Initial Branch Research Articles

Impact of Gas Accumulation on the Stability of Parallel Upward Ventilation in High-Temperature Sloped Shafts of Deep Wells

To explore the causes and influencing factors of wind flow oscillations in high-temperature inclined aisles of deep wells under parallel upward ventilation, this study conducts a comprehensive investigation using theoretical analysis and numerical simulations. Based on the kinetic analysis of gas flow, a discriminant formula for wind flow reversal in the side branch is derived. Further analysis identifies initial wind speed and branch length as key factors influencing the reversal. Both gas pressure and thermal pressure contribute to wind flow reversal in the side branch, and the opposing directions of these pressures cause high-temperature gas to periodically flow between the two branches, resulting in wind flow oscillations. A higher initial wind speed can effectively reduce the oscillation amplitude due to increased initial kinetic energy and a larger pressure difference, but it does not extend the oscillation duration. Increasing the branch length can suppress wind flow oscillations by increasing airflow frictional resistance and damping.

Exploring submergence impact on flow-induced motion energy-harvesting with circular-triangular prisms

AbstractRecent advancements in energy-harvesting have utilized Flow-Induced Motion (FIM) as a renewable source, diverging from past efforts aimed at minimizing FIM's adverse effects. This study introduces kinetic energy converters using alternating lift technology (ALT), employing a prism with a Circular-Triangular (Cir-Tria) shape, coupled with a spring and damper, to generate energy. Utilizing computational fluid dynamics in OpenFOAM for Reynolds numbers between 2 × 103 and 13 × 103 and varying submergence depth ratio from 0.98 to 5.91, this research employs a moving computational grid, two-dimensional incompressible Navier–Stokes equations, the k-omega Shear Stress Transport (SST) turbulence model, the Volume of Fluid, VOF, two-phase model, and the cylinder mass–spring–damper equation. Findings show that approaching the flow surface negatively impacts the FIM response due to the interaction of vortices from the flow surface and the prism’s upper shear layer. This interaction weakens and neutralizes the upper vortices, altering the flow structure around the prism and the governing FIM phenomena. Proximity to the free surface significantly affects FIM responses, with a notable decrease in vibration amplitude and energy conversion as the submergence depth ratio increases from 0.98 to 5.91. Maximum system efficiency of 1.4% is observed in the VIV initial branch at infinite submergence (single-phase flow). Beyond a submergence depth ratio of 5.91, FIM amplitude and energy conversion flatten, indicating negligible free surface effects.

Sublethal dosing exposure risk of kochia (Bassia scoparia (L.) A.J. Scott) to carfentrazone-ethyl

Kochia is a troublesome, multiple herbicide-resistant tumbleweed which infests Prairie field crops. Kochia has developed resistance to systemic, foliar-applied herbicides from groups 2, 4, and 9, leaving only contact herbicides for post-emergence control. Group 14 chemistry is an important mode of action for resistance management. Weed staging considerations are important as recurrent sub-lethal herbicide exposure can increase risk of nontarget site resistance evolution. The study objective was to evaluate loss-of-control and estimate sublethal dosing exposure risk (SLDER) with a contact-type herbicide (carfentrazone-ethyl) based on initial kochia height, leaf number, and branch number. The SLDER from a single application to a single plant was conceptualized to increase due to escaping plant “volume” or immediate flowering. Kochia was only consistently controlled (100% injury) when dosed at ≤5 cm in height. The estimated maximum size for treated kochia was 21 cm in height, 18 branches plant−1, and the maximum accumulated biomass was between 2.6 and 5.1 g plant−1 for models developed using the initial plant height, branch number, or leaf number as predictors. These estimates represent the largest plant escapes, which would be associated with 100% risk through vegetative considerations into SLDER. Kochia plant size for a 5% risk scenario using the SLDER model was 4 cm in height, 0 branches plant−1, and 11 leaves plant−1 when carfentrazone-ethyl was applied at the labeled dosing. Caution is advised when spraying kochia above 5 cm as incorrect staging may lead to sublethal exposure, escape, reproduction, and escalated risk of nontarget site resistance evolution.

