Search Results (169)

The Absolute Nodal Coordinate Formulation (ANCF) is extensively utilized in the field of flexible multibody dynamics because it offers a constant mass matrix and inherently eliminates Coriolis forces. However, ANCF requires the computation of complex nonlinear elastic internal forces and thermal deformation forces at each time step, which imposes a significant computational burden. To alleviate this burden, researchers have developed local linearization (LL) methods. The local linearization method constructs constant elastic and thermal stiffness matrices within a small range by means of Taylor expansion, effectively reducing the number of stiffness matrix updates. But the method suffers from error accumulation and relies on displacement-based update criteria that are inefficient for systems with large rigid-body motion. This paper proposes an improved local linearization (I-LL) method to address these issues. Two key enhancements are introduced: (1) the update criterion for the elastic and thermal stiffness matrices is modified from displacement-based to total strain-based, enabling more accurate and size-independent updates; (2) accurate elastic or thermal deformation force calculations are inserted within the local linearization iteration cycle to mitigate error accumulation. These two improvements reduce the number of calculations of the nonlinear internal forces and, at the same time, lessen the error accumulation in the simplified model. The accuracy and effectiveness of the I-LL algorithm are demonstrated through three numerical examples. Full article

Accurate prediction of discharge coefficients (C_d) in rotating orifices is essential for the design of aero-engine internal air systems, yet existing correlations usually treat axial and radial orifices separately and do not fully represent intermediate wall inclination angles. In this study, steady-state RANS simulations in a rotating reference frame, supported by validation against published data and by rotating orifice experiments, are used to investigate the combined effects of wall inclination angle α and length-to-diameter ratio L/d on C_d. The numerical results show that, under typical conditions (N = 3000 rpm, Π = 1.03, L/d = 1.5), C_d increases from 0.301 to 0.340 as α increases from π/2 to π, corresponding to a 12.96% increase. Under low rotational speeds and high pressure ratios, the Coriolis force reduces the relative tangential velocity and the incidence angle, thereby increasing C_d with α; however, at high rotational speeds and low pressure ratios, the centrifugal resistance to radial inflow becomes dominant, and at N = 7000 rpm, the C_d for the α = π orifice is 38.96% lower than that for the α = π/2 orifice. Increasing L/d promotes flow redevelopment and amplifies the Coriolis-force effect, leading to a larger C_d increase for orifices with larger α. Based on these mechanisms, a generalized incidence-angle formulation incorporating Coriolis and centrifugal effects is developed, and a C_d prediction model applicable to π/2 ≤ α ≤ π and different L/d values is proposed. Experimental validation shows that the maximum prediction error is reduced to 2.37%, demonstrating the accuracy of the proposed model for rotating inclined orifices. Full article

To improve the operational stability and mass transfer performance of fluidized bed reactors under dynamic conditions, this study examines radial particle velocity distributions at different bed cross-sections using a dual-probe measurement method across a range of rocking frequencies and superficial gas velocities. The analysis identifies the dominant influence of additional inertial forces generated by rocking motion, including the Euler force and Coriolis force, in determining the time-averaged flow structure, leading to the development of a spatiotemporally averaged flow field model and clarification of the interaction mechanisms between these forces. Results indicate that the flow field exhibits two representative macroscopic patterns governed by the interplay between inertial forcing and particle response characteristics: at low frequencies, the slowly varying Euler force combines with gravity to produce a coherent large-scale single-circulation structure, whose stability is sustained under higher gas velocities due to reduced internal energy dissipation associated with stronger drag; at high frequencies, the Coriolis force promotes structural division while the rapidly oscillating Euler force introduces disturbances, resulting in the formation and persistence of double or multi-circulation flow structures under their combined action. Full article

