Spectral Properties of Water Hammer Wave

Sarker, Shiblu; Sarker, Tonmoy

doi:10.3390/applmech3030047

Cited by 13 publications

(9 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The Hurst exponent represents structure over asymptotically longer periods [46]. It is an effective method to quantitatively describe the long-range dependence of time series, and is a measure of a data series' "mild" or "wild" randomness [47,48]. It has to do with time series autocorrelations and the pace at which they drop as the lag between pairs of values grows longer [48].…”

Section: Hurst Analysismentioning

confidence: 99%

“…It is an effective method to quantitatively describe the long-range dependence of time series, and is a measure of a data series' "mild" or "wild" randomness [47,48]. It has to do with time series autocorrelations and the pace at which they drop as the lag between pairs of values grows longer [48]. It was established in hydrology for the purpose of calculating the optimum dam size [49].…”

Section: Hurst Analysismentioning

confidence: 99%

See 1 more Smart Citation

Linear and Nonlinear Characteristics of Long-Term NDVI Using Trend Analysis: A Case Study of Lancang-Mekong River Basin

Zhong

Wang

et al. 2022

Remote Sensing

View full text Add to dashboard Cite

Vegetation is the main body of the terrestrial ecosystem and is a significant indicator of environmental changes in the regional ecosystem. As an essential link connecting South Asia and Southeast Asia, the Lancang-Mekong River Basin(LMRB) can provide essential data support and a decision-making basis for the assessment of terrestrial ecosystem environmental changes and the research and management of hydrology and water resources in the basin by monitoring changes in its vegetation cover. This study takes the Lancang-Mekong River Basin as the study area, and employs the Sen slope estimation, Mann–Kendall test, and Hurst exponent based on the MODIS NDVI data from 2000 to 2021 to study the spatial and temporal evolution trend and future sustainability of its NDVI. Besides, the nonlinear characteristics such as mutation type and mutation year are detected and analyzed using the BFAST01 method. Results demonstrated that: (1) In the past 22 years, the NDVI of the Lancang-Mekong River Basin generally exhibited a fluctuating upward trend, and the NDVI value in 2021 was the largest, which was 0.825, showing an increase of 4.29% compared with 2000. However, the increase rate was different: China has the most considerable NDVI growth rate of 7.25%, followed by Thailand with an increase of 7.21%, Myanmar and Laos as the third, while Cambodia and Vietnam have relatively stable vegetation changes. The overall performance of NDVI is high in the south and low in the north, and is dominated by high and relatively high vegetation coverage, of which the area with vegetation coverage exceeding 0.8 accounts for 62%. (2) The Sen-MK trend showed that from 2000 to 2021, the area where the vegetation coverage in the basin showed a trend of increase and decrease accounted for 66.59% and 18.88%, respectively. The Hurst exponent indicated that the areas where NDVI will continue to increase, decrease, and remain unchanged in the future account for 60.14%, 25.29%, and 14.53%, respectively, and the future development trend of NDVI is uncertain, accounting for 0.04%. Thus, more attention should be paid to areas with a descending future development trend. (3) BFAST01 detected eight NDVI mutation types in the Lancang-Mekong River Basin over the past 22 years. The mutations mainly occurred in 2002–2018, while 2002–2004 and 2014–2018 were the most frequent periods of breakpoints. The mutation type of “interruption: increase with negative break” was changed the most during this period, which accounts for 36.54%, and the smallest was “monotonic decrease (with negative break)”, which only accounts for 0.65%. This research demonstrates that combining the conventional trend analysis method with the BFAST mutation test can more accurately analyze the spatiotemporal variation and nonlinear mutation of NDVI, thus providing a scientific reference to develop ecological environment-related work.

show abstract

Section: Hurst Analysismentioning

confidence: 99%

Section: Hurst Analysismentioning

confidence: 99%

Linear and Nonlinear Characteristics of Long-Term NDVI Using Trend Analysis: A Case Study of Lancang-Mekong River Basin

Zhong

Wang

et al. 2022

Remote Sensing

View full text Add to dashboard Cite

show abstract

“…Under the action of test pressure along pipelines, stresses arise, due to which the probability of pipe failure with defects reaches a high level. Sarker and Sarker [19] demonstrated an approach to estimate the power of the pressure wave generated by hydrostroke. In addition, Nordhagen et al [20] presented an experimentally obtained time of action and pressure decay rate in a cracked pipe with methane at a pressure equal to 12.2 MPa.…”

