Ejection Of Fluid Research Articles

자기변형 잉크젯헤드의 고점도 유체 토출 요구 압력에 관한 연구

This paper presents ejection of high viscosity fluids with magnetostrictive inkjet printhead(Magjet), which is not common with any other printhead. The MagJet uses a magnetostrictive material, Terfenol-D rod with 10-mm in diameter and 50-mm in length, as an actuation mechanism. It has been known that high viscosity is often an obstacle in ejecting small and mono-disperse droplets. We calculated required pressure with fluidic inertia (Bernoulli equation) and viscous loss (Hagen Poiseuille equation). The required pressure for ejecting a droplet is 1300kPa. The generated force and displacement with Terfenol-D rod are estimated to be 480N (2600kPa) and 28µm, respectively. It was enough that Magjet eject high viscosity fluid (Max 1000cP). The experiments are performed to eject the high viscosity fluid with Magjet. The ejection of high viscosity fluids is successful with the aid of Terfenol-D’s high performance.

Fluid fragmentation shapes rain-induced foliar disease transmission.

Plant diseases represent a growing threat to the global food supply. The factors contributing to pathogen transmission from plant to plant remain poorly understood. Statistical correlations between rainfalls and plant disease outbreaks were reported; however, the detailed mechanisms linking the two were relegated to a black box. In this combined experimental and theoretical study, we focus on the impact dynamics of raindrops on infected leaves, one drop at a time. We find that the deposition range of most of the pathogen-bearing droplets is constrained by a hydrodynamical condition and we quantify the effect of leaf size and compliance on such constraint. Moreover, we identify and characterize two dominant fluid fragmentation scenarios as responsible for the dispersal of most pathogen-bearing droplets emitted from infected leaves: (i) the crescent-moon ejection is driven by the direct interaction between the impacting raindrop and the contaminated sessile drop and (ii) the inertial detachment is driven by the motion imparted to the leaf by the raindrop, leading to catapult-like droplet ejections. We find that at first, decreasing leaf size or increasing compliance reduces the range of pathogen-bearing droplets and the subsequent epidemic onset efficiency. However, this conclusion only applies for the crescent moon ejection. Above a certain compliance threshold a more effective mechanism of contaminated fluid ejection, the inertial detachment, emerges. This compliance threshold is determined by the ratio between the leaf velocity and the characteristic velocity of fluid fragmentation. The inertial detachment mechanism enhances the range of deposition of the larger contaminated droplets and suggests a change in epidemic onset pattern and a more efficient potential of infection of neighbouring plants. Dimensionless parameters and scaling laws are provided to rationalize our observations. Our results link for the first time the mechanical properties of foliage with the onset dynamics of foliar epidemics through the lens of fluid fragmentation. We discuss how the reported findings can inform the design of mitigation strategies acting at the early stage of a foliar disease outbreak.

Foil-Level Inkjet-Printed pyroMEMS Balloon Actuators: Fabrication, Modeling, and Validation

A cleanroom-free fabrication process adapted to microfluidic devices is presented for pyrotechnical microelectromechanical systems balloon actuators. The actuators are intended for on-chip pumping and fluid ejection to replace tabletop pumping solutions in low-cost portable single-use microfluidic devices. The fabrication process leveraged polymeric foils (polyethylene terephthalate, SU-8, polydimethylsiloxane) for the structure, directly bonded using surface treatments, heat and pressure, and inkjet printing and electroplating for the igniter. This paper also presents a semianalytical model that successfully predicted the inflation height of the balloon for a given device geometry and propellant loading.

Application of the Monopole Source to Quantify Explosive Flux during Vulcanian Explosions at Sakurajima Volcano (Japan)

