Flow fields of the M2.2 jets impinging on an inclined flat plate at high plate-angles are experimentally investigated using surface pressure measurement with Pressure Sensitive Paint and Schlieren flow visualization. The present experiments show that x/Ls', (the distance from nozzle lip to the point where the jet first impinges on a plate normalized by the distance from nozzle lip to the point where jet expands the most), is still the dominant parameter defining the flow types at high plate angles between 60 and 90 degrees. The present study also shows that the flow type prediction method proposed for the plate angles between 30 and 60 degrees by Nakai et al. requires other considerations when being applied to the flows at higher plate angles. In the present experiments, a new flow type (axisymmetric jet with bubble) is also observed.

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Aerodynamic interaction between a panhead and an articulated system strongly affects aerodynamic and aeroacoustic characteristics of the Shinkansen pantograph. Hence, to clarify the features of the aerodynamic interaction is very important for developing a new pantograph and for its design. In this study, surface pressure field on the panhead were measured in a wind tunnel with pressure-sensitive paint (PSP) specially dispensed for use in low-speed range. This measurement provided detail information of pressure distribution on a panhead. As a result, some significant features of the aerodynamic interaction between the panhead and the articulated system were clarified, showing that the pressure measurements with PSP proved to be a powerful tool to estimate the aerodynamics interaction of the Shikansen pantograph system.

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A new optical pressure measurement technique has recently received wide attention. This scheme is based on the fact that some compounds emit light when excited by a suitable light source (photoluminescence).The intensity of the light is inversely related to partial pressure of oxygen (oxygen quenched), and is of longer wavelength than the excitation light. Taking pressure distribution on the surface is now practical. However, pressure distribution in space is not. Taking pressure distribution in space approached by lifetime method is discussed. As a result, it was confirmed to be able to measure the three-dimensional pressure distribution by using the time constant method.

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A temperature sensitive particle, which can be utilized for the three-dimensional non-intrusive simultaneous measurement of velocity and temperature of water flow, had been developed by one of the author of this study. Presently, non-intrusive measurement of surface temperature has been carried out by developing a temperature sensitive paint and its thermo-optical characteristics are quantified. Even though the temperature sensitive particle can be formed by introducing a fluorescent substance into polystyrene, it cannot be used as a paint which elastically covers many kind of surface. Presently, several polymers have been investigated for the base material for the paint and the polyvinylbuthyral (PVB) is found to fit the condition very well. The thermo-optical characteristics of the temperature sensitive paint made from PVB has been intensively investigated. The optimal concentration of the fluorescent dye and the solvent has been quantified. The effect of the thickness of a paint and its unsteady response are also investigated.

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Flow analysis of medical blood pump for assist circulation is important method to evaluate pump character. CFD (computer fluid dynamics), flow visualization, used to apply for these analysis. These methods could not evaluate the all surface of real blood pump. In this study, we used PSP (Pressure Sensitive Paint) to analyze the pump surface especially impeller surface of centrifugal blood pump. The impeller of centrifugal pump painted on PtTFPP was in the test circulation system and changed the oxygen concentration of water by oxygenator (artificial lung). The intensity of PtTFPP was measured by CCD camera with UV LED excitation. When concentration of oxygen induced into the oxygenator changed from 21% to 100%, the intensity changed on Stern-Volmer's low.

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In recent years, the interest in microdevices and systems has increased rapidly. Gaseous flow through and within such devices is a principal consideration in many applications, and its understanding can be crucial for optimization of performance. Most of the sensors applied to MEMS devices measurement have limited resolution restricted by the sensor size and device geometry. Pressure-sensitive paint (PSP) is one of the options for global distribution measurement in MEMS devices. PSP is a "molecular sensor, " and has an enough resolution for MEMS. In this paper, we demonstrate the use of PSP for quantitative measurement of pressure distribution in a supersonic micronozzle of the nozzle throat 250μm, such as those that might be employed for flow control and/or small satellite orbit maintenance.

