PIV Analysis Research Articles

Visualization of the phase change behavior of sodium acetate trihydrate for latent heat storage

A latent heat storage system has higher storage capacity than a sensible heat storage system. Sodium acetate trihydrate has large latent heat at its melting point of 58 °C, which is suitable for a hot-water supply system. The crystal growth rate, convective flow and temperature fields during the phase change of sodium acetate trihydrate were quantitatively visualized using PIV analysis with temperature sensitive particles (TSPs) which has enabled a simultaneous measurement of the velocity and temperature fields. The velocity field was obtained by the PIV analysis of TSPs and the temperature field was simultaneously visualized from the intensity decay of TSPs. The visualized temperature of the solid–liquid multiphase flow increased slowly as crystals grew. The temperature around the crystal was lower than the melting temperature during the phase change process with the convection because the crystal was needle-shaped and a liquid phase was also present between crystals. After the convective velocity rapidly decreased due to the solidification, the temperature started to increase to around the melting point. Buoyancy-driven convection occurred under certain conditions of supercooling temperature and concentration of sodium acetate trihydrate. However, convection could not be fully developed over a certain range of concentration and supercooling temperature because the crystal growth rate was too fast and solidification was completed quickly.

羽ばたき機構を有する楕円翼に生じる流体力測定とPIV解析

Recently, various studies of Micro Air Vehicle (MAV) and Unmanned Air Vehicle (UAV) have been reported from wide range points of view. The aim of this study is to research the aerodynamic improvement of a flapping wing in low Reynold’s number region to develop an applicative these air vehicle. The six kinds of elliptical wings made of stainless steel are used in the flapping wing. The effects of flapping amplitude and wing configuration regarding the aerodynamic characteristics are investigated in detail. The fluid force measurement by six component load cell and PIV analysis are performed as the experimental method. In the flapping wing experiment, the simultaneous measuring of the fluid force measurement and PIV analysis is tried by using the trigger signal from the encoder attached to the flapping model. The relations between the aerodynamic superiority and the vortex behavior around the models are demonstrated.

S0530401 プラズマアクチュエータを用いたGurney Flap効果による翼周りの流れの能動制御

Active control of lift force on NACA0015 airfoil by jets induced by a dielectric barrier discharge plasma actuator (DBD-PA) was experimentally investigated. The exposed electrode of DBD-PA was varied at x/c=0.6, 0.7, 0.8 and 0.9 on the pressure surface of NACA0015. Tangential jet, which maximum velocity in terms of the free stream is u_<j-max>/U_∞ &ap; 0.12, was induced by applying 5.0 kV_<p-p> at 20 kHz toward the upstream direction under Reynolds number Re = 3.3×10^4. It was found that lift coefficient increases in the cases of x/c=0.8 and 0.9 whilst it tends to decrease for x/c = 0.6 and 0.7. It was confirmed by PIV analysis that v component of velocity in the downstream from the trailing edge decreases in comparison with that of no flow control when lift coefficient is enlarged.

S0530204 鋸歯多電極プラズマアクチュエータの噴流特性

The objective of this research is to demonstrate the advantage and characterize the thrust performance and the induced flow field generated by the TED plasma actuator with sawtooth electrode. The induced body force of the sawtooth TED plasma actuator was investigated on quiescent air, by measuring thrust of the induced jet. A time-resolved PIV was used to acquire velocity field. From the results of the thrust measurement, it was confirmed that the sawtooth TED actuator enhances the thrust compared to the straight-edge TED actuator. From the PIV analysis, it was clearly found that the sawtooth TED actuator generates uniform facing jet from both of the electrode, by the uniform generation of the plasma from the sawtooth vertexes.

1203 間欠駆動プラズマアクチュエータを用いたブラフボディ剥離制御流れ場の時系列PIV解析(流体工学II)

1203 間欠駆動プラズマアクチュエータを用いたブラフボディ剥離制御流れ場の時系列PIV解析(流体工学II)

301 ホール型電気集じん装置内におけるイオン風と粒子挙動のPIV解析(大気環境保全・改善技術(1))

301 ホール型電気集じん装置内におけるイオン風と粒子挙動のPIV解析(大気環境保全・改善技術(1))

1619 トルクコンバータモデル内部流れのダイナミックステレオPIV計測と速度場の空間再構築

Unsteady flow field inside a torque converter model made of acrylic resign is measured using a dynamic stereo PIV system. The index-matching technique is used to visualize the flow field in the gap between an impeller and a turbine. The rotation speed of the impeller is 250rmp while those of the turbine are 25rmp and 150rpm, giving the speed ratios of 0.1 and 0.6, respectively. The instantaneous velocity maps obtained from the stereo PIV analysis are phase averaged according to the relative angles of the impeller, the turbine and the stator. Those phase averaged three-component velocity maps are reconstructed to visualize 3-D characteristics of this complex unsteady flow field.