A primary goal in volcano seismology is to characterize source motions internal to a volcano in terms of their representative forces. In a similar manner, much volcano infrasound research strives to recover eruptive force time histories corresponding to material accelerations occurring at Earth’s free surface. These motions may correspond to explosive emission of gas and pyroclasts (e.g., Banister, 1984), rapid ground distensions of a volcanic dome (e.g., Johnson and Lees, 2010), and/or gravity driven rock fall or pyroclastic flows (e.g., Yamasato, 1997). When free surface motion is unsteady it imposes stresses upon the surrounding atmosphere, which are propagated as acoustic airwaves. Typically, the sounds produced by volcanic phenomena are recorded with low‐frequency infrasound sensitive microphones. The intervening atmosphere is relatively homogeneous and nonattenuating for infrasound propagation of a few kilometers, therefore the recorded excess pressures closely represent volcano source time functions. Such force time histories are equivalent to volumetric accelerations of the atmosphere at or near to the source. Many volcano explosion signals begin with intense, impulsive bipolar pulses (compression followed by rarefaction) with durations of a few seconds or less (e.g., Morrissey and Chouet, 1997). These volcano explosion waveforms are often similar to chemical explosion signals recorded in the far field and are suggestive of a rapid release and expansion of gases (Kitov et al. , 1997). Several volcano infrasound studies have made use of the Lighthill (1978) simple acoustic source to characterize ejection of fluid from the volcanic vent (e.g., Johnson, 2003). Volcanic explosions generate bipolar infrasound pulses with durations of a few seconds (Firstov and Kravchenko, 1996; Johnson, 2003) that have been attributed to simple acoustic sources. A simple acoustic source, or a monopole, corresponds to a point approximation of fluid injection or extraction. Although most volcanic vents possess length scales of tens of meters to …

Spatio-temporal and modal analysis of unsteady fluctuations in a high-subsonic base flow

The high-subsonic flow over an axisymmetric backward facing step is investigated at a Mach number of 0.7, with high-speed particle image velocimetry operating at acquisition frequency up to 20 kHz to resolve the time dependent behavior of the separated flow in the longitudinal plane. The statistical flow properties such as the approaching boundary layer thickness, mean and fluctuating velocity field and shear layer growth are quantified. It is found that the shear layer growth is nearly linear up to x/D = 0.6; downstream this location, the reattachment surface influences the shear layer growth rate, causing it to decrease. The visualization of the high-speed measurements shows a quasi-cyclic behavior of the separated region characterized by a fluctuation of the flow reattachment location. The growing and shrinking of the separated region is accompanied by large-scale fluctuations that dominate the flow motions and the momentum exchange across the shear layer. The analysis of the large-scale fluctuations based on proper orthogonal decomposition (POD) of the velocity field indicates that the separated region exhibits pulsating behaviour as associated to the highest energy mode. The second and third modes are approximately in phase quadrature and can be associated to the growth of large azimuthal vortices that undulate the shear layer approaching the mean reattachment location. Conditional averaging of the data indicates that the second/third mode is associated to either the entrainment of high momentum fluid or ejection of low momentum fluid from the separated region depending on the phase. The high-speed measurements enable the spectral analysis of the velocity; the power spectral density of the POD time coefficients for the first three modes is evaluated. The first mode associated to pulsatile growth and collapse of the separated region yields a dominant frequency at StrD = 0.13 (f = 585 Hz) while the second mode features a broader frequency distribution in the range from 1 to 3 kHz (0.22 < StrD < 0.67) with a distinguishable peak at StrD = 0.4. The dynamical correlation between these two modes shows that time derivative of the first mode temporal coefficient and second mode coefficient are strongly correlated. This suggests that the entrainment of high momentum fluid into the separated region is responsible for the wake growth phenomenon.

Study of Droplet Formation Process during Drop-on-Demand Inkjetting of Living Cell-Laden Bioink

Biofabrication offers a great potential for the fabrication of three-dimensional living tissues and organs by precisely layer-by-layer placing various tissue spheroids as anatomically designed. Inkjet printing of living cell-laden bioink is one of the most promising technologies enabling biofabrication, and the bioink printability must be carefully examined for it to be a viable biofabrication technology. In this study, the cell-laden bioink droplet formation process has been studied in terms of the breakup time, droplet size and velocity, and satellite formation using a time-resolved imaging approach. The bioink has been prepared using fibroblasts and sodium alginate with four different cell concentrations: without cells, 1 × 10(6), 5 × 10(6), and 1 × 10(7) cells/mL to appreciate the effect of cell concentration on the droplet formation process. Furthermore, the bioink droplet formation process is compared with that during the inkjetting of a comparable polystyrene microbead-laden suspension under the identical operating conditions to understand the effect of particle physical properties on the droplet formation process. It is found that (1) as the cell concentration of bioink increases, the droplet size and velocity decrease, the formation of satellite droplets is suppressed, and the breakup time increases, and (2) compared to the hard bead-laden suspension, the bioink tends to have a less ejected fluid volume, lower droplet velocity, and longer breakup time.

