The effects of radiative heat loss on the intrinsic instability of premixed flames were investigated numerically based on the Navier-Stokes equation adopting the one-step irreversible chemical reaction, and the visualizations of the behaviors of cellular flames in large domain were simulated. As the radiative heat loss parameter became larger, the amplitude growth rate decreased and the unstable range narrowed either the Lewis number was lower or larger than unity. This is because of the decrease of burning velocity of a planar flame owing to radiative heat loss. The unstable behaviors of cellular flames were strong at low Lewis numbers due to the intense intrinsic instability. In large domain, the lateral movement of flames and overshoot of the temperature distribution became stronger, and division and combination of cells appeared. Moreover, the burning velocities of cellular flames increased with time. The radiative heat loss promoted (demoted) the unstable behaviors of cellular flames at Lewis numbers lower (larger) than unity.

Formation and evaporation mechanisms of the microlayer beneath a flat bubble of working fluid in the mini-channel have been investigated by measuring the local wall temperature with the original MEMS thermal sensor and the bubble and microlayer behavior captured with high speed observation. The thin liquid film thickness (called microlayer thickness) and the amount of evaporation were evaluated from the local wall heat flux by one-dimensional transient heat conduction analysis with the wall temperature data. The correlation equation of dimensionless initial microlayer thickness was proposed as the function of Bond number, Weber number and Capillary number using dimension analysis. Almost the formed microlayer is incompletely evaporated in the all working fluid, and therefore the amount of evaporation corresponded to a few-50% of the formed microlayer in all working fluid.

It is known that in a boundary layer subjected to a few percent of free stream turbulence intensity, streaks appear and eventually break down to turbulence after wavy motions. However, the boundary layer transition subjected to lower free stream turbulence intensity is still not been fully elucidated. The present paper focused on revealing effects on intensity and scales of free stream turbulence on boundary layer transition, especially on how it effects the boundary layer transition as well as the growth rate of disturbance energy in the streamwise direction. In this study we performed flow visualization and hot-wire measurements in order to investigate transition points and process with wide-range of free stream turbulence intensity and scales. From the flow visualizations at intensity 1.42%<Tu<3.99% indicate that, the streak structures elongated in streamwise direction and collapse to turbulent downstream. This is similar to that at a few percent of turbulent intensity. Even though the turbulence intensity is the same, the Transition Reynolds number increases with free stream velocity. So, it is strongly suggests that, the Transition Reynolds number is depends on the ration between the boundary layer thickness and turbulence scales.

In this experiment, a natural transition of turbulent spots in a water channel flow was observed. With addition of polymer as we know the polymer particles suspended in water affect to turbulent flow in pipe and channels, skin friction decrease. In this study, the effect of Polyacrylamide (PAM) dosing in water channel flow to the turbulent spot is observed. We investigate growing rate of the spot, to know how the polymer change generation of turbulent on the boundary between laminar and turbulent at the edges of the spot.

α gels are widely used in the cosmetic field. It has weak structure and it causes yield like behavior. After the structure is destroyed by flow, it recovers quickly and gels exhibits yield like behavior again. Using the glass plate which is nano-order surface roughness and the stainless plate which is micro-order surface roughness, first yield behavior which occur in low shear rate have depended on the cell surface roughness and the gap between plates. However, second yield behavior have not depended on the cell surface roughness but the gap between plates.

Flow-induced orientation of xanthan gum aqueous solutions in a planar channel with an abrupt expansion were examined by measurement of the flow-induced birefringence along the centerline of the channel. Four kinds of the xanthan gum solutions with different concentrations (0.45, 0.5, 0.7, 0.9 wt.%) were tested in this experiment. Characteristic times were evaluated from G′ and G′′ curves respectively. The birefringence changes were delayed corresponding to the characteristic times. Typical sizes of regions where the flow structure of polymers were affected by the abrupt expansion were estimated with the birefringence changes. The normalized sizes have a good correlation with a viscoelastic factor (apparent Weissenberg number) estimated in upstream region regardless of the concentrations of the solution.

In order to investigate the applicability of the dynamic Smagorinsky model, which was originally developed for turbulent flow of Newtonian fluid, to large eddy simulations (LES) of non-Newtonian viscous fluid, LES of turbulent channel flow of power-law model fluid as non-Newtonian viscous fluid were performed, and the simulation results were compared to those of direct numerical simulations (DNS). According to the observation of instantaneous turbulent structures, the spatial scale of velocity streaks of non-Newtonian viscous fluid predicted with LES looks similar to that with DNS, although weaker quasi-streamwise vortices are observed in the LES results. Additionally, from a statistical viewpoint, it was found that LES with the dynamic Smagorinsky model could not accurately predict the strength of velocity streaks, while the spatial scale corresponded to that of DNS. Consequently, the present results means that we need to modify the traditional dynamic Smagorinsky model for applying to the non-Newtonian viscous fluid.

