Experimental Investigation has been carried out on turbulent flow around an obstacle placed on the lower wall of a square duct. Particular emphasis is placed on the velocity distribution of turbulent flow, the reattachment length, and the static pressure distribution on the upper wall of the duct. Two types of obstacles are used: a backward-facing step and a diffuser-like constriction. A flow visualization method is used for measuring the velocity distribution and reattachment length. Soap bubbles are used as the tracer. A pressure transducer is used for measuring the static pressure distribution. A blockage factor is introduced to correlate the static pressure distribution. The reattachment length depends strongly on the shape and size of an obstacle. An empirical equation is proposed for the reattachment length.
Dispersion of fine particles in a molten metal bath is responsible for the efficiency of metals refining processes such as the desulphurization process. Model experiments have been carried out to understand the behavior of a poorly wetted sphere penetrating into a molten metal bath. Water is used as a model liquid for the molten metal. Three kinds of solid spheres of densities greater than that of water are chosen as models for the particle. The wettability of the sphere is changed by coating repellent on its surface. The poorly wetted sphere thus coated accompanies an air bubble on its rear surface in the course of penetrating into the bath. An empirical equation is proposed for the drag coefficient of the poorly wetted sphere.
Dispersing fine particles uniformly into a molten metal bath is one of key technologies for enhancing the efficiency of metals refining processes such as the desulphurization process. Model experiments have been carried out in this study to understand the behavior of a poorly wetted sphere penetrating into a molten metal bath. Water is used as a model liquid for molten metal. Solid spheres of different three diameters are chosen as models for the particle. Their densities are the same and smaller than that of water. The wettability of each sphere is changed by coating repellent on its surface. The poorly wetted sphere thus coated with repellent pulls an air column into the bath in the course of penetrating into the bath, accompanies an air bubble on its rear surface after braking up of the column, reaches a certain position in the bath and finally comes back to the bath surface. Empirical equations are proposed for the penetration depths of the air column and the sphere.
Horizontal gas injection into a molten metal bath is widely used in the refining processes such as the desulphurization process and AOD process. Gas is injected from a nozzle (nozzles) at a relatively high flow rate and, hence, a jet of a mixture of gas and liquid is formed in front of the nozzle. This jet is called the bubbling jet. The efficiency of the refining processes is closely associated with the dispersion behavior of the bubbling jet. It is therefore important to understand it dispersion behavior in the horizontal direction. Information on the locus of the bubbling jet is available in the literature. However, the bubbling jet sometimes oscillates in a complex manner, for example, due to interaction with the bath surface. The unsteady behavior of the locus is not understood yet. In this study water is used as a model for molten metal because the kinematic viscosity of water is nearly equal to that of molten metal. Air is used as a model gas for argon or nitrogen used in the real processes. A bubbling jet is generated with a top lance having a single-hole nozzle facing in the horizontal direction. The period and amplitude of the oscillation of the bubbling jet are measured with a high-resolution video camera. In addition, discussion is made on the mechanism of the oscillation of the bubbling jet.
A constant acceleration flow is generated in a square duct using a butterfly valve driven by a stepping motor. The valve is opened at programmed rotation speeds until the opening area attains a predetermined value. The acceleration of flow therefore changes suddenly from a constant non-zero value to zero. Transition to turbulence occurs when an instantaneous Reynolds number is raised above a certain critical value. This critical Reynolds number depends on the acceleration and becomes greater than the steady flow value of approximately 3000 with an increase in the acceleration. It is possible to delay the transition to turbulence by changing the final opening area. The period from the start of flow to the initiation of turbulence can be predicted by an empirical equation. This equation is derived in this study by taking the burst period into consideration.
An understanding of the behavior of bubbles in the refining processes is of essential importance because the bubbles affect the quality of steel significantly. Many investigations have been carried out to reveal the behavior of bubbles. Most of them are concerned with bubbles rising away from the wall of the reactor. Information on the behavior of bubbles rising near a poorly wetted wall is very limited, although this bubble rising situation is often encountered in the real refining processes. In this water model study the width and thickness of a bubbling jet formed along a poorly wetted flat plate vertically placed in a water bath are measured in addition to a mean size and a mean rising velocity of bubbles.
Investigation on the characteristics of unsteady pipe and duct flows is increasingly important because of precise control of these flows and safety of pipelines in many industrial processes. A variety of methods have been developed for producing various types of unsteady flows. Unfortunately, those capable of producing unsteady flows of arbitrary history are very limited. In this study a butterfly valve is used and it is driven by a stepping motor following programmed rotation speed. The valve is not rotated but swung around its supporting rod. Constant-acceleration flows, constant-deceleration flows, and pulsating flows with sinusoidal and triangular waveforms can be generated with sufficient accuracy.