Duration of urination does not change with body size.

Many urological studies rely on models of animals, such as rats and pigs, but their relation to the human urinary system is poorly understood. Here, we elucidate the hydrodynamics of urination across five orders of magnitude in body mass. Using high-speed videography and flow-rate measurement obtained at Zoo Atlanta, we discover that all mammals above 3 kg in weight empty their bladders over nearly constant duration of 21 ± 13 s. This feat is possible, because larger animals have longer urethras and thus, higher gravitational force and higher flow speed. Smaller mammals are challenged during urination by high viscous and capillary forces that limit their urine to single drops. Our findings reveal that the urethra is a flow-enhancing device, enabling the urinary system to be scaled up by a factor of 3,600 in volume without compromising its function. This study may help to diagnose urinary problems in animals as well as inspire the design of scalable hydrodynamic systems based on those in nature.

Flow topology around a simplified two-wheel landing gear

Flow topology around a simplified model of a two-wheel landing gear is studied using the hydrogen-bubble visualization technique. The complete test model consists of two wheels, an axle, a main strut and a support strut. A number of wheel models with varying geometric details are considered. During the analyses, the flow field around the wheels is divided into three main regions: upper, central and lower. (1) In the upper (wing side) flow region, the flow along the inner side surface of the wheels either remains attached until the wheel aft or it separates prematurely and periodically forms slant vortices in the near wake. The wheel geometry is found to control the type of separation. (2) In the central flow region, comparison of the flow sections above and below the axle shows that main strut blockage has a significant influence on the separation behavior of the flow between the wheels. Furthermore, the addition of interior wells to the wheel geometry is found to result in a cross-stream jet at the level of the axle. This highly-erratic fluid ejection has the potential to be a source of aeroacoustic noise. (3) In the lower (ground side) flow region, the near wake is shown to accommodate periodically forming large-scale structures.

On the evolution of vortex rings with swirl

A laminar vortex ring with swirl, which has the meridional velocity component inside the vortex core, was experimentally generated by the brief fluid ejection from a rotating outlet. The evolution of the vortex ring was investigated with flow visualizations and particle image velocimetry measurements in order to find the influence of swirling flow in particular upon the transition to turbulence. Immediately after the formation of a vortex ring with swirl, a columnar strong vortex along the symmetric axis is observed in all cases of the present experiment. Then the characteristic fluid discharging from a vortex ring with swirl referred to as “peeling off” appears. The amount of discharging fluid due to the “peeling off” increases with the angular velocity of the rotating outlet. We conjectured that the mechanism generating the “peeling off” is related to the columnar strong vortex by close observations of the spatio-temporal development of the vorticity distribution and the cutting 3D images constructed from the successive cross sections of a vortex ring. While a laminar vortex ring without swirl may develop azimuthal waves around its circumference at some later time and the ring structure subsequently breaks, the swirling flow in a vortex ring core reduces the amplification rate of the azimuthal wavy deformation and preserved its ring structure. Then the traveling distance of a vortex ring can be extended using the swirl flow under certain conditions.

Numerical and Experimental Investigations of the Supersonic Microramp Wake

The flow past a microramp immersed in a supersonic turbulent boundary layer is studied by means of numerical simulations with the implicit large-eddy simulation technique and experiments conducted with tomographic particle image velocimetry. The experimental data are mostly used to verify the validity of the numerical results by ample comparisons on the time-averaged velocity, turbulent statistics, and vortex intensity. Although some discrepancies are observed on the intensity of the upwash motion generated by the streamwise vortex pair, the rates of the recovery of momentum deficit and the decay of streamwise vortex pair intensity are found in good agreement. The instantaneous flow organization is inspected, making use of the flow realizations available from implicit large-eddy simulation. The flow behind the microramp exhibits significant large-scale unsteady fluctuations. Notably, the quasi-conical shear layer enclosing the wake is strongly undulated under the action of Kelvin–Helmholtz (K–H) vortices. The resulted vortices induce localized high-speed arches in the outer region and a deceleration within the wake associated with ejection of low-momentum fluid. Because of the presence of the K–H vortex, the streamwise vortex filaments exhibit downward and outward motions. The further evolution of vortical structures within the wake features the development of K–H vortices from arch shape to full ring in the far wake, under the effects of the streamwise vortices, which induce an inward motion of the vortex legs and eventually connect the vortex at the bottom.

