scholarly journals Small-Scale Drilling Test Rig For Investigation of Axial Excitation On The Drilling Process

2018 ◽  
Vol 148 ◽  
pp. 16001
Author(s):  
A. Austefjord ◽  
S. Blaylock ◽  
I. Forster ◽  
M. Sheehan ◽  
C. Wright
Keyword(s):  
High Frequency ◽  
High Speed ◽  
Low Frequency ◽  
Advanced Technology ◽  
Small Scale ◽  
Drilling Process ◽  
Generation Process ◽  
Rock System ◽  
Drilling Rig ◽  
Axial Excitation

This paper describes the design, construction and operation of a small-scale drilling rig for the purpose of investigation of the effect of axial excitation on the drilling process. The rig is bench top in size and has been designed to drill small rock samples, whilst at the same allowing axial excitation to be induced into the drilling process. The rig has been designed to drill the rock without any drilling fluids – so allowing improved observation of the chip generation process. Additionally, the drilling weight on bit is applied via masses, so allowing greater representation of the dynamic behavior of the drilling process – i.e. capturing more natural frequencies. The results from the rig have been obtained over two frequency ranges – low frequency (0-50 Hz) and high frequency (50-250 Hz). Results show that improved rate of penetration is obtained with axial excitation – with low and high frequency optima occurring. These optima can be related to the behavior of the string in the two frequency ranges – in the low frequency range, the entire string acts in unison; whereas at high frequency, only the bit/rock system is active. As a result, it is concluded that for low frequency operation, only information about the drill string is required to optimize performance; whereas for high frequency operation, information about the bit/rock system is required to optimize performance. Observation of the chip generation process via high speed video has shown that during axial excitation, regular shaped bricks are ejected when compared with the typical wedge- shaped chips that are normally ejected during the drilling process. It is concluded that, during the axial excitation process, the chips are being ejected via a levering action, so allowing a more efficient and quicker process. MIT [1] provided background classes, project guidance and project review as part of an NOV/MIT advanced technology program. Larger scale lab tests and/or field tests are required to verify/validate these conclusions.

scholarly journals Stochastic Subgrid-Scale Ocean Mixing: Impacts on Low-Frequency Variability

2017 ◽  
Vol 30 (13) ◽  
pp. 4997-5019 ◽  
Author(s):  
Stephan Juricke ◽  
Tim N. Palmer ◽  
Laure Zanna
Keyword(s):  
Southern Ocean ◽  
Interannual Variability ◽  
Time Scales ◽  
High Frequency ◽  
Low Frequency ◽  
Global Ocean ◽  
Small Scale ◽  
Subgrid Scale ◽  
Low Frequency Variability ◽  
Ocean Models

In global ocean models, the representation of small-scale, high-frequency processes considerably influences the large-scale oceanic circulation and its low-frequency variability. This study investigates the impact of stochastic perturbation schemes based on three different subgrid-scale parameterizations in multidecadal ocean-only simulations with the ocean model NEMO at 1° resolution. The three parameterizations are an enhanced vertical diffusion scheme for unstable stratification, the Gent–McWilliams (GM) scheme, and a turbulent kinetic energy mixing scheme, all commonly used in state-of-the-art ocean models. The focus here is on changes in interannual variability caused by the comparatively high-frequency stochastic perturbations with subseasonal decorrelation time scales. These perturbations lead to significant improvements in the representation of low-frequency variability in the ocean, with the stochastic GM scheme showing the strongest impact. Interannual variability of the Southern Ocean eddy and Eulerian streamfunctions is increased by an order of magnitude and by 20%, respectively. Interannual sea surface height variability is increased by about 20%–25% as well, especially in the Southern Ocean and in the Kuroshio region, consistent with a strong underestimation of interannual variability in the model when compared to reanalysis and altimetry observations. These results suggest that enhancing subgrid-scale variability in ocean models can improve model variability and potentially its response to forcing on much longer time scales, while also providing an estimate of model uncertainty.