Accurate forecasting of agricultural product prices is crucial for informed decision-making in agricultural markets; however, such time series are inherently characterized by non-stationarity, multi-scale dynamics, and substantial noise, posing significant challenges to conventional methods. To overcome these limitations, this study proposes a novel hybrid framework, termed TOC-CNN-BiLSTM-SA, built upon a “quadratic decomposition–clustering–optimization” paradigm. Specifically, a composite CEEMDAN–K-means++–VMD approach is first employed to hierarchically decompose the raw price series via coarse decomposition, feature clustering, and refined decomposition, enabling effective noise suppression and multi-scale feature extraction. Subsequently, a deep learning architecture integrating Convolutional Neural Networks (CNNs), Bidirectional Long Short-Term Memory networks (BiLSTM), and a self-attention mechanism is developed, where CNN captures local patterns, BiLSTM models bidirectional temporal dependencies, and the attention mechanism enhances global feature representation. Furthermore, the Tornado Optimizer with Coriolis force (TOC) is introduced to adaptively tune key hyperparameters, thereby improving model robustness and generalization capability. Empirical results based on wheat price data from Henan Province, China, demonstrate that the proposed model achieves outstanding predictive performance, with RMSE, MAE, MAPE, and R² values of 4.425, 3.9372, 0.16%, and 99.97%, respectively, significantly outperforming existing benchmark models. These research indicate that the proposed framework effectively captures complex price dynamics and offers a reliable and practical solution for agricultural price forecasting. Full article

General relativity is often perceived by undergraduate and advanced high-school students as conceptually and mathematically inaccessible. This paper does not provide new results in gravitation but rather introduces a lucid pedagogical framework for understanding gravitomagnetic effects in rotating systems. Starting from the Langevin metric, which describes flat spacetime in a uniformly rotating reference frame, the paper considers an apparent paradox: two clocks moving with identical velocities in an inertial frame but located at different radii on a rotating platform. While the equality of proper time of the clocks is expected in the inertial frame, its reconstruction in the rotating frame is not immediately transparent. It is shown here that this equality emerges from an exact compensation between three distinct contributions: a centrifugal potential term, a kinematic time dilation term, and a velocity-dependent term being formally analogous to a gravitomagnetic potential. The explicit identification and interpretation of these contributions constitute the pedagogical significance of this paper. Although the consideration presented is performed in flat spacetime, the formal analogy with gravitomagnetic effects provides students with an accessible pathway to more advanced concepts such as frame-dragging and the Sagnac effect, while highlighting the importance of velocity-dependent interactions in relativistic physics. Full article

Carbon capture, utilization, and storage (CCUS) plays an important role in meeting the European Union’s target to reduce greenhouse gas emissions by 55% by 2030 and become carbon neutral by 2050. Accurate flow metering is required throughout the carbon capture and storage (CCS) chain to meet fiscal and regulatory requirements. To establish accurate CO₂ flow metering, flow meters must be calibrated with traceability to international standards of measurement at relevant flow conditions. To ensure confidence, reliability, and comparability of calibration results, calibration facilities perform interlaboratory comparisons. However, there is currently a lack of CO₂ gas flow meter calibration facilities. The flow metering calibration facilities of VSL, NEL, INRIM, DNV, and FORCE participated in an interlaboratory comparison with CO₂ up to 400 m³/h and 31 bar(a) to compare the calibration results with several flow metering principles. At the intermediate-scale facilities of NEL, VSL, and INRIM, the difference in results between the VSL and INRIM facilities were within the facilities’ CMC values, while NEL’s facility showed a significant difference primarily due to vibrational relaxational effects of CO₂ with small critical flow Venturi nozzles. At the large-scale facilities of NEL, DNV, and FORCE, 91% of the test points passed the equivalency criteria in the range of 20 m³/h to 400 m³/h with a Coriolis meter, confirming traceability for carbon dioxide across the facilities. Overall, the interlaboratory comparison has made it possible for the CCUS industry to calibrate gaseous CO₂ flow meters with traceability to international standards. Full article

