Mm-diameter Pipe Research Articles

Centrifuge test of large-diameter segmented ductile iron pipes crossing strike-slip faults

Seismic ground faults are severe hazards for buried pipes. To explore and model the failure mechanisms of segmented pipes crossing faults, a centrifuge test of a socket-type ductile iron pipe crossing a strike-slip fault is conducted. In the test, a segmented ductile iron pipe with five segments is buried in a soil box. Then, at a centrifugal gravity level of 30.7 g, 60 mm ground displacements are applied through translation of half of the test soil box. Thus, a 2646.2 mm-diameter pipe with a length of 27.4 m subjected to a 1.84 m-long strike-slip fault is simulated. The responses of the joint deformation and the pipe strain are obtained. Results show that the joint deformation is the main response of the pipes subjected to strike-slip faults, the joint near the fault trace is vulnerable, the pipe strain is relatively small, and the peak pipe strain occurs at a certain distance from the fault. Lastly, a theoretical method is presented to obtain the joint deformation of the pipes crossing a strike-slip fault, and a good agreement between the test and theoretical results is observed. The test can be a benchmark for theoretical and numerical models. Meanwhile, the proposed theoretical method has clear physical mechanisms and can obtain the pipe joint deformation effectively.

Double-layered blood vessels over 3 mm in diameter extruded by the inverse-gravity technique

One of the most promising techniques for treating severe peripheral artery disease is the use of cellular tissue-engineered vascular grafts (TEVGs). This study proposes an inverse-gravity (IG) extrusion technique for creating long double-layered cellular TEVGs with diameters over 3 mm. A three-layered coaxial laminar hydrogel flow in an 8 mm-diameter pipe was realised simply by changing the extrusion direction of the hydrogel from being aligned with the direction of gravity to against it. This technique produced an extruded mixture of human aortic smooth muscle cells (HASMCs) and type-I collagen as a tubular structure with an inner diameter of 3.5 mm. After a 21 day maturation period, the maximal burst pressure, longitudinal breaking force, and circumferential breaking force of the HASMC TEVG were 416 mmHg, 0.69 N, and 0.89 N, respectively. The HASMC TEVG was endothelialised with human umbilical vein endothelial cells to form a tunica intima that simulated human vessels. Besides subcutaneous implantability on mice, the double-layered blood vessels showed a considerably lower adherence of platelets and red blood cells once exposed to heparinised mouse blood and were considered nonhaemolytic. The proposed IG extrusion technique can be applied in various fields requiring multilayered materials with large diameters.

Phase Distribution Characteristics of Bubbly Flow in Mini Pipes Under Normal and Microgravity Conditions

The axial development of the void fraction, interfacial area concentration and Sauter mean bubble diameter profiles of adiabatic air-water bubbly flows in 5.0 and 3.0 mm-diameter pipes were measured using a stereo image processing method under two gravity conditions, vertical upward (normal gravity) and microgravity. The flow measurements were performed at four axial locations. The axial distances from the pipe inlet (z) normalized by the pipe diameter (D) were z/D = 5.5, 34, 72 and 110 for 5.0 mm-diameter pipe and z/D = 15, 62, 120 and 188 for 3.0 mm-diameter pipe. Data were collected for superficial gas and liquid velocities respectively in the ranges of 0.00434–0.0500 m/s and 0.205–0.754 m/s. The effect of gravity on the radial distribution of bubbles and the axial development of two-phase flow parameters is discussed in detail, based on the obtained database. The phase distributions in pipe cross-sections were classified into 3 basic patterns: core peak, intermediate peak and wall peak distributions, based on two normalized parameters: a normalized void peak position and a normalized void peak intensity. Phase distribution pattern maps under normal and microgravity conditions were generated for bubbly flows in 5.0 and 3.0 mm-diameter pipes. The data obtained in the current experiment are expected to contribute to the benchmarking of CFD simulation of void fraction and interfacial area concentration distribution patterns in forced convective pipe flow under microgravity conditions.

