scholarly journals Experimental and Numerical Vibration Analysis of Hydraulic Pipeline System under Multiexcitations

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Peixin Gao ◽  
Hongquan Qu ◽  
Yuanlin Zhang ◽  
Tao Yu ◽  
Jingyu Zhai
Keyword(s):  
Pressure Fluctuations ◽  
Fluid Motion ◽  
Fluid Pressure ◽  
Point Of View ◽  
Pipeline System ◽  
Base Excitation ◽  
Fem Method ◽  
Pipeline Systems ◽  
Pump Pressure ◽  
Improved Model

Pipeline systems in aircraft are subjected to both hydraulic pump pressure fluctuations and base excitation from the engine. This can cause fatigue failures due to excessive vibrations. Therefore, it is essential to investigate the vibration behavior of the pipeline system under multiexcitations. In this paper, experiments have been conducted to describe the hydraulic pipeline systems, in which fluid pressure excitation in pipeline is driven by the throttle valve, and the base excitation is produced by the shaker driven by a vibration controller. An improved model which includes fluid motion and base excitation is proposed. A numerical MOC-FEM approach which combined the coupling method of characteristics (MOC) and finite element method (FEM) is proposed to solve the equations. The results show that the current MOC-FEM method could predict the vibration characteristics of the pipeline with sufficient accuracy. Moreover, the pipeline under multiexcitations could produce an interesting beat phenomenon, and this dangerous phenomenon is investigated for its consequences from engineering point of view.

Designing Offshore Pipeline Systems Divided Into Sections of Different Design Pressures

2004 ◽  
Author(s):  
Gunnar Staurland ◽  
Morten Aamodt
Keyword(s):  
Uniform Design ◽  
External Pressure ◽  
Transportation Systems ◽  
Point Of View ◽  
Pipeline System ◽  
Operating Pressure ◽  
Pipeline Systems ◽  
Upstream Pressure ◽  
Transmission Pipeline ◽  
Design Pressure

Norwegian waters have been a main arena for development of subsea pipeline technology over the last 25 year. The gas transportation systems from Norway to continental Europe comprise the largest and longest sub sea pipelines in the world. Codes traditionally require a pipeline to be designed with a uniform design pressure between stations with overpressure protection capabilities. However, the downstream part of a very long gas transmission pipeline may, after commissioning, rarely, if ever, see pressures near the pressure at the upstream end. There is, therefore, a potential for cost reduction and capacity improvement if two, or several, sections of different design pressure could be used without having to implement sub sea pressure regulation and overpressure protection facilities at the point of transition between the different sections of design pressure. In determining the lower design pressure the shutdown of the pipeline outlet facilities, at any point in time allowing for a practicable, achievable delay for closure of the upstream inlet valve has to be taken into account. The settle out pressure in a “normal” shut-in situation shall then not exceed the lower design pressure. In addition, deep water pipelines are often designed to withstand buckling due to bending and external pressure during installation, and may therefore locally tolerate a much higher internal pressure than the pipeline was designed for. Transmission pipelines crossing deepwater areas may therefore be designed for two or more operating pressures along the pipeline, thereby optimizing the cost. Even more important, for already existing pipelines, the capacity may be significantly increased by utilizing the upstream heavy wall sections. The operating pressure range for a long offshore gas transmission pipeline is very wide compared to an onshore line, typically between an upstream pressure of 150–250 bar, and a downstream pressure of 60 to 80 bar over a distance of several hundred kilometers. It may take hours to notice the closure of a downstream valve on the upstream pressure. Unless the pipeline is extensively packed, it is obvious that the pressure drop along the pipeline may be taken into account by allowing a lower design pressure for downstream part than for the upstream part. Thereby, the investment cost can be reduced. This paper describes the principles of designing a pipeline system divided into sections of different design pressures from a hydraulic point of view. The basis is the offshore standard for designing submarine pipeline systems, DNV OS-F101. The focusing will be on improvements in transportation efficiency, cost reductions and operational issues.

