H/D t, and α, as a function of the dimensionless parameters such as tip Reynolds number, Re t, dimensionless value of g/(D t (.) V t), the dimensionless time, tV t/D t, and the distance between the edge of the micropipette and the free surface, D/D t. The bolus radius for 0.2 < Re t < 30 grows according to t (1/2) in the entire time range, which allows us to estimate the time for complete bolus formation.

Battle for the skies [jet engine

In the airline business, margins are everything. Large modern jet engines make up a huge proportion of an aircraft's weight, and the fuel used is a huge part of an operator's costs. A reduction in either could be the difference between profit and loss. Fluctuating oil prices, fierce competition and challenging carbon reduction targets set by regulators are all increasing pressure on manufacturers to improve engine efficiency. The world's 'big three' jet engine builders - General Electric (GE), Rolls-Royce and Pratt & Whitney - have all responded, unveiling new ranges of engines packed full of innovative technology and engineering. Speed here isn't the most important thing - in fact, the engines will operate at similar speeds to those in service today. It's all about improving efficiency, minimising the environmental impact and - most importantly - reducing operating cost. Using lightweight but ultra-tough composite materials, advanced high-pressure compressors, new planetary gearing systems and even 3D-printed components, competition is hotting up in a worldwide commercial engine market that in 2013 was estimated to have reached around $25bn.

Analysis and design of a water pump with accumulators absorbing pressure pulsation in high-velocity water-jet propulsion system

A large capacity and high-pressure piston water pump is often used as the power supply in a high-pressure water-jet propulsion system (HWPS). When the piston water pump works, some flow and pressure pulsation is generated and then creates large thrust pulsation and jet noise. In most cases, an accumulator charged constant pressure gas is always installed near the outlet of the water pump to absorb the flow and pressure pulsation. If the thrust of HWPS is required to alter, the rotation and output pressure of the water pump will change. So, the function of the accumulator absorbing flow pulsation and pressure pulsation will weaken. To solve this problem, an effective means that makes multiple accumulators which are charged different pressures to connect with the outlet chamber of the water pump is put forward in this paper. According to the structural pattern of water pump, working pressure range of HWPS and allowable value of pressure pulsation factor, some key parameters, could be worked out by optimal calculation method proposed first, such as the number of accumulators, volume and charged pressure of each accumulator. Finally, results of simulation and experiment revealed that three pairs of accumulators, whose parameters were optimally calculated from actual working conditions, could keep the pressure pulsation factor to about the allowable value all along when working pressure of HWPS varied over the range.

Stability of jets in a shallow water layer

Purpose – The present work is devoted to the numerical study of the stability of shallow jet. The effects of important parameters on the stability behavior for large scale shallow jets are considered and investigated. Connections between the stability theory and observed features reported in the literature are emphasized. The paper aims to discuss these issues. Design/methodology/approach – A linear stability analysis of shallow jet incorporating the effects of bottom topography, bed friction and viscosity has been carried out by using the shallow water stability equation derived from the depth averaged shallow water equations in conjunction with both Chézy and Manning resistance formulae. Effects of the following main factors on the stability of shallow water jets are examined: Rossby number, bottom friction number, Reynolds number, topographic parameters, base velocity profile and resistance model. Special attention has been paid to the Coriolis effects on the jet stability by limiting the rotation number in the range of Ro∈[0, 1.0]. Findings – It is found that the Rossby number may either amplify or attenuate the growth of the flow instability depending on the values of the topographic parameters. There is a regime where the near cancellation of Coriolis effects due to other relevant parameters influences is responsible for enhancement of stability. The instability can be suppressed by the bottom friction when the bottom friction number is large enough. The amplification rate may become sensitive to the relatively small Reynolds number. The stability region using the Manning formula is larger than that using the Chézy formula. The combination of these effects may stabilize or destabilize the shallow jet flow. These results of the stability analysis are compared with those from the literature. Originality/value – Results of linear stability analysis on shallow jets along roughness bottom bed are presented. Different from the previous studies, this paper includes the effects of bottom topography, Rossby number, Reynolds number, resistance formula and bed friction. It is found that the influence of Reynolds number on the stability of the jet is notable for relative small value. Therefore, it is important to experimental investigators that the viscosity should be considered with comparison to the results from inviscid assumption. In contrast with the classical analysis, the use of multi-parameters of the base velocity and topographic profile gives an extension to the jet stability analysis. To characterize the large scale motion, besides the bottom friction as proposed in the related literature, the Reynolds number Re, Rossby number Ro, the topographic parameters and parameters controlling base velocity profile may also be important to the stability analysis of shallow jet flows.

