Research on pressure fluctuation phenomenon using the smart isolation tool in subsea pipeline maintenance operation

2018 ◽  
Vol 233 (2) ◽  
pp. 643-652 ◽  
Author(s):  
Kang Zhang ◽  
Qingxin Ding ◽  
Shuhai Liu ◽  
Shimin Zhang ◽  
Xiaoxiao Zhu
Keyword(s):  
Aspect Ratio ◽  
Flow Velocity ◽  
Pressure Fluctuation ◽  
Subsea Pipeline ◽  
Control Precision ◽  
Time Flow ◽  
Fluctuation Phenomenon ◽  
Accurate Position ◽  
Peak Value ◽  
Deceleration Time

A new isolation technology in subsea pipeline maintenance has been gradually developed in recent years. During the operation, the smart isolation tool is desired to decelerate and stop in the accurate position, which will cause a pressure surge in pipe, it was named “pressure fluctuation phenomenon” in this article. For control precision and sealing reliability, avoiding or reducing the fluctuation phenomenon has been necessary. The characteristics of this phenomenon and the effects of parameters have been investigated using numerical methodologies. The results indicated that this phenomenon mainly affected by deceleration time, flow velocity and aspect ratio, and the optimal parameters are t = 1.5 s, v = 1 m/s and γ = 1.2, respectively. The identical results could be achieved from the sensitivity analysis. It can be concluded that the peak value is more sensitive to deceleration time, less sensitive to flow velocity and least sensitive to aspect ratio. All the studies in this article will provide a reference to improve the control precision and seal reliability using smart isolation tool in subsea pipeline maintenance.

Fluttering Amplitude Amplification by Utilizing Flapping Moment in Flutter-Driven Triboelectric Nanogenerator

2021 ◽  
Author(s):  
Yi Zhang ◽  
Ka Chung Chan ◽  
Sau Chung Fu ◽  
Christopher Yu Hang Chao
Keyword(s):  
Flow Velocity ◽  
High Speed ◽  
Aerodynamic Force ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Energy Output ◽  
Small Scale ◽  
Triboelectric Nanogenerator ◽  
Peak Value

Abstract Flutter-driven triboelectric nanogenerator (FTENG) is one of the most promising methods to harvest small-scale wind energy. Wind causes self-fluttering motion of a flag in the FTENG to generate electricity by contact electrification. A lot of studies have been conducted to enhance the energy output by increasing the surface charge density of the flag, but only a few researches tried to increase the converting efficiency by enlarging the flapping motion. In this study, we show that by simply replacing the rigid flagpole in the FTENG with a flexible flagpole, the energy conversion efficiency is augmented and the energy output is enhanced. It is found that when the flag flutters, the flagpole also undergoes aerodynamic force. The lift force generated from the fluttering flag applies a periodic rotational moment on the flagpole, and causes the flagpole to vibrate. The vibration of the flagpole, in turn amplifies the flutter of the flag. Both the fluttering dynamics of the flags with rigid and flexible flagpoles have been recorded by a high-speed camera. When the flag was held by a flexible flagpole, the fluttering amplitude and the contact area between the flag and electrode plates were increased. The energy enhancement increased as the flow velocity increased and the enhancement can be 113 times when the wind velocity is 10 m/s. The thickness of the flagpole was investigated. An optimal output of open-circuit voltage reaching 1128 V (peak-to-peak value) or 312.40 V (RMS value), and short-circuit current reaching 127.67 μA (peak-to-peak value) or 31.99 μA (RMS value) at 12.21 m/s flow velocity was achieved. This research presents a simple design to enhance the output performance of an FTENG by amplifying the fluttering amplitude. Based on the performance obtained in this study, the improved FTENG has the potential to apply in a smart city for driving electronic devices as a power source for IoT applications.