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Pressure-sensitive luminescent coating on porous anodized aluminum (AA-PSP) was applied to measure non-periodic unsteady pressure distribution on a wind-tunnel model. A high-speed digital video camera was used to capture the PSP signal. A hydrophobic coating was applied on the anodized aluminum surface to suppress the humid sensitivity of the AA-PSP. A temperature sensitive paint was used to obtain the temperature distribution instantaneously with the pressure. The temperature data was used to correct the PSP response. The present system was applied to measure the pressure distribution on a delta wing at a high angle of attack in transonic flow. The non-periodic unsteady pressure distribution on the delta wing was successfully measured with the sampling rate of 1 kHz and within a few percents error in absolute pressure level.

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An aerospike nozzle has been expected as a candidate for an engine of reusable space shuttle to respond to growing demand for rocket-launching and its cost reduction. It has been reported that sidewalls of linear-type aerospike nozzles can suppress undesirable sideward flow expansion.
In this study, the flow field around the linear-type aerospike nozzle with sidewalls and the nozzle without sidewalls are compared to confirm the effect of the sidewalls experimentally. Laser induced fluorescence is used to visualize and analyze flow fields around the nozzles. PSP is also applied to measurement of pressure distribution on the nozzle surfaces. The nozzles are set into a vacuum chamber to achieve larger pressure ratios PR (P _s: source pressure in a reservoir, P _a: ambient pressure in a vacuum chamber) because jet structures are affected mainly by pressure ratios.

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The intensity-based method is a most common technique by which Pressure-Sensitive Paint images can be converted to the surface pressure. However, this method cannot be applied to a cryogenic wind tunnel because the thermal equilibrium condition cannot be achieved when stopping the tunnel to take the wind-off reference image. In the present experiment, we applied the lifetime-based method to a cryogenic wind tunnel to calculate surface pressure from two images obtained during the wind-on condition. In this experiment, the circular-arc bump model sprayed with PtTFPP/PTMSP paint was tested at the JAXA 0.1m Cryogenic Transonic Wind Tunnel using a UV-LED pulse illuminator and a multi-gated CCD camera. As a result, we could succeed in visualizing surface pressure distribution induced by a shock wave on the model by using lifetime PSP imaging method. This result has demonstrated a feasibility of using lifetime imaging method to a cryogenic wind tunnel.

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Heat flux measurement in a wind tunnel is an indispensable requirement for the next generation re-entry vehicle design. Heat flux is usually calculated from a temporal change in surface temperature. Temperature-Sensitive Paint (TSP) is a global temperature measurement technique based on photochemical reaction. This technique has been already applied to a hypersonic shock tunnel, but poses some problems caused by TSP layer thickness. In this paper, the relationship between TSP layer thickness and measurement accuracy in heat flux was studied systematically. A test model is made of engineering ceramic, which coated with TSP composed of Ru(phen) ³⁺ as luminophore and polyacrylic acid as binder. The layer thickness was varied from 1 to 9 micro meters. Wind tunnel tests were conducted in the JAXA 0.44-m Hypersonic Shock Tunnel. The model was tested in Mach 10 hypersonic flow and heat flux caused by aerodynamic heating was measured. A comparison between TSP data and conventional thermocouple data showed that the relationship between the layer thickness and the temperature error is not a simple liner relationship predicted by the theory. The deviation from the theory is significant particularly for the cases with very thin coatings.

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A variety of ways to enhance the heat exchange have been proposed and investigated. We have developed a new-type heat exchanger by means of rotating a heat transfer pipe, which attained a high overall heat transfer rate. The heat transfer mechanism of the high-performance exchanger has been investigated based on the flow structure by flow prediction studies. This pipe-rotating heat exchanger system increases the coefficients of heat transfer of both the heating fluid and the heated fluid. By inserting stationary blades near the pipe wall surface, vortex flow is formed. The flow structure of the inner pipe changes with the pipe rotation speed. The vortex flows caused by the inner pipe rotation and the blades enhance the heat transfer not only in the inner pipe but also in the outer pipe.