Intrinsic features of flow-induced stability of a square cylinder

Vortex-induced vibrations and galloping of an elastically mounted square cylinder are investigated for cylinder mass ratio m* = 2–50, damping ratio ζ = 0–1.0, mass-damping ratio m*ζ = 0–50 and flow reduced velocity Ur = 1–80. We home in on the effects of m*, ζ, m*ζ, $({m^\ast } + m_{a\textrm{0}}^\ast )\zeta$ and $({m^\ast } + m_{ae}^\ast )\zeta$ on the critical reduced velocity Urc marking the onset of galloping, where $m_{a\textrm{0}}^\ast $ is the quiescent-fluid added mass ratio and $m_{ae}^\ast $ is the effective added mass ratio. Vibration responses, forces, vibration frequencies and added mass ratios are studied and discussed. The different branches of vortex-induced vibrations have different dependencies of $m_{ae}^\ast $ on Ur. The $m_{ae}^\ast $ in the initial branch is positive and drops rapidly with Ur, but that in the lower branch is negative and declines gently. In the galloping regime, $m_{ae}^\ast $ jumps from negative to positive at the onset of galloping, declining slightly with increasing Ur. Our results and prediction equations show that when ζ = 0, Urc is independent of m* for m* ≥ 5, albeit slightly higher for m* = 3. The latter is ascribed to mode competition. When ζ > 0, Urc linearly increases with increasing ζ. Detailed analysis substantiates that m*ζ or $({m^\ast } + m_{a\textrm{0}}^\ast )\zeta$ does not serve as the unique criterion to predict the galloping occurrence. Here, we propose a new combined mass-damping parameter $({m^\ast } + m_{ae}^\ast )\zeta$ in the relationship between galloping onsets and structural properties, which successfully scales all data of Urc at different m* and ζ values.

Mechanism Analysis of the Effect of Wake Vortex on Cylinder Vibration in Flow Induced Motion

Abstract Unsteady Reynolds-averaged Navier–Stokes (RANS) method combined with Spalart–Allmaras turbulence model and dynamic mesh technology was used to investigate the impact of wake vortex on the vibration response of a cylinder. By analyzing the phase difference between the wake vortex force and the displacement under different mass parameters in flow-induced vibration (FIV), the study reveals that the influence of wake vortex on the cylinder varies significantly in different vibration branches. The wake vortex of the initial branch enhances the cylinder's vibration, whereas the wake vortices of the upper, lower, and desynchronized branches suppress the vibration. At the critical point between the initial branch and the upper branch of vortex-induced vibration (VIV), there is a 90 degree phase jump, and the instantaneous phase difference fluctuation between the wake vortex force and displacement of the VIV branch remains relatively constant. In the galloping branch, there are wake vortices in different directions that affect the cylinder's vibration every quarter of the vibration period, and the phase difference undergoes periodic large fluctuations (either in-phase or out-of-phase), with the result that the wake vortex force periodically promotes or restrains the cylinder's vibration, which can serve as a novel criterion for identifying the occurrence of galloping. Furthermore, when varying the mass parameters at a constant reduced velocity, the impact of the wake vortex in the initial branch is relatively insignificant. However, as the mass ratio increases in other vibration branches, the suppressive effect increases, and the wake vortex force can prevent VIV induced galloping phenomenon by affecting the vibration intensity.

Full-Section Deformation Monitoring of High-Altitude Fault Tunnels Based on Three-Dimensional Laser Scanning Technology.

