Numerical evaluation of the transient acoustic waveform due to a point source in a fluid‐filled borehole

Geophysics ◽  
1979 ◽  
Vol 44 (10) ◽  
pp. 1706-1720 ◽  
Author(s):  
Leung Tsang ◽  
Dennis Rader
Keyword(s):  
Numerical Methods ◽  
Point Source ◽  
Numerical Evaluation ◽  
Close Agreement ◽  
Time Windows ◽  
Computation Time ◽  
Head Wave ◽  
Oil Well ◽  
Additional Information ◽  
Frequency Domains

A key measurement employed in oil well wireline logging is the acoustic wave traveltime over a specified formation interval, typically 1 ft. In the traditional measurement, only the compressional head wave is monitored, but for some time it has been obvious that there is significant additional information, such as the shear head wave arrival, in the received waveform. We describe two numerical methods for computing the profile and parameter dependence of the transient waveform based on a model of the acoustic logging problem consisting of a point source on the axis of a fluid‐filled cylindrical borehole. The response to this excitation is determined at a distance from the source, generally on the borehole axis. In the first of the two numerical methods, called “real axis integration”, the complete acoustic waveform is obtained. The second method, called “branch‐cut integration”, evaluates the first compressional and shear‐pseudo‐Rayleigh arrivals individually with much less computation time than the first method. The validity and accuracy of the two methods are demonstrated by their close agreement within appropriate time windows. It is also shown that the results from the ordinary asymptotic method that exist in the literature predict different behavior. The dependence of the transient arrivals on formation parameters is illustrated by various numerical results in both time and frequency domains.

Seismic waves generated by an impulsive point source in a solid/fluid configuration with a plane boundary

Geophysics ◽  
1985 ◽  
Vol 50 (7) ◽  
pp. 1083-1090 ◽  
Author(s):  
Adrianus T. de Hoop ◽  
Jos H. M. T. van der Hijden
Keyword(s):  
Point Source ◽  
Seismic Waves ◽  
Integral Transform ◽  
Vertical Plane ◽  
Computation Time ◽  
Plane Boundary ◽  
Head Wave ◽  
Transform Method ◽  
Expansion Model ◽  
Fluid Configuration

The space‐time acoustic wave motion generated by an impulsive point source in a solid/fluid configuration with a vertical plane boundary is calculated with the aid of the modified Cagniard method. Two types of sources are considered in detail, viz. (1) a point source of expansion (model for an explosive source), and (2) a point force parallel to the vertical interface (model for a mechanical vibrator). Numerical results are presented for the transmitted scalar traction in the fluid in those regions of space where head wave contributions occur. There is a marked difference in the time response observed for the two types of sources and for the different positions of the receiver in the fluid with respect to the position of the source in the solid. These waveform differences are important when the transmitted wave in the fluid is used to determine experimentally the elastic properties of the solid. Scholte waves are observed only when the source is close to the fluid/solid interface. As compared with the traditional Fourier‐Bessel integral transform method of handling this problem, the computation time with the method presented here is considerably less.

scholarly journals A Heuristics-Based Parthenogenetic Algorithm for the VRP with Potential Demands and Time Windows

2016 ◽  
Vol 2016 ◽  
pp. 1-12
Author(s):  
Chenghua Shi ◽  
Tonglei Li ◽  
Yu Bai ◽  
Fei Zhao
Keyword(s):  
Genetic Algorithm ◽  
Time Windows ◽  
Computation Time ◽  
Routing Problem ◽  
Split Delivery ◽  
Soft Time Windows ◽  
Comparison Results ◽  
Potential Demand ◽  
The Cost

We present the vehicle routing problem with potential demands and time windows (VRP-PDTW), which is a variation of the classical VRP. A homogenous fleet of vehicles originated in a central depot serves customers with soft time windows and deliveries from/to their locations, and split delivery is considered. Also, besides the initial demand in the order contract, the potential demand caused by conformity consuming behavior is also integrated and modeled in our problem. The objective of minimizing the cost traveled by the vehicles and penalized cost due to violating time windows is then constructed. We propose a heuristics-based parthenogenetic algorithm (HPGA) for successfully solving optimal solutions to the problem, in which heuristics is introduced to generate the initial solution. Computational experiments are reported for instances and the proposed algorithm is compared with genetic algorithm (GA) and heuristics-based genetic algorithm (HGA) from the literature. The comparison results show that our algorithm is quite competitive by considering the quality of solutions and computation time.

An Efficient Method for Simulating Frequency-Dependent Friction in Transient Liquid Flow

1975 ◽  
Vol 97 (1) ◽  
pp. 97-105 ◽  
Author(s):  
A. K. Trikha
Keyword(s):  
Liquid Flow ◽  
Method Of Characteristics ◽  
Computation Time ◽  
Approximate Expression ◽  
Test System ◽  
Exact Expression ◽  
Frequency Dependent ◽  
Efficient Procedure ◽  
Liquid Line ◽  
Frequency Domains

An efficient procedure is developed for simulating frequency-dependent friction in transient laminar liquid flow by the method of characteristics. The procedure consists of determining an approximate expression for frequency-dependent friction such that the use of this expression requires much less computer storage or computation time than the use of the exact expression. The derived expression for frequency-dependent friction approximates the exact expression very well in both time and frequency domains. Calculated results for a test system are compared with the experimental results so show that the approximate expression predicts accurately the surge pressures, pressure wave distortion as well as pressure attenuation in a liquid line.

GPU Based Acceleration of MPS Method for Three-Dimensional Dam-Break Flows

2018 ◽  
Author(s):  
Xiang Chen ◽  
Decheng Wan
Keyword(s):  
Numerical Methods ◽  
Computational Efficiency ◽  
Three Dimensional ◽  
Computation Time ◽  
Dam Break ◽  
Gpu Acceleration ◽  
Mps Method ◽  
Acceleration Technique ◽  
Dam Break Flow ◽  
Moving Particle

The Moving Particle Semi-implicit (MPS) method has been proven effective to simulate violent flows such as dam-break flow, liquid sloshing and so on. But the low computational efficiency is one disadvantage of MPS. In the field of scientific computations, GPU based acceleration technique is widely applied to reduce the computation time of various numerical methods. In this paper, an in-house solver MPSGPU-SJTU is developed based on modified MPS method and GPU acceleration technique. A three-dimensional (3-D) dam-break flow is simulated by present solver and the validity and accuracy of GPU code are investigated by comparing the results with those by other researches. By comparisons, the flow field of GPU-based calculation is in better agreement with the experiment. In addition, the computation times of GPU and CPU solvers are compared to demonstrate the effect of GPU acceleration technique on the computational efficiency of MPS method.

On some numerical methods for solving 2D radial flow towards an oil well

1998 ◽  
Vol 47 (1) ◽  
pp. 17-36 ◽  
Author(s):  
Gabriela B. Savioli ◽  
Pablo M. Jacovkis ◽  
M. Susana Bidner
Keyword(s):  
Numerical Methods ◽  
Radial Flow ◽  
Oil Well

NUMERICAL EVALUATION OF FEM WITH APPLICATION TO THE 1-D ADVECTION–DIFFUSION PROBLEM

2002 ◽  
Vol 12 (02) ◽  
pp. 205-228 ◽  
Author(s):  
GIANCARLO SANGALLI
Keyword(s):  
Finite Element ◽  
Numerical Methods ◽  
General Framework ◽  
Numerical Evaluation ◽  
Numerical Procedure ◽  
Diffusion Problem ◽  
Empirical Justification ◽  
Eigenvalue Computation ◽  
Advection Diffusion

In this paper we present a numerical procedure to evaluate the efficiency of finite element numerical methods. We improve some of the ideas proposed in previous works and give a partly theoretical, partly empirical justification in a general framework. The proposed procedure performs an eigenvalue computation, and requires the knowledge of the behavior of the exact operator in order to choose proper norms for the evaluations. In the experiments we focus our attention on the 1-D advection–diffusion problem: we show that our numerical procedure actually gives very sharp indications about the optimality of the tested numerical methods.

scholarly journals Different Bayesian Methods for Updating the Fatigue Crack Size Distribution in a Tubular Joint

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
H. Khalili ◽  
S. Oterkus ◽  
N. Barltrop ◽  
U. Bharadwaj
Keyword(s):  
Numerical Methods ◽  
Probability Distribution ◽  
Size Distribution ◽  
Fatigue Damage ◽  
Crack Size ◽  
Offshore Platforms ◽  
Additional Information ◽  
Joint Reliability ◽  
Service Lifetime ◽  
Tubular Joint

Abstract Offshore platforms are prone to fatigue damage. To evaluate the fatigue damage, these platforms are periodically inspected during the in-service lifetime. Inspection activities provide additional information, which includes detection and measurement of crack size. A Bayesian framework can be used to update the probability distribution of the uncertain parameters such as crack size. After updating the distribution of the crack size, it is possible to improve the estimation of joint reliability. The main purpose of this study is to present different methods of Bayesian inference to update the probability distribution of the crack size using the inspection results and to demonstrate how the results are different. Two different methods are presented: analytical (conjugate) and numerical methods. The advantages and shortcomings of each method are discussed. To compare the results of the analytical and numerical methods, two different situations are considered; updating the crack size distribution for a particular joint and updating the crack size distribution for several joints that have almost the same conditions. Although the proposed methodology can be applied to different kinds of structures, an example of tubular joints in a specific jacket platform is presented to demonstrate the proposed approach and to compare the results of two methods.

scholarly journals Heart Rate Variability Duration: Expanding the Ability of Wearable Technology to Improve Outpatient Monitoring?

2021 ◽  
Vol 12 ◽  
Author(s):  
David C. Sheridan ◽  
Karyssa N. Domingo ◽  
Ryan Dehart ◽  
Steven D. Baker
Keyword(s):  
Mental Health ◽  
Heart Rate ◽  
Heart Rate Variability ◽  
Time Windows ◽  
Low Frequency ◽  
Frequency Component ◽  
Wearable Technology ◽  
Mental Health Research ◽  
High Frequency Component ◽  
Frequency Domains

Heart rate variability (HRV) evaluates beat-to-beat interval (BBI) differences and is a suggested marker of the autonomic nervous system with diagnostic/monitoring capabilities in mental health; especially parasympathetic measures. The standard duration for short-term HRV analysis ranges from 24 h down to 5-min. However, wearable technology, mainly wrist devices, have large amounts of motion at times resulting in need for shorter duration of monitoring. The objective of this study was to evaluate the correlation between 1 and 5 min segments of continuous HRV data collected simultaneously on the same patient. Subjects wore a patch electrocardiograph (Cardea Solo, Inc.) over a 1–7 day period. For every consecutive hour the patch was worn, we selected a 5-min, artifact-free electrocardiogram segment. HRV metric calculation was performed to the entire 5-min segment and the first 1-min from this same 5-min segment. There were 492 h of electrocardiogram data collected allowing calculation of 492 5 min and 1 min segments. 1 min segments of data showed good correlation to 5 min segments in both time and frequency domains: root mean square of successive difference (RMSSD) (R = 0.92), high frequency component (HF) (R = 0.90), low frequency component (LF) (R = 0.71), and standard deviation of NN intervals (SDNN) (R = 0.63). Mental health research focused on parasympathetic HRV metrics, HF and RMSSD, may be accomplished through smaller time windows of recording, making wearable technology possible for monitoring.

scholarly journals Technical note: Interpretation of field observations of point-source methane plume using observation-driven large-eddy simulations

2021 ◽  
Author(s):  
Anja Ražnjević ◽  
Chiel van Heerwaarden ◽  
Bart van Stratum ◽  
Arjan Hensen ◽  
Ilona Velzeboer ◽  
...  
Keyword(s):  
Point Source ◽  
Large Scale ◽  
Added Value ◽  
Relative Dispersion ◽  
Scale Model ◽  
Length Scale ◽  
Oil Well ◽  
Plume Dispersion ◽  
Field Observations ◽  
Large Eddy

Abstract. This study demonstrates the ability of large-eddy simulation (LES) forced by a large-scale model to reproduce plume dispersion in an actual field campaign. Our aim is to bring together field observations taken under non-ideal conditions and LES to show that this combination can help to derive point source strengths from sparse observations. We prepared a one-day case study based on data collected near an oil well during the ROMEO campaign (ROmanian Methane Emissions from Oil and gas) that took place in October 2019. We set up our LES using boundary conditions derived from the meteorological reanalysis ERA5 and released a point source in line with the configuration in the field. The weather conditions produced by the LES show close agreement with field observations, although the observed wind field showed complex features due to the absence of synoptic forcing. In order to align the plume direction with field observations, we created a second simulation experiment with manipulated wind fields. The estimated source strengths using the LES plume agrees well with the emitted artificial tracer gas plume, indicating the suitability of LES to infer source strengths from observations under complex conditions. To further harvest the added value of LES, higher order statistical moments of the simulated plume were analysed. Here, we found good agreement with plumes from previous LES and laboratory experiments in channel flows. We derived a length scale of plume mixing from the boundary layer height, the mean wind speed and convective velocity scale. It was demonstrated that this length scale represents the distance from the source at which the predominant plume behaviour transfers from meandering dispersion to relative dispersion.

scholarly journals Interoperability Improvement in Internet of Things Using Fog Assisted Semantic Frame Work

2020 ◽  
Vol 2 (1) ◽  
pp. 56-68
Author(s):  
Dr. Joy Iong Zong Chen ◽  
Dr. Smys S.
Keyword(s):  
Internet Of Things ◽  
Computation Time ◽  
Mapping Technique ◽  
The Internet ◽  
Additional Information ◽  
Proposed Model ◽  
Frame Work ◽  
Semantic Resources ◽  
Support Software ◽  
The Internet Of Things

Cloud computing is equipped with the numerous of advantageous features to support software and utilities on the Internet of Things (IoT). Cloud-based technology is widely used when offering support for heterogeneous applications integrating specific IoT that follows various semantics. Attaching additional information to raw data sensed with the help of ontology is accomplished in semantic model. The longer distance between the cloud and IoT applications, however, is a bottleneck for vital IoT software. So the paper puts forth a semantic frame work assisted by the fog to enhance the interoperability in the internet of things. The structure put forth moves some of the cloud's commonly used semantic resources sensor networks edge and also offers an effective off-loading technique between fog – fog and fog – cloud devices to diminish total computation time of the task and the energy consumed by the nodes in the fog. The proposed method further follows an efficient mapping technique to transform the data’s sensed into a RDF-format such that it is compatible for processing. The proposed model is evaluated on the basis of delay in the service provision, the energy consumed , and the total cost of the system and further the results obtained are compared with the relevant cloud based computing models , to reveal the proficiency of the proposed.

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