Jets from jets: re-clustering as a tool for large radius jet reconstruction and grooming at the LHC

Jets with a large radius $R\gtrsim 1$ and grooming algorithms are widely used to fully capture the decay products of boosted heavy particles at the Large Hadron Collider (LHC). Unlike most discriminating variables used in such studies, the jet radius is usually not optimized for specific physics scenarios. This is because every jet configuration must be calibrated, insitu, to account for detector response and other experimental effects. One solution to enhance the availability of large-$R$ jet configurations used by the LHC experiments is {\it jet re-clustering}. Jet re-clustering introduces an intermediate scale $r<R$ at which jets are calibrated and used as the inputs to reconstruct large radius jets. In this paper we systematically study and propose new jet re-clustering configurations and show that re-clustered large radius jets have essentially the same jet mass performance as large radius groomed jets. Jet re-clustering has the benefit that no additional large-R calibration is necessary, allowing the re-clustered large radius parameter to be optimized in the context of specific precision measurements or searches for new physics.

Landing Gear Ground Load Measurement and Verification Test for a Large Passenger Jet

Engineered Material Arresting System (EMAS) could be constructed in runway end safety area to arrest an overrun aircraft. EMAS bed is the main part of EMAS and consists of the EMAS material, such as foam concrete. EMAS and its design method should be verified by actual aircraft test. A large passenger jet, one main aircraft type of civil aviation should be used in actual aircraft verification test of EMAS. The jet came from an airline operation front line. To minimize the effect of the test on the jet's airworthiness, the landing gears of the jet should not be remove in the measurement system mounting. The jet's motion in EMAS could be analyzed, and the performance requirement of landing gear load measurement system could be studied. Accordingly, landing gear load measurement system and field calibration test method were presented. For the verification of measurement system, the aircraft taxi tests such as taxi brake test, engine ground run up test and a short EMAS bed test had been done with the system. Through analyzing the measured loads of the landing gears, weight of the jet and the limit load of landing gears, the system could be verified. The results show that the load measurement system could satisfy EMAS actual aircraft verification test, and the test and verification method should satisfy other large aircraft landing gear load measurement

Generation of large-scale structures and vortex systems in numerical experiments for rotating annular channels

Numerical methods for shallow-water equations describing flows in rotating annular channels and the results of numerical calculations are considered. The possibility of generation of global large scale flows, narrow jets and numerous small-scale vorticies in laboratory experiments is analyzed. Methods for inducing external effects in fluids involve a source-sink method and an MHD-method of interaction of electric current with magnetic field generated by a system of permanent magnets. A central-upwind method adopted to geophysical hydrodynamics is used in the numerical scheme. Initially the method was applied to shallow water equations in hydraulic problems: channels, dam break, rivers, and lakes. In geophysical hydrodynamics (in addtition to free water surface and bottom elevation) the main effects arise when external rotation is taken into account with appearence of numerous vorticies, jets and turbulence. So the basic foundations of the central-upwind method should be changed. Modifications concern the well-balanced scheme and interpolation method. In the numerical scheme the structure of artifical viscosity is considered. The main achievement of the modification is the possibility of controlling the numerical dissipation affecting the fluid motion variety. Hence, we obtain the active dynamics of vorticies transfomed into jets or large scale streams, which is more preferable for geophysical hydrodynamics. The numerical experiment provides opportunities for studying flows generated by numerous source-sinks, because the creation of an appropriate laboratory experimental setup presents some difficulties. The MHD-method can readily be realized in experiments to generate a large variety of flows and vortex currents in the channel by means of a relatively small number of magnets. Specifically, large scale circular flows, narrow jets and system of interacted vorticies were obtained in numerical experiments. For the purpose of experiments, the distribution of source-sinks and systems of permanent magnets over the bottom of annular channels is defined.