In traditional tunnel monitoring, the characteristic points of an object within a tunnel are measured to obtain information about the object. Considering the limitations of the traditional method in measuring the complex surface structure of tunnels, such as limited monitoring points, a long measurement period, and low precision, this study introduces an approach that uses three-dimensional (3D) laser scanning for monitoring tunnel cross-section deformation. Using this approach, the soft surrounding rock of a high-altitude ultralong tunnel was taken as the monitoring object. The test tunnel was first scanned using a 3D laser scanner, and the collected data were processed. The internal structural data of the tunnel were subsequently compared with its actual contour lines and the data of its primary branch and secondary lining on different dates. The results indicate that the arch roof of the tunnel tended to be stable within a certain time range when the positions of the primary branch and secondary lining were at different measuring points with different pile numbers. The deformation of the pile number on the left and right sides did not generally exceed 0.02 m, except at a few measuring points. A comparison between the actual cross section of the initial branch and that of the designed section showed that the actual elevation of the arch of the initial branch of the tunnel was greater than its designed elevation by no more than 0.3 m. Hence, through this study, a convenient and practical method is presented for monitoring deformation in complex curved tunnel structures.

Numerical Analysis of Flow-Induced Transverse Vibration of a Cylinder with Cubic Non-Linear Stiffness at High Reynolds Numbers

Numerical calculations were performed to study the vortex-induced vibration (VIV) of a circular cylinder, which was elastically supported by springs of linear and cubic terms. These simulations were conducted at high Reynolds numbers ranging from 4200 to 42,000. To simulate the cylinder’s motion and the associated aerodynamic forces, Computational Fluid Dynamics were employed in conjunction with dynamic mesh capabilities. The numerical method was initially verified by testing it with various grid resolutions and time steps, and subsequently, it was validated using experimental data. The response of cubic nonlinearities was investigated using insights gained from a conventional linear vortex-induced vibration (VIV) system. This 2D study revealed that both the amplitude and frequency of vibrations are contingent on the flow velocity. The highest output was achieved within the frequency lock-in region, where internal resonance occurs. In the case of a hardening spring, the beating response was observed from the lower end of the initial branch to the upper end of the initial branch. The response displacement amplitude obtained for the linear spring case was 27 mm, whereas in the cubic nonlinear case, the value was 31.8 mm. More importantly, the results indicate that the inclusion of nonlinear springs can substantially extend the range of wind velocities in which significant energy extraction through vortex-induced vibration (VIV) is achievable.

DateLife: Leveraging Databases and Analytical Tools to Reveal the Dated Tree of Life.

Chronograms-phylogenies with branch lengths proportional to time-represent key data on timing of evolutionary events, allowing us to study natural processes in many areas of biological research. Chronograms also provide valuable information that can be used for education, science communication, and conservation policy decisions. Yet, achieving a high-quality reconstruction of a chronogram is a difficult and resource-consuming task. Here we present DateLife, a phylogenetic software implemented as an R package and an R Shiny web application available at www.datelife.org, that provides services for efficient and easy discovery, summary, reuse, and reanalysis of node age data mined from a curated database of expert, peer-reviewed, and openly available chronograms. The main DateLife workflow starts with one or more scientific taxon names provided by a user. Names are processed and standardized to a unified taxonomy, allowing DateLife to run a name match across its local chronogram database that is curated from Open Tree of Life's phylogenetic repository, and extract all chronograms that contain at least two queried taxon names, along with their metadata. Finally, node ages from matching chronograms are mapped using the congruification algorithm to corresponding nodes on a tree topology, either extracted from Open Tree of Life's synthetic phylogeny or one provided by the user. Congruified node ages are used as secondary calibrations to date the chosen topology, with or without initial branch lengths, using different phylogenetic dating methods such as BLADJ, treePL, PATHd8, and MrBayes. We performed a cross-validation test to compare node ages resulting from a DateLife analysis (i.e, phylogenetic dating using secondary calibrations) to those from the original chronograms (i.e, obtained with primary calibrations), and found that DateLife's node age estimates are consistent with the age estimates from the original chronograms, with the largest variation in ages occurring around topologically deeper nodes. Because the results from any software for scientific analysis can only be as good as the data used as input, we highlight the importance of considering the results of a DateLife analysis in the context of the input chronograms. DateLife can help to increase awareness of the existing disparities among alternative hypotheses of dates for the same diversification events, and to support exploration of the effect of alternative chronogram hypotheses on downstream analyses, providing a framework for a more informed interpretation of evolutionary results.