Antimicrobial effect of ultra-fine bubble (UFB) mixtures and electrolytic UFB mixtures (EUB), which was UFB mixtures including hypochlorite, on the viable bacterial count (VBC) was observed in an alternating flow. We investigated washing effect against fresh vegetable (Chinese cabbage) by using deionized water (DW), sodium hypochlorite (SH), SH including UFB (S-UFB), and EUB. Agreement between VBC values for our experimental results of before treatment (BT) and those for previous results was obtained, and our experimental set-up was thus suitable. The VBC for SH was less than those for BT (The differences were approximate 102 order within the experimental errors.). The effect on the VBC for S-UFB and EUB was strongly expressed with an alternating flow, although hypochlorite concentration of S-UFB was smaller than thst of SH alone. Thus, higher efficiency was suggested by using S-UFB and EUB, compared with SH alone. Furthermore, relationship between strong mechanical action in an alternating flow and influence of free radical generation was discussed.

Freeze-concentration system using metallic belt can continuously produce plate ice and keep the ice making speed constant. Generally, in progressive freeze-concentration, efficiency of concentration decreases because discharge solute is concentrated near of freezing surface. Therefore, it's important to remove higher concentrated solution from freezing surface. Since this system can hold freezing surface position, we attempted to enhance removal of solute using a rib plate. In this study, the effect of stirring enhancement using rib plate on distribution coefficient was clarified.

This study was focused on the relation between water jet characteristics and runner performance for a submerged impulse turbine utilizing drinking water pipelines. The performance tests were conducted experimentally for various casing pressure and with changing the number of nozzles. As a result, the cavitation jet was observed at the lowest casing pressure. The performance drastically drops down when the cavitation occurs. That is why the performance of runner improves by increasing casing pressure. It is also revealed that the number of nozzles is important for the runner performance. This is because that the input energy from the nozzle is increased with the number of nozzles. The friction and mixing loss on the runner is only depended on the runner rotation speed in this study, therefore increase of input energy by increase of number of nozzles brings improvement of the runner efficiency.

Small hydropower development is one of the best way for enhancement of energy security and good solution of global environmental issues. A new submerged impulse turbine has been developping for generation by replacing pressure reducing valve in drinking water pipe lines. This study is especially focused on torque loss on the turbine, but it is not fully understood the reason why the loss is occurred. The torque loss is serious problem for a submerged turbine performance. Thus the torque loss on the runner and a disk was measured, and flow visualization by oil film method was conducted. As a result, the trque loss on the runner becomes four times larger than that on a disk. It is revealed that the flow field near the surface on a disk is a little different from that on the disk, and impinging water flow on the suction side of blade enhances the torque loss on the runner.

This study was focused on the noise characteristics of axisymmetric supersonic impinging jet. The diameter of the jet is D= 5.2 mm. The jet was issued from Laval nozzle with designed Mach number M_j = 2.0. The impinging plate was inserted into the jet and the impinging distance between nozzle exit and the center on the plate surface was varied 15≦ L ≦40. Moreover the plate was inclined for three angle conditions, α=0, 15, 30 deg. and NPR, which was pressure ratio of chamber pressure P_c to atmospheric pressure P_a, was changed from 3.0 to 4.0. As a result SPL is increased with impinging distance for NPR ≧ 3.5. The static pressure on the plate is decreased with increasing the impinging distance. For NPR = 4.0, the both of SPL and the pressure varies cyclically and some peaks and valleys are observed. Especially impinging distances where show peaks of SPL, dominant frequency was observed in frequency analysis results, and these tendencies vary with impinging distance and inclined angle of the plate.

This study is focused on cavitation phenomenon in a spool valve for water hydraulic system. Some servo valves have been developped and used in Aqua Drive System (ADS). Cavitation is one of the most serious problem for ADS devices especially for valves and pumps. To obtain knowledge of cavitaion in ADS devices from practical point of view is very important. In this study, visualization study was conducted under various pressure conditions upstream and downstream a spool model. The model is made of transparent acrylic resin for easy optical access. As a results, it is clarified that cavitation jet pattern issuing from a control orifice changes with differential pressure between the orifice and setting downstream pressure.