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Unsteady heat transfer to air is observable by measuring fluctuating temperatures on a heated surface having a low heat capacity. In this work, the time-spatial characteristics in the heat transfer on the wall of a turbulent boundary layer were investigated using an infrared thermograph having a frame rate of 120 per second. A titanium-foil of 2 pm thick was employed as the heated surface. The attenuation of the heat transfer coefficient in both space and time was reconstructed using a series of measured temperatures by solving the heat conduction equation.

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In the present paper, an experimental technique of digital-laser-speckle method is described to measure the temperature distributions accurately in a diluted hydrogen flame by helium. In order to improve the measurement accuracy, the influence of species concentrations of the flame were taken into account in the temperature evaluation measured by gas-chromatography technique. It was found that the temperature corrections up to 200K were observed in the flame near the fuel nozzle, suggesting an importance of species concentrations on the temperature measurement.

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In this paper, surface forming process on glass plate was studied by using pulsed CO₂ laser irradiation. The process was visualized by a high speed camera. Surface forming process of humped lens-like surface that had 470 μm in diameter and 18.3 μm in height and ablated surface that had 522 μm in diameter and 3.2 μm in depth were visualized. In comparatively high laser intensity the center of lens-like surface ablate and the surface get dented.

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A knuckle ball shooted by a knuckle ball launcher was captured using one digital high-speed camera. The aspect of the change of the knuckle ball was analyzed from the image. As a result, we got 3-D numerical data of its trajectory. And 3-D features of this trajectory were expressed as a 3-D fright figures. This invisible we could recognize knuckle ball loop-like change.

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In this study, a technique of in-line digital holography was applied to particle counting in 3D space. In order to detect very small particles, holograms were captured by the CCD with a zoom lens. Then, we found that the distance used in the hologram reconstruction is measured from the focal plane, and that depth of field is limited depending on the magnification. This technique is expected to be applied to micro-bubble measurements.

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This paper describes a real-time visualization method for birefringence distribution using the correlation image sensor (CIS). The sensing principle is based on heterodyne imaging interferometry. The imaging system simultaneously demodulates the retardation and orientation distributions of a birefringent material from the amplitude and phase of an incident heterodyne interference pattern at an ordinary frame rate of the CIS. An experimental system is composed of a 64×64-pixel three-phase CIS camera and a two-frequency He-Ne laser with a beat frequency of 25 kHz. Experimental results obtained with a Babinet-Soleil compensator and a quarter-wave plate reveal that the measurement accuracy of the proposed imager is less than 5° in orientation and 3.5° in retardation. Imaging applications to a transparent plastic sheet and a liquid-crystal display panel are also demonstrated.

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Measurements of fluctuating static-pressure in a rectangular jet were conducted to educe three-dimensional vortical structure with phase-averaging technique. The experiments were performed for the air issuing from a sharp-edged rectangular orifice. The jet was excited at the interaction mode, where the stable interaction of vortices was generated. For phase-averaging processing, the reference signals were detected by a single normal hot-wire probe fixed at a downstream station whose distance from the jet exit corresponded to an equivalent diameter of the exit, and fluctuating static-pressure were measured over the flow field by a static pressure probe. Phase-average incoherent fluctuating static-pressure, which is related to jittering motions of vortices and is defined in phase-averaging, and adequacy of Taylor hypothesis to obtain three-dimensional structure were discussed. The results suggested that interaction and stretching of vortices contributes to generation of the incoherent vortex motions, and the use of a constant convection velocity in the hypothesis is acceptable for qualitative consideration.