Dual solutions of Darcy-Forchheimer radiative-convective magneto-nanofluid flow over an exponentially stretching/shrinking surface: Stability and entropy generation analysis

A numerical investigation was conducted to examine the existence of dual solutions over exponentially stretching or shrinking permeable surfaces. The study aimed to analyze the impact of thermal and second-order velocity slip on magnetohydrodynamic (MHD) mixed convective radiative nanofluid flow within a Darcy-Forchheimer porous medium while considering heat generation. Two distinct types of nanofluids, namely Cu-water and TiO 2/water, were employed in the investigation. To address the nonlinear partial differential equations (PDEs), similarity transformations were utilized to transform them into a system of ordinary differential equations (ODEs). The resulting coupled higher-order nonlinear ODEs were then solved using a MATLAB-based boundary value algorithm known as bvp4c. Two distinct solutions are observed within a restricted range of the stretching/shrinking parameter ξ ( ξ > ξ c ) and suction parameter S ( S > S c ), terminating respectively at ξ = ξ c or S = S c . The critical values are identified as ξ c = − 1.1952 ( Cu − water ) , − 0.9304 ( Ti O 2 − water ) and S c = 1.6437 ( Cu − water ) , 1.8900 ( Ti O 2 − water ) , maintaining the fixed values of the remaining physical parameters. Notably, the critical value for Cu-water is lower than that of TiO 2-water. Moreover, in both solution branches, the range of skin-friction coefficient and local Nusselt number for Cu-water surpasses that of TiO 2-water. An evaluation of the temporal stability of these solutions reveals that only the first solution remains stable. This is supported by the positivity of the smallest eigenvalues ( γ 1 > 0 ), indicating stability. Conversely, for the second solution, the smallest eigenvalues ( γ 1 < 0 ) are negative, signifying its instability. Also, Cu-water nanofluid exhibits higher fluid velocity and lower fluid temperature than TiO 2-water nanofluid for stable solutions and the opposite behavior for unstable solution branches. Significantly, within the initial solution branch, there is an escalation in velocity profiles attributed to the magnetic parameter, Grashof number, porous parameter, and first- and second-order velocity slip parameter. Conversely, a decrease is observed for the Forchheimer number, while the opposite holds true for the second solution branch. For both solution branches, the temperature profiles experience a reduction due to thermal slip and stretching/shrinking parameters, whereas enhancements are noted for thermal radiation and heat generation parameters. Furthermore, an increase in the suction parameter leads to elevated skin friction coefficient and local Nusselt number in the first stable solution, thereby promptly improving heat transfer efficiency. Moreover, improvements in entropy generation arise from factors such as thermal radiation, magnetic field, and nanoparticle solid volume fraction, presenting opportunities to optimize heat transmission in cooling and heating systems.

Supershear triggering and cascading fault ruptures of the 2023 Kahramanmaraş, Türkiye, earthquake doublet.

On 6 February 2023, two large earthquakes (moment magnitude 7.8 and 7.6) shocked a vast area of southeastern Türkiye and northern Syria, leading to heavy casualties and economic loss. To investigate the rupture process over multiple fault segments, we performed a comprehensive analysis of local seismic and geodetic data and determined supershear ruptures on the initial branch and the Pazarcık and Erkenek segments and subshear ruptures on the Amanos segment of event 1. The bilateral rupture of event 2 also presents distinct sub- and supershear velocities. The dynamic stress of the branch fault rupture triggered the Pazarcık segment initial rupture at a point 9 kilometers west of the junction of these two faults, boosting the supershear rupture of the Pazarcık segment of the main fault. The geometry and prestress level of multiple segments controlled the rupture behaviors and influenced the ground shaking intensity.