Section: Introductionmentioning

confidence: 99%

Finite-Element Modeling of the Temperature Effect on Extended Avalanche Damage of Gas Main Pipelines

Zhangabay,

Ibraimova,

Ainabekov

et al. 2024

Materials

View full text Add to dashboard Cite

The dynamic stress–strain state and fracture of a steel main gas pipe section between supports with a straight-through crack was analyzed with consideration of the temperature effect on changes in the mechanical properties of the pipe material. The numerical solution of the problem was implemented in the ANSYS-19.2/Explicit Dynamics software package. The process of fracture in a section of the gas pipeline “Beineu–Bozoy–Shymkent” with a linear crack in the temperature range of −40 °C to +50 °C at the operating pressure of 7.5 MPa and critical pressure equal to 9.8 MPa was considered. As a result, it was found that at the initial growth of the internal pressure from working pressure to critical pressure, the length of the crack doubled. At the same time, the process had a local characteristic. Further development of the crack had the nature of avalanche fracture and depended on the temperature of the steel pipeline. With increasing temperature, there was also an increase in the length of the crack at the avalanche fracture. Thus, at a temperature of 40 °C, the crack lengthened 67.75-fold; at a temperature of −10 °C, the crack lengthened 68-fold; at a temperature of +20 °C, the crack lengthened 68.25-fold; and at a temperature of +50 °C, the crack lengthened 68.5-fold. In this work, this difference was 75% of the initial crack length. This fact will be used for further development of the technique of strengthening damaged pipe sections using bandages.

show abstract

“…To obtain the power spectrum, we employed the Fourier transform, a method to convert continuous timeseries data with a certain time step into its power distribution in the frequency domain [30]. Mathematically, the Fourier transform can be expressed as [31]…”

mentioning

confidence: 99%

“…where F(t) refers to the water level or water current at certain time (t), t1 and t2 denote the start and end times of the analyzed period, and k represents the wave number. The power spectrum is then obtained by multiplying the discrete Fourier transform with its complex conjugate, as shown by the following equation [31] S…”

mentioning

confidence: 99%

Subtidal Dynamics in a Tidal River with Limited Discharge

Gusti

Kawanisi

Sawaf

et al. 2022

Water

View full text Add to dashboard Cite

Investigating subtidal friction and mass transport is pivotal for examining subtidal dynamics in tidal rivers. Although the behavior of subtidal friction and transport has been discussed in recent years, most studies have been conducted on tidal rivers that are affected by high amounts of river runoff. The aim of this study is to offer an initial understanding of the spatial and temporal behaviors of subtidal friction and subtidal flux in a tidal river channel with limited river runoff. This study utilized the frequency domain and theoretical decomposition analyses to determine the dominant tidal and subtidal mechanisms. Frequency domain analysis indicated the dominance of semidiurnal and diurnal tides in the observed tidal river channel. The rate of energy transfer owing to shallow water interaction was found to be stronger for the current velocity than for the water elevation. Decomposition analysis showed that subtidal friction and flux in a low-discharge tidal river channel were largely influenced by subtidal flow-induced subtidal friction and Eulerian return flux, respectively. The key findings of this study are as follows: (i) the limited amount of river runoff (4–20 m3/s) leads to the vertical variability of subtidal friction contributions from subtidal flow and subtidal-tidal interaction, as well as Eulerian return flux, and (ii) the vertical variability of the aforementioned terms can be associated with the existence of influential longitudinal subtidal density gradients along the tidal river. We believe that these findings advance our understanding of subtidal dynamics in tidal river systems, particularly those with limited discharge.

show abstract

Spectral Properties of Water Hammer Wave

Cited by 13 publications

References 28 publications

Linear and Nonlinear Characteristics of Long-Term NDVI Using Trend Analysis: A Case Study of Lancang-Mekong River Basin

Linear and Nonlinear Characteristics of Long-Term NDVI Using Trend Analysis: A Case Study of Lancang-Mekong River Basin

Finite-Element Modeling of the Temperature Effect on Extended Avalanche Damage of Gas Main Pipelines

Subtidal Dynamics in a Tidal River with Limited Discharge

Contact Info

Product

Resources

About