深野 徹

鉛直管内上昇気液二相流における液膜厚さに与える円筒形障害物長さの影響(流体工学,流体機械)

A ring-type obstacle, which simulated a spacer in Light Water Reactor or a flow obstruction supporting heat exchanger tube, was set in an upward air-water two-phase flow within a vertical tube to investigate the effects of the obstacle on liquid film thickness in relation to the drypatch generation. We measured the axial distributions of time varying liquid film thickness near the obstacle in the range of the superficial water velocity of 0.06-1.6 m/s and the superficial air velocity of 0.5-36 m/s and discussed the effects of the length of the obstacle on the liquid film thickness. The results are summarized as follows: (1) The minimum film thickness and the mean film thickness near the obstacle become thinner as the length of the obstacle becomes shorter. (2) The length of the obstacle has stronger effects on both the minimum and the mean film thickness near the obstacle as the superficial water velocity becomes lower. (3) The generation of drypatch is possible under the flow conditions examined in the present experiment if heat is applied.

Turbulent Noise Generated from A Multiple-Disk Fan

We proposed a theory for estimating the spectral density distribution and the overall sound pressure level of the turbulent noise radiated from a multiple-disk fan. In the theory, experimental data of correlations of the longitudinal and the lateral correlation length as well as the pressure spectral densities were used. The effects of the casing on the radiated noise were clarified by experiments by comparing the spectral density distributions with and without casing. The validity of theoretically obtained formula was examined with respect to the effects of parameters such as the gap between two disks, the rotational speed, the number of disks, the thickness of disks, the radius of an impeller and the flow rate. The agreement between the theoretical and the experimental results was generally satisfactory.

Experimental Investigation into the Mechanism of Discrete Frequency Noise (DFN) Generation from a NACA 0012 Blade

An experimental investigation was made into the mechanism of discrete frequency noise ( DFN )generation from a NACA 0012 blade placed in a uniform oncoming flow. It was clarified that DFN was generated when the boundary layer on the blade surface was laminar and separated at the location upstream of the trailing edge. A dead air region was formed just after the trailing edge of the blade. Therefore a Karman vortex street occurred. Meanwhile we could not observe a close relationship between the existence of a separation bubble and the generation of DFN. That is, DFN was generated even when the attack angle of the flow was nearly zero and no separation bubble was observed. When a separation bubble existed, the boundary layer became turbulent and the flow did not separate up to the trailing edge, so a dead air region was not formed behind the blade, which resulted in the disappearance of DFN. The prediction of the sound pressure level of DFN generated from this stream lined blade by Fukanos theory for a flat plate model agreed well with the measured value.

回転する単独平板翼の後流に関する研究 : 第3報, 速度の周期変動現象に及ぼす後縁形状の影響

We have experimentally investigated the influence of the shape near the trailing edge of a flat-plate blade on the periodic velocity fluctuation in the near wake of the single rotating blade. The results show that the characteristics of the near wake in the rotating flow field are similar to those in the uniform flow field; i. e., the periodic velocity fluctuation did not occur when the suction surface of the blade was scraped near the trailing edge, and did occur if the pressure surface was scraped. In the latter case, the two types of trailing edge separations occur. The flow always separates at the trailing edge of the blade on the suction side, while the flow separation alternately originates from two different points, i. e., from either the starting point of the scraping or from a fixed point on the scraped surface.

回転する単独平板翼の後流に関する研究 : 第1報,迎え角が大きい場合の流動様相に与える先端すきまの影響

The characteristics of the wake of a rotating flat plate with a large attack angle were investigated experimentally with special attention of the flow near the tip of the plate. When the tip clearance is small, the dead air region becomes large towards the tip of the plate and the shear layer of the suction side of the plate curves outward as a result of the accumulation of low-energy fluid. On the other hand, when the tip clearance is large, the leakage flow is so large that the leakage vortex is generated from the trailing edge of the suction side and the shear layer forms by contacting the leakage flow and the dead air region. The variations of the flow rate and the momentum of the wake flow are closely related to those of the leakage flow.

一端を中心として回転する断面が軸対称な物体の後流に関する研究 : 第1報,二次元後流との比級

The characteristics of a velocity fluctuation in the wake of an axisymmetric body were measured from a rotating frame of reference. The results were compared with those in a two-dimensional flow. The following was made clear. In the rotating flow field, the mixing and diffusion of the wake are promoted by both the oncoming flow which is sheared in the spanwise direction and the intense radial outward flow in the dead flow region of the wake. Therefore the dead flow region becomes narrower and the wake width increases more quickly than in the two-dimensional flow. Vortex shedding is less regular and the circulation of the vortex is weakened. The amplitude of velocity fluctuation is smaller and its maximum position, representing vortex shedding, is closer to the body than that in the two-dimensional case. The velocity fluctuation shows a cellular structure in the spanwise direction, the scale of which is about one characteristic length of the body. This mechanism is related to the radial flow in the wake.

Effects of Tip Clearance on the Noise Generated from Low Pressure Axial Flow fans : Difference Caused by the Width and Location of a Ring Set in the Tip Clearance and the Blade Tip Profile

The effect of the width and the location of a ring set in the clearance between a duct inner wall and a blade tip and the profile of a blade tip on fan noise are experimentally investigated by using three rings of different widths and four impellers with different tip geometry. The results are summarized as follows : A considerable amount of noise reduction can be expected by setting a ring within a tip clearance, when its initial gap is rather large. Both the noise and the aerodynamic characteristics at the maximum efficiency point are better in the case with a larger gap on the leading edge side than on the trailing edge side. In the lower flow rate range, however, the fan with a smaller tip clearance on the leading edge side is superior.

低圧軸流送風機の共鳴騒音に関する研究 : 丸棒の位置、回転数および翼先端形状の影響

Resonance tone is minimized by reducing the tip clearance, say less than about 1 mm. Even in these conditions it occurs with a sufficiently high level if a rod is attached near the leading edge on the suction surface of the blade, as well as if a part of the blade tip is cut off. The fundamental resonance frequency, f, is about 60 70% of the blade passing frequency and is correlated by a Strauhal number as f = St. WD, where St = 0.2 and W is the relative velocity. D is the characteristic length, which is without exception equal to the integer multiple of 0.0078 t, where t is the blade pitch.

障害物による沸騰流の液膜破断に関する研究 : 第2報, 障害物直前におけるADRの性質

沸騰を伴う垂直上昇蒸気-水二相流中の流動障害物の直下にみられるドライパッチの生成消滅の16mm映画フィルムを解析し, 蒸気スラグの存在時間, その通過ひん度, ドライパッチ発生ひん度などを求め, これらの間の関係を検討する. さらに, 流動障害物を蒸気スラグが通過する際に出現するドレーニジによって, 障害物直下にきわめて薄い粘性水膜が形成されるが, この水膜の蒸発の結果としてドライパッチが生じることを示す.