Effect of a rotatable water-drop plate on vortex-induced vibration of cylinder

To suppress the Vortex-induced vibration (VIV) response, a cylinder with a rotatable water-drop plate is investigated. The influence of the side curves (concave, linear, convex) of the water-drop plate and angle α (α means the angle between the positive half axis of the X-axis and the straight line where the side of the water-drop plate is located, taking 15°, 30°, 45°, and 60°) on the vibration response are studied by adopting uRANS equations and Newmark-β method. It is shown that the water-drop plate has a certain suppression effect on the VIV of the cylinder in the initial and upper branches. A convex plate with a smaller angle is more effective in suppressing the vibrations of cylinders. When the angle decreases to 30°, the suppression effect of the convex plate on the cylinder no longer increases significantly even if the angle continues to be reduced. In the lower branch and desynchronization, the phenomenon of galloping is clearly observed and the amplitude of the cylinder increases continuously.

Flow-induced vibrations of elastically coupled tandem cylinders

We numerically study the transverse flow-induced vibration (FIV) of elastically coupled tandem cylinders at Reynolds number $100$ , using an in-house immersed boundary method-based solver in two-dimensional coordinates. While several previous studies considered tandem cylinders coupled through flow between them, a hitherto unexplored elastic coupling with fluid flow between them significantly influences FIV. We consider a wide range of gap ratio, reduced velocity, an equal mass ratio of both cylinders and zero damping. A systematic comparison between the classic elastically mounted tandem cylinders and elastically coupled cylinders is presented. The latter configuration exhibits two vibration modes, in-phase and out-of-phase, with corresponding natural frequencies approaching the Strouhal frequency of the system. We quantify variation of the following output variables with reduced velocity and gap ratios: cylinders’ displacement; fluid forces; amplitude spectral density of displacement and force signals; phase characteristics; energy harvesting potential; and discuss the wake characteristics using flow separation, pressure distribution, gap flow quantification, and dynamic mode decomposition characterization. The FIV response is classified into several regimes: initial desynchronization with and without gap vortices; final desynchronization; mixed mode; initial branch; lock-in; upper and lower branch; wake-induced vibration; galloping. We draw upon similarities of computed FIV characteristics with those of an isolated cylinder, in which the lower branch exhibits larger a amplitude than the upper branch. The elastically coupled cylinders show a galloping response similar to an isolated D-section cylinder. By invoking the elastic coupling, we demonstrate FIV suppression and augmentation for in-phase and out-of-phase systems. Our calculations show larger energy harvesting potential at reduced cost for elastically coupled cylinders.

Relationship between wake and cylinder dynamics for a cylinder undergoing modulated vortex-induced vibrations

Vortex-induced vibrations (VIV) in the initial branch are investigated for a 2-degree-of-freedom circular cylinder placed near a plane boundary (Re=UDν=200, where U is the inflow average streamwise velocity, D is the cylinder diameter, and ν is the kinematic viscosity) with imposed sinusoidal perturbations of the free stream at resonant, 2fo, and near-resonant conditions, 2.2fo (fo is the natural shedding frequency). The cylinder exhibits a quasi-periodic response, which challenges the comprehension of its relationship with the wake dynamics obtained through conventional VIV models. The total force acting on the cylinder is decomposed into a vortex-induced force, FV, linearly coupled to VIV, and a force induced by the effective mass of the cylinder, FS, which is non-linearly coupled to VIV. The proposed semi-empirical model reveals that the time-varying nature of the effective mass in FS drives the non-linear response. The model's physical consistency is verified against simulation results. While focusing on VIV in the initial branch, the validity of the proposed model is expected to extend to other branches of response, offering a promising avenue for developing a robust predictive model for VIV under various flow conditions.

