Fast Meshless Solution With Lumped Friction for Water Hammer

2020 ◽  
Author(s):  
Yuanzhi Xu ◽  
Zongxia Jiao ◽  
Longfei Zhao
Keyword(s):  
Computational Grid ◽  
Water Hammer ◽  
Friction Model ◽  
Time Cost ◽  
Improved Method ◽  
Fluid Friction ◽  
Time Line ◽  
Practical Applications ◽  
Distributed Friction ◽  
Mesh Grid

Abstract The water hammer in pipelines, with the absence of fluid friction, could be solved by a time-domain exact solution, using a simple recursive process. No computational grid was needed, but the calculation time cost was extremely high. Its improved method, named as the fast meshless solution (FMS), was developed to speed the computation by introducing the time-line interpolation. For the purpose of practical applications, the attempt to consider fluid friction in the FMS is presented here. As there is no mesh grid in the distance-time plane, the distributed friction model can not be employed upon the presented method directly. The fluid friction lumped at the pipe end is proposed, and both steady and unsteady friction are studied. A benchmark problem of the water hammer in a reservoir-pipe-valve (RPV) system is employed for the validation and comparison. The water hammer considering lumped friction can be calculated fast by the FMS, and the accuracy is acceptable. The method discussed here may be of interest in a quick assessment of the piping water hammer.

Improved Exact Solution for Axial FSI Model of Liquid-Pipes Considering Complex Constraints

2016 ◽  
Author(s):  
Yuanzhi Xu ◽  
Zongxia Jiao ◽  
Yaoxing Shang ◽  
Shuai Wu
Keyword(s):  
Exact Solution ◽  
Method Of Characteristics ◽  
Inertial Effects ◽  
Time Cost ◽  
Axial Vibration ◽  
Time Line ◽  
Pipe System ◽  
Practical Applications ◽  
Complex Constraints ◽  
Distributed Friction

The fluid-structure interaction (FSI) can be observed significantly in the axial vibration of the liquid-filled pipe system. When distributed friction was neglected, the model could be solved with an exact solution without numerical error, developed from the method of characteristics (MOC). Then time-line interpolations have been employed to reduce the high time cost and retain the accuracy, named as the improved exact solution. For the purpose of practical applications, series connection of double-pipes is discussed in this paper. And complex constraints, including elastic, damping and inertial effects at connections, are studied. Models and methods are validated by numerical cases.

Adhesive and normal stress-dependent dynamic friction of a gelatin hydrogel

2021 ◽  
pp. 135065012110446
Author(s):  
Nitish Sinha ◽  
Arun Kumar Singh ◽  
Vinit Gupta ◽  
Jitendra Kumar Katiyar
Keyword(s):  
Experimental Data ◽  
Normal Stress ◽  
Scaling Law ◽  
Shear Velocity ◽  
Friction Model ◽  
Dynamic Friction ◽  
Practical Applications ◽  
Soft Solids ◽  
Gelatin Hydrogel ◽  
Stress Dependent

Adhesion and friction of soft solids on hard surfaces are the important properties for a variety of practical applications. In the present study, Coulomb's law of friction is used for characterizing adhesive friction as well as normal stress-dependent dynamic friction of a gelatin hydrogel on a fixed glass surface. The experimental data, concerning normal stress-dependent dynamic friction of different shear velocity, are obtained from literature. It is observed that both components of friction increase with shear velocity. More importantly, the scaling law shows that adhesive stress varies almost linearly with corresponding coefficient of friction of the hydrogel. A dynamic friction model is also used to analyze the same experimental data to predict a negative normal stress at which dynamic friction reduces to zero, and this result matches closely with the experimental value.

scholarly journals Improved Method to Suppress Azimuth Ambiguity for Current Velocity Measurement in Coastal Waters Based on ATI-SAR Systems

2020 ◽  
Vol 12 (20) ◽  
pp. 3288
Author(s):  
Na Yi ◽  
Yijun He ◽  
Baochang Liu
Keyword(s):  
Coastal Waters ◽  
Velocity Measurement ◽  
Phase Fluctuation ◽  
Ocean Surface ◽  
Pollution Monitoring ◽  
Speed Ratio ◽  
Improved Method ◽  
Eigenvalue Spectrum ◽  
Practical Applications ◽  
Along Track

Measurements of ocean surface currents in coastal waters are crucial for improving our understanding of tidal atlases, as well as for ecosystem and water pollution monitoring. This paper proposes an improved method for estimating the baseline-to-platform speed ratio (BPSR) for improving the current line-of-sight (LOS) velocity measurement accuracy in coastal waters with along-track interferometric synthetic aperture radar (ATI-SAR) based on eigenvalue spectrum entropy (EVSE) analysis. The estimation of BPSR utilizes the spaceborne along-track interferometry and considers the effects of a satellite orbit and an inaccurate baseline responsible for azimuth ambiguity in coastal waters. Unlike the existing methods, which often assume idealized rather than actual operating environments, the proposed approach considers the accuracy of BPSR, which is its key advantage applicable to many, even poorly designed, ATI-SAR systems. This is achieved through an alternate algorithm for the suppression of azimuth ambiguity and BPSR estimation based on an improved analysis of the eigenvalue spectrum entropy, which is an important parameter representing the mixability of unambiguous and ambiguous signals. The improvements include the consideration of a measurement of the heterogeneity of the scene, the corrections of coherence-inferred phase fluctuation (CPF), and the interferogram-derived phase variability (IPV); the last two variables are closely related to the determination of the EVSE threshold. Besides, the BPSR estimation also represents an improvement that has not been achieved in previous work of EVSE analysis. When the improved method is used on the simulated ocean-surface current LOS velocity data obtained from a coastal area, the root-mean-square error is less than 0.05 m/s. The other strengths of the proposed algorithm are adaptability, robustness, and a limited user input requirement. Most importantly, the method can be adopted for practical applications.