Effects of Shield Gas Flow on Meltpool Variability and Signature in Scanned Laser Melting

2020 ◽  
Author(s):  
David C. Deisenroth ◽  
Jorge Neira ◽  
Jordan Weaver ◽  
Ho Yeung
Keyword(s):  
Additive Manufacturing ◽  
Aspect Ratio ◽  
Flow Velocity ◽  
Process Monitoring ◽  
Gas Flow ◽  
Laser Energy ◽  
Flow Speed ◽  
Powder Bed ◽  
Flow Speeds ◽  
Gas Flow Velocity

Abstract In laser powder bed fusion metal additive manufacturing, insufficient shield gas flow allows accumulation of condensate and ejecta above the build plane and in the beam path. These process byproducts are associated with beam obstruction, attenuation, and thermal lensing, which then lead to lack of fusion and other defects. Furthermore, lack of gas flow can allow excessive amounts of ejecta to redeposit onto the build surface or powder bed, causing further part defects. The current investigation was a preliminary study on how gas flow velocity and direction affect laser delivery to a bare substrate of Nickel Alloy 625 (IN625) in the National Institute of Standards and Technology (NIST) Additive Manufacturing Metrology Testbed (AMMT). Melt tracks were formed under several gas flow speeds, gas flow directions, and energy densities. The tracks were then cross-sectioned and measured. The melt track aspect ratio and aspect ratio coefficient of variation (CV) were reported as a function of gas flow speed and direction. It was found that a mean gas flow velocity of 6.7 m/s from a nozzle 6.35 mm in diameter was sufficient to reduce meltpool aspect ratio CV to less than 15 %. Real-time inline hotspot area and its CV were evaluated as a process monitoring signature for identifying poor laser delivery due to inadequate gas flow. It was found that inline hotspot size could be used to distinguish between conduction mode and transition mode processes, but became diminishingly sensitive as applied laser energy density increased toward keyhole mode. Increased hotspot size CV (associated with inadequate gas flow) was associated with an increased meltpool aspect ratio CV. Finally, it was found that use of the inline hotspot CV showed a bias toward higher CV values when the laser was scanned nominally toward the gas flow, which indicates that this bias must be considered in order to use hotspot area CV as a process monitoring signature. This study concludes that gas flow speed and direction have important ramifications for both laser delivery and process monitoring.

scholarly journals Buckling Behaviors of Staggered Nanostructure of Biological Materials

2015 ◽  
Vol 83 (3) ◽  
Author(s):  
Zhiling Bai ◽  
Yewang Su ◽  
Baohua Ji
Keyword(s):  
Aspect Ratio ◽  
Mechanical Model ◽  
Volume Fraction ◽  
Biological Materials ◽  
Protein Matrix ◽  
Buckling Strength ◽  
Upper Limits ◽  
Staggered Arrangement ◽  
The Stability ◽  
Peak Value

The nanostructure of biological materials is built with hard mineral crystals embedded in soft protein matrix in a staggered manner. The staggered arrangement of the crystals is assumed to be critically important for the stability of the nanostructure. But the mechanism is not fully understood. In this paper, a mechanical model, considering the effects of overlapping ratio between the crystals, i.e., the staggering position, is developed for analyzing the buckling behaviors of the nanostructure. It is found that the buckling strength increases with the overlapping ratio λ in the range of 0–1/2 and reaches a peak value at λ = 1/2 that is generally adopted by nature's design of the biological materials. The effect of aspect ratio and volume fraction of mineral crystals are further analyzed at various overlapping ratios, and the results are in general consistent with previous studies for the case of λ = 1/2. In addition, the lower and upper limits of the buckling strength are obtained. Finally, we show that the contact between mineral tips can significantly enhance the buckling strength of the nanostructure when the aspect ratio of minerals is small.