To address the challenges of difficult feature extraction for rolling bearing vibration signals, low efficiency in optimizing diagnostic model parameters, and the tendency to get trapped in local optima, this paper proposes an improved ICEEMDAN feature extraction method based on Bayesian optimization and adaptive noise signal ratio enhancement (BAYES-ICEEMDAN-SNR) and combines it with the improved Coriolis force optimization algorithm (ITOC) to optimize the least squares support vector machine (LSSVM) fault diagnosis model. Firstly, Bayesian optimization is used to adaptively determine the noise parameters and introduce a dynamic signal-to-noise ratio adjustment mechanism to enhance the robustness of feature extraction; secondly, Chebyshev chaotic mapping, Cauchy mutation, and dynamic reverse learning strategies are applied to enhance the global search and local escape capabilities of ITOC, thereby optimizing the hyperparameters of LSSVM; and finally, the Keesey-Chestnut University bearing dataset and Huazhong University of Science and Technology gear dataset are used for verification. The experimental results show that the average fault identification accuracy of the proposed method reaches over 97%, which is superior to that of the comparison models, and the effectiveness of each core improvement module of the proposed model is verified through ablation experiments, providing an effective solution for intelligent fault diagnosis of rolling bearings and gears. Full article

The residual current is the ocean current after the tidal component has been removed. Understanding the spatiotemporal distribution characteristics of sea surface residual currents is key to revealing the local current field evolution and typical physical oceanographic processes. The Taiwan Strait is in the East Asian monsoon region, where residual currents are significantly influenced by monsoons during periods of high wind speeds. However, the characteristics and dynamic mechanisms of residual currents under low wind speed conditions (≤5 m/s) remain unclear. Based on high-frequency surface wave radar current data and wind field reanalysis data, this study analyzed the characteristics of residual currents in the southwestern Taiwan Strait under low wind speed conditions, focusing on two orthogonal directions: cross-shore and along-shore. During these periods, residual currents exhibit counter-wind current characteristics. These currents cross the Taiwan Bank and generate wave signals with wavelengths ranging from 35.6 km to 65.8 km and durations of 6 to 12 h in the Xiapeng Depression area. These fluctuations are triggered by the combined timing of low winds and nonlinear current–topography interactions. In terms of dynamic mechanisms, the Coriolis force term and the acceleration term dominate the momentum equations in both two orthogonal directions, indicating that the current field is in a non-steady inertial adjustment phase during this period. Furthermore, this study constructs a two-layer ocean model of rotationally modified gravity waves to analyze the influences of topography, oceanic stratification, and steady current velocity on the characteristics of residual current fluctuations under low wind speed conditions. The theoretical model yields spatial scales that closely match the observed wavelength characteristics. Full article

Baroclinic wave resonance, particularly Rossby waves, has attracted great interest in ocean and atmospheric physics since the 1970s. Research on Rossby wave resonance covers a wide variety of phenomena that can be unified when focusing on quasi-stationary Rossby waves traveling at the interface of two stratified fluids. This assumes a clear differentiation of the pycnocline, where the density varies strongly vertically. In the atmosphere, such stationary Rossby waves are observable at the tropopause, at the interface between the polar jet and the ascending air column at the meeting of the polar and Ferrel cell circulation, or between the subtropical jet and the descending air column at the meeting of the Ferrel and Hadley cell circulation. The movement of these air columns varies according to the declination of the sun. In oceans, quasi-stationary Rossby waves are observable in the tropics, at mid-latitudes, and around the subtropical gyres (i.e., the gyral Rossby waves GRWs) due to the buoyant properties of warm waters originating from tropical oceans, transported to high latitudes by western boundary currents. The thermocline oscillation results from solar irradiance variations induced by the sun’s declination, as well as solar and orbital cycles. It is governed by the forced, linear, inviscid shallow water equations on the β-plane (or β-cone for GRWs), namely the momentum, continuity, and potential vorticity equations. The coupling of multi-frequency wave systems occurs in exchange zones. The quasi-stationary Rossby waves and the associated zonal/polar and meridional/radial geostrophic currents modify the geostrophy of the basin. Here, it is shown that the ubiquity of resonant forcing in (sub)harmonic modes of Rossby waves in stratified media results from two properties: (1) the natural period of Rossby wave systems tunes to the forcing period, (2) the restoring forces between the different multi-frequency Rossby waves assimilated to inertial Caldirola–Kanai (CK) oscillators are all the stronger when the imbalance between the Coriolis force and the horizontal pressure gradients in the exchange zones is significant. According to the CK equations, this resonance mode ensures the sustainability of the wave systems despite the variability of the forcing periods. The resonant forcing of quasi-stationary Rossby waves is at the origin of climate variations, as well-known as El Niño, glacial–interglacial cycles or extreme events generated by cold drops or, conversely, heat waves. This approach attempts to provide some new avenues for addressing climate and weather issues. Full article