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A scanning stereo particle image velocimetry system was applied to measure the three-dimensional distribution of three-component velocity in a round impinging jet. A water jet formed by a round nozzle with an exit diameter of D=5 mm was diagnosed by the current technique. The jet impinges vertically on the flat plate that was located at 45D from the nozzle. The jet Reynolds number was set at Re _D≈l000 and a measurement region was set to contain the stagnation region. A measurement volume (-80 x 80 x 80 mm ³) containing 50 velocity planes was scanned in 131.25 ms, which was sufficiently short to capture the instantaneous vortical structures. The iso-vorticity surfaces depict vortical structures in the stagnation region. The budget equation for the mean-square vorticity fluctuations was evaluated.

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In the present study, non-intrusive interferometric technique was developed for the temperature field visualization of cylinder surfaces of melting polymer and surrounding fluid flows. Since the temperature is determined as the integration of refractive index, neither span wise temperature distribution nor temperature around the curved surface could be obtained by the conventional interferometers. For such distributed fields, computed tomography is one of the significant techniques that makes an internal structure clear and facilitates the understanding of the volumetric structure in fluid. The interferometer and thermocouple were firstly compared to assess the validity of the present technique and both measured results agreed well. The technique was applied to the tomographic measurement of metal cylinder with angular temperature gradient.

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A detecting method on quantity and oil existence in a model tank using ultrasonic pulse echo method have been assuming the remained oil inside sunken ships C scope which is one of the method of the pulse-echo method was used for the construction of image. This experiment showed that the measurement of the remained oil inside the sunken ship was possible using ultrasomcpulse echo. The goal of thisreseamh will be the establishment of this technology to can measure remained oil inside sunken ships quantitatively and three-dimensionally by tomography-method using many measuring points.

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Ultrasound thermometry is based on the variation of the speed of sound with temperature in medium. The speed of sound is measured using the pulse-transit-time technique. A transducer on one side of the test section is used to generate a pulse, which travels across the test section and is monitored by a receiver on the opposite side at a known separation distance. The time taken for the transit of the pulse is related to the average temperature along the signal path. To visualize the temperature distribution within the test section, the principle of Computer Tomography is applied.
In the case of a gas, a non-uniform temperature field was measured by this method. It was compared with measurement data from a thermocouple array. The thermocouple data. indicated that the temperature of the central part of the heat source was lower than that of the region surrounding it. However, the ultrasound results yielded a uniform temperature for the heat source.

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This paper presents a novel measurement method using pulse ultrasound on air-water mixtures flow. The method has the capability to measure an instantaneous echo intensity profile along an ultrasonic beam, so it is expected to apply on pattern recognition of two-phase flow. The principle of the flow pattern recognition is based on delay time and strength of a pulse echo. In this paper, the echo signals reflected on a boundary between water and air, were obtained using an ultrasonic system with a clamp-on transducer, and estimated the effects of two-phase flow pattern, which is from bubbly to slug flow, on the signals.

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As for the flow rate measurement in a conventional open channel, there is a problem to change the instruction value of flow rate. Highly accurate flow rate was studied by measuring the instantaneous velocity distribution of the flow field with ultrasonic velocity profiler (UVP) and integrating the cross section. The velocity distribution was able to be obtained by measuring at the direction of the crossing and depth, to understand the flow field in three dimensions, and to have constructed the open channel monitor system that was able to make a change with the lapse of time of the flow field visible.

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In this study, experiment was carried out for Taylor-Couette vortex flow between a rotating inner cylinder and a fixed outer cylinder with small aspect ratio. It is two concentric rotating cylinders with a 25mm gap in aspect ration 3 and radial ratio 0.375 by mean of an ultrasonic velocity profiler (UVP). Successive instantaneous and mean velocity profiles were obtained by an ultrasonic Doppler velocity profile method, and the spatio-temporal velocity field had been the four-cell mode, N-2Cell, N-4Cell, A-3Ce11 and A-4Cell mode.

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The non-destructive examination technique using X-ray computer tomography was developed for the purpose of post irradiation examination. This X-ray CT technique is characteristic of using a pulsed high energy X-ray source in order to reduce the effects of gamma ray emissions from an irradiated fuel assembly, and then made it possible to obtain the clear cross section image.