Effect of pulsatile flow on hydrodynamic characteristics of vortex induced vibration of square cylinder

Vortex Induced Vibration (VIV) of an elastically mounted square cylinder subjected to pulsatile flow conditions is solved numerically for Reynolds number (Re = 100) and low mass ratio (Mred = 2). The focus of the present work is on investigating the effects of pulsatile frequency on the response of the cylinder. Effects of variation in Keulegan-Carpenter number, KC ϵ [10- 40, step of 10] and reduced velocity, Ured, ϵ [3-25, step of 1], on hydrodynamic characteristics is studied. An Arbitrary-Lagrangian Euler (ALE) formulation is used to write the governing equations in two space dimensions. Maximum cross-flow displacement is observed for Ured = 7 for KC=10. It is found that, the lock-in becomes slightly wider with increase in KC. Different regimes like Initial Branch , Lower Branch and desynchronized have been identified for all KC. Beyond KC = 20, cylinder starts to vibrate with the pulsatile frequency. Moreover, in the Lock-in zone flow amplitude is not always enhanced, and it sometimes gets reduced. This is basically due to state of synchronization between displacement and forcing. For all KCs, in-phase and out-of-phase regimes were also identified for X and Y-direction displacements. Wake width and vortex strength are maximum at the lock-in.

Analysis of Control Technology for Large Deformation of a Geological Bedding Bias Tunnel with Weakly Cemented Surrounding Rock

The Baishitou Tunnel of the Dali–Lincang railway project is a weakly cemented surrounding rock tunnel with geological bedding bias. The deformation of the surrounding rock on the side with the greatest stress is nearly 1 m, which seriously affects construction progress and significantly increases construction cost. In order to achieve the goal of safe, efficient, economic, and socially sustainable development in tunnel construction, it is necessary to study the large deformation of weakly cemented surrounding rock in the geological bedding bias tunnel. Engineering technicians first used field measurement methods to monitor the pressure and deformation of surrounding rock and studied the deformation law of surrounding rock pressure and deformation over time. Secondly, numerical simulation methods were used to study the stress distribution law, plastic failure depth, and initial support stress of tunnel-surrounding rock under different support schemes, and they independently designed a yielding anchor bolt with enhanced anchoring, which plays a key role in controlling the deformation of the surrounding rock. The main conclusions are as follows: (1) Through the analysis of the measured pressure data of the initial branch of the section and the displacement monitoring data of the measuring point, it is found that the deformation of the surrounding rock of the weakly cemented tunnel is large and fast. At the same time, the pressure and deformation of the surrounding rock of the tunnel are greatly affected by geological bedding bias. After the excavation of the inverted arch, the pressure and deformation of the surrounding rock at the right arch shoulder of the tunnel are the highest, reaching 0.832 MPa and 0.53 m, which are significantly greater than those on the left arch shoulder. (2) Using the numerical simulation software FLAC3D 5.0 and ANSYS 16.0, a three-dimensional numerical model of the roadway was established to simulate the stress distribution, plastic failure depth, and initial support stress of the tunnel’s surrounding rock under the influence of geological bedding bias. By comparing the support effects of different support schemes, it was concluded that under the support scheme of “I25 arch + yielding anchor bolt”, the surrounding rock failure depth was small, the stress concentration was weak, and the initial support deformation was controllable as a whole. (3) The self-designed yielding anchor bolt has good economic and applicable value, and it has received the expected support effect after field verification. (4) Various special support measures such as advanced grouting anchor rods, casing arches, or temporary cross supports are used to assist in controlling the large deformation of weakly cemented surrounding rock tunnels to a certain extent.