Air Impingement Cooling by Synthetic Jet

Modern consumer electronic trends point to a demand for thinner and more portable electronic devices. Conventional cooling systems of these portable electronic devices are challenging to miniaturize in thin profile applications that are typically on the order of several millimeters in thickness. In order to overcome some of these challenges, a synthetic jet, which is also considered as micro fluidic device, is developed. This device which operates based on Piezo electricity is called Dual Cooling Jet (DCJ). DCJ disturbs the boundary layer over a hot component and hence increases heat transfer compare to conventional blower. DCJ is typically defined as a device using a partially enclosed cavity with oscillating walls/diaphragms to create alternating suction and ejection of fluid across an interface or orifice. In this work, the results of cooling performance investigation of DCJ are shown and compared with natural convection cooling. Also, several experiments have been done to study the cooling effect of DCJ at different configuration with respect to heat source and the results are compared. At the end, the effects of heat source size is investigated which are helpful to understand how effective DCJ is when used for cooling several size chips. In addition, the results of this work show that DCJ can be combined with low profile heat sink as a promising next generation ultra thin thermal solution module.

Turbulent structure of high-amplitude pressure peaks within the turbulent boundary layer

AbstractThe positive and negative high-amplitude pressure peaks (HAPP) are investigated in a turbulent boundary layer at $R{e}_{\theta } = $ 1900 in order to identify their turbulent structure. The three-dimensional velocity field is measured within the inner layer of the turbulent boundary layer using tomographic particle image velocimetry (tomo-PIV). The measurements are performed at an acquisition frequency of 10 000 Hz and over a volume of $418\times 149\times 621$ wall units in the streamwise, wall-normal and spanwise directions, respectively. The time-resolved velocity fields are applied to obtain the material derivative using the Lagrangian method followed by integration of the Poisson pressure equation to obtain the three-dimensional unsteady pressure field. The simultaneous volumetric velocity, acceleration, and pressure data are conditionally sampled based on local maxima and minima of wall pressure to analyse the three-dimensional turbulent structure of the HAPPs. Analysis has associated the positive HAPPs to the shear layer structures formed by an upstream sweep of high-speed flow opposing a downstream ejection event. The sweep event is initiated in the outer layer while the ejection of near-wall fluid is formed by the hairpin category of vortices. The shear layers were observed to be asymmetric in the instantaneous visualizations of the velocity and acceleration fields. The asymmetric pattern originates from the spanwise component of temporal acceleration of the ejection event downstream of the shear layer. The analysis also demonstrated a significant contribution of the pressure transport term to the budget of the turbulent kinetic energy in the shear layers. Investigation of the conditional averages and the orientation of the vortices showed that the negative HAPPs are linked to both the spanwise and quasi-streamwise vortices of the turbulent boundary layer. The quasi-streamwise vortices can be associated with the hairpin category of vortices or the isolated quasi-streamwise vortices of the inner layer. A bi-directional analysis of the link between the HAPPs and the hairpin paradigm is also conducted by conditionally averaging the pressure field based on the detection of hairpin vortices using strong ejection events. The results demonstrated positive pressure in the shear layer region of the hairpin model and negative pressure overlapping with the vortex core.

Lymphatic Vascular Response to Acute Inflammation

During acute inflammation, functioning lymphatics are believed to reduce edema and to provide a transiting route for immune cells, but the extent at which the dermal lymphatic remodeling impacts lymphatic transport or the factors regulating these changes remains unclear. Herein we quantify the increase in lymphatic endothelial cells (LECs) and examine the expression of pro-angiogenenic and lymphangiogenic factors during acute cutaneous hypersensitivity (CHS). We found that LECs actively proliferate during CHS but that this proliferation does not affect the lymphatic vessel density. Instead, lymphatic remodeling is accompanied by lymphatic vessel leakiness and lower ejection of lymph fluid, which is observed only in the proximal lymphatic vessel draining the inflamed area. LECs and the immune cells release growth factors and cytokines during inflammation, which impact the lymphatic microenvironment and function. We identified that FGF-2, PLGF-2, HGF, EGF, and KC/CXCL17 are differentially expressed within tissues during acute CHS, but both VEGF-C and VEGF-D levels do not significantly change. Our results indicate that VEGF-C and VEGF-D are not the only players and other factors may be responsible for the LECs proliferation and altered lymphatic function in acute CHS.