Cell Divisions Cause Long-Range Well-Ordered Vorticity Patterns in Endothelial Tissue

Endothelial cells line the blood vessels of the circulatory system and adhere tightly to their neighbors to prevent leakage, thus causing the cells to move within the endothelial monolayer i a highly collectively fashion. In healthy blood vessels with a laminar blood flow, the endothelial cell division rate is low, only sufficient to replace apoptotic cells. The division rate significantly increases during embryonic development and under halted or turbulent flow. Using PIV analysis we investigated the long-range dynamics induced by cell division in an endothelial monolayer under non-flow conditions, thus mimicking the conditions during vessel formation or around blood clots. A cell division locally injects energy into the system and strongly influences monolayer dynamics. We show that cell divisions induce long-range, well-ordered vortex patterns extending several cell diameters away from the division site. This is rather surprising considering the system's low Reynolds number. Our experimental results are reproduced by a hydrodynamic continuum model simulating division as a local pressure increase in a non-nematic, meso-scale turbulent state. The long-range physical communication may be crucial for embryonic development and for healing endothelial tissue around blood clots.View Large Image | View Hi-Res Image | Download PowerPoint Slide

Feasibility of Particle Imaging Velocimetry in Cone Calorimeter experiments

Experimental results are reported on the feasibility of particle imaging velocimetry in a cone calorimeter. PolyMethyl MethAcrylAte (PMMA) plates have been contaminated at their surface by alumina particles (Dev=4.4 ?m) as seeding particles allowing PIV analysis. Particles are released by bubble bursting during the thermal degradation of the PMMA for each heat flux investigated (25, 35 and 45 kW/m2). A “layer” of particles could be noticed for the highest heat flux (35 and 45 kW/m2) while for the smallest flux (25 kW/m2), the release is confined and more erratic. Velocity increases as a function of the height above the polymer surface from 0.03 m/s at the PMMA surface to 0.3 m/s at the bottom of the conical heater and these results are in good agreement with previous experiments and numerical simulations. As an overall conclusion, this first attempt demonstrates the huge potential of PIV analysis, associated to our deposition set-up, for investigating flow field during cone calorimeter experiments involving bubbling polymers.

0517 電界共役流体のマイクロジェット発生メカニズム解明のための可視化実験

An electro-conjugate fluid is a new type of functional fluid, which can exhibit functional properties in an applied electric field. The application of a high voltage to a pair of electrodes immersed in a certain dielectric fluid induces the occurrence of a strong micro-jet between the positive and negative electrodes. These fluids are called the electro-conjugate fluid, and the phenomenon of the occurrence of the micro-jet is called the ECF effect. We have performed a flow visualization experiment with the 2D PIV analysis. For the case of the cylinder-cylinder electrodes, the maximum velocity of the micro-jet arises on the line connected between the centers of the positive and negative electrodes. A micro-jet occurs at the position of the maximum gradient of the electric field at the surface of the positive electrode and flows toward the largest gradient position of the negative electrode.

The rheology of dense granular flows in a disc impeller high shear granulator

The aim of the present study is to evaluate the new approach to dense particulate systems proposed by Jop et al. [1], in the dense regions of a High Shear Granulator (HSG). Wet granulation in high shear mixers is a common process in pharmaceutical technologies and a good understanding of the local mixing and flow patterns is a pre-requisite for this step. In the aforementioned model a dense granular flow is characterized as a visco-plastic fluid. Therefore the local rheology of the system can be predicted assuming averaged and virtual properties and a constant solid volume fraction.A simple disc impeller granulator with glass spheres was chosen for this study. The dynamics of the system have been studied using several techniques including PIV analyses, CFD simulation and image processing. The flow behaviour has been characterized for various impeller speeds and particle loads. Several cases have been analyzed from different aspects both in experiments and through equivalent simulations to evaluate the validity of the model in these particular applications.Results look promising in spite of the simplicity of the model. The model was found to give a good general description of the flow field and bed shape. On the other hand the model is insufficient in some aspects; mostly related to the regions with low volume fraction. The next step would be to combine the model with conventional models on rapid granular flow such as Kinetic Theory of Granular Flows (KTGF).

10704 プラズマアクチュエータによる縦渦対の誘起(OS5-1【流れの計測と制御(1)】)

The aim of this study is to introduce streamwise vortex pairs generated by plasma actuators into separated shear layer from circular cylinder. The electrodes of the plasma actuator placed on the surface of the circular cylinder were arranged in the spanwise direction. Induced jets by the actuators interacted each other and produced streamwise vortex pairs. Flow visualizations in still fluid and in the wake region of the cylinder were performed by a high speed camera and PIV analysis. Vortex structure in the wake behind the circular cylinder was measured by X-type hot-wire measurement. It was found that the streamwise vortex pairs affected the vortical structure in shear layer from circular cylinder.

J013012 回転円盤周りの3次元流動様相に関する実験的研究([J013-01]流体情報学とデータ解析(1))

In a study of a flow caused by a rotating disk in a casing, as for many of past studies, most of the form of the rotating disk is not considered. However, it became clear by the study of late years that a radial gap affected the flow between the casing base and rotating disks greatly. In this study, we used the rotating disk having different forms and changed the size of the gap in the cylinder casing and tested it about the influence that the radial gap gave to the flow near the fixed disk. As a result, it has been observed that "bead-like-vortex" is generated in a disk. "Bead-like-vortex" is investigated in detail and the result of the experiment and PIV analysis is shown in this paper.

High-Reynolds-Number Flow past a Pipe

The present aim is to reveal the flow past a pipe which is immersed parallel to the mainstream at high Reynolds numbers. In a wind tunnel, we carry out (1) base-pressure measurements, (2) velocity-fluctuation measurements using a hot-wire anemometer and (3) flow visualisations by a smoke-wire method with PIV analyses, where we take consecutive picutures using a high-speed camcorder to obtain quantitative flow-field information such as velocity vector and vorticity. The tested parameter ranges are as follows: Re = 2.0×103 - 1.3×104, d/t = 4.0 - 10.0 and l/t = 1.0 - 10.0, where Re, d, t and l are the Reynolds number, mean diameter, thickness and length of the pipe, respectively. As a result, the Re effects are negligible. The base-suction coefficient -Cpb monotonically decreases with decreasing d/t, or with increasing l/t. We propose a unified formula to predict -Cpb, which are consistent with both a two-dimensional prism and a rod for l/t < 4.0 in addition to a ring. In contrast, the Strouhal number St almost coincides with that for a two-dimensional prism at any l/t, if we can detected any dominant frequencies. In addition, we conduct flow visualisations, and reveal the effects upon axisymmetry of wake. Finally, we classify the flow into three modes based on both periodicity and axisymmetry. Such a modal classification reveals that the enhancement of flow's irregularity corresponds to the decrease of -Cpb.

Visualization of nodal flow that determines left-right asymmetry in the mouse embryo

Our body has left-right asymmetry of internal organs. In the mouse embryo, left-right asymmetry is established at 8.0 days after fertilization (E 8.0). At E 8.0, the node cavity that has motile cilia appears at the midline of the embryo. The cilia rotate in clockwise direction and generate leftward fluid flow. The leftward flow (nodal flow) breaks symmetry of body by controlling gene expression. In this work, we quantitatively visualized flow field of the nodal flow in wild type and ciliary mutant embryo. PIV analysis reveals that the local fluid flow is sufficient to break left-right symmetry of mouse embryo. This suggests that the node cells have sensitive system for fluid flow. We conclude that PIV is very powerful tool for dissecting biological issues.

1P2-4 PIV analysis of Acoustic Streaming Generated by a Polyurea Ultrasonic Transducer(Poster Session)

1P2-4 PIV analysis of Acoustic Streaming Generated by a Polyurea Ultrasonic Transducer(Poster Session)

0615 同軸型DBDプラズマアクチュエータを用いた噴流制御(OS6-3 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)

This study investigated the use of a coaxial dielectric barrier discharge plasma actuator at a nozzle exit for jet diffusion control. In order to achieve enhanced mixing of the primary jet flow, the influence of the input voltage and frequency to the plasma actuator was examined. Intermittent control using the plasma actuator was also attempted by varying the driving frequency and the duty ratio. Based on the results of a PIV analysis, the optimum conditions for jet diffusion control were found to be a driving frequency that matched the preferred frequency and a duty ratio at 50%.