Effects of superhydrophobicity on VIV control of a circular cylinder

We conducted an experimental study on the vortex-induced vibration (VIV) dynamics of cylinders featuring a specific superhydrophobic band. The superhydrophobic band refers to the pattern where the cylinder's surface is featured with equispaced bands of normal surface and superhydrophobic coating in an alternate manner. The experiments were conducted over a range of reduced velocities from Ur = 3 to 11, corresponding to Reynolds numbers between 1500 and 5900. To capture the near-field wake of the cylinders, a time-resolved particle image velocimetry (TR-PIV) system was employed, while the hydrodynamic forces were acquired using a six-component load cell. We found that the fully coated cylinder consistently displays the smallest amplitude of oscillation in the VIV initial branch, achieving a maximum reduction of approximately 38.9% at Ur = 5.0. Upon applying a superhydrophobic coated band, the patterned cylinder experiences a substantial enhancement in VIV amplitude (about 22.5% at Ur = 5.0) compared to the normal cylinder. On the other hand, in the VIV lower branch, the patterned cylinder effectively suppresses oscillation, whereas the fully coated cylinder exhibits slightly larger oscillation amplitudes than the normal cylinder. This finding agrees well with the trend of lift forces. The analysis of phase-averaged flow structures suggests that this difference can be attributed to the delayed vortex shedding from the superhydrophobic surface and the emergence of three-dimensional vortex structures created by the superhydrophobic band.

Electrical properties of hierarchical nitrogen-doped multi-walled carbon nanotubes obtained using cobalt nanoparticles

In this work, for the first time, both initial and secondary branches of hierarchical nitrogen-doped multi-walled carbon nanotubes (h-N-MWCNTs) were obtained using chemical vapor deposition due to the decomposition of ace-tonitrile over Co-based nanoparticles. The results of a study of the electrical conductivity of h-N-MWCNTs for a wide temperature range of 300−4.2 K are presented. It was shown that fluctuation-assisted tunneling between delocalized states is the dominant conduction mechanism at temperatures above 50 K. An analysis of the temperature and electric field dependences of the resistance indicates that the transfer of electric charges below 50 K occurs due to hoppings between localized states located in the vicinity of the Fermi level. It was shown that the Coulomb interaction affects the charge carrier transport. The width of the Coulomb gap estimated from the temperature dependence of the resistance is 0.5 meV. The electrical conductivity of h-N-MWCNTs in the temperature range of 50−4.2 K occurs by the Efros–Shklovskii variable range hopping conduction mechanism. It was found that the charge localization length is ≈150 nm. Electrical property analysis indicates that the dielectric constant of the h-N-MWCNTs is ≈ 100.

Coupled responses of the flow-induced vibration and flow-induced rotation of a rigid cylinder-plate body

In this study, coupled responses of flow-induced vibration and rotation for an elastically mounted cylinder-plate body are numerically investigated at a low Reynolds number of 120. A wide vibrational reduced velocity range of Uy = 3–18 under four rotational reduced velocities Uθ = 5, 8, 12, and 18 are considered. The non-bifurcation responses, bifurcation only in rotation responses, and bifurcation in both vibration and rotation responses are identified. Typical vortex-induced vibration (VIV) responses are recognized when considering the passive rotations, different from the full interactions between VIV and galloping for the vibration-only case. As Uθ increases, the peak vibration amplitudes increase, the onset Uy of the lock-in region becomes larger, and the lock-in region is wider. The phase angles of displacements versus lift coefficients experience a jump from 0° to 180° in the lock-in region, and the larger the Uθ, the wider the Uy range of phase jump. Whether the instantaneous posture of the cylinder-plate body is streamlined or not is determined by oscillation amplitudes and phase differences between displacements versus rotation angles. Streamlined profiles can be achieved under small oscillation amplitudes or when the phase angles are nearly 90°. The 2S (two isolated vortices) vortex shedding mode dominates the initial and desynchronization branch, while the 2P (two pairs of vortices), 2S* (two isolated vortices with tendency to split), and 2T (two triplets of vortices) modes appear in the lock-in region. After the symmetry-breaking bifurcation, the reattachment behavior becomes simpler and the length of the recirculation region is significantly increased, as compared with those in non-bifurcation region. With the above study, a new method of improving energy harvesting from flow-induced vibration, by incorporating passive rotations simultaneously, is first introduced. It is found that passive rotations can enhance the vibration responses and thus lead to the increased output power and energy transfer ratio, although they make less contributions to the total power. Generally, this mechanical system presents a promising opportunity for energy harvesting through flow-induced vibration.