Development of an Expanded Arduino Interface Board PCB Module for Large Commercial Jet Simulator

Development of an Expanded Arduino Interface Board PCB Module for Large Commercial Jet Simulator

High Performance Computation of a Jet in Crossflow by Lattice Boltzmann Based Parallel Direct Numerical Simulation

Direct numerical simulation (DNS) of a round jet in crossflow based on lattice Boltzmann method (LBM) is carried out on multi-GPU cluster. Data parallel SIMT (single instruction multiple thread) characteristic of GPU matches the parallelism of LBM well, which leads to the high efficiency of GPU on the LBM solver. With present GPU settings (6 Nvidia Tesla K20M), the present DNS simulation can be completed in several hours. A grid system of 1.5 × 108is adopted and largest jet Reynolds number reaches 3000. The jet-to-free-stream velocity ratio is set as 3.3. The jet is orthogonal to the mainstream flow direction. The validated code shows good agreement with experiments. Vortical structures of CRVP, shear-layer vortices and horseshoe vortices, are presented and analyzed based on velocity fields and vorticity distributions. Turbulent statistical quantities of Reynolds stress are also displayed. Coherent structures are revealed in a very fine resolution based on the second invariant of the velocity gradients.

Transverse Momentum Dependent (TMD) Parton Distribution Functions: Status and Prospects

We provide a concise overview on transverse momentum dependent (TMD) parton distribution functions, their application to topical issues in high-energy physics phenomenology, and their theoretical connections with QCD resummation, evolution and factorization theorems. We illustrate the use of TMDs via examples of multi-scale problems in hadronic collisions. These include transverse momentum q_T spectra of Higgs and vector bosons for low q_T, and azimuthal correlations in the production of multiple jets associated with heavy bosons at large jet masses. We discuss computational tools for TMDs, and present an application of a new tool, TMDlib, to parton density fits and parameterizations.

Idealized large‐eddy simulations of nocturnal low‐level jets over subtropical desert regions and implications for dust‐generating winds

Nocturnal low‐level jets (LLJs) are maxima in the wind profile, which often form above the stable nocturnal boundary layer. Over the Sahara, the world's largest source of mineral dust, this phenomenon is of particular importance to the emission and transport of desert aerosol. We present the first ever detailed large‐eddy simulations of dust‐generating LLJs. Using sensitivity studies with the UK Met Office large‐eddy model (LEM), two key controls of the nocturnal LLJ are investigated: surface roughness and the Coriolis force. Functional relationships derived from the LEM results help to identify optimal latitude–roughness configurations for a maximum LLJ enhancement. Ideal conditions are found in regions between 20 and 27°N with roughness lengths &gt;0.0001 m providing long oscillation periods and large jet amplitudes. Typical LLJ enhancements reach up to 3.5 m s−1 for geostrophic winds of 10 m s−1. The findings are largely consistent with results from a theoretical LLJ model applied for comparison. The results demonstrate the importance of latitude and roughness in creating regional patterns of LLJ influence. Combining the functional relationships with high‐resolution roughness data over northern Africa gives good agreement with the location of morning dust uplift in satellite observations. It is shown that shear‐induced mixing plays an important role for the LLJ evolution and surface gustiness. With decreasing latitude the LLJ oscillation period is longer and, thus, shear‐induced mixing is weaker, allowing a more stable nocturnal stratification to develop. This causes a later and more abrupt LLJ breakdown in the morning with stronger gusts, which can compensate for the slower LLJ evolution that leads to a weaker jet maximum. The findings presented here can serve as the first step towards a parametrization to improve the representation of the effects of nocturnal LLJs on dust emission in coarser‐resolution models.

Flow behavior around a square cylinder subject to modulation of a planar jet issued from upstream surface

The flow behavior in the up- and downstream regions of a square cylinder subject to the modulation of a planar jet issued from the cylinder׳s front surface was studied using the laser-assisted smoke flow visualization method and hot-wire anemometer measurement. Reynolds numbers were from 1628 to 13000. The drag force experienced by the square cylinder was obtained by measuring the surface pressures on the up- and downstream faces. The temporally evolving smoke flow patterns in the up- and downstream regions were synchronously revealed through the smoke flow visualization. The frequency characteristics of the instability waves in the up- and downstream regions were synchronously detected by the two hot-wire anemometers. Four characteristic flow modes were observed within the different ranges of the injection ratios. At the low injection ratios (IR<1), the ‘swinging jet’ appeared. The jet swung periodically leftward and rightward and formed a fluid bubble on the front surface. The fluid bubble contained a pair of counter-rotating vortices and presented a periodic variation in its height. At moderately low injection ratios (1<IR<4.3), the ‘deflected oscillating jet’ appeared. The jet was deflected in either the left or the right direction and wrapped around one of the edges of the square cylinder. Both the swinging and oscillating motions of the jet in the swinging jet and deflected oscillating jet modes were induced by the periodic feedback pressure signals generated by the vortex shedding in the wake. At the moderately high (4.3<IR<8.3) and high (IR>8.3) injection ratios, the ‘deflection jet’ and ‘penetrating jet’ appeared. The jet detached from the cylinder׳s front surface and penetrated a long distance into the upstream region due to large jet momentum. Neither periodic jet oscillation in the upstream region nor vortex shedding in the wake was observed. The drag coefficient was found to be decreasing quickly with increasing the injection ratio.