A Preliminary Evaluation of Plasma B-Type Natriuretic Peptide as a Screening Test for Left Ventricular Diastolic Dysfunction in Non-Cardiac Intensive Care

Left ventricular filling and thus diastolic function are frequently monitored and managed in critical care. However, scant data exist regarding possible screening tests for diastolic dysfunction in the intensive care unit (ICU). The present study aimed to evaluate plasma b-type natriuretic peptide (BNP) as a marker of diastolic dysfunction in a single-centre cohort of 'non-cardiac' ICU patients. The ICU is non-cardiac in that it provides mixed medical/surgical services with the exception of cardiology, cardiac surgery and solid organ transplantation. Clinical data were recorded over the first 24 hours of ICU stay for 32 consecutive patients. Transthoracic echocardiogram and blood collection for BNP assay were then performed. Diastolic dysfunction was demonstrated in 34% (n=11). Mean ± standard deviation BNP values were higher with diastolic dysfunction (238 ± 195 vs 72 ± 78 pg/ml; P=0.003). A BNP threshold of >43 pg/ml yielded a sensitivity of 80% and a specificity of 59%; area under the receiver operating characteristic curve was 0.82. BNP correlated independently with E/e' (R=0.425; P=0.015) (E/e': peak early transmitral velocity [E]/early diastolic mitral annular velocity [e']) but not left ventricular ejection fraction (P=0.8), illness severity (Acute Physiological and Chronic Health Evaluation II; P=0.3) or fluid balance (P=0.4). Diastolic dysfunction was common in this cohort of non-cardiac ICU patients and was independently associated with a significantly higher BNP. The potential application as a screening test for diastolic dysfunction is likely to require a threshold lower than previously proposed for heart failure.

Turbulent separation upstream of a forward-facing step

AbstractThe turbulent flow over a forward-facing step is studied using two-dimensional time-resolved particle image velocimetry. The structure and behaviour of the separation region in front of the step is investigated using conditional averages based on the area of reverse flow present. The relation between the position of the upstream separation and the two-dimensional shape of the separation region is presented. It is shown that when of ‘closed’ form, the separation region can become unstable resulting in the ejection of fluid over the corner of the step. The separation region is shown to grow simultaneously in both the wall-normal and streamwise directions, to a point where the maximum extent of the upstream position of separation is limited by the accompanying transfer of mass over the step corner. The conditional averages are traced backwards in time to identify the average behaviour of the boundary-layer displacement thickness leading up to such events. It is shown that these ejections are preceded by the convection of low-velocity regions from upstream, resulting in a three-dimensional interaction within the separation region. The size of the low-velocity regions, and the time scale at which the separation region fluctuates, is shown to be consistent with the large boundary layer structures observed in the literature. Instances of a highly suppressed separation region are accompanied by a steady increase in velocity in the upstream boundary layer.

Automatic Block Detection for Ink Jet Head

Inkjet printing technology has been used in several areas and the inkjet printer uses different inks, for example oil ink for cloth printing, color glaze ink for ceramic printing and so on. The printer ink jet head uses these inks are blocked frequently. An automatic block detection system has been presented in this paper. The system provides droplet deposition apparatus comprising of: a fluid chamber; a nozzle in fluid communication with the chamber for ejection of fluid; a monitor; CCD camera; image capturing and processing module. The system has applied to ink jet and droplet image detection and it is proved effective and the detection result is accuracy.