scholarly journals Influence of Random Forest Hyperparameterization on Short-Term Runoff Forecasting in an Andean Mountain Catchment

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 238
Author(s):  
Pablo Contreras ◽  
Johanna Orellana-Alvear ◽  
Paul Muñoz ◽  
Jörg Bendix ◽  
Rolando Célleri
Keyword(s):  
Random Forest ◽  
Model Performance ◽  
Early Warning Systems ◽  
Point Of View ◽  
Lead Times ◽  
Physical Parameters ◽  
Runoff Forecasting ◽  
Spatio Temporal ◽  
Improved Model ◽  
Search Approach

The Random Forest (RF) algorithm, a decision-tree-based technique, has become a promising approach for applications addressing runoff forecasting in remote areas. This machine learning approach can overcome the limitations of scarce spatio-temporal data and physical parameters needed for process-based hydrological models. However, the influence of RF hyperparameters is still uncertain and needs to be explored. Therefore, the aim of this study is to analyze the sensitivity of RF runoff forecasting models of varying lead time to the hyperparameters of the algorithm. For this, models were trained by using (a) default and (b) extensive hyperparameter combinations through a grid-search approach that allow reaching the optimal set. Model performances were assessed based on the R2, %Bias, and RMSE metrics. We found that: (i) The most influencing hyperparameter is the number of trees in the forest, however the combination of the depth of the tree and the number of features hyperparameters produced the highest variability-instability on the models. (ii) Hyperparameter optimization significantly improved model performance for higher lead times (12- and 24-h). For instance, the performance of the 12-h forecasting model under default RF hyperparameters improved to R2 = 0.41 after optimization (gain of 0.17). However, for short lead times (4-h) there was no significant model improvement (0.69 < R2 < 0.70). (iii) There is a range of values for each hyperparameter in which the performance of the model is not significantly affected but remains close to the optimal. Thus, a compromise between hyperparameter interactions (i.e., their values) can produce similar high model performances. Model improvements after optimization can be explained from a hydrological point of view, the generalization ability for lead times larger than the concentration time of the catchment tend to rely more on hyperparameterization than in what they can learn from the input data. This insight can help in the development of operational early warning systems.

A Critical Review of Tube and Sheet Metal Hydroforming Technology

1996 ◽  
Author(s):  
Jian An ◽  
A. H. Soni
Keyword(s):  
Sheet Metal ◽  
Thickness Distribution ◽  
Fluid Pressure ◽  
Point Of View ◽  
Parameter Design ◽  
Back Side ◽  
Part Quality ◽  
Element Simulation ◽  
Part Surface ◽  
Hydroforming Process

Abstract The hydroforming technology, which is rapidly gaining popularity in the sheet metal and tube forming industry is reviewed. The features and the characteristics of the hydroforming process are described. The uniformly distributed fluid pressure covers the back side of the sheet as a die generates many advantages in the technical point of view as improving the part surface quality, reducing the forming severity and smoothing the thickness distribution. The benefits of using hydroforming technology are examined and analyzed in a technical level. The better part quality, less cost of tooling, materials saving and part weight reduction can be achieved using the hydroforming technology. The design methodologies for the hydroforming process parameters are reviewed and discussed in a certain detail. Computer-aided-engineering such as finite element simulation is suggested for such process parameter design.