Vortex-induced vibration of an elastically mounted cylinder subject to planar inflow shear

We have numerically investigated the effect of planar inflow shear on the vortex-induced vibration of a three-dimensional circular cylinder mounted on elastic supports in streamwise and cross-stream directions. At a Reynolds number Re=300, the reduced velocity (U∗) is varied in the range U∗=2−12 for a fixed mass ratio m∗=2. The effect of inflow shear is brought about by varying the shear parameter βy=0,0.05,0.1. We have observed four distinct branches in the structural response curve: Initial Branch (IB), High Amplitude Branch-1 (HAB1), High Amplitude Branch-2 (HAB2), and Desynchronization Branch (DS). The response of the cylinder is locked in with the near wake during IB, HAB1, and HAB2, where the inline oscillation amplitude of the cylinder triggers for increasing βy. The cylinder oscillates with a tilt against the high-velocity side at larger βy for HAB1 and HAB2 responses. During IB response at βy=0, the near wake shows the formation of vortex filaments clustered through the spanwise extent. However, in the HAB1 and HAB2 regimes, the propagation of secondary instability yields random occurrences of vortex splits in the wake. Similar consequences of vortex splits are found at βy=0.1 for IB, HAB1, and HAB2 regimes, where we observe fragmented vortex filaments wrapping around the vortex rings. For βy=0, we have found mode B-type wake instability in the IB response at a plane x=2, where the vortex structures form a staggered array with a spatial periodicity λ≈D. At z=0 plane, the vortex shedding mode is “2S” for the IB response at βy=0.05, while the “P+S” mode is at βy=0.1. The vortex strands experience stretching in the DS branch, where no specific shedding mode is discerned. The cross-stream evolution of time-averaged streamwise velocity shows a data collapse with an asymmetric localization above the cylinder for increasing βy. The streamwise and spanwise velocity fluctuations at βy=0.1 are insignificant compared to the cross-stream. However, for the IB and DS regimes, the growth of the rms velocities reveals spanwise invariance. In contrast, we found small-scale fluctuations of cross-stream velocities about the mean in the HAB1 regime. The temporal growth of the sectional drag coefficients (CDs) along the span shows a negative value in the IB regime for βy=0,0.5. However, we observe the quasiperiodic behavior of CDs along the span for the HAB1 regime at βy=0. The spanwise growth of CDs for the DS regimes shows intermittent transitions via the positive, zero, and negative values for different βy. For both IB and DS regimes at βy=0, the time evolution of sectional lift coefficients (CLs) is asymmetric along the span and represents a helical pattern. However, for increasing βy, the growth of CLs for HAB1 and HAB2 regimes is intermittent. An increase in βy triggers the magnitudes of CLs in the DS branch, where the spanwise evolution shows symmetric periodic bands of sectional lift coefficients.

Algorithms of hysteresis interference

The calculated distribution of the electric voltage U at the output of the magnetic head (MG) scanning the magnetic carrier (MN) along the x coordinate is presented. The coordinates and amplitudes of the first maxima of hysteresis interference (HI) obtained in a pulsed magnetic field were found. Calculations with repeated use of the initial branch of the residual magnetization of the MN when constructing hysteresis interference are proposed. An analysis of the initial and hysteresis branches of signals for MH and other information carriers, signal converters and control systems has been carried out. The use of the obtained results allows to improve the quality of control of the properties of materials and objects.