Contractile signaling pathways in mouse prostate smooth muscle

Prostate smooth muscle plays an important role in the physiological ejection of prostatic fluid and also in the pathogenesis of benign prostate hyperplasia. Although mouse is the best genetically engineered animal model to identify potential molecular targets for human diseases, only fragmentary information is available for basic mechanism of mouse prostate contraction. Small smooth muscle tubular rings were excised from four mouse prostate lobes to measure their isometric contractions. High K(+) , noradrenaline (NA), or acetylcholine (ACh) was applied with and without various antagonists and/or inhibitors to examine the contractile signaling pathways. Maximum amplitude of agonist-induced contractions varied greatly with different lobes but not with different locations or orientations within each lobe. Both NA and ACh produced large contractions in ventral and dorsal rings, whereas only small contractions were elicited in lateral and anterior rings. Combination of alpha-1 and muscarinic antagonists suppressed K(+) depolarization-induced contraction potently in ventral rings, but slightly in anterior rings. Blocking of either Ca(2+) -release or Ca(2+) -influx reduced agonist-induced contraction of ventral rings, however, a considerable amount of contractility remained even with both blockers. Inhibitors of ROCK and PKC partially inhibited NA-induced contractions, whereas a combination of Ca(2+) -blockers and Ca(2+) -sensitization inhibitors strongly suppressed the contraction. The ejection of prostatic fluid is differentially regulated in each prostate lobe. In ventral prostate smooth muscle, Ca(2+) -release, Ca(2+) -influx, and ROCK- and PKC-mediated Ca(2+) -sensitizations are all involved in NA-induced contractions. This finding is a useful step toward the understanding of the phenotypic changes in the smooth muscle of BPH prostate.

0604 円形噴流にサイドジェットを形成するための噴出条件(OS6-1 噴流,後流およびはく離流れ現象の探求と先端的応用,OS6 噴流,後流およびはく離流れ現象の探求と先端的応用)

When a low density fluid is discharged from a round nozzle, side jets that are radial ejections of jet fluid may be generated at the initial region of the jet. The density ratio between the jet fluid and the ambient fluid is a main parameter for the side-jet formation. Since the side-jet formation is also related to the instability of shear layer, it depends on the velocity gradient of the shear layer in the jet. The velocity gradient is evaluated by a ratio of the momentum thickness and the nozzle diameter at the nozzle exit. Compressibility suppresses the instability and the generation of the side jets. The compressibility is evaluated by a Mach number, which is a ratio defined by an issuing velocity of the jet and a sound velocity in the ambient fluid. Influence of these three parameters on the side-jet formation was examined experimentally. Existence of side jets was confirmed by flow visualization using a laser sheet. Moreover, velocity fluctuations in the core region were measured using a hot-wire anemometer during the side-jet formation.

1100 MASS TRANSPORT USING VORTEX RINGS WITH SWIRL

Behavior of laminar vortex rings with circumferential flow, so-called swirl, were investigated using flow visualization, to evaluate the transport efficiency of the ejected fluid as vortex rings. In this study, the interval time of the vortex ring ejection, the formation number of vortex ring LO/DO (the normalized length of the ejected slug of fluid), and the angular velocity of the ejected fluid ? are changed, while the mean ejection velocity is fixed. When vortex rings were generated at a short time interval, independent of LO/DO and ?, they were broken, and most of the fluid included in them was diffused near the orifice. When the vortex rings with little mutual interference were generated at an appropriate interval time, the breakdown of vortex ring structure is suppressed with moderate swirling flow. In those cases, each vortex ring moves separately for a long distance and the distribution area becomes wider as LO/DO increases.

Effect of pore fluid pressure on the frictional strength of antigorite serpentinite

Triaxial deformation experiments on antigorite serpentinite show a systematic correlation between shear stress and effective normal stress over a wide range of pore pressures (50<Pp<143MPa). Under dry conditions using Ar gas as the pore fluid, the steady-state friction coefficient (μ) is estimated to be 0.66±0.01. In contrast, under wet conditions using distilled water as the pore fluid, μ=0.51±0.01 (i.e., less than under dry conditions). This difference in μ may be caused by charged water on the serpentine surface, which reduces the frictional resistance of the sliding surface in wet environments. The linear correlation between shear stress and effective normal stress suggests that Coulomb's law applies to sliding surfaces during the injection and ejection of pore fluids. This results in a significant mechanical weakening due to elevated pore fluid pressures; consequently, the locations of asperities on plate boundaries may be controlled by the heterogeneous distribution of fluids on the subducting plate interface.