Overview of image processing tools to extract physical information from JET videos

In magnetic confinement nuclear fusion devices such as JET, the last few years have witnessed a significant increase in the use of digital imagery, not only for the surveying and control of experiments, but also for the physical interpretation of results. More than 25 cameras are routinely used for imaging on JET in the infrared (IR) and visible spectral regions. These cameras can produce up to tens of Gbytes per shot and their information content can be very different, depending on the experimental conditions. However, the relevant information about the underlying physical processes is generally of much reduced dimensionality compared to the recorded data. The extraction of this information, which allows full exploitation of these diagnostics, is a challenging task. The image analysis consists, in most cases, of inverse problems which are typically ill-posed mathematically. The typology of objects to be analysed is very wide, and usually the images are affected by noise, low levels of contrast, low grey-level in-depth resolution, reshaping of moving objects, etc. Moreover, the plasma events have time constants of ms or tens of ms, which imposes tough conditions for real-time applications. On JET, in the last few years new tools and methods have been developed for physical information retrieval. The methodology of optical flow has allowed, under certain assumptions, the derivation of information about the dynamics of video objects associated with different physical phenomena, such as instabilities, pellets and filaments. The approach has been extended in order to approximate the optical flow within the MPEG compressed domain, allowing the manipulation of the large JET video databases and, in specific cases, even real-time data processing. The fast visible camera may provide new information that is potentially useful for disruption prediction. A set of methods, based on the extraction of structural information from the visual scene, have been developed for the automatic detection of MARFE (multifaceted asymmetric radiation from the edge) occurrences, which precede disruptions in density limit discharges. An original spot detection method has been developed for large surveys of videos in JET, and for the assessment of the long term trends in their evolution. The analysis of JET IR videos, recorded during JET operation with the ITER-like wall, allows the retrieval of data and hence correlation of the evolution of spots properties with macroscopic events, in particular series of intentional disruptions.

Control of the electric field–polymer solution interaction by utilizing ultra-conductive fluids

Dramatically raising the conductivity of a polymer solution by using a salt additive allows control over the electric field-induced jet feed rate when electrospinning from an unconfined fluid without altering the applied voltage. As the solution conductivity increases, the flow rate drops by an order of magnitude. At a high voltage level and fluid conductivity value, the jets undergo a whipping instability over almost the entire path from the source to the collector experiencing only a negligibly short linear region which, along with the flow rate data, indicates that the jet narrows due to the high conductivity. Under these conditions, even while possessing relatively large individual jet feed rates, thin diameter nanofibers (200–300 nm) are readily produced. In contrast with other approaches to obtain narrow fibers from unconfined fluids (e.g., voltage reduction to control feed rate), here the fiber forming jets are present indefinitely. Continuous, scaled up nanofiber production rate of >125× over the traditional single needle electrospinning method is observed from the presence of multiple jets, each possessing a relatively high solution feed rate. These fundamental experiments reveal new pathways for exploring novel electrospinning configurations where the jet feed rate can be controlled by manipulating the solution conductivity.

The North Middle Lobe of Centaurus A

AbstractWe present new, deep VLA 327 MHz, GALEX Far-UV, and Hα images of the inner ~50 kpc of Centaurus A. We find the structure identified by Morganti et al. 1999 as a possible “large scale jet” is part of a knotty, linear feature within a broader region of diffuse radio emission. The linear feature is coincident with a narrow ribbon of Far-UV and Hα emission that extends 6-35 kpc from the galaxy core, as well with a similar ridge of soft X-ray emission. The Far-UV image also shows that a strong starburst is occurring in the central dusty disk, with a star-formation rate of ~ 2M⊙ yr−1. We suggest that the various peculiar phenomena seen to the NE of the galaxy can be explained by a wind from the starburst disk, enhanced by energy input from the AGN.