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The high frequency ultrasonic cleaning of 1-2MHz is indispensable in the manufacturing process such as semiconductors. However, the absolute measurement of the output sound pressure level (S.P.L.) in the cleaning device is not established currently. The structure of sound pressure probe widely used at high frequency is the piezoelectric element (PZT) bonded to a quartz rod at the end surface. In the type of the probe, the other end surface is a probe point. And, hence, the electrical output on the PZT element is greatly influenced by vibration in the side surface of the rod. Moreover, the positioning precise of the probe in the measurement has to be micrometer order.
In this present, the authors propose the new measurement method of the S.P.L. for the high frequency ultrasonic cleaning machine. As the magnitude of the vibration depends on the S.P.L., the measurement of vibration velocity is to be a measurement of the S.P.L. The vibration velocity at a frequency of several MHz can be measured by Laser Doppler Vibrometer (LDV).

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On the seabed all over the world, the ships which sank during the war and marine disaster exist in great number. The cargo and fuel oil remain inside many wrecks. The wrecks become attenuated for long years. Then the oil is gradually discharged from the ship hull and rarely spouts resulting in a serious marine pollution. This paper describes the possibility of applying the Echoscope to the oil leakage monitoring and measurement method of the quantity of remained oil inside the tank using ultrasonic wave.

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Particles concentration on a cross section in a fluidized bed has been qualitatively visualized by a capacitance CT during the drug coating and drying processes. As a result, the high concentration is located near the tube wall at the drug coating process. However, the concentration tends to be uniform on the cross section. The originality of the present study lies in the application of capacitance CT to particles movement in a fluidized bed in jet coating as a first step of active control of drug production in order to prevent agglomeration of cohesion particles in pharmaceutical industry. Finally, the CT image is compared with the DEM simulation qualitatively to discuss the availability.

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The aim of this study is to estimate seaweed and herbivore distributions at deep ocean water (DOW) discharged area by using seaweed ecosystem model. The ecosystem model has been developed based on the results of field survey and biological experiments, and consists of three seaweed species, a sea urchin species and fore herbivorous fish species. The results of numerical simulations suggest that the DOW discharge may restore seaweed bed and herbivore biomasses increase at the restored seaweed bed.

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Spurious multibeam depths have been eliminated in bathymetry measurements so far. However, those would occasionally become valuable in finding fishes, seagrass, seaweed, benthos, and thermal plume. So we had studied acoustical characteristics of seagrass by using multi-frequency transducers and a mutibeam echo sounder. As a result, the high frequency multi-beam echo sounder was very useful for observation of the growth of sea weed and seagrass. By means of calculating standard deviations of bottom echoes, we could divide echoes efficiently into bottom echoes and water column echoes. It followed that three dimensional measurement and visualization of seagrass and seaweed above the seabottom was carried out successfully.

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Acoustic imaging sonar DIDSON is very useful for observation of creature and inspection of objects underwater, which gives near optical video quality images. As the beam width is 28.8°in the horizontal and 12°in elevation, it is proved difficult to image the whole picture of survey. In this study we have developed several softwares for observing underwater creature using image-mosaicing and image-processing to overcome the above weakness. The experimental results on real images show the effectiveness of the proposed method.

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Zinc pyrithione (ZnPT) is widely used as booster biocide in antifouling paints after banning on use of organotin compounds. Photolysis of ZnPT in aquerious solution was investigated using a photospectroscopic technique Photolysis experiment using xenon lamp was found to simulate the decomposition by natural sunlight. The photospectroscopic study successfully identified one of the degradation products and measured the kinetics of ZnPT's photolysis. It is concluded that ZnPT was decomposed by the irradiation to form Pyridine-2-sulfonic acid (PSA). Kinetics constant of ZnPT photolysis was proportional to the irradiation power and independent of temperature. The half live of ZnPT in solution was estimated to be about 17 minutes in Tokyo, Japan.

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Chemical tankers in Japan transport various kinds and large amount of chemical substance. Some of them have adverse effects to the human health condition. However they are VOC (Volatile Organic Compound) and vapor gas emits into the atmospheric environment easily. Considering this background, we developed a calculation model to estimate vapor gas concentration distribution evaporated from spilled chemical substances on the sea. The calculation model is composed of four elements, wind profile estimation model, dispersion model for the spilled liquid on the sea, evaporation rate estimation including a spilled liquid spreading model and atmospheric dispersion model. The calculation result agreed with observed concentration obtained from an oil spill accident in Tokyo bay.

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A tanker accident is a potential crisis leading to severe ocean pollution. The operation for recovering oil spill needs precise information of position, scale and type of oil. A new oil spill monitoring system is required in full-time and all-weather wide area coverage. National, Maritime Research Institute (NMRI) developed a new helicopter-based fluorescence imaging lidar (laser radar) system for remote sensing of oil spill. It consists of a 355nm UV pulsed laser, four-wavelength optical systems, and a gated ICCD imaging camera. Since this system discriminates the oil from seawater by the presence of laser induced fluorescence light, it is possible to visualize the oil spill in all weather, day or night. Not only diesel, fuel or crude oil, but also some petroleum chemicals on the ocean, normally hard to identify with the naked eye, can be targeted.
The first oil spill observation was conducted on May 2004 on the French coast in collaboration with "DEPOL04", the international oil spill observation and recovery experiment. We succeeded in observing the 2-D images of the fluorescent light from artificially-spilled oil, and the water Raman scattering light from sea water. The discrimination of oil and water was examined by the signal ratio of the three wavelength signals to the 405nm signal, which is water Raman dominant.

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Depending upon the high-resolution satellite imagery of recent years, distinction of the one-meter-length object of terrestrial has become possible. Advanced usage of satellite imagery is getting popular in civil engineering field. However, in maritime transportation field, it is not utilized yet sufficiently. At East Asian region, the marine traffic density has increased attendant upon recent economic development, but the actual condition and the behavior of that traffic style is still grasped only roughly. In this research, at the area whose such traffic control system is insufficient, we aim toward the development of the observation system on maritime traffic with the satellite imagery. In order to examine the ship type identification method from the imagery, the ship images in this paper are drawn up from Multispectral data making use of the picture of the ship at Kobe, Tokyo and Yokohama port using IKONOS satellite.

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In this study, method of correlation PIV is applied to the ice movement of Okhotsuk Sea using millimeter radar images of DMSP and ADEOSE-II satellites with 12.5km resolution that can penetrate thick clouds usually covering over the Okhotsuk Sea and prevents us from seeing the sea ice via visible light. PIV method in present research emploies very standard correlation algorithm using 15×15 matrix which shows motion of ice properly. With the PIV, movements of sea ice are analysed to investigate the growth of ice.

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The characteristics of fluid forces on a rotationally oscillating circular cylinder in a uniform flow are studied experimentally at various forcing frequencies and rotational amplitudes of cylinder oscillation. The measurements are made on the pressure fields around the circular cylinder by using the velocity data measured by PIV in conjunction with the pressure Poisson equation. The present result indicates that the fluid forces are enhanced by the low-frequency oscillation and are reduced at high-frequency oscillation, which are due to the modification of the wake structure by the influence of rotational oscillation. This trend is further magnified by an increase in rotational amplitude.

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In case that result of a large-scale two-phase flow simulation were visualized, especially, under the condition that a lot of bubbles and liquid films with various scale sizes become entangled intricately, it is not easy to distinguish the bubbles and liquid films distributed in three dimensions using the conventional visualization software. Then, a new visualization method which can reproduce faithfully with high accuracy the physical phenomenon predicted by the simulations is required. This paper shows the large-scale bubbly flow simulation results and describes the visualization results using the ray-tracing method that reflection and penetration of the light on the interface between the liquid and gas are considered. Regarding the mechanism of bubble coalescence and fragmentation the useful knowledge was obtained.

