Flow Characteristics of Fluid Droplet Obtained From Air Assisted Atomizer

Air assisted atomizer system was designed and developed for fuel injection. The present purpose is to utilize a low pressure in supplying of atomized fuel. Distilled water was used as test liquid on the experiments for the system of atomization. The results revealed air assisted atomizer had a capability to inject the test liquid in the range of the rates of 0.0019–0.00426 kg/s, with the use of air pressure supplied from 68.9 to 689 kPa. In this research, the test liquid supply pressure was kept constant and the air flow rate through the atomizer was varied over a range of air supply pressure to obtain the variation in air liquid mass flow ratio (ALR). The spray solidity was studied by taking pictures of the spray at different liquid air supply pressures. The experimental investigations suggest that spray cone angle tends to increase with increasing in air liquid mass flow ratio because the kinetic energy of the flow keeps on increasing. The solid cone spray has a pattern of penetration depth between 408–446 mm. and cone angle between 14.5–23.6°. It was observed that spray formed the solid cone at all the operating conditions.

Observation and Scaling of Tip Vortex Cavitation on Elliptical Hydrofoils

Experimental study on tip vortex cavitation (TVC) was carried out for elliptical hydrofoils with various chord lengths. The purpose of the experiment was to clarify the influences of Reynolds number and water quality on tip vortex cavitation. Experiments were made in a large cavitation tunnel of the Naval Systems Research Center, TRDI/Ministry of Defense Japan. The elliptical hydrofoils tested were NACA 0012 cross section with chord lengths of 500mm, 250mm and 50mm. Reynolds number based on hydrofoil chord length was 2×105 < ReC < 7.4×106. Water quality of the tunnel was characterized by air content and nuclei distribution. Air content of the tunnel was varied between 30% and 80%. Nuclei distribution was measured by a cavitation susceptibility meter (CSM) with center-body venturi. Cavitation inception was determined from high speed video observation. A standard formula, (σL/σS) = (ReL/ReS)n, was applied for the scaling. In the present study, exponent of the scaling law n was found to be 0.2 < n < 0.4. High speed video observation showed that the process of the TVC inception strongly depends on water quality. In the experiments, unsteady behaviors of TVC were also investigated. Strong interactions between sheet cavitation and TVC were observed.

PIV Measurements of Propeller Flow Field in a Large Cavitation Tunnel

Flow field around a marine propeller was measured by means of PIV technique in a large cavitation tunnel of the Naval Systems Research Center, TRDI/Ministry of Defense, Japan. Test section of the tunnel is 2m(W) × 2m(H) × 10m(L) and it contains 2000m3 of water. 2-dimensional PIV (2-D PIV) and stereo PIV (SPIV) measurements were made for a five-bladed highly skewed marine propeller. In the case of 2-D PIV measurements, high spatial resolution measurements were possible by seeding relatively small amount of tracer particles. Phase-averaged flow fields showed details on evolution of tip vortices. In the case of SPIV measurements, much larger amounts of tracer particles were required, and it was difficult to perform high resolution measurements. Phase averaged velocity profiles from SPIV measurements showed good agreement with 2-D PIV-measured results. PIV-measured results were compared with results of LDV measurements. Although PIV-measured velocity profiles showed fairly good agreements with LDV-measured results, some discrepancies were found at the blade tip region.

The Development of Extremely-Compact Static Pressure Probe for the Simultaneous Measurement of Pressure and Velocity in the Turbulent Flows

A new static pressure probe was developed to improve the space resolution and the measurement accuracy of the combined probe for the simultaneous measurement of the static pressure and the velocity in turbulent flows. The external diameter of the static pressure tube is 0.3 mm and its internal diameter is 0.2 mm. There are 8 static pressure holes on the wall of the static pressure tube and their diameters are 0.1 mm. The MEMS microphone is used as the pressure sensor and embedded inside the flare of the static pressure tube. The diameter of the MEMS microphone is 2.54 mm and has the wide range flat frequency response. The measurement results by the new static pressure probe in the two-dimensional turbulent jet show that the measurement accuracy of the static pressure probe is sufficient and the seven-thirds power law is clearly observed in the power spectra of the fluctuating pressure measured at the position of a half width of the mean velocity distribution in the cross-streamwise direction apart from the jet center line. In addition, the yaw angle characteristics of this new pressure probe shows that the measurement accuracy of the static pressure has less dependency on the yaw angle of the probe to the flow direction than the one of the previous static pressure tube (its external diameter is 0.5 mm). From these results, it is found that the new static pressure probe is effective for the measurement of static pressure in turbulent flows and useful to improve the space resolution and the measurement accuracy of the combined probe for the simultaneous measurement of the velocity and the static pressure. By using this static pressure tube, the space resolution of the combined probe is reduced approximately 40%. Further, by combing two X-type hot-wire probes with the new pressure probe, the simultaneous measurement of three velocity components and static pressure is realized.