Control of vortex shedding from a blunt trailing edge using plasma actuators

An experimental investigation on the use of plasma actuators for vortex shedding suppression is performed. The vortex shedding phenomenon at the blunt trailing edge of an elongated D-shaped body is specifically investigated. The study is focused on the laminar boundary layer regime on an elongated D-shaped flat plate of 12mm thickness at free-stream velocity up to approximately 10m/s. Dielectric barrier discharge plasma actuators are utilized in several geometrical configurations at the trailing edge of the plate and are operated in continuous and pulsed mode. Several operational parameters such as applied voltage, carrier and pulse frequency and duty cycle are investigated. Results reveal that tangential actuation both in the downstream or upstream direction yields very limited effects on the coherent organization in the wake. Instead, symmetrical actuation from the base edges towards the wake centerline, proved to be very effective prompting a more detailed study of this actuator configuration. At external flow conditions, the reduction of the Kármán wake component is monitored by the modal energy spectrum obtained from proper orthogonal decomposition of PIV data in the stream-wise/wall-normal plane of the developing wake region. The suppression of coherent vortex shedding is further ascertained with time-resolved visualizations obtained by high-speed PIV and spectral analysis conducted with hot-wire anemometry. In order to gain a complete understanding of the forcing mechanism, the velocity field induced by this actuator configuration is additionally investigated by means of high-speed PIV measurements conducted in initially quiescent flow. It is verified that the suppression mechanism involves the breakup of communication between the two shear layers simultaneously to moderate momentum addition into the recirculation area.

PIV analysis of merging flow in a simplified model of a rotary kiln

Rotary kilns are used in a variety of industrial applications. The focus in this work is on characterizing the non-reacting, isothermal flow field in a rotary kiln used for iron ore pelletization. A downscaled, simplified model of the kiln is experimentally investigated using particle image velocimetry. Five different momentum flux ratios of the two inlet ducts to the kiln are investigated in order to evaluate its effect on the flow field in general and the recirculation zone in particular. Time-averaged and phase-averaged analyses are reported, and it is found that the flow field resembles that of two parallel merging jets, with the same characteristic flow zones. The back plate separating the inlet ducts acts as a bluff body to the flow and creates a region of reversed flow behind it. Due to the semicircular cross-section of the jets, the wake is elongated along the walls. Conclusions are that the flow field shows a dependence on momentum flux ratio of the jets; as the momentum flux ratio approaches unity, there is an increasing presence of von Karman-type coherent structures with a Strouhal number of between 0.16 and 0.18. These large-scale structures enhance the mixing of the jets and also affect the size of the recirculation zone. It is also shown that the inclination of the upper inlet duct leads to a decrease in length of the recirculation zone in certain cases.

Automatic segmentation of ultrasound contrast images of arteries for determining boundaries between arterial inner walls and blood flows: in vivo animal studies

Ultrasound contrast images could be used together with ultrasonic particle image velocimetry technology to obtain multi-component field of arterial blood velocity and shear stress, which is helpful to understand atherogenic process and predict plaque rupture. Near-wall flow can hardly be measured accurately due to artery pulsation and tissue movement. Measuring accuracy for PIV analysis can be improved by detecting the boundaries between arteries and blood flow and determining region of interest in arterial ultrasound contrast images. A fully-automatic algorithm is proposed, which is named as time frame difference snake(TFDS). The ultrasound contrast images are subjected to median filter using a window frame difference method to de-speckle the lumen and highlight the arterial wall. The filtered image is subsequently subjected to an automatic initialization procedure to obtain the initial contour for the snake model. The TFDS model takes advantages of the standard deviation matrix of consecutive images, and is applied to obtain the final delineation of the boundary. Ultrasound contrast images of mouse carotid arteries are used for performance evaluation. The computer-generated segmentation is compared with the hand-outlined delineations. Statistical analysis shows that our algorithm's segmentations agree with that of trained operators for both the near-end and far-end carotid artery wall.