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The purpose of this study is to pursue each vortex in the Taylor vortex flow appeared between two concentric rotating cylinders. Formation processes of the modes are analyzed in detail. This study visualizes each vortices using Stokes' stream function, and pursues the centers of vortices. This visualization system shows the mode formation processes of the normal and anomalous mode. It can pursue the development of extra cells near the end walls. Furthermore, 3-Dimensional visualization using Java 3D library helps tracking the time-dependent flow structure.

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A confined jet sometimes causes self-exited oscillations due to an existence of a downstream obstacle.This phenomenon is useful for fluidic oscillators, heat/material mixers and flowmeters, in order to realise a low-cost high-reliability device without mechanically moving components. In the present study, the authors deal with this phenomenon at low Reynolds numbers (Re=500), experimentally. More specifically, the autors conduct a time series of flow visualisations and PIV(Particle Image Verocimatry) analyses, with the measurement by UVP for accuracy check. As a result, the autors propose a new definition of length scale of vertical structures and propose a formula to predict the oscillation frequency using the length scale.

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A visual digital recorder system (DVR) is widely used to visualize and analyze the dynamic image of moving body. The simultaneous instrumentation system of the DVR and infrared radiometer (IR) was applied to study two-dimensional moving images of the human body under walking and Gymnastic training. Dynamic behaviors of human body segments like location velocity and force are measured and analyzed by DVR, IR and the personal computer. Single-and multi-flash imaging methods of the human body were visualized and evaluated by using the multi flash motion recorder. Lastly, a fluctuation performance of the moving human body was quantitatively obtained and expressed in form of frequency, power spectrum density and coherence coefficient

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In order to clarify the flight mechanism of butterfly, we have observed the butterfly flight using high-speed camera. The Test butterfly is Cynthia cardui and its diameter is 25mm in wing chord length, 30mm in wing span length, 254mm2 in wing area and 160mg in weight. Especially, we have discussed the dynamic behavior of butterfly wing in flight motion, such as the elastic deformation of wing, the trajectory of wing tip and the flapping angle of wing. In flight motion of butterfly, the wing carried out elastic deformation not only in the wing span direction but also in the wing chord direction. The flapping angle shows the periodic triangular waveform and the ratio of between the up stroke and down stroke of flapping motion is about 1:1.25.

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This study presents characteristics of the development of an intermittent high-speed natural gas jet with pulsed operation under the atmospheric condition by means of a schlieren method. Methane was used as the test gas, that is a major component of the natural gas. To measure the jet penetration and the dispersion angle, instantaneous images of the methane jet were obtained using a CCD camera with an image intensifire. It is shown that the jet angle decreases with time. Jet penetration could be predicted satisfactorily by a modified momentum theory by considering the change of the jet dispersion angle and the transient characteristics of the injector. It was found that characteristics of the injector have an effect on development process of an intermittent high-speed natural gas jet.

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Spray characteristics of arblast atomizers for aero engines are visualized by means of the interferometric laser imaging technique. Different atomizer configurations are tested, including co-swirl and counter-swirl configurations, with and without inner- and (or) outer- ring adapters, which modify the shapes of inner- or outer- flow passages, respectively, to increase the velocity near the lip of the pre-filmer for expected better atomization. The spatial distributions of number density and mean droplet size show different characteristics between the co-swirl and counter-swirl cases, which can be explained considering the effect of centrifugal force on droplets. The installation of outer-ring generally shows slight improvement of atomization characteristic without changing spray dispersion. On the other hand, for the co-swirling case, the installation of inner-ring results in remarkable increase of droplet size except the region just downstream of the nozzle exit, and also results in narrower spray dispersion. In the present study, the number density and mean velocity fields of droplets in different size classes are also visualized, which provide further information to examine spray characteristics in detail.

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