Characteristics of developing vertical bubbly flow under normal and microgravity conditions

The axial development of the void fraction profile, interfacial area concentration and Sauter mean bubble diameter of adiabatic nitrogen–water bubbly flows in a 9 mm-diameter pipe were measured using stereo image processing under normal and microgravity conditions. The flow measurements were performed at four axial locations (axial distance from the inlet, z normalized by the pipe diameter, D, z/ D = 5, 20, 40 and 60) and with various flows: superficial gas velocity of 0.00840–0.0298 m/s, and superficial liquid velocity of 0.138–0.914 m/s. The effect of gravity on radial distribution of bubbles and the axial development of two-phase flow parameters is discussed in detail based on the obtained database and visual observation. Following Serizawa–Kataoka’s phase distribution pattern criteria under normal gravity conditions, the phase distribution pattern map was developed. Similar to normal gravity two-phase flows, wall, core and intermediate void peak patterns are observed under microgravity conditions but a transition void distribution pattern is not observed in the current experimental conditions. The data obtained in the current experiment are expected to contribute to the benchmarking of CFD simulation of phase distribution pattern and interfacial area concentration in forced convective pipe flow under microgravity conditions.

ICONE19-43162 EFFECT OF GRAVITY ON DISTRIBUTION PARAMETER AND DRIFT VELOCITY IN VERTICAL UPWARD BUBBLY TWO-PHASE FLOW

In view of the practical importance of the drift-flux model for two-phase flow analyses in microgravity conditions, the distribution parameter and the drift velocity were estimated by experimentally for vertical upward bubbly flows in a 9 mm-diameter pipe in normal- and micro-gravity conditions by using a stereo imageprocessing method. The effects of gravity and liquid Reynolds number on the distribution parameter and the drift velocity were discussed in detail. It was confirmed that the drift velocity in microgravity conditions didn't become zero and the local slip effect due to the wall friction couldn't be ignored. Comparison of the previously proposed constitutive equations of the distribution parameter and the drift velocity with the experimental data showed a good agreement.

Effect of Gravity on Flow Characteristics of Developing Vertical Upward Bubbly Flow (1st Report, Measurement of Local Flow Parameter)

In relation to the development of the interfacial area transport equation, axial developments of void fraction profile, interfacial area concentration and Sauter mean diameter of adiabatic nitrogen-water bubbly flows in a 9 mm-diameter pipe were measured by using a stereo image-processing method at normal-and micro-gravity conditions. The flow measurements were performed at four axial locations (axial distance from the inlet normalized by the pipe diameter, z/D=5, 20, 40 and 60) at various flow conditions of superficial gas velocity (0.008 40-0.029 8 m/s) and superficial liquid velocity (0.138-0.914 m/s). The effect of gravity on radial distribution of bubbles and the axial developments of two-phase flow parameter was discussed in detail based on the obtained data and the visual observation.

E202 水平ミニチャンネル内気液二相流の流動特性(OS-10 混相流動(2),一般講演,地球温暖化防止と動力エネルギー技術)

Accurate prediction of the interfacial area concentration is essential to successful development of the interfacial transfer terms in the two-fluid model. Mechanistic modeling of the interfacial area concentration entirely relies on accurate local flow measurements over extensive flow conditions and channel geometries. From this point of view, accurate measurements of flow parameters such as void fraction, interfacial area concentration, gas velocity, bubble Sauter mean diameter, and bubble number density were performed by the image processing method at five axial locations in horizontal bubbly flows using 1.03 mm-diameter pipe. In the experiments, the obtained data give near complete information on the time-averaged local hydrodynamic parameters of two-phase flow. These data can be used for the development of reliable constitutive relations which reflect the true transfer mechanisms in two-phase flow.

Effect of Gravity on Flow Characteristics of Developing Vertical Upward Bubbly Flow (2nd Report, Cross-Sectional Phase Distribution Pattern)

Local flow measurements were performed for vertical upward bubbly flows in a 9 mm-diameter pipe at normal- and micro-gravity conditions. A stereo image-processing method was used for measuring void fraction profile, interfacial area concentration and Sauter mean diameter. The flow measurements were performed at four axial locations (axial distance from the inlet normalized by the pipe diameter, z/D=5, 20, 40 and 60) at various flow conditions of superficial gas velocity (0.00840-0.0298 m/s) and superficial liquid velocity (0.138-0.914 m/s). By taking into account the normalized parameters on void peak fraction and void peak intensity in pipe cross-section, the phase distribution pattern was quantitatively-classified into three patterns : a wall peak, a core peak and an intermediate peak. The phase distribution pattern maps were newly presented for vertical upward bubbly flows at normal-and micro-gravity conditions.