Unsteady Structure Measurement of Cloud Cavitation on a Foil Section Using Conditional Sampling Technique

1989 ◽  
Vol 111 (2) ◽  
pp. 204-210 ◽  
Author(s):  
A. Kubota ◽  
H. Kato ◽  
H. Yamaguchi ◽  
M. Maeda
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Laser Doppler Anemometry ◽  
Low Frequency ◽  
Sampling Technique ◽  
Experimental Result ◽  
Small Scale ◽  
Conditional Sampling ◽  
Cloud Cavitation ◽  
Structure Of Flow

The structure of flow around unsteady cloud cavitation on a stationary two-dimensional hydrofoil was investigated experimentally using a conditional sampling technique. The unsteady flow velocity around the cloud cavitation was measured by a Laser Doppler Anemometry (LDA) and matched with the unsteady cavitation appearance photographed by a high-speed camera. This matching procedure was performed using data from pressure fluctuation measurements on the foil surface. The velocities were divided into two components using a digital filter, i.e., large-scale (low-frequency) and small-scale (high frequency) ones. The large-scale component corresponds with the large-scale unsteady cloud cavitation motion. In this manner, the unsteady structure of the cloud cavitation was successfully measured. The experimental result showed that the cloud cavitation observed at the present experiment had a vorticity extremum at its center and a cluster containing many small cavitation bubbles. The convection velocity of the cavitation cloud was much lower than the uniform velocity. The small-scale velocity fluctuation was not distributed uniformly in the cavitation cloud, but was concentrated near its boundary.

Experimental Study of Drillstring Dynamics Using a High-Speed Camera As a Non-Invasive Motion Sensor

2019 ◽  
Author(s):  
Ekaterina Wiktorski ◽  
Milad Khatibi ◽  
Suranga Geekiyanage ◽  
Dan Sui ◽  
Rune W. Time
Keyword(s):  
High Speed ◽  
Pressure Fluctuations ◽  
Displacement Sensor ◽  
Surface Measurement ◽  
Small Scale ◽  
Sufficient Information ◽  
High Speed Camera ◽  
Image Processing Algorithm ◽  
Drilling Rig ◽  
Directional Control

Abstract In the last decades, drilling industry has been developing solutions to overcome challenges that impede drilling of long directional wells as excessive friction, poor directional control, narrow drilling windows, etc. One of the problems that is identified, yet not solved is the drillstring vibrations. Drillstring vibrations result in low ROP, fatigue and failure of the drillstring elements and weakened wellbore integrity. They are often detected through surface symptoms, as large surface WOB fluctuations (axial vibrations), torque and RPM fluctuations (torsional vibrations), reduced ROP, pressure fluctuations, rig/top drive shaking, etc. To control vibrations, a good understanding of basic mechanisms of vibrations initiation and propagation is required. Therefore, this paper aims at the experimental investigation of the drillstring dynamics using a small-scale drilling rig constructed at the University of Stavanger. The experimental drilling rig is equipped with a WOB surface sensor, which works as a strain gauge, as well as RPM and torque encoder and other sensors. For a small-scale system, measurements of the surface sensors represent the combined responses of the whole rig structure, not just the drillstring. Therefore, more information to show drillstring dynamics (displacements and frequencies) is desired, besides surface measurement. This paper presents experiments designed to detect vibrations of the drillstring using a high-speed camera, which in this study serves as an along-the-pipe downhole sensor. The paper also provides the image-processing algorithm that was developed to extract the signal from the images, digitize and normalize it. The high-speed camera has proved to be an accurate and practically noise-free displacement sensor. As a part of this study, analysis of the captured frequencies and decaying amplitudes (damping) was performed for both the high-speed camera and the load cells data. It helped to evaluate whether the surface sensors are able to provide sufficient information about the downhole vibrations. We have seen that in the case where the drillstring interacts with the wellbore, the downhole vibrations are reflected to the surface. However, when the string hangs freely, surface and downhole sensors measure responses from different parts of the system. These conclusions are mostly valid for small-scale vertical systems, however, can also be considered for drilling shallow vertical wells/top sections.

scholarly journals Self-Motion and the Shaping of Sensory Signals

2010 ◽  
Vol 103 (4) ◽  
pp. 2195-2207 ◽  
Author(s):  
Robert A. Jenks ◽  
Ashkan Vaziri ◽  
Ali-Reza Boloori ◽  
Garrett B. Stanley
Keyword(s):  
High Frequency ◽  
High Speed ◽  
External Environment ◽  
Low Frequency ◽  
Head Rotation ◽  
Object Localization ◽  
Behavioral Variability ◽  
Sensory Signals ◽  
Behavioral Variables ◽  
Self Motion