This paper presents a mathematical model that describes the propagation of internal inertia–gravity waves in a stratified atmosphere under the approximations of an incompressible fluid and a traditional β-plane. It demonstrates that, in the incompressible fluid approximation, the temperature field is inconsistent with the heat conduction equation. The system of equations that describes internal inertia–gravity waves is considered in the general case, taking into account the buoyancy force, and reduced to a single equation. The solution is sought in the form of traveling plane waves. A dispersion relation has been obtained in the form of a cubic equation that represents a hypersurface in wave number space, without the assumption of small vertical wavelength. Cross-sections of this surface are plotted, and an extremum study is performed. This shows that a new frequency region appears in the low-frequency spectrum $0<\omega <f_{0z}$ that was not present in the f-plane approximation. Here, $f_{0z}=2{\omega }_0\cdot \sin \phi$ is the Coriolis parameter, and $\phi$ is the latitude. Furthermore, these waves only propagate in the negative direction of the x-axis, i.e., in the opposite direction of the Earth’s rotation. It is also shown that there is a region with a minimum frequency in the “high-frequency” spectrum determined by buoyancy $\omega <f_{0z}$, and that waves propagate in the negative direction as well. Thus, the dispersion surface is shown to have two extremum points. The first is a minimum in the “high-frequency” spectrum ${\omega }_1\approx 0.826f_{0z}$ and the second is a maximum in the “low-frequency” spectrum ${\omega }_2\approx 0.564f_{0z}$. Full article

This study experimentally investigates single-phase forced convection heat transfer and flow characteristics of Al₂O₃-water nanofluids under rotating hypergravity conditions ranging from 1 g to 5.1 g. While nanofluids offer enhanced thermal properties for advanced cooling applications in aerospace and rotating machinery, their performance under hypergravity remains poorly understood. Experiments employed a custom centrifugal test rig with a horizontal test section (D = 2 mm, L = 200 mm) operating at constant heat flux. Alumina nanoparticles (20–30 nm) were dispersed in deionized water at mass fractions of 0.02–0.5 wt%, with stability validated through transmittance measurements over 72 h. Heat transfer coefficients (HTC), Nusselt numbers (Nu), friction factors (f), and pressure drops were measured across Reynolds numbers from 500 to 30,000. Results demonstrate that hypergravity significantly enhances heat transfer, with HTC increasing by up to 40% at 5.1 g compared to 1 g, most pronounced at the transition from 1 g to 1.41 g. This enhancement is attributed to intensified buoyancy-driven secondary flows quantified by increased Grashof numbers and modified particle distribution. Friction factors increased moderately (15–25%) due to Coriolis effects and enhanced viscous dissipation. Optimal performance occurred at 0.5 wt% concentration, effectively balancing thermal enhancement against pumping penalties. Random forest (RF) and eXtreme gradient boosting (XGBoost) achieved R² = 0.9486 and 0.9625 in predicting HTC, respectively, outperforming traditional correlations (Gnielinski: R² = 0.9124). These findings provide crucial design guidelines for thermal management systems in hypergravity environments, particularly for aerospace propulsion and centrifugal heat exchangers, where gravitational variations significantly impact cooling performance. Full article