On the isometric motion of a charged fluid in the Einstein-Maxwell theory

1974 ◽  
Vol 336 (1606) ◽  
pp. 273-284 ◽  
Keyword(s):  
Killing Vector ◽  
Fluid Motion ◽  
Fluid Pressure ◽  
Field Equations ◽  
Maxwell Theory ◽  
Charged Fluid ◽  
Spherically Symmetric Solution ◽  
Electromagnetic Field Tensor ◽  
Discrete Values ◽  
Full Solution

It is shown that in the Einstein-Maxwell theory a class of four-dimensional charged fluid space-times exists, with non-zero fluid pressure, satisfying the conditions that (i) the fluid motion is isometric, (ii) the dual of the electromagnetic field tensor has no projection in the direction of a Killing vector - equivalent to the condition that in a static space time the local field of an observer moving with the fluid is purely electric - and (iii) the ratio of charge to mass is constant. For the case of a diagonal static metric it is seen that a group of quasi-conformal transformations may be determined which leaves the field equations unchanged. This may be used to obtain a full solution of the field equations, in three independent variables, from a given solution in one independent variable. A spherically symmetric solution of this kind is obtained which is seen to be expressible in terms of hypergeometric functions. An interesting aspect of this is that the charge/mass ratio can only have discrete values depending on the eigenvalues of a linear boundary-value problem.

scholarly journals Oscillatory and steady streaming flow in the anterior chamber of the moving eye

2019 ◽  
Vol 863 ◽  
pp. 904-926 ◽  
Author(s):  
M. Dvoriashyna ◽  
R. Repetto ◽  
J. H. Tweedy
Keyword(s):  
Anterior Chamber ◽  
Fluid Motion ◽  
Three Dimensional ◽  
Frequency Component ◽  
Dominant Frequency ◽  
Point Of View ◽  
Dimensional Structure ◽  
Steady Streaming ◽  
Constant Height ◽  
Angular Amplitude

We study the flow induced by eye rotations in the anterior chamber (AC) of the eye, the region between the cornea and the iris. We model the geometry of the AC as a thin domain sitting on the surface of a sphere, and study both the simpler case of a constant-height domain as well as a more realistic AC shape. We model eye rotations as harmonic in time with prescribed frequency $\unicode[STIX]{x1D714}_{f}$ and amplitude $\unicode[STIX]{x1D6FD}$, and use lubrication theory to simplify the governing equations. We write the equations in a reference frame moving with the domain and show that fluid motion is governed by three dimensionless parameters: the aspect ratio $\unicode[STIX]{x1D716}$ of the AC, the angular amplitude $\unicode[STIX]{x1D6FD}$ and the Womersley number $\unicode[STIX]{x1D6FC}$. We simplify the equations under the physiologically realistic assumptions that $\unicode[STIX]{x1D716}$ is small and $\unicode[STIX]{x1D6FC}$ large, leading to a linear system that can be decomposed into three harmonics: a dominant frequency component, with frequency $\unicode[STIX]{x1D714}_{f}$, and a steady streaming component and a third component with frequency $2\unicode[STIX]{x1D714}_{f}$. We solve the problem analytically for the constant-height domain and numerically as the solution of ordinary differential equations in the more realistic geometry. Both the primary flow and the steady streaming are shown to have a highly three-dimensional structure, which has not been highlighted in previous numerical works. We show that the steady streaming is particularly relevant from the clinical point of view, as it induces fluid mixing in the AC. Furthermore, the steady flow component is the dominant mixing mechanism during the night, when the thermal flow induced by temperature variations across the AC is suppressed.

scholarly journals The Draupner Event: The Large Wave and the Emerging View

2017 ◽  
Vol 98 (4) ◽  
pp. 729-735 ◽  
Author(s):  
L. Cavaleri ◽  
A. Benetazzo ◽  
F. Barbariol ◽  
J.-R. Bidlot ◽  
P. A. E. M. Janssen
Keyword(s):  
Relevant Information ◽  
Space Time ◽  
Point Of View ◽  
Extreme Waves ◽  
Sea State ◽  
Wave Groups ◽  
Large Wave ◽  
Open Sea ◽  
Improved Model ◽  
2D Space

Abstract In a parallel paper mainly focused on the meteorological and oceanographic aspects, the conditions were described for the storm during which the iconic Draupner wave was recorded. Because of increased spatial resolution and improved model physics, the results provided new and previously unrecognized features of the storm, in particular of the wave spectra, features relevant for assessing the wave’s conditions nearby the Draupner platform. Starting from these, and after briefly summarizing the relevant information, the focus of this paper is on the nonlinear analysis of the local situation, with the main purpose of assessing if and how the conditions existed for the possible appearance of very large waves. An intensive analysis of the related probability is carried out, attacking the problem with two different statistical approaches, both briefly described: a completely new one working from the point of view of envelope heights, and a recent, though established, one based on space–time extreme waves. It is remarkable, and certainly supports this line of work, that the two different approaches lead independently to consistent results, supporting the idea, already derived from the meteo-oceanographic hindcast, that the wave conditions were indeed special at the position of the Draupner platform. This is related to a general analysis of high waves showing, also on the basis of 3D (2D space + time) measured wave data at open sea, how, given the severe sea state, the Draupner wave features represent what is expected at certain times and positions as the natural documented temporal evolution of wave groups.

High Resolution DCE-MRI Vascular Characterization of Murine Sarcoma and Human Renal Cell Carcinoma for Computational Modeling

2008 ◽  
Author(s):  
Gregory L. Pishko ◽  
Garrett W. Astary ◽  
Thomas H. Mareci ◽  
Malisa Sarntinoranont
Keyword(s):  
Interstitial Fluid ◽  
Tumor Tissue ◽  
Fluid Motion ◽  
Fluid Pressure ◽  
Bulk Fluid ◽  
Human Renal Cell Carcinoma ◽  
Dce Mri ◽  
Heterogeneous Tissue ◽  
Murine Sarcoma

Non-uniform extravasation from blood vessels, elevated interstitial fluid pressure (IFP), and transport by bulk fluid motion in the extracellular space have all been determined to contribute to the non-uniform tissue distribution of systemically delivered agents in solid tumors. The aforementioned factors can lead to inadequate and uneven uptake in tumor tissue which has been shown to be a major obstacle to macromolecules in clinical cancer therapy [1]. Recently developed computational tumor models have described blood flow either in a single vessel or capillary network with variations in space and time [2]. These studies do not account for heterogeneous tissue transport properties in regions of leakier vessels [3].

scholarly journals Hydraulic Engineering at 100 BC-AD 300 Nabataean Petra (Jordan)

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3498
Author(s):  
Charles R. Ortloff
Keyword(s):  
Water Supply ◽  
Flow Rate ◽  
Distribution Systems ◽  
Maximum Flow ◽  
Hydraulic Engineering ◽  
World Heritage Site ◽  
Maximum Flow Rate ◽  
Pipeline System ◽  
Supply And Distribution ◽  
Pipeline Systems

The principal water supply and distribution systems of the World Heritage site of Petra in Jordan were analyzed to bring forward water engineering details not previously known in the archaeological literature. The three main water supply pipeline systems sourced by springs and reservoirs (the Siq, Ain Braq, and Wadi Mataha pipeline systems) were analyzed for their different pipeline design philosophies that reflect different geophysical landscape challenges to provide water supplies to different parts of urban Petra. The Siq pipeline system’s unique technical design reflects use of partial flow in consecutives sections of the main pipeline to support partial critical flow in each section that reduce pipeline leakage and produce the maximum flow rate the Siq pipeline can transport. An Ain Braq pipeline branch demonstrated a new hydraulic engineering discovery not previously reported in the literature in the form of an offshoot pipeline segment leading to a water collection basin adjacent to and connected to the main water supply line. This design eliminates upstream water surges arising from downstream flow instabilities in the two steep pipelines leading to a residential sector of Petra. The Wadi Mataha pipeline system is constructed at the critical angle to support the maximum flow rate from a reservoir. The analyses presented for these water supply and distribution systems brought forward aspects of the Petra urban water supply system not previously known, revising our understanding of Nabataean water engineers’ engineering knowledge.

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