The impact pressure occurred in new containers used for liquid products subjected to impact loads due to dropping was investigated, and compared with that of conventional paper containers. The new containers consist of a paper container with and without ribs and a liquid packaging bag and contain about 1000ml of water. The paper container and bag in the new containers were made of a sheet of recycled paper and a plastic film, respectively. The impact test with the bottom due to drop from a height of 0.25m to 1.5m was carried out. The impact pressure was measured using a pressure sensor. Results indicated that the maximum impact pressure occurred in the new containers was lower than that of the conventional containers. The impact pressure calculated by the water hammer theory was five times higher than that obtained from the experiment. However, the impact pressure calculated by the water hammer theory with modified pressure diffusion speed was the almost same as similar to that obtained from the experiment.
In this study, polylactic acid(PLA) was used as a biodegradable plastic. Plastic fibers of PLA were drawn with the drawing ratio of 3 to 15, at the drawing temperature of 25 to 120°C, and at drawing speed of 1%/s to 100%/s. Tensile test were carried out for drawn fibers. Tensile strength was increased with increase of drawing ratio. The tensile strength and Young’s modulus of the drawing biodegradable plastics were 9.2 times and 6.2 times higher as compared with the non-drawing fiber, respectively. Effects of drawing on microstructure were observed with X-ray diffraction, polarization microscope, and differential scanning calorimeter(DSC). Consequently, tensile strength and Young°Cs modulus were linearly increased with increase of orientation ratio, and relationships of mechanical properties with orientation of molecular chains and crystallization of the polymer were made clear.
The purpose of this study is to propose a new flow rate control structure and to verify the characteristics of a flow control device when the structure is actually installed in a section of pipe. In the present a viscoelastic magnetic silicone gel body is prepared by mixing ferromagnetism fine particles and the silicone gel. The viscoelastic magnetic silicone gel body with a tiny hole inherited from the manufacturing process is then installed in a section of a pipe. The flow rate, especially water in the present study, is controlled by applying magnetic field. The study examined the characteristic relationship between applied magnetic field and opening area for a condition of the body alone in the first place without running water. It is also examined for opening and shutting response time with and without applied pressure difference. In order to verify the actual valve, the flow control performance, the pressure loss coefficient is then obtained for various Reynolds numbers with varying magnetic field strength. Based on results, the possibility of application to the flow rate control valve is discussed.
Model study has been carried out on the effect of chicken bones on the basic characteristic of a swirl motion of a bath agitated by a liquid jet. A ball of elliptical in shape is used as a model for cut chicken bone. A predetermined number of elliptical balls are immersed in a water bath and then the bath is agitated by a water jet generated above a centered bottom nozzle. The water thus injected is circulated with a pump to keep the bath depth constant. The jet becomes to swirl in the bath as the water flow rate is raised above a critical value. The water existing near the bath surface also swirls in the same direction. The initial thickness of the ball layer is found to play an essential role on the basic characteristic of the swirl motion of the bath. Some empirical equations are proposed to describe them.
The investigation of oscillatory air flow at the zone of respiratory bronchiole in human lungs is important to analyze the ventilation mechanism of human respiration not only in natural breathing but also in artificial breathing. HFOV (High Frequency Oscillatory Ventilation) is one of the artificial ventilation methods, and it is effective for medical care for neonates with respiratory disorder. The ventilation mechanism in HFOV is not simple, and pendelluft is known as one of the ventilation mechanism in it. The generation of pendelluft has been analyzed theoretically and experimentally, however, the practical flow structure of pendelluft has not been experimentally clarified enough. In this report, the flow pattern of pendelluft generated in a micro-channel with multi-bifurcations as a model of respiratory bronchiole has been investigated experimentally by applying micro-PIV technique.
By using a damper with a magnetic functional fluid, we can change damping force without using any complicated mechanisms. Magnetorheological fluids and magnetic fluids are generally used for the damping force variable damper. The particles in the magnetorheological fluids subside immediately, and the magnetic fluid does not have high saturation magnetization, while it is expected that the magnetic functional fluid including both magnetic particles of micrometer size and magnetic particles of nanometer size outperform them. When the magnetic functional fluid that has two kinds of particles of different size is used, the mixture ratio of the particles affects damping properties of the damper. On the other hand, wide range of damping force and quick response are important properties for the damping force variable damper. In this study, damping properties of a damping variable damper are investigated experimentally. Five magnetic functional fluids that mixture ratios of a magnetic fluid and magnetorheological fluid are different were prepared for the experiments. Poly-α-olefin was used for the solvent of the magnetic functional fluids. It is shown that the damping force, shape of the damping force-displacement curve, the absorption energy and the damping force response are affected by the mixture ratio of the magnetic fluid and the magnetorheological fluid.