Experimental Validation of Existing Numerical Models for the Interaction of Fluid Transients With In-Line Air Pockets

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Jane Alexander ◽  
Pedro J. Lee ◽  
Mark Davidson ◽  
Huan-Feng Duan ◽  
Zhao Li ◽  
...  
Keyword(s):  
Time Delay ◽  
Wave Speed ◽  
Numerical Models ◽  
Diagnostic Process ◽  
Air Pocket ◽  
Fluid Transients ◽  
Entrapped Air ◽  
Air Pockets ◽  
The Given ◽  
Potential Tool

Entrapped air in pipeline systems can compromise the operation of the system by blocking flow and raising pumping costs. Fluid transients are a potential tool for characterizing entrapped air pockets, and a numerical model which is able to accurately predict transient pressures for a given air volume represents an asset to the diagnostic process. This paper presents a detailed study on our current capability for modeling and predicting the dynamics of an inline air pocket, and is one of a series of articles within a broader context on air pocket dynamics. This paper presents an assessment of the accuracy of the variable wave speed and accumulator models for modeling air pockets. The variable wave speed model was found to be unstable for the given conditions, while the accumulator model is affected by amplitude and time-delay errors. The time-delay error could be partially overcome by combining the two models.

On the Hydraulics of Downward Sloping Pipes With Entrapped Air Pockets

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
H. A. Warda ◽  
E. M. Wahba ◽  
E. N. Ahmed
Keyword(s):  
Hydraulic Jump ◽  
Open Channel ◽  
Numerical Results ◽  
Navier Stokes ◽  
Experimental Investigations ◽  
Dynamics Model ◽  
Computational Fluid Dynamics Model ◽  
Air Pocket ◽  
Entrapped Air ◽  
Air Pockets

Abstract In this study, air–water flow in a downward sloping pipe subsequent to the entrapping of an air pocket is investigated both numerically and experimentally. A transient, two-dimensional computational fluid dynamics model is applied to study the different possible flow regimes and their associated phenomena. The numerical model is based on the Reynolds-averaged Navier–Stokes (RANS) equations and the volume of fluid (VOF) method. Both numerical and experimental investigations provide visualization for the hydraulic jump, the blowback regime, and the full gas transport regime. The numerical results predict that the flow structure in the pipe downstream the toe of the hydraulic jump is subdivided into three distinct regions including the jet layer, the shear zone, and the circulation region, which agrees qualitatively with the previous investigations of the hydraulic jump characteristics in open channel flow. Numerical results are in reasonable agreement with the experimental measurements of the circulation length and the hydraulic jump head loss.

scholarly journals Numerical Study on the Commissioning Charge-Up Process of Horizontal Pipeline with Entrapped Air Pockets

2014 ◽  
Vol 6 ◽  
pp. 838926 ◽  
Author(s):  
Xinyu Zhang ◽  
Bo Yu ◽  
Yan Wang ◽  
Jianyu Xie ◽  
Dongping Qiu ◽  
...  
Keyword(s):  
Process Design ◽  
Pressure Field ◽  
Numerical Study ◽  
Critical Parameters ◽  
Hydraulic Characteristics ◽  
Oil Pipeline ◽  
Air Pocket ◽  
Acute Change ◽  
Entrapped Air ◽  
Air Pockets

Accurately predicting hydraulic characteristics in the charge-up process of horizontal pipeline with entrapped air pocket is of great significance for the process design and field operation of the oil pipeline commissioning. In this paper, this process is simulated and its hydraulic characteristics are analyzed. Finite difference method and characteristic method are combined to obtain the velocity and pressure field of the whole line. Results show that when air pockets reach the outlet of the pipeline, they blow out tempestuously and the velocity of gas may reach tens times of its normal flow velocity. At the beginning and end of the blowing out, velocity and pressure of the whole line suffer acute change. Based on this, the influence of several critical parameters is compared and analyzed by several groups of examples.

Understanding of the Risks of High Pressures Following Rapid Pressurization in Pipelines Containing Entrapped Air Pockets: A Novel Energy Auditing Approach

2014 ◽  
Author(s):  
Ahmad Malekpour ◽  
Bryan Karney
Keyword(s):  
High Pressures ◽  
Numerical Models ◽  
Pressure Rise ◽  
Complex Nature ◽  
Maximum Pressure ◽  
Physical Parameters ◽  
Pipe System ◽  
Energy Auditing ◽  
Entrapped Air ◽  
Air Pockets

Rapid pressurization of liquid pipelines containing entrapped air may result in extreme overpressures. Both experimental and numerical studies have shown that the magnitude of the induced pressure has important sensitivities to many physical parameters even though the complex nature of the system’s transient responses has tended to obscure the physical mechanisms themselves. To provide insight and guidance to key design issues, this paper proposes an energy auditing approach to elucidate the physics of the transient events leading to the extreme pressure rise during pipe rapid pressurization events. The proposed approach is then utilized to provide physical understanding of the features of the flow and the system parameters affecting the maximum pressure rise during rapid pressurization of pipe system. Both rigid column and elastic numerical models are then employed to verify the results obtained from the proposed approach.