Research on the Step by Step Sliding Mode Variable Structure Adaptive Control

2013 ◽  
Vol 721 ◽  
pp. 591-600
Author(s):  
Xu Xiao Hu ◽  
Han Tao Chen ◽  
Gang Chen ◽  
Xin Rong Xu
Keyword(s):  
Adaptive Control ◽  
Sliding Mode ◽  
Variable Structure ◽  
Step Method ◽  
Small Peak ◽  
Control Precision ◽  
Adaptive Control Strategy ◽  
Sliding Mode Variable Structure ◽  
High Control ◽  
Peak Value

In order to increase the control precision in meeting the robust request, a step by step sliding mode variable structure adaptive control strategy is presented in accordance with kind of two order time-invariant controlled object. Because the chatter amplitude is decreased when the system cuts in the position of equilibrium by the small peak-to-peak value, the mathematical model is firstly established and using the adaptive algorithm determined the control quantity to achieve the target value, then uses by the step by step method about, in the proper attention to both rapidity and robustness, reduces the peak-to-peak value deviation gradually which cuts, thus obtains the high control precision.

scholarly journals Performance of Silt Protector in Three Dimensional Flows

2014 ◽  
Vol 2 ◽  
pp. 19-29
Author(s):  
Rajesh P. Dubey ◽  
Bitanjaya Das ◽  
Parasar K. Mohanty
Keyword(s):  
Flow Velocity ◽  
Simple Procedure ◽  
Three Dimensional ◽  
Diffusion Time ◽  
Experimental Results ◽  
Construction Site ◽  
Construction Work ◽  
Series Of Experiments ◽  
Peak Value

Performance of silt-curtain in three dimensional sea is investigated through a series of experiments. It is found that there are three mechanisms to reduce concentration and flux of turbidity generated by the construction work from flowing out of the construction site enclosed with silt curtains. The first is the temporal storage of turbidity and retardation of the flow of turbidity around the curtain. The second is the acceleration of dispassion of turbidity caused by the turbulence generated around the curtain that decreases the peak value of concentration of turbidity. The last one is the reduction of flow velocity in the enclosed area. As a result, the diffusion time increases and the amount of turbidity settled down in the enclosed region increases. Taking these mechanisms into account a simple procedure to predict reduction of flow velocity and the flux of turbidity is proposed. The applicability of the proposed procedure is examined using experimental results.

scholarly journals Strength and compressibility characteristics of soil stabilized with plastic bag strips

2021 ◽  
Author(s):  
Jayasree P K ◽  
Monica Simon ◽  
Vismaya A ◽  
Vinod J S
Keyword(s):  
Compressive Strength ◽  
Aspect Ratio ◽  
Significant Influence ◽  
Unconfined Compressive Strength ◽  
Reinforced Soil ◽  
Aspect Ratios ◽  
Laboratory Results ◽  
Plastic Bag ◽  
Compressibility Characteristics ◽  
Peak Value

Abstract This study investigates the potential application of utilizing plastic bag strips (PBS) in improving the strength and compressibility behavior of soils. A series of unconfined compressive strength (UCS) and consolidation tests were carried out for different proportions of plastic bag strip reinforced soil. The effect of the thickness (t) and aspect ratio (AR) on the UCS and compressibility characteristics of PBS reinforced soil was investigated. The thicknesses of PBS used were 15 µm, 30 µm and 45 µm which were added in varying concentrations (0.1%-0.7%) at different aspect ratios 1, 2 and 2.5. The laboratory results clearly show that PBS have a significant influence on the UCS and compressibility behavior of soil. In addition, the peak value of UCS (qu) increases with the thickness and AR of PBS. A significant improvement in qu has been found for 0.5% addition of PBS. Moreover, the swelling behavior of soil has significantly reduced with the addition of PBS.

Shortened Deceleration Time of Early Peak Flow Velocity in Apparent Normal Transmitral Doppler Flow in Patients with Dilated Cardiomyopathy

1992 ◽  
Vol 6 (4) ◽  
pp. 252-256 ◽  
Author(s):  
Makoto Suzuki ◽  
Mareomi Hamada ◽  
Michihito Sekiya ◽  
Yasushi Fujiwara ◽  
Takumi Sumimoto ◽  
...  
Keyword(s):  
Dilated Cardiomyopathy ◽  
Flow Velocity ◽  
Peak Flow ◽  
Doppler Flow ◽  
Peak Flow Velocity ◽  
Early Peak ◽  
Deceleration Time
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