Sensory systems must form stable representations of the external environment in the presence of self-induced variations in sensory signals. It is also possible that the variations themselves may provide useful information about self-motion relative to the external environment. Rats have been shown to be capable of fine texture discrimination and object localization based on palpation by facial vibrissae, or whiskers, alone. During behavior, the facial vibrissae brush against objects and undergo deflection patterns that are influenced both by the surface features of the objects and by the animal's own motion. The extent to which behavioral variability shapes the sensory inputs to this pathway is unknown. Using high-resolution, high-speed videography of unconstrained rats running on a linear track, we measured several behavioral variables including running speed, distance to the track wall, and head angle, as well as the proximal vibrissa deflections while the distal portions of the vibrissae were in contact with periodic gratings. The measured deflections, which serve as the sensory input to this pathway, were strongly modulated both by the properties of the gratings and the trial-to-trial variations in head-motion and locomotion. Using presumed internal knowledge of locomotion and head-rotation, gratings were classified using short-duration trials (<150 ms) from high-frequency vibrissa motion, and the continuous trajectory of the animal's own motion through the track was decoded from the low frequency content. Together, these results suggest that rats have simultaneous access to low- and high-frequency information about their environment, which has been shown to be parsed into different processing streams that are likely important for accurate object localization and texture coding.

Measurement of High Frequency Viscoelastic Properties of Deformed Rubber

2016 ◽  
Vol 715 ◽  
pp. 139-146 ◽  
Author(s):  
Tadayoshi Shoyama ◽  
Koji Fujimoto
Keyword(s):  
Resonance Frequency ◽  
High Frequency ◽  
High Speed ◽  
Dynamic Properties ◽  
Loss Modulus ◽  
Low Frequency ◽  
Soft Materials ◽  
Load Cell ◽  
Universal Prediction ◽  
Response Method

Bearings of small turbo machines support high speed rotors rotating with the frequency over 1 [kHz]. Such bearings are often supported with O-rings made of soft materials like rubber to attenuate high frequency oscillations. Dynamic properties of rubber supporters have been measured experimentally for individual dimensions, but the universal prediction of dynamic properties for various frequencies is difficult not only because rubbers exhibit nonlinearity against its strain, but because O-ring supporters deform heterogeneously. For the precise prediction, it is necessary to investigate the viscoelasticity of rubber under various deformations and frequencies. Such properties can be measured by the standard shear vibration non-response method of ISO 6721-6 (JIS K 7244-6). However this is applicable only to low frequency range under 100 [Hz] because of the limitation of resonance frequency of the load cell. In this research, based on BERM (Base Excitation Resonant Mass) method, a new method was developed to measure the complex shear modulus at high frequencies up to 1 [kHz] of rubber sheets under homogeneous shear deformations. In the presented method, the force is calculated from the acceleration of the mass instead of the direct measurement by a load cell. Hence accurate measurement became possible even in the range beyond the resonance frequency of a load cell. The measured shear storage modulus G’ and shear loss modulus G” of deformed rubber were presented.

scholarly journals Wall pressure beneath a transitional hypersonic boundary layer over an inclined straight circular cone

2020 ◽  
Vol 2 (1) ◽  
Author(s):  
Siwei Dong ◽  
Jianqiang Chen ◽  
Xianxu Yuan ◽  
Xi Chen ◽  
Guoliang Xu
Keyword(s):  
Boundary Layer ◽  
High Frequency ◽  
High Speed ◽  
Low Frequency ◽  
Axial Direction ◽  
Wall Pressure ◽  
Hypersonic Boundary Layer ◽  
High Frequency Signal ◽  
Local Boundary ◽  
Half Angle

AbstractProperties of wall pressure beneath a transitional hypersonic boundary layer over a 7∘ half-angle blunt cone at angle of attack 6∘ are studied by Direct Numerical Simulation. The wall pressure has two distinct frequency peaks. The low-frequency peak with f≈10−50 kHz is very likely the unsteady crossflow mode based on its convection direction, i.e. along the axial direction and towards the windward symmetry ray. High-frequency peaks are roughly proportional to the local boundary layer thickness. Along the trajectories of stationary crossflow vortices, the location of intense high-frequency wall pressure moves from the bottom of trough where the boundary layer is thin to the bottom of shoulder where the boundary layer is thick. By comparing the pressure field with that inside a high-speed transitional swept-wing boundary layer dominated by the z-type secondary crossflow mode, we found that the high-frequency signal originates from the Mack mode and evolves into the secondary crossflow instability.