Effect of Spray-Wall Interaction On Thermoacoustic Instability Prediction by Flame Transfer Function and the Convective Time Delay Method

2021 ◽  
Author(s):  
Sheng Meng ◽  
Man Zhang
Keyword(s):  
Time Delay ◽  
Transfer Function ◽  
Numerical Models ◽  
Time Lag ◽  
Interaction Model ◽  
Phase Lag ◽  
Thermoacoustic Instability ◽  
Spray Flame ◽  
Wall Interaction ◽  
Definition Of

Abstract This study numerically investigates the effect of spray-wall interactions on thermoacoustic instability prediction. The LES-based flame transfer function (FTF) and the convective time delay methods are used by combining the Helmholtz acoustic solver to predict a single spray flame under the so-called slip and film spray-wall conditions. It is found that considering more realistic film liquid and a wall surface interaction model achieves a more accurate phase lag in both of the time lag evaluations compared to the experimental results. Additionally, the results show that a new time delay exists between the liquid film fluctuation and the unsteady heat release, which explains the larger phase value in the film spray-wall condition than in the slip condition. Moreover, the prediction capability of the FTF framework and the convective time delay methodology in the linear regime are also presented. In general, the instability frequency differences predicted using the FTF framework under the film condition are less than 10 Hz compared with the experimental data. However, an underestimation of the numerical gain value leads to requiring a change in the forcing position and an improvement in the numerical models. Due to the ambiguous definition of the gain value in the convective time delay method, this approach leads to arbitrary and uncertain thermoacoustic instability predictions.

scholarly journals Minimal Wave Speed in a Predator-Prey System with Distributed Time Delay

2018 ◽  
Vol 2018 ◽  
pp. 1-8
Author(s):  
Fuzhen Wu ◽  
Dongfeng Li
Keyword(s):  
Time Delay ◽  
Traveling Wave ◽  
Wave Speed ◽  
Upper And Lower Solutions ◽  
Traveling Wave Solutions ◽  
Predator Prey ◽  
Wave Solutions ◽  
Prey System ◽  
Minimal Wave Speed ◽  
Distributed Time Delay

This paper is concerned with the minimal wave speed of traveling wave solutions in a predator-prey system with distributed time delay, which does not satisfy comparison principle due to delayed intraspecific terms. By constructing upper and lower solutions, we obtain the existence of traveling wave solutions when the wave speed is the minimal wave speed. Our results complete the known conclusions and show the precisely asymptotic behavior of traveling wave solutions.

scholarly journals Development of Pant-Type Harness with Fabric Air-Pocket for Pain Relief

2019 ◽  
Vol 9 (9) ◽  
pp. 1921
Author(s):  
Dongwoo Nam ◽  
Miyeon Kwon ◽  
Juhea Kim ◽  
Bummo Ahn
Keyword(s):  
Contact Area ◽  
Peak Pressure ◽  
Applied Pressure ◽  
The Body ◽  
Area Measurement ◽  
Medical Applications ◽  
Air Pocket ◽  
Long Time ◽  
Developed Pressure ◽  
Air Pockets

Harnesses can be used in various applications, such as entertainment, rescue operations, and medical applications. Because users are supported on the harness for a long time, they should feel comfortable wearing the harnesses. However, existing commercial harnesses are uncomfortable to wear and cause continuous serious pain. Therefore, in this study, a new pant-type harness with a fabric air pocket to reduce the applied pressure on the body, especially in the groin, is proposed. Keeping this in mind, we have designed and developed the pant-type harness. In addition, we performed pressure and contact area measurement experiments using the harness developed, pressure sensor, and a human mannequin. Peak and mean pressures and contact areas near the groin and waist were measured in the experiments. From the results, when air is injected in the air pockets, the peak pressure and contact area near the waist increased, and the peak pressure near the groin decreased. This means that the pressure applied on the human mannequin near the groin reduces because of the increased contact area near the waist, which is achieved by multi-layered air pockets. In this study, we proposed the optimal design of a novel pant-type harness that can address the limitations of existing harnesses. The proposed harness can be used for a prolonged time in applications, such as virtual reality entertainment, rescue operations, and rehabilitation.

scholarly journals Development of the computerized decision-making support system for the prevention and revealing of dangerous zones of flooding

2019 ◽  
Vol 97 ◽  
pp. 05040 ◽  
Author(s):  
Farrukh Shaazizov ◽  
Bakhtiyar Uralov ◽  
Elyor Shukurov ◽  
Aydar Nasrulin
Keyword(s):  
Cross Sections ◽  
Calculation Method ◽  
Visual Inspection ◽  
Wave Speed ◽  
Emergency Situation ◽  
Technical Condition ◽  
The Common ◽  
The Given ◽  
Modern Condition ◽  
Partial Destruction

In considered article the results are presented of the carried out researches on high-mountainous lakes of the Tashkent area. Visual inspection of a modern condition of natural dams of considered high-mountainous lakes of the Tashkent oblast is carried out. On the basis of the analysis of visual inspection it is possible to note, that the common technical condition of natural dams of the submitted high-mountainous lakes safe and does not represent danger to downstream situated territories. It was carried out the modeling of occurrence of emergency situation on high-mountainous lakes of the Tashkent oblast in case of full or partial destruction of natural dams. By an available calculation method of flooding waves are determined its key parameters, height of a wave, speed of distribution of a wave of break on the certain distances and reaching time the given wave up to the certain distances. On the basis of calculation method have been calculated and put on cross-sections of the rivers Pskem and Kocy zones of possible flooding in full and partial destruction of dams of high-mountainous lakes. Results of the carried out calculations have been put on the digital map, created on platform ArcView 3.2a.

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