Water-Hammer Analysis Including Fluid Friction

1963 ◽  
Vol 128 (1) ◽  
pp. 1491-1524 ◽  
Author(s):  
Victor L. Streeter ◽  
Chintu Lai
Keyword(s):  
Water Hammer ◽  
Fluid Friction

Determination of a Dimensionless Equation for Shear Friction Factor in Cold Forging

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
K. H. Jung ◽  
Y. T. Im
Keyword(s):  
Friction Factor ◽  
Friction Model ◽  
Cold Forging ◽  
Practical Applications ◽  
Dimensionless Equation ◽  
Bulk Forming ◽  
Highly Nonlinear ◽  
Shear Friction ◽  
Shear Friction Factor ◽  
Cold Bulk

In cold bulk forming processes, a constant shear friction model is widely used to apply friction. However, it is not easy to predict the shear friction factor since frictional behavior is highly nonlinear and is dependent upon a number of processing variables, such as the hardness of the material, lubricity, sliding velocity, surface contact conditions, and the environment, etc. This paper presents a dimensionless equation that predicts the shear friction factor at the counter punch interface mfd that was empirically determined by dimensional analysis, using the tip test results available in the literature as a function of selected process variables, such as the yield strength and initial specimen's radius of the deforming material, hardness, and surface roughness of the deforming material and the counter punch, viscosity of the lubricant, and deformation speed. To verify the determined equation, a new set of experiments were carried out for specimens made of AL7075-O. The prediction of the shear friction factor at the punch interface was also achieved by simply dividing the dimensionless equation by the x ratio defined by x = mfd/mfp, which is dependent on the hardening exponent of the deforming material based on previous studies. The predicted mfd and mfp were found to be reasonable owing to comparisons with the experimental data obtained for AL7075–O in this study. These results will be beneficial in scientifically assessing the effect of the processing parameters on the friction, individually and economically selecting the lubrication condition for cold bulk forming for practical applications.

scholarly journals Mining Recent Maximal Frequent Itemsets Over Data Streams with Sliding Window

2018 ◽  
Vol 16 (6) ◽  
pp. 961-969 ◽  
Author(s):  
Saihua Cai ◽  
Shangbo Hao ◽  
Ruizhi Sun ◽  
Gang Wu
Keyword(s):  
Data Streams ◽  
Sliding Window ◽  
Frequent Itemsets ◽  
Memory Usage ◽  
Time Cost ◽  
Improved Method ◽  
Huge Number ◽  
Frequent Itemsets Mining ◽  
Series Of Experiments ◽  
Maximal Frequent Itemsets

Abstract: The huge number of data streams makes it impossible to mine recent frequent itemsets. Due to the maximal frequent itemsets can perfectly imply all the frequent itemsets and the number is much smaller, therefore, the time cost and the memory usage for mining maximal frequent itemsets are much more efficient. This paper proposes an improved method called Recent Maximal Frequent Itemsets Mining (RMFIsM) to mine recent maximal frequent itemsets over data streams with sliding window. The RMFIsM method uses two matrixes to store the information of data streams, the first matrix stores the information of each transaction and the second one stores the frequent 1-itemsets. The frequent p-itemsets are mined with “extension” process of frequent 2-itemsets, and the maximal frequent itemsets are obtained by deleting the sub-itemsets of long frequent itemsets. Finally, the performance of the RMFIsM method is conducted by a series of experiments, the results show that the proposed RMFIsM method can mine recent maximal frequent itemsets efficiently

Closure to “Water-Hammer Analysis Including Fluid Friction”

1963 ◽  
Vol 89 (3) ◽  
pp. 307-313
Author(s):  
Victor L. Streeter ◽  
Chintu Lai
Keyword(s):  
Water Hammer ◽  
Fluid Friction

Water-Hammer Analysis Including Fluid Friction

1962 ◽  
Vol 88 (3) ◽  
pp. 79-112 ◽  
Author(s):  
Victor L. Streeter ◽  
Chintu Lai
Keyword(s):  
Water Hammer ◽  
Fluid Friction

Discussion of “Water-Hammer Analysis Including Fluid Friction”

1962 ◽  
Vol 88 (6) ◽  
pp. 221-223
Author(s):  
Franklin DeFazio ◽  
I. W. McCraig ◽  
F. H. Jonker ◽  
B. A. Sutton
Keyword(s):  
Water Hammer ◽  
Fluid Friction
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