An Investigation of Cavitation and Suction Vortices Behavior in Pump Sump

A numerical and an experimental investigation on a suction vortices including cavitation, free vortices and subsurface vortices behavior in the model sump system with multi-intakes is performed at several flow rates and water levels. A test model sump and piping system were designed based on Froude similitude for the prototype of the recommended structure layout by HI-9.8 American National Standard for Pump Intake Design of the Hydraulic Institute. An experiment is performed according to the sump model test procedure of Hyosung Goodsprings, Inc. A numerical analysis of three dimensional multiphase flows through the model sump is performed by using the finite volume method of the CFX code with multi-block structured grid systems. A k-ω Shear Stress Transport turbulence model and the Rayleigh-Plesset cavitation model are used for solving turbulence cavitating flow. Several types of free surface and submerged vortex which occurs with each different water level are identified through the experimental investigation. From the numerical analysis, the vortices are reproduced and their formation, growing, shedding and detailed vortex structures are investigated. To reduce abnormal vortices, an anti-vortex device is considered and its effect is investigated and discussed.

6 Degree of Freedom Motion Analysis of Surface Ship Models

A 6 degree of freedom (DOF) optical motion analysis system has been adapted for the measurement of surface ship model motion. The motions measured by the optical system are surge, sway, heave, roll, pitch, and yaw. Apparently, the calibration of the system is not traceable to a National Metrology Institute (NMI). Measurement results are compared to on-board instruments for the measurement of roll, pitch, and heave, which were calibrated prior to the test. Test results are presented for a Large Medium Speed Roll-on Roll-off (LMSR) ship model with a Transformable Craft (T-Craft) Surface Effect Ship (SES) in tandem connected by a ramp. The LMSR model was attached to a carriage in a rectangular wave-making basin. The results presented in this paper were conducted at a simulated Sea-State 4 and model speed of 0.372 m/s. The results were in reasonable agreement in pitch and roll where the instrument calibration uncertainties were between ±0.19° and ±0.67°, while the manufacturer’s specification is ±1.0°. Heave was measured near the stern by the optical system. The uncertainty in the correction to the center of gravity is estimated to be ±17 mm for the LMSR in comparison to the direct measurement of heave by a string pot at the cg, where the calibration uncertainty was ±1.3 mm.

Effects of Phospholipid Layers on the Motion of Microbubbles Under Pressure Variations

The shrinking and growth of microbubbles under pressure variations are observed with a CCD camera. The influence of gas diffusion on the stability of microbubbles covered with phospholipid layers is investigated. The microbubbles are made with acoustic liposomes encapsulating phosphate buffer solution and perfluoropropane gas. It is shown that when the ambient liquid pressure increases, the observed microbubbles shrink accompanied with the cyclic surface buckling and smoothing process. The bubble surface smoothing in the process shows that the excess phospholipid layers are removed from the surface, which results in the instantaneous bubble shrinkage. It is also shown that the smaller the initial radius is, the more the growth of microbubbles is reduced. The bubble model by Takahira and Ito, in which the dynamic surface tension and the gas permeation resistance of molecular layers are considered, is utilized to simulate the experiments. The simulation is in qualitative agreement with the experimental result except for the instantaneous bubble shrinkage. The model is improved so as to consider the instantaneous increase of surface tension. The instantaneous bubble shrinkage is simulated successfully with the improved model. The results suggest that the instantaneous increase of surface tension is caused by the shedding of the excess phospholipid layer material due to the zippering process proposed by Borden and Longo.

Micro-PIV Measurement on Transient Flows in Pneumatic MEMS Device for Cell Trapping

This paper presents a micro-PIV measurement for investigation of flow characteristics in a micro chamber for trapping of a live cell. The micro cell chip consisting of pneumatic vibrator arrays and a trap chamber was fabricated through a replica molding technology with a SU-8 mold and Polydimethylsiloxane (PDMS) polymer. The single cell in the trap chamber was manipulated and trapped in the equilibrium region by exploiting the geometrical symmetry of the vibrators. The x-axial velocity of the viscous fluid induced by the deformation of the flexible diaphragms was eliminated or minimized at the center of vibrators. From the measurement results, the proper operational conditions of the vibrators were determined and it is also verified that the particle can be actively manipulated and trapped as desired.

Size-Exclusion Surface Plasmon Resonance Sensing With a Microslit Array Chip

In this study, we propose a novel surface plasmon resonance (SPR) chip on which the microslit array was fabricated. The microslit excludes micrometer-size objects that are larger than its slit size from sensing field, so that it acts as a filter. In order to confirm the filtereffect, we demonstrated the sensing of microparticles of different diameters using the SPR chip. As the demonstration of the biotechnology application, we performed the discrimination of aggregation of bio-molecules using SGNP (Sugar chain imobilized Gold Nano Particle) as a model sample.

Development of Polydiacetylene-Embedded Microfibers Using 3-D Hydrodynamic Focusing Technique

Polydiacetylene (PDA), conjugated polymer, is an attractive sensor material that has a unique optical property to transform its color from visible blue to fluorescent red upon environmental perturbations like heat, pH, specific metal ions, and etc. In this study, we propose a novel method to detect metal ions by using polydiacetylene (PDA)-embedded sensor microfibers fabricated with a 3-D hydrodynamic focusing technique using alginate and calcium solutions. Moreover, by changing the head groups of PDA, we successfully detected Al3+ and Zn2+ ions up to 1mM using PDA micro fibers.