scholarly journals Analytical Model for Seal Contact Pressure

2021 ◽  
Author(s):  
Sayyad Zahid Qamar ◽  
Maaz Akhtar ◽  
Tasneem Pervez
Keyword(s):  
Contact Pressure ◽  
Computational Effort ◽  
Large Strains ◽  
Large Set ◽  
Key Factors ◽  
Zonal Isolation ◽  
Simulation Results ◽  
Numerical Finite Element ◽  
Important Design ◽  
Elastomer Seal

Swellable elastomers are used for zonal isolation and as an alternate to cementing is a new approach, resulting in significant reduction in time, cost, and weight. Very large strains, flexibility, resilience, and durability are their special features. Performance analysis is important design improvement and appropriate selection of swell packers. Experimental evaluation of swelling-elastomer seal performance can be very costly, and is not even possible in many cases. Numerical simulations (Chapters 8 and 9) can be more convenient, but computational effort and cost can be high. Development of closed-form (analytical) solutions is presented in this chapter to estimate the variation of contact pressure along the length of the elastomer seal. Major relevant parameters are properties of the material elastomer, seal configuration and size, magnitude of seal compression, and differential pressure across the seal. Numerical (finite element) modeling and simulation is also performed. There was good conformity between analytical and simulation results, validating the soundness of the analytical solution, and providing assurance that it can reliably predict the sealing response of the elastomer. A comprehensive parametric study is then conducted to assess seal performance while varying different key factors. Properties of the elastomer material (as it swells with exposure time) are required to run the analytical and the FE models. A large set of experiments were therefore designed and conducted to evaluate mechanical properties (E, G, K, and v) of the elastomer with gradual swelling (Chapters 3 and 7).

scholarly journals Linking Climate, Basin Morphology and Vegetation Characteristics to Fu’s Parameter in Data Poor Conditions

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2333 ◽  
Author(s):  
Dario Ruggiu ◽  
Francesco Viola
Keyword(s):  
Water Balance ◽  
Potential Evapotranspiration ◽  
Seasonal Pattern ◽  
Computational Effort ◽  
Model Parameters ◽  
Large Set ◽  
Regression Equations ◽  
Water Balance Components ◽  
Water Partitioning

The prediction of long term water balance components is not a trivial issue, even when empirical Budyko’s type approaches are used, because parameter estimation is often hampered by missing or poor hydrological data. In order to overcome this issue, we provided regression equations that link climate, morphological, and vegetation parameters to Fu’s parameter. Climate is here defined as a specific seasonal pattern of potential evapotranspiration and rain: five climatic scenarios have been considered to mimic different conditions worldwide. A weather generator has been used to create stochastic time series for the related climatic scenario, which in turn has been used as an input to a conceptual hydrological model to obtain long-term water balance components with low computational effort, while preserving fundamental process descriptions. The morphology and vegetation’s role in determining water partitioning process has been epitomized in four parameters of the conceptual model. Numerical simulations explored a large set of basins in the five climates. Results show that climate superimposes partitioning rules for a given basin; morphological and vegetation watershed properties, as conceptualized by model parameters, determine the Fu’s parameter within a given climate. A sensitive analysis confirmed that vegetation has the most influencing role in determining water partitioning rules, followed by soil permeability. Finally, linear regressions relating basin characteristics to Fu’s parameter have been obtained in the five climates and tested in a basin for each case, obtaining encouraging results. The small amount of data required and the very low computational effort of the method make this approach ideal for practitioners and hydrologists involved in annual runoff assessment.

Radiative transfer simulations and observations of airborne infrared emission spectra in the presence of PSCs: Detection of clouds and discrimination of cloud types

2020 ◽  
Author(s):  
Christoph Kalicinsky ◽  
Sabine Grießbach ◽  
Reinhold Spang
Keyword(s):  
Radiative Transfer ◽  
Spectral Feature ◽  
Polar Vortex ◽  
Emission Spectra ◽  
Infrared Emission ◽  
Medium Size ◽  
Large Set ◽  
Cloud Detection ◽  
Simulation Results ◽  
New Feature

<p>Polar stratospheric clouds (PSCs) have an important influence on the spatial and temporal<br>evolution of different trace gases, (e.g. ozone, HNO<sub>3</sub>) in the polar vortex in winter due to direct<br>and indirect processes (e.g. activation of chlorine, redistribution of HNO<sub>3</sub>). Thus, the detection<br>of PSCs and a detailed distinction between the different PSCs types Nitric Acid Trihydrade<br>(NAT), Supercooled Ternary Solution (STS), and ice are important as they build a basis for<br>model comparisons to reduce uncertainties in the representation of PSCs in models. Infrared<br>limb sounder are well suited for this purpose as they enable both, the detection of clouds and<br>the discrimination between the different types.<br>The CRISTA-NF instrument, an airborne infrared limb sounder, observed a new spectral fea-<br>ture during measurements inside PSCs within the RECONCILE aircraft campaign. In contrast<br>to the previously known feature at 820 cm<sup>-1</sup>, which has been used in former studies for the<br>detection of NAT PSCs, the new feature was detected at about 816 cm<sup>-1</sup>. We performed a<br>large set of radiative transfer simulations for different PSC situations (varying PSC altitude<br>and thickness, PSC type, number density and median radius of the particle size distribution)<br>for the airborne viewing geometry of CRISTA-NF. The simulation results show that under the<br>assumption of spherical NAT particles the spectral feature transforms from the original feature<br>at 820 cm<sup>-1</sup> to a shifted version (peak shifts to smaller wavenumbers) and finally to a step-like<br>feature with increasing median radius. Based on this behaviour we defined different colour ra-<br>tios to detect PSCs containing NAT particles and to subgroup them into three sizes regimes:<br>small NAT, medium size NAT, and large NAT. In addition, we used the simulation results to<br>adopt a method, which has been used to detect ice in MIPAS-ENV observations, to the airborne<br>geometry and to refine the corresponding threshold values.<br>We applied all methods of cloud detection and type discrimination to the CRISTA-NF observa-<br>tions during the RECONCILE campaign. The new defined NAT detection method is capable<br>to detect the shifted NAT feature, which is clearly visible in the radiance spectra.</p>

Performance of micropiled raft in sand subjected to vertical concentrated load: centrifuge modeling

2015 ◽  
Vol 52 (1) ◽  
pp. 33-45 ◽  
Author(s):  
A.M. Alnuaim ◽  
H. El Naggar ◽  
M.H. El Naggar
Keyword(s):  
Contact Pressure ◽  
Bending Moment ◽  
Centrifuge Modeling ◽  
Design Parameters ◽  
Concentrated Load ◽  
Centrifuge Testing ◽  
Geotechnical Centrifuge ◽  
Piled Raft Foundation ◽  
Overall Performance ◽  
Important Design

Initial applications of micropiles have involved retrofitting foundations of existing buildings. In these applications, the overall performance of the micropiles–raft (MPR) foundation system is similar to a piled raft foundation where the load is transmitted through both the raft and micropiles. However, there is no guidance available regarding the performance of MPR foundations. In this study, geotechnical centrifuge testing was conducted to investigate the behavior of MPR foundations in sand and evaluate their performance characteristics. The study investigated the effect of raft flexibility on a number of important design parameters, including raft total and differential settlements, raft contact pressure, raft bending moment, and load sharing between the raft and micropiles. In addition, the use of micropiles as settlement reducers was investigated. The results showed that the micropiles carried 42%–59% of the applied load for the MPR configuration considered, which resulted in redistribution of the raft contact pressure. It was found that the Poulos–Davis–Randolph (PDR) method can be used to evaluate the performance of MPR systems with relatively stiff rafts; however, it is not applicable for MPR with flexible raft. A correction factor was proposed to account for the raft flexibility in the PDR method.

Vehicle-to-Vehicle Communications: Reception and Interference of Safety-Critical Messages (Fahrzeug-zu-Fahrzeug-Kommunikation: Empfang und Interferenz sicherheitskritischer Nachrichten)

2008 ◽  
Vol 50 (4) ◽  
Author(s):  
Felix Schmidt-Eisenlohr ◽  
Moritz Killat
Keyword(s):  
Traffic Safety ◽  
Ad Hoc Network ◽  
Large Scale ◽  
Ad Hoc ◽  
Computational Effort ◽  
Vehicular Communications ◽  
Radio Communication ◽  
Simulation Methodology ◽  
Vehicle To Vehicle ◽  
Simulation Results

SummaryA robust exchange of messages between vehicles via radio communication represents a key problem of vehicular ad hoc network (VANET) research. Environmental influences and the multitude of communicating nodes result in challenging communication conditions that have to be taken into account when assessing the potential benefit of VANETs for traffic safety and efficiency applications. In this paper we discuss an appropriate modeling of three influencing factors on the communication behavior to establish a basis for credible simulation results. In detail, we analyze the effects of fast-fading, capturing, and cumulative noise on vehicular communications and illustrate their considerable influence on a simulation's outcome. As a second contribution, we provide an empirical model for the probability of packet reception that is based on the proposed simulation methodology. The model thus allows to determine credible simulation results without being dependent on the complexity of detailed simulations. The saved computational effort facilitates the assessment of VANETs in large-scale scenarios and the consideration of communication specifics in the design process.

Highway Alignment Parameters Design and Capacity Analysis on Two-Lane Highway

2014 ◽  
Vol 539 ◽  
pp. 860-866
Author(s):  
Jiang Liu
Keyword(s):  
Capacity Analysis ◽  
Horizontal Curve ◽  
Mountainous Areas ◽  
Key Factors ◽  
Horizontal Curves ◽  
Percent Time ◽  
Simulation Results ◽  
Relationship Of ◽  
Highway Alignment ◽  
The Relationship

A two-lane highway is an undivided highway with only one lane of traffic in each direction. Two-lane highways are one of the most common roadways at mountainous areas in China. Due to the wider range to choose the horizontal and vertical curves in the design of two-lane highways, the combination of both leads to larger differences on two-lane highway capacities. Thus, the highway alignments are one of the key factors which affect the two-lane highway capacities. According to the empirical data and existing studies, it is regarded that there is no impacts on the capacity for horizontal curves with a radius more than 400m and vertical curves with the gradient less than 3%. Two concepts are defined as effective bending and effective gradient which represent the extent the horizontal curve bends and the steepness of vertical curve respectively. The method to calculate effective bending of horizontal curve and steepness of vertical curve is given and its relevant properties are also discussed. According to the simulation results and the principle of speed differences, the effective bending and effective gradient have been classified into 7 and 6 levels, separately. As a result, there will be 42 combinations of different highway alignments of two-lane highways based on the different combinations of the effective bending and effective gradient. Under this circumstance, the relationship of speed-volume and volume-PTSF (percent time spend following) are obtained from the simulation results. Finally, the capacity of two-lane highway is given under different highway alignments of two-lane highway at mountainous areas in China.

Numerical Simulation of Machining Distortion of Residually Stressed Aircraft Aluminum Components

2006 ◽  
Vol 315-316 ◽  
pp. 235-238 ◽  
Author(s):  
Q.C. Wang ◽  
Xiao Dong Hu ◽  
W. Li ◽  
Ju Long Yuan
Keyword(s):  
Numerical Simulation ◽  
Residual Stress ◽  
Energy Density ◽  
Square Root ◽  
Stress Range ◽  
Key Factors ◽  
Machining Distortion ◽  
Simulation Results ◽  
Aluminum Component ◽  
Good Agreement

The presence of residual stress in aircraft aluminum components can give rise to distortion after machining. Excessive distortion may result in the rejection of a part or the need for costly and time-consuming rework prior to placement in service. The purpose of this research was to develop a methodology for the prediction of machining-induced distortions of residually stressed aircraft aluminum components. Numerical simulation results show that the magnitude of machining distortion is strongly related to the square root of Stain Energy Density W or Stress Range σ . The experimental results demonstrate good agreement with the predicted machining distortions of 7075T73 bulkheads. It included that the original residual stress in the blocks of aircraft aluminum component is one of key factors to cause machining distortion.

scholarly journals Numerical Validation of Drilling of Al6061-T6 with Experimental Data

2019 ◽  
Vol 23 (1) ◽  
pp. 287-290 ◽  
Author(s):  
Prashant Elango ◽  
K. Prakash Marimuthu
Keyword(s):  
Experimental Data ◽  
Material Property ◽  
Feed Rate ◽  
Reaction Force ◽  
Drill Bit ◽  
Element Simulation ◽  
Circular Profile ◽  
Simulation Results ◽  
Numerical Finite Element ◽  
The Right

Abstract Drilling is a cutting process that uses a drill bit to cut a circular profile in workpiece. Forces acting on the drill bit reduce its life expectance. Analysis of forces acting on the drill bit during drilling prevents the tool from failing prematurely because of wear and excess feed rate. Excess feed rate can induce excessive internal stress on both the tool and workpiece. This paper aims to study the effects of reaction force acting on a drill bit during drilling of Al6061-T6. A numerical finite element simulation study is performed with commercially available software called Abaqus. Simulation results depend on the right choice of material property such as Johnson–Cook material property and Johnson–Cook damage property. Validation of material property is achieved by comparison of experimental results with simulative results. Reaction force acting against the drill bit during drilling is compared.

scholarly journals Numerical Investigation of Elastomer Seal Performance

2021 ◽  
Author(s):  
Sayyad Zahid Qamar ◽  
Maaz Akhtar ◽  
Tasneem Pervez
Keyword(s):  
Numerical Models ◽  
Analytical Models ◽  
Oil Well ◽  
Actual Application ◽  
Open Hole ◽  
Simplifying Assumptions ◽  
Numerical Finite Element ◽  
Elastomeric Seals ◽  
Performance Analysis And Design ◽  
Elastomer Seal

Analytical models for swelling of rubberlike materials are difficult to formulate, and restricted in actual application due to their need for simplifying assumptions. Tests conducted on laboratory size samples of swelling elastomers cannot reproduce actual oil well conditions, and cannot cover all possible variations of testing parameters. However, these laboratory tests do provide useful information about material response of swellable elastomers in various conditions, serving as a basis for analytical and numerical modeling. Properly developed and robust numerical models can be used to predict near-actual performance of elastomeric seals. The current chapter describes the use of numerical (finite element) simulation to investigate swelling elastomer seal behavior in downhole petroleum applications. Variations in sealing (contact) pressure are studied for seal length, seal thickness, compression ratio, water salinity, swelling time, and type of well completion (open-hole or cased-hole). Month-long swelling experiments on samples of two actual elastomers (Chapters 3 and 7) provide input to the numerical model in terms of real material and deformation data. On the basis of these results, petroleum engineers can make informed decisions about the selection of elastomer material and seal geometry appropriate for the well type and conditions encountered. Application developers and researchers can also find this investigation useful in performance analysis and design of swelling elastomer seals.

The improvement of stress correction in post-necking tension of cylindrical specimen

2019 ◽  
Vol 54 (3) ◽  
pp. 209-222 ◽  
Author(s):  
Junfu Chen ◽  
Zhiping Guan ◽  
Pinkui Ma ◽  
Zhigang Li ◽  
Xiangrui Meng
Keyword(s):  
Cross Section ◽  
Strain Distribution ◽  
Prediction Accuracy ◽  
Inverse Method ◽  
Cylindrical Specimen ◽  
Analytical Models ◽  
Large Strains ◽  
Stress And Strain ◽  
Simulation Results ◽  
Prediction Capability

In post-necking tension of cylindrical specimen, the stress corrections based on the current analytical models have relatively significant errors at large strains. In this study, the prediction capability of these models involving Bridgman model, Siebel model and Chen model is evaluated by performing a series of finite element simulations of uniaxial tension of cylindrical specimen with different hardening exponents varied from 0.05 to 0.3. Numerical analysis of stress and strain distributions on the necking cross section indicates that the considerable errors of the corrected stresses corresponding to large strains might be mainly attributed to the assumption of uniform strain distribution on the necking cross section in these analytical models. The modification strategies of these models are presented in order to improve their prediction accuracy of post-necking stresses, taking geometrical configuration of neck and material properties into consideration. Accordingly, the modification formulas are proposed based on simulation results, involving the radius of cross section of neck and the hardening exponent. Finally, these formulas are used to correct the stresses in the post-necking tension of Q345 cylindrical specimen, which are compared with the stresses identified through inverse method. The results indicate that the modified models significantly improve the prediction accuracy of post-necking stresses at large strains.

scholarly journals The Evaluation Model of Network QoS Based on Intelligent Water Droplets Algorithm

2020 ◽  
Vol 2020 ◽  
pp. 1-7
Author(s):  
Fang Li ◽  
Yunlan Wang ◽  
Peng Li
Keyword(s):  
Evaluation Model ◽  
Water Droplets ◽  
Key Factors ◽  
Evaluation Indexes ◽  
Factors Influencing ◽  
Depth Study ◽  
Optimization Function ◽  
Simulation Results ◽  
Qos Evaluation

In order to solve the problem of the user demands to the quality of service (QoS) of network, this paper provides a novel QoS evaluation model based on the intelligent water droplets (IWD) algorithm. The model firstly gives the evaluation indexes of network QoS and establishes a multiobjective optimization function for solution in combination with the improved IWD. Then, mathematical simulation is used to conduct the in-depth study of the key factors influencing the evaluation model. Compared with the other methods, the algorithm has shown better adaptability in the simulation results.

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