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Noise color influence on escape times in nonlinear oscillators-experimental and numerical results

Theoretical & Applied Mechanics Letters 2023年第2期13卷 149-158页

作者： Thomas Breunung balakumar balachandran Department of Mechanical Engineering University of MarylandCollege ParkMD 20742United States

The interplay between noise and nonlinearites can lead to escape *** nonlinear phe-nomena have been observed in various applications ranging from climatology to biology and *** reasons of computational ease,in most studies,Gaussian white noise is ***,this noise model is not physical due to the associated infinite energy ***,the authors present extensive experimental investigations and numerical simulations conducted to examine the impact of noise color on escape times in nonlinear *** a careful parameterization of the numerical simulations,the authors are able to make quantitative comparisons with experimental *** the experi-ments and simulations,it is illustrated that the noise color can drastically influence escape times and escape probability.

关键词： Colored noise Non-Gaussian excitation Experiments Escape times

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A new solution to enhance cuttings transport in mining drilling by using pulse jet mill technique

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Science China(Technological Sciences) 2019年第5期62卷 875-884页

作者： LIU YongSheng GAO DeLi WEI Zheng balachandran balakumar WANG ZhenQuan TAN LeiChuan MOE Key Laboratory of Petroleum Engineering China University of Petroleum Department of Mechanical Engineering University of Maryland College Park

In horizontal drilling, the cuttings bed is frequently formed to result in severe problems such as backing pressure, binding of bottom hole assembly(BHA) and even sticking of tool. Practice and research show that the smaller particle size is, the more favorable to carry out from bottom of hole in extended reach well or horizontal well. This paper presented a new solution to enhance cuttings transport in mining drilling through a new type of bit called pulsed mill bit(PMB) by using pulse jet mill technique. It provides a promising solution to enhance the efficiencies of rock breaking and cuttings carrying for pulsed jet,sucking cuttings to decrease the chip hold down effect, and reducing cuttings' diameter to eliminate cuttings bed. The design was supported by the calculation models of Helmholtz resonator natural frequency, optimal drilling fluid flow rate of resonator,drilling fluid flow velocity in forward jet channel, critical impact velocity of cuttings and minimum length of the accelerating cavity. Meanwhile, factors affecting optimal drilling fluid flow rate, critical impact velocity of cuttings and minimum length of accelerating cavity were investigated. Case study showed a good consistency between the calculation results and the related theories. It is concluded that optimal drilling fluid flow rate increases with the increase of inlet and outlet cavity's diameter, and decreases with the increase of the diameter of the resonant cavity. Critical impact velocity of cuttings increases with the energy conversion factor(β) and ROP, while decreasing with the final size of the cuttings(d_t). This effect is obvious when β<0.2, ROP<3.048 mh^(-1) and d_t<0.3 mm. Minimum length of the accelerating cavity decreases with the increase of the resonator's natural frequency and separation coefficient(α) of drilling fluid flow rate. This study provides a promising solution to remove cuttings bed in horizontal well.

关键词： pulse jet mill technique cuttings bed Helmholtz resonator optimal flow rate critical impact velocity

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Motion visualization and estimation for flapping wing systems

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Acta Mechanica Sinica 2017年第2期33卷 327-340页

作者： Tzu-Sheng Shane Hsu Timothy Fitzgerald Vincent Phuc Nguyen Trisha Patel balakumar balachandran Department of Mechanical Engineering University of Maryland College Park MD 20742 USA

Studies of fluid-structure interactions associated with flexible structures such as flapping wings require the capture and quantification of large motions of bodies that may be opaque. As a case study, motion capture of a free flying Manduca sexta, also known as hawkmoth, is considered by using three synchronized high-speed cameras. A solid finite element (FE) representation is used as a reference body and successive snapshots in time of the displacement fields are reconstructed via an optimization procedure. One of the original aspects of this work is the formulation of an objective function and the use of shadow matching and strain-energy regularization. With this objective function, the authors penalize the projection differences between silhouettes of the captured images and the FE representation of the deformed body. The process and procedures undertaken to go from high-speed videography to motion estimation are discussed, and snapshots of representative results are presented. Finally, the captured free-flight motion is also characterized and quantified.

关键词： Insect flight Deformable body High-speed videography Motion estimation

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Corrigendum to“Noise colour influence on escape times in nonlinear oscillators-experimental and numerical results”[***.13(2023)100420]

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Theoretical & Applied Mechanics Letters 2023年第3期13卷 247-248页

作者： Thomas Breunung balakumar balachandran Department of Mechanical Engineering University of MarylandCollege ParkMD 20742United States

The original article includes the incorrectly printed Figs.1,2 and *** correct figures are included in this ***.1.(a)Experimental setup:The shaker is used to generate the external,harmonic and random excitation to the base of the metal *** resulting oscillations are measured with a strain gauge.A nonlinear restoring force follows from the magnets mounted at the cantilever tip and the fixed frame.(b)Measured cantilever response to sinusoidal excitation and experimental procedure:A sweep up is used to realize the high amplitude *** the excitation frequency reaches 39.6 Hz,noise is added to the input and a noise induced escape is observed.(c)Time series of a strain gauge signal:The forcing frequency is 39.6 Hz and the response is initiated in the high energy *** about 37.0 s an escape towards the low amplitude orbit is observed.

关键词： excitation cantilever nonlinear

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Noise aided control of rotor-stator system dynamics

Noise aided control of rotor-stator system dynamics

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23rd International Congress of Theoretical and Applied Mechanics

作者： Nicholas A.Vlajic Xianbo Liu Xinhua Long balakumar balachandran Department of Mechanical Engineering University of MarylandCollege ParkMarylandUSA School of Mechanical Engineering Shanghai Jiaotong University

＜正＞Rotor-stator systems that account for torsional vibrations are of interest for several applications,including drill-string dynamics. Failures of such rotor systems often originate from contact and collisions between the rotor and *** instances where the rotor may stay in continuous contact with the stator arise when the

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