As typical examples of rotational rate sensors, microelectromechanical system (MEMS) gyroscopes have been widely applied as inertial devices in various fields, including national defense, aerospace, healthcare, etc. This review systematically summarizes research advancements in MEMS gyroscope structural forms and processing technologies, which are evaluated through performance indices. The review encompasses several areas. First, it outlines the modelling principles and processes of gyroscopes on the basis of the Coriolis force and resonance, establishing a theoretical foundation for MEMS gyroscope development. Second, it introduces and analyzes the latest research advances in MEMS gyroscope structures and corresponding processing technologies. On the basis of published research advances, this review categorically discusses multidisciplinary technology properties, statistical results, the existence of errors, and compensation methods. Additionally, it identifies challenges in MEMS gyroscope technologies through classification analysis. Full article

Understanding sediment transport timescales is essential for predicting morphological evolution, pollutant accumulation, and ecosystem health in estuaries. This study examines seasonal hydrodynamics and sediment transport in the Pearl River Estuary using a well-calibrated numerical model. The results indicate that plume dynamics largely control sediment transport in both the wet and dry seasons. During the wet season, sediments are exported along both estuary flanks with the expanding freshwater plume. Under the combined effects of topography and the Coriolis force, a greater proportion of sediments exits via the confluence of the West Channel and West Shoal. In the dry season, prevailing northeasterly winds suppress sediment export along the East Channel, redirecting most of the riverine sediment westward. Sediment transport timescales, quantified by sediment age, further show that, during the wet season, export via the East Channel requires approximately 30 days, whereas export along the western flank takes about 45 days due to the weaker dynamics over the West Shoal. Reduced river discharge in the dry season increases sediment age overall; offshore delivery within the plume region takes roughly 50 days, while transport via the East Channel may require an additional 30–60 days. Comparative simulations with and without wind forcing reveal that southerly winds during the wet season weaken plume intensity and prolong transport timescales, whereas northeasterly winds in the dry season enhance plume dynamics, accelerating sediment export from the estuary. Collectively, these findings clarify the mechanisms underlying the seasonal variability in sediment transport and provide a scientific basis for estuarine management and engineering. Full article

This study explores the dynamic behavior of a vertical pipe conveying gas-liquid two-phase flow with rotationally restrained boundaries, employing the generalized integral transform technique (GITT). The rotationally restrained boundary conditions are more realistic for practical engineering applications in comparison to the classical simply-supported and clamped boundary conditions, which can be viewed as limiting scenarios of the rotationally restrained boundary conditions when rotational stiffness approaches zero and infinity, respectively. Utilizing the small-deflection Euler-Bernoulli beam theory, the governing equation of motion for the deflection of the pipe is transformed into an infinite set of coupled ordinary differential equations, which is then numerically solved following truncation at a finite order $NW$. The proposed integral transform solution was initially validated against extant literature results. Numerical findings demonstrate that as the gas volume fraction increases, there is a reduction in both the first-order critical flow velocity and the vibration frequency of the pipe conveying two-phase flow. Conversely, as the rotational stiffness factor enhances, both the first-order critical velocity and vibration frequency increase, resulting in improved stability of the pipe. The impact of the bottom-end rotational stiffness factor $r_2$ on the dynamic stability of the pipe is more pronounced compared to the top-end rotational factor $r_1$. The variation in two-phase flow parameters is closely associated with the damping and stiffness matrices. Modifying the gas volume fraction in the two-phase flow alters the distribution of centrifugal and Coriolis forces within the pipeline system, thereby affecting the pipeline’s natural frequency. The results illustrate that an increase in the gas volume fraction leads to a decrease in both the pipeline’s critical velocity and vibration frequency, culminating in reduced stability. The findings suggest that both the gas volume fraction and boundary rotational stiffness exert a significant influence on the dynamic behavior and stability of the pipe conveying gas-liquid two-phase flow. Full article

The mechanisms by which rotation influences zonal flows (ZFs) in plasma are incompletely understood, presenting a significant challenge in the study of plasma dynamics. This research addresses this gap by investigating the role of non-inertial effects—specifically centrifugal and Coriolis forces—on Geodesