Study of wave-induced seabed response around twin pipelines in sandy seabed through laboratory experiments and numerical simulations

2022 ◽  
Vol 244 ◽  
pp. 110344
Author(s):  
Yanyan Zhai ◽  
Jisheng Zhang ◽  
Yakun Guo ◽  
Zihao Tang ◽  
Tiantian Zhang
2019 ◽  
Vol 51 (1) ◽  
pp. 129-154 ◽  
Author(s):  
Leon Boegman ◽  
Marek Stastna

Large-amplitude internal waves induce currents and turbulence in the bottom boundary layer (BBL) and are thus a key driver of sediment movement on the continental margins. Observations of internal wave–induced sediment resuspension and transport cover significant portions of the world's oceans. Research on BBL instabilities, induced by internal waves, has identified several mechanisms by which the BBL is energized and sediment may be resuspended. Due to the complexity of the induced currents, process-oriented research using theory, direct numerical simulations, and laboratory experiments has played a vital role. However, experiments and simulations have inherent limitations as analogs for oceanic conditions due to disparities in Reynolds number and grid resolution, respectively. Parameterizations are needed for modeling resuspension from observed data and in larger-scale models, with the efficacy of parameterizations based on the quadratic stress largely determining the accuracy of present field-scale efforts.


Author(s):  
Greg W. Gmurczyk ◽  
Ashwani K. Gupta

Abstract Constant and significant progress in both computer hardware and numerical algorithms, in recent years, have made it possible to investigate complex phenomena in engineering systems using computer modeling and simulations. Advanced numerical simulations can be treated as an extension of traditional analytical-theoretical analyses. In such cases, some of the simplifying assumptions can usually be dropped and the nonlinear interactions between various processes can be captured. One of the most complex engineering processes encountered in industry is a combustion process utilized either for power/thrust generation or incineration. However, even nowadays, because of the high level of complexity of the general problem of a combustion process in practical systems, it is not currently possible to simulate directly all the length and time scales of interest. Simplifying assumptions still need to be made, but they can be less drastic than in analytical approaches. Therefore, another view of numerical simulations is as a tool to simulate idealized systems and conduct numerical experiments. Such numerical experiments can be complementary to laboratory experiments and can also provide more detailed, nonintrusive diagnostics. Therefore, simulations, along with theory and laboratory experiments, can provide a more complete picture and better understanding of a combustion process. As an example of computer modeling of industrial combustion systems, an enclosed spray flame was considered. Such a flame can frequently be encountered in power generation units, turbine engines, and incinerators. Both the physical and mathematical models were formulated based on data from earlier laboratory studies and results obtained for open air spray flames. The purpose of this study was to use those data as model input to predict the characteristics of a confined flame and provide a means of optimizing the system design with a PC computer.


2018 ◽  
Vol 40 ◽  
pp. 05043
Author(s):  
Laurent Schindfessel ◽  
Tom De Mulder ◽  
Mia Loccufier

Confluences with dominant tributary inflow are found to exhibit long-periodic alternations of the flow patterns. They are shown to exist both in laboratory experiments and in numerical simulations. By means of a modal decomposition, insight is given into these long-periodic oscillations. The origin of these oscillations is investigated and their significant influence on the secondary flow patterns in the downstream channel is revealed.


Energies ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4616
Author(s):  
Chen Wei ◽  
Xianqiang Li ◽  
Ming Yang ◽  
Zhiyuan Ma ◽  
Hui Hou

The remanence (residual flux) in the core of power transformers needs to be determined in advance to eliminate the inrush current during the process of re-energization. In this paper, a novel method is proposed to determine the residual flux based on the relationship between residual flux and the measured magnetizing inductance. The paper shows physical, numerical, and analytical explanations on the phenomenon that the magnetizing inductance decreases with the increase of residual flux under low excitation. Numerical simulations are performed by EMTP (Electro-Magnetic Transient Program) on a 1 kVA power transformer under different amounts of residual flux. The inductance–remanence curves are nearly the same when testing current changes. Laboratory experiments conducted on the same transformer are in line with the numerical simulations. Furthermore, numerical simulation results on a 240 MVA are reported to demonstrate the effectiveness of the proposed method.


2012 ◽  
Vol 106 (6) ◽  
pp. 557-573 ◽  
Author(s):  
Stefania Espa ◽  
Isabella Bordi ◽  
Thomas Frisius ◽  
Klaus Fraedrich ◽  
Antonio Cenedese ◽  
...  

2005 ◽  
Vol 128 (1) ◽  
pp. 157-163 ◽  
Author(s):  
Shihai Feng ◽  
Alan L. Graham ◽  
Patrick T. Reardon ◽  
James Abbott ◽  
Lisa Mondy

Laboratory experiments and numerical simulations are performed to determine the accuracy and reproducibility of the falling-ball test for viscosity determination in Newtonian fluids. The results explore the wall and end effects of the containing cylinder and other possible sources that affect the accuracy and reproducibility of the falling ball tests. A formal error analysis of the falling-ball method, an evaluation of the relative merits of calibration and individual measurements, and an analysis of reproducibility in the falling-ball test are performed. Recommendations based on this study for improving both the accuracy and reproducibility of the falling-ball test are presented.


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