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In this study, the turbulent flow field is simultaneously measured by stereoscopic particle image velocimetry (SPIV) and the wall mass transfer coefficient using the limiting diffusion current technique (LDCT). SPIV measurements of the flow field behind an orifice in a round pipe are performed in the cross and longitudinal sections. One-point linear and quadratic stochastic estimations are employed to calculate the conditional average of the flow field associated with the large wall mass transfer coefficient. The results suggest that the counter-rotating vortex pairs play an important role in the large wall mass transfer coefficient. The flow structures associated with a large wall mass transfer coefficient in the cross sections are found to be similar to the flow structures enhancing the wall heat transfer obtained by a theoretical analysis and numerical study in literature.

This study presents the effects of the orifice to pipe diameter ratio (defined as the β ratio) on the flow field behind a thin circular square-edged orifice plate. We adopted a planar particle image velocimetry (PIV) system using two side-by-side cameras to measure velocity fields of a large area covering the reattachment region. The core, recirculation, and axisymmetric shear-layer regions are first suitably defined, and the characteristic length and velocity scales in different regions are then determined. When the orifice step height and mean streamwise velocity at the vena contracta are selected as the characteristic length and velocity scale, respectively, the mean flow field in the recirculation region shows nearly no β -ratio dependence. When the orifice pipe radius and local maximum mean streamwise velocity in the core region are selected as the characteristic length and velocity scales, respectively, the local peak Reynolds stresses are found to be independent of the β ratio in the shear-layer region close to the orifice plate. However, a β -ratio dependence appears as the flow progresses, and the pipe wall increasingly affects the shear-layer region. Although the mean streamwise velocity profiles in the shear layer show self-similarity, the Reynolds stresses do not maintain a self-similar property, indicating that the normalized statistical quantities at different streamwise locations follow the same profiles in the transverse direction.

We have investigated the particle flux flowing into the axisymmetric end-target in the transient state from attached to detached divertor conditions in the linear plasma device NAGDIS-II. In the transient state, a dramatic decrease of the mean particle flux and a large-amplitude fluctuation with negative and positive spikes were observed. We have analyzed the fluctuation with a newly suggested analysis technique: pre-multiplied cubic spectrum with the wavelet transform. Analysis result indicates that these spikes consist of a few kilohertz components. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this paper, particle image velocimetry and electrochemical measurements were applied simultaneously to examine the relationship between wall shear stress and the three-component velocity field in pipe flow. Moreover, the large-scale motions in the velocity field were separated into very-large-scale motions (VLSMs) and large-scale motions (LSMs) to investigate their respective influences on the wall shear stress fluctuations. The conditional velocity field during negative wall shear stress fluctuations confirmed the existence of the “footprints” of the streamwise and wall-normal velocity components in VLSMs. Further, a pair of counter-rotating roll modes was found to appear in the VLSMs, exhibiting length scales of λx>3R, where λx is the streamwise wavelength and R is the pipe radius. In contrast, in LSMs, which exhibit length scales of 0.6R

For the purpose of future visualization of the flow field in superfluid helium-4, clusters of the triplet state excimer 4He2* are generated along the micro-scale recoil tracks of the neutron-absorption reaction n + 3He → 3T + p. This reaction is induced by neutron irradiation of the 3He fraction contained in natural isotopic abundance liquid helium with neutron beams either from the Japan Proton Accelerator Research Complex, Materials and Life Science Experimental Facility (JPARC)/Materials and Life Science Experimental Facility or from the Kyoto University Institute for Integrated Radiation and Nuclear Science. These 4He2* clusters are expected to be ideal tracers of the normal-fluid component in superfluid helium with several advantageous properties. Evidence of the excimer generation is inferred by detection of laser induced fluorescence emitted from the 4He2* clusters excited by a purpose-built short pulse gain-switched titanium:sapphire (Ti:sa) laser operating at a wavelength of 905 nm. The setup and performance characteristics of the laser system including the Ti:sa and two continuous wave re-pumping lasers are described. Detection at the fluorescence wavelength of 640 nm is performed by using optical bandpass filtered photomultiplier tubes (PMT). Electrical noise in the PMT acquisition traces could successfully be suppressed by post-processing with a simple algorithm. Despite other laser-related backgrounds, the excimer was clearly identified by its fluorescence decay characteristics. Production of the excimer was found to be proportional to the neutron flux, adjusted via insertion of different collimators into the neutron beam. These observations suggest that the apparatus we constructed does function in the expected manner and, therefore, has the potential for groundbreaking turbulence research with superfluid helium.

Direct numerical simulations of turbulent channel flows up to $R\phantom{\rule{0}{0ex}}{e}_{\ensuremath{\tau}}=8000$ find logarithmic variations both in the mean velocity and streamwise turbulent variance, although these logarithmic regions do not agree with each other.

In order to investigate the blobby plasma transport in the Large Helical Device, we have measured electrostatic fluctuations around the divertor leg by using a newly-designed multi-pin reciprocating Langmuir probe. Near the low-field side edge of the divertor leg, positive spikes of ion saturation current fluctuation were observed. In addition, the electric field which correlates with the ion saturation current fluctuation was firstly evaluated with the neighboring floating potential measurement. Considering the positional relationship with the magnetic geometry, the identified direction of the electric field inside the blobs is consistent with the theoretically predicted E × B motion. By applying the conditional averaging method, a quantitative speed of the blobs was preliminary estimated.

Uterine inversion is a state wherein the endometrial surface is inverted. Although this condition may be observed in nonpregnant women, it most commonly develops at the time of delivery. In the present case, a 37-year-old woman without any remarkable history developed acute puerperal uterine inversion after the successful induction of labor. Following the delivery, she complained twice of severe lower abdominal pain; subsequently, hemorrhage was noted at the site of partial detachment of the placenta. These findings led to a diagnosis of placenta accreta, and the patient developed a state of shock. A Bakri postpartum balloon was inserted into the uterine cavity under ultrasonographic guidance and was filled with physiological saline for treatment of this condition. With this procedure, the uterine inversion was completely reduced and the hemorrhage was stopped. Moreover, no reinversion was observed in the postoperative period. These findings suggest that a Bakri postpartum balloon can be used to noninvasively reduce uterine inversion and prevent its recurrence.

In this paper, we report on high Reynolds number and highly accurate experimental facilities for turbulent pipe flow established by the National Metrology Institute of Japan (NMIJ). One of the facilities, called the High Reynolds number actual flow facility (Hi-Reff), is capable of handling a maximum bulk Reynolds number of \({Re}_\mathrm{D} = 2.0 \times 10^7\). The most remarkable feature of this facility is its highly accurate flow rate measurements. The expanded uncertainty of the volumetric flow rate is estimated as 0.040–0.10%. Such a low flow rate measurement uncertainty contributes to extremely accurate estimations of inner-scale variables such as friction velocity. This paper presents the details and advantages provided by this NMIJ facility in relation to turbulent pipe experiments.

Fractal property of the helium irradiated nanostructured tungsten was investigated from the scanning electron microscope (SEM) micrographs, gas adsorption isotherms, and transmission electron microscope (TEM) micrographs. From the SEM micrographs, fractal dimension and the parameter d min , which characterizes the SEM texture image, were deduced, and the fractal dimension was compared with the one obtained from the gas adsorption isotherms. It was revealed that the fractal dimension obtained from the top view SEM micrographs was significantly lower than that from the adsorption isotherms. From the cross sectional SEM micrographs, two power law relations were identified in two different scales, and the fractal dimension from the adsorption was in between the two fractal dimensions. From the TEM micrographs, it was found that the porosity distribution also has fractal relation with height of the nanostructures when the nanostructures were sufficiently grown.

We study the logarithmic behavior of the pressure variance from the datasets obtained from direct numerical simulations of turbulent channel flow for friction Reynolds number Reτ up to 4000. The higher-order moments of p were found to follow logarithmic behaviors at the same distances from the wall where shows its log profile. The same results have been confirmed for the spanwise velocity fluctuations w at the same Reynolds numbers, with both p and w following a super-Gaussian behavior. The minimum Reynolds number for and log profiles to appear is Reτ ≈ 500, where flow structures O(h) or less were found to significantly contribute to these profiles. The configuration of the hairpin eddy structures obtained from the conditional sampling at different wall-normal locations showed a strong link between p and w fluctuations. Positive pressure fluctuations are located between the legs of the hairpin eddy, while the negative pressure fluctuations are consistent with the head part of the hairpin eddy. Positive and negative spanwise velocity fluctuations are strongly positioned with the legs of the hairpin eddy, consistent with the counter-rotating motion resulting from the eddy legs. The structures were also found to be geometrically self-similar such that their length and their width increase linearly with the distance from the wall.

We investigate the turbulent structures associated with positive and negative high-amplitude wall pressure peaks in fully developed turbulent channel flows. The analysis is performed by conditional sampling of a channel flow dataset computed in direct numerical simulations. The Reynolds number was varied from 180 to 4000 based on the channel half-depth h and the friction velocity u τ . Positive and negative wall pressure events were associated with small-scale vortex structures identified by Q-criterion. When scaled in wall units, the overall size of the structure was independent of Reynolds number. Positive and negative wall pressure events were also associated with a large-scale sweep motion (of ) from the outer layer, which constitutes a shear layer in the near-wall region. In a statistical analysis of the instantaneous pressure field, a sequence of negative and positive pressure peaks was found to predominate at the wall. The relative contributions from the large- and small-scale structures were qualitatively assessed by investigating the rapid and slow pressure terms from Poisson's equation. Both terms contributed nearly equally to the positive wall pressure peaks, but the slow term dominated the negative pressure peaks (with a relative contribution of approximately 60%).

The relationship between the flow resistance of a turbulent flow over triangular ribs regularly distributed on a wall surface and the velocity distribution around the ribs was investigated experimentally. A concentric cylinder device composed of an inner test cylinder and an outer cylinder was employed to measure the flow resistance using the torque of the shaft of the inner cylinder and the velocity distribution of the flow around a rib by laser Doppler velocimetry (LDV) simultaneously. We prepared four inner test cylinders having 4, 8, 12 and 16 triangular ribs on the surface with the same interval between them. Each rib had an isosceles right triangle V-shape and a height of 2 mm. To investigate the relationship between flow resistance and velocity distribution, we estimated the frictional drag and pressure drag acting on the surface of the ribs separately using the velocity distribution. Therefore, we could also estimate the total flow resistance using the velocity distribution. As a result of the experiment, the flow resistance and the attachment point downstream of the rib were shown to depend on the distance between ribs. Moreover, the flow resistance estimated using the velocity distribution had good agreement with the flow resistance measured using the torque of the inner cylinder.

A new statistical analysis technique is applied to the spatial behavior of coherent plasma structures around the plasma column in the linear plasma device NAGDIS-II. The two-dimensional behavior of visible light emission is measured using a fast-imaging camera, and the movie data shows that spiral shaped structures appear intermittently and rotate around the plasma column. The ejection position of the structures in the azimuthal direction is detected and then analyzed. To extract detailed statistics in the spatial domain, the effect of the global rotation is removed. By reconstructing the trajectory of a structure over a 360° range and using rescaled range (R/S) analysis, it is found that the trajectory is similar to a Brownian motion superimposed upon the global rotation. This result indicates that the process of generation of these structures is influenced by previous ejection events (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We measured the correlation spectrum ${\hat {Q} }_{p} (\mathbi{k})$ of pressure fluctuations in a driving mixing layer with a Taylor-scale Reynolds number ${R}_{\lambda } $ up to ${\simeq }700$ by a newly developed pressure probe with spatial and temporal resolutions that are sufficient to analyse inertial-subrange statistics. The influence of the mean velocity gradient tensor ${S}_{ij} $ in the mixing layer, which is almost constant near its centreline, is studied using an idea similar to that underlying the linear response theory developed in statistical mechanics for systems at or near thermal equilibrium. If we write the spectrum ${\hat {Q} }_{p} (\mathbi{k})$ as ${\hat {Q} }_{p} (\mathbi{k})= { \hat {Q} }_{p}^{(0)} (\mathbi{k})+ \mrm{\Delta} {\hat {Q} }_{p} (\mathbi{k})$, where ${ \hat {Q} }_{p}^{(0)} (\mathbi{k})$ is the isotropic Kolmogorov spectrum in the absence of mean shear, then for small ${S}_{ij} $ the deviation $ \mrm{\Delta} {\hat {Q} }_{p} (\mathbi{k})$ due to the shear is approximately linear and is determined by a few non-dimensional universal constants in addition to ${S}_{ij} $, $k$ and the mean energy dissipation rate. We also measured the pressure–velocity and velocity–velocity correlation spectra. Deviations from isotropy due to shear are shown to be approximately proportional to ${S}_{ij} $ at large ${R}_{\lambda } $.

Flow Accelerated Corrosion (FAC) is one of the issues to be noticed considerably in plant piping management. For the integrity and safety of the plant, the wall-thinning and thinning rate due to FAC should be clearly predicted in pipe wall inspection. In this paper, we study FAC from the view point of flow dynamics. The mass transfer coefficient is measured by the electrochemical method behind the orifice. Changing the orifice size, the peak location of mass transfer coefficient and its maximum value is evaluated by the flow condition and orifice parameter. The future problems are briefly summarized.

In IFMIF/EVEDA, tasks for lithium target system consist of 5 validation tasks (LF1-5) and a design task (LF6), and are shared by Japan and Europe. Japan is covering LF1, LF2, LF4, LF5 and LF6, and JAEA as an Implementing Agency is organizing these tasks. Japanese universities contribute these tasks. The purpose of LF1 task is to construct and operate EVEDA Li test loop (ELTL) with diagnostics and purification systems for the validation of Li target facility. ELTL will be constructed at the end of February in 2011 and the operation will be started at the summer in 2011. LF2 and LF4 are basic research for the diagnostics and purification system, respectively. And LF2 and LF4 have also contributed the construction of the ELTL (LF1). LF5 is focusing on the remote handling for the replacement of the target assembly. Major deliverable of LF6 is finally engineering design report, which is assembled with all validation tasks, and this activity will be gradually enhanced to the end of IFMIF/EVEDA.

The Engineering Validation and Engineering Design Activities (EVEDA) of the International Fusion Materials Irradiation Facility (IFMIF) have been started. As Japanese activities for the target system, the EVEDA Lithium (Li) Test Loop to simulate hydraulic and impurity conditions of the IFMIF Li loop is under design. The feasibility of the thermo-mechanical structure of the target assembly and the replaceable back-plate made of F82H and 316L stainless steel is a key research subject. Toward final validation at the EVEDA loop, diagnostics systems applicable to the high-speed free-surface Li flow and hot traps to control nitrogen and hydrogen in Li loop have been investigated. In the remote handling subject of target assemblies and the replaceable back-plates activated by irradiation up to 50 dpa/y, lip welds on 316L-316L by laser and dissimilar metal welds on F82H-316L are necessary. Water experiments and hydraulic/thermo-mechanical analyses of the back-plate are underway.

Large-scale circulation in the confined thermal turbulence of mercury is studied experimentally. The instantaneous velocity profile at 128 points is directly measured using ultrasonic velocimetry and the temperature fluctuation is simultaneously obtained by a small thermistor at the cell center. The periodic velocity oscillation is observed for aspect ratios Γ = 1 , 2 , but for Γ = 0.5 . The temperature oscillation is confirmed only in the Γ = 2 cell. It is found that the flow patterns depending on the aspect ratio are characterized sufficiently by the joint probability density function up to R a = 4 × 10 8 .

This paper reports further experimental results obtained in high Reynolds number actual flow facility in Japan. The experiments were performed in a pipe flow with water, and the friction Reynolds number was varied up to Reτ = 5.3 × 104. This high Reynolds number was achieved by using water as the working fluid and adopting a large-diameter pipe (387 mm) while controlling the flow rate and temperature with high accuracy and precision. The streamwise velocity was measured by laser Doppler velocimetry close to the wall, and the mean velocity profile, called log-law profile U+ = (1/κ) ln(y+) + B, is especially focused. After careful verification of the mean velocity profiles in terms of the flow rate accuracy and an evaluation of the consistency of the present results with those from previously measurements in a smaller pipe (100 mm), it was found that the value of κ asymptotically approaches a constant value of κ = 0.384.

We have analyzed the 2D convective motion of coherent structures, which is associated with plasma blobs, under attached and detached plasma conditions of a linear divertor simulator, NAGDIS-II. Data analysis of probes and a fast-imaging camera by spatio-temporal correlation with three decomposition and proper orthogonal decomposition (POD) was carried out to determine the basic properties of coherent structures detached from a bulk plasma column. Under the attached plasma condition, the spatio-temporal correlation with three decomposition based on the probe measurement showed that two types of coherent structures with different sizes detached from the bulk plasma and the azimuthally localized structure radially propagated faster than the larger structure. Under the detached plasma condition, movies taken by the fast-imaging camera clearly showed the dynamics of a 2D spiral structure at peripheral regions of the bulk plasma; this dynamics caused the broadening of the plasma profile. The POD method was used for the data processing of the movies to obtain low-dimensional mode shapes. It was found that the m = 1 and m = 2 ring-shaped coherent structures were dominant. Comparison between the POD analysis of both the movie and the probe data suggested that the coherent structure could be detached from the bulk plasma mainly associated with the m = 2 fluctuation. This phenomena could play an important role in the reduction of the particle and heat flux as well as the plasma recombination processes in plasma detachment (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)