Application of the time reversal technique to the focusing of long-range ultrasound in pipelines

The novel time reversal method of focusing has been applied to long-range ultrasonic propagation in pipelines. Some preliminary results on a 170 mm-diameter pipe of 7.1 mm wall thickness with a 9% CSA simulated crack defect are presented which show that significant increases in the signal-to-noise ratio of defect echoes can be obtained with this approach. The results equated to a signal-to-noise ratio of 2 (6 dB), which gives a 95% POD (probability of detection) according to the normal probability integral, for a 1% CSA crack. Using the same instrumentation without focusing, the crack size must be increased to 2% CSA to achieve the same POD. The results were also slightly better than those obtained using phased array focusing with a four-element array encircling the pipe. These preliminary results display promise of further improvement. The time reversal principle is described in simple terms both by a particle mechanics analogy and using geometrical optics, ie ray theory.

Some characteristics of developing bubbly flow in a vertical mini pipe

Accurate prediction of the flow parameters is essential to successful development of the interfacial transfer terms in the two-phase flow formulation in a mini channel. From this point of view, axial measurements of flow parameters such as void fraction, interfacial area concentration, gas velocity, bubble Sauter mean diameter, and bubble number density were performed by the image processing method at five axial locations in vertical upward developing bubbly flows using a 1.02 mm-diameter pipe. The frictional pressure loss was also measured by a differential pressure cell. In the experiment, the superficial liquid velocity and the void fraction ranged from 1.02 m/s to 4.89 m/s and from 0.980% to 24.6%, respectively. The constitutive equation for the drift velocity applicable to mini channel flow was developed by considering the effect of the frictional pressure loss on the drift velocity. The constitutive equation for the distribution parameter was also developed by considering the flow transition from laminar to turbulent flows. The drift-flux model with the modeled constitutive equations for the distribution parameter and drift velocity agreed with the measured void fractions within the averaged prediction accuracy of ±6.76%. The applicability of the existing interfacial area concentration model to mini channel flow was validated by the measured interfacial data.

D102 微小重力下における垂直管固液二相流の流動構造の計測

Radial distributions of solid-water flows in a 9 mm-diameter pipe were measured by a stereo image-processing method and a hough transform method at normal- and micro-gravity conditions. The flow measurements were performed at an axial locations (axial distance from the inlet normalized by the pipe diameter=40) under various flow conditions of superficial liquid velocity (0.355-1.59 m/s). The effect of gravity on phase distribution patterns was discussed based on the obtained experimental data.

Effect of Gravity on Interfacial Area Transport of Vertical-upward Bubbly Flow

In relation to the development of the interfacial area transport equation, axial developments of void fraction profile, bubble number density, interfacial area concentration and Sauter mean diameter of adiabatic nitrogen-water bubbly flows in a 9 mm-diameter pipe were measured by using a stereo image-processing method under normal- and micro-gravity environment. The flow measurements were performed at four axial locations (axial distance from the inlet normalized by the pipe diameter, z/D = 5, 20, 40 and 60) at various flow conditions of superficial gas velocity (0.00823-0.0303 m/s) and superficial liquid velocity (0.147-0.907 m/s). The effect of gravity on radial distribution of bubbles and axial developments of two-phase flow parameter was discussed in detail based on the obtained data and the visual observation.

Axial development of interfacial structure of vertical downward bubbly flow

Accurate prediction of the interfacial area concentration is essential to successful development of the interfacial transfer terms in the two-fluid model. Mechanistic modeling of the interfacial area concentration entirely relies on accurate local flow measurements over extensive flow conditions and channel geometries. From this point of view, accurate measurements of flow parameters such as void fraction, interfacial area concentration, and interfacial velocity were performed by a multi-sensor probe at three axial locations as well as seven radial locations in vertical downward bubbly flows using a 25.4 mm-diameter pipe. In the experiment, the superficial liquid velocity and the void fraction ranged from −1.25 to −3.11 m/s and from 1.61% to 21.0%, respectively.

A challenge of an ultra-large section tunnel project in unconsolidated ground - design and construction of the Minoh toll road tunnel -