A comprehensive optimal design method for magnetorheological dampers utilized in DMU power package

2021 ◽  
pp. 146442072110496
Author(s):  
Fanghui Xu ◽  
Dawei Dong ◽  
Yan Huang ◽  
Rui Zhang ◽  
Shizhe Song ◽  
...  
Keyword(s):  
Optimal Design ◽  
High Frequency ◽  
High Speed ◽  
Low Frequency ◽  
Mr Damper ◽  
Magnetic Flux Density ◽  
Objective Functions ◽  
Damping Force ◽  
Optimal Method ◽  
Mr Dampers

The diesel multiple unit (DMU) has been widely used in high-speed railway service due to its flexibility and economy. Considering the broadband and complex vibration generated by DMU power package, the advanced semi-active suspension with magnetorheological (MR) dampers is introduced to promote anti-vibration performance. In this work, a comprehensive optimal design approach for MR damper used in DMU power package is proposed. Quasi-static modeling process is conducted to obtain MR damper's low-frequency outputs, while its high-frequency damping forces are calculated by physical modeling considering the fluid compressibility and piston assembly inertia. Then the objective functions and optimization variables are determined. Based on response surface and linear correlation analysis, the influence of the optimal variables on the objective functions is discussed. Using reference-point based nondominated sorting approach (NSGA-III), the evolutionary many-objective optimization is conducted. In addition, magnetic design is incorporated into the optimal process to ensure the magnetic flux density in the effective working area. Finally, an optimized MR damper prototype is manufactured and tested. By comparing the experimental damping force with calculated results in both low-frequency and high-frequency ranges, the effectiveness of the presented optimal method for MR dampers is validated.

Comparative Feature Analysis of Ground Surface Vibration Induced by High-Speed Train Running on Viaduct and Embankment

2014 ◽  
Vol 638-640 ◽  
pp. 1229-1232
Author(s):  
Kun Ming Mao ◽  
Ting Ting Wang ◽  
Qian Wen Ru ◽  
Yan Li
Keyword(s):  
Frequency Band ◽  
High Frequency ◽  
High Speed ◽  
Fourier Spectrum ◽  
Three Dimensional ◽  
Low Frequency ◽  
Ground Surface ◽  
Vertical Acceleration ◽  
High Frequency Band ◽  
Surface Vibration

Based on the Abaqus parallel computing cluster system platform, the three-dimensional finite element model of train-track-viaduct/embankment-foundation-soil coupling is established. The three-dimensional space-time variation and Fourier spectrums characters of ground surface vibration vertical accelerations by high-speed train running on viaduct and embankment are simulated. The result shows that ground surface vibration is mainly excited by periodic axle force of the train in the site near the viaduct pier. In the site far from the viaduct pier, ground surface vibration is mainly from the transmission of the site near the viaduct pier. With the increased distance between the viaduct pier, the peak value of ground surface vibration vertical acceleration decreases, and decreases significantly when the distance is within 10m. There are two main frequency bands of Fourier spectrum of ground surface vibration vertical acceleration: low-frequency band 0-12Hz and high-frequency band 35-47Hz of viaduct route, and low-frequency band 0-21Hz and high-frequency band 25-45Hz of embankment route. In general, with the increased distance between viaduct/embankment, Fourier spectrum amplitude of every frequency band decrease, and attenuation speed of high-frequency band is much faster than-frequency band’s.

The Design and Control of a Rigid-flexible Coupling Positioning Stage for Enhanced Settling Performance

2021 ◽  
Author(s):  
Hao Peng ◽  
Zhijun Yang ◽  
Wenchao Xue ◽  
Ruirui Huang ◽  
Yi Huang
Keyword(s):  
High Frequency ◽  
High Speed ◽  
Mechanical Design ◽  
Dead Zone ◽  
Low Frequency ◽  
Poor Performance ◽  
Experimental Tests ◽  
Control Performance ◽  
Flexible Coupling ◽  
Positioning Stage

Abstract Traditional high-speed precision motion stage (HSPMS) design pursues high-stiffness structure to achieve fast response. However, such structure leads to high-frequency disturbance near dead zone of friction, which causes poor performance in controlling HSPMS. To this end, this paper proposes the active disturbance rejection control (ADRC) based mechanical design to reduce the bandwidth of friction disturbance and improve the control performance of HSPMS. It is proved that the low-frequency disturbance can be more effectively tackled by the extended state observer (ESO) in the frame of ADRC. In particular, rigid-flexible coupling (RFC) positioning stage is presented for converting the high-frequency friction disturbance into the low-frequency elastic deformation disturbance by flexure hinges. The experimental tests are carried out for both traditional stage and RFC stage. It is clearly shown that compared with traditional design, the control performance of RFC stage is remarkably promoted.

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