Minoh toll road, part of the bypass for National Highway No. 423, is a northward extension of the Shin-Midosuji highway, which runs from central Osaka to the north of the city. In the future, it will be connected to the Second Meishin Expressway to be part of the broad network of highways. The Minoh toll road tunnel is a mountain tunnel about 5.6 km long that goes through the Hokusetsu Mountains (200-600 m in altitude) in the northern part of Osaka Prefecture. The southern sector of this tunnel discussed in this paper is approximately 2.2 km long. The geology around the southern entrance is unconsolidated ground characterized by gravel, sand and clay of the Osaka Group. Beyond this region, heavily fractured shale of the Tanba Zone is found. In addition to these adverse conditions, the entry and exit ramps must be constructed inside the tunnel because of the road location and alignment. This requires planning of a huge tunnel having an excavation section more than 300 m2. The challenging project is now being performed under adverse conditions Before starting the excavation of the main tunnel, a working tunnel (excavation section 41 m2, 347 m long) was parallelly driven to the north. In the Osaka Group and the heavily fractured zone of the Tanba Zone, the face was unstable, causing a large face extrusion, failure and significant deformations of the ground. This behavior made the tunneling very difficult. Considering the construction of the working tunnel, and the records of the main tunnel excavated toward the south from the crossing between working tunnel and main tunnel (about 350 m to the north from the south portal), the design and construction of the ultra-large section tunnel in unconsolidated ground were reviewed in detail. The sector with an excavation section exceeding 300 m2 was initially designed with the multiple side drift method. However, as a result of comparative study with other methods such as side drift and top heading, the side drift method was finally selected. Additional stability is achieved with a 800 mm-diameter pipe roof (slurry) in the largest section sector and for the preceding sector having a 260 m2 section, long forepiles and glass fiber reinforced plastic tubes were driven. This paper deals with the design and construction of the ultra-large section tunnel in the adverse geological conditions. It refers to the verification of the optimized design and establishment of the work management criteria, backed up with the numerical analysis and with the feedback of work records and measurement data obtained in the working tunnel and main tunnel. (A). Reprinted with permission from Elsevier. For the covering abstract see ITRD E124500.

画像処理による細管内気液二相流界面輸送の計測(FR2 計測制御の最先端)

Accurate prediction of the interfacial area concentration is essential to successful development of the interfacial transfer terms in the two-fluid model. Mechanistic modeling of the interfacial area concentration entirely relies on accurate local flow measurements over extensive flow conditions and channel geometries. From this point of view, accurate measurements of flow parameters such as void fraction, interfacial area concentration, gas velocity, bubble Sauter mean diameter, and bubble number density were performed by the image processing method at five axial locations in vertical upward bubbly flows using a 1.02 mm-diameter pipe. The factional pressure loss was also measured by a differential pressure cell. In the experiment, the superficial liquid velocity and the void fraction ranged from 1.02 m/s to 4.89 m/s and from 0.980 % to 24.6 %, respectively. The obtained data give near complete information on the time-averaged local hydrodynamic parameters of two-phase flow. These data can be used for the development of reliable constitutive relations which reflect the true transfer mechanisms in two-phase flow. As the first step to understand the flow characteristics in mini-channels, the applicability of the existing drift-flux model, interfacial area correlation, and frictional pressure correlation was examined by the data obtained in the mini-channel.

Interfacial area transport of bubbly flow under microgravity environment

In relation to the development of the interfacial area transport equation, axial developments of one-dimensional void fraction, bubble number density, interfacial area concentration, and Sauter mean diameter of adiabatic nitrogen–water bubbly flows in a 9 mm-diameter pipe were measured by using an image-processing method under microgravity environment. The flow measurements were performed at four axial locations (axial distance from the inlet normalized by the pipe diameter=7, 30, 45 and 60) under various flow conditions of superficial gas velocity (0.0083–0.022 m/s) and superficial liquid velocity (0.073–0.22 m/s). The interfacial area transport mechanism under microgravity environment was discussed in detail based on the obtained data and the visual observation. These data can be used for the development of reliable constitutive relations which reflect the true transfer mechanisms in two-phase flow under microgravity environment.

Drag reduction of Newtonian fluid in a circular pipe with a highly water-repellent wall

Drag reduction phenomena, in which 14% drag reduction of tap water flowing in a 16 mm-diameter pipe occurs in the laminar flow range, have been clarified. Experiments were carried out to measure the pressure drop and the velocity profile of tap water and an aqueous solution of glycerin flowing in pipes with highly water-repellent walls, by using a pressure transducer and a hot-film anemometer, respectively. The same drag reduction phenomena also occurred in degassed tap water when using a vacuum tank. The velocity profile measured in this experiment gives the slip velocity at the pipe wall, and it was shown that the shear stress is directly proportional to the slip velocity.The friction factor formula for a pipe with fluid slip at the wall has been obtained analytically from the exact solution of the Navier–Stokes equation, and it agrees well qualitatively with the experimental data.The main reasons for the fluid slip are that the molecular attraction between the liquid and the solid surface is reduced because the free surface energy of the solid is very low and the contact area of the liquid is decreased compared with a conventional smooth surface because the solid surface has many fine grooves. Liquid cannot flow into the fine grooves owing to surface tension. These concepts are supported by the experimental result that drag reduction does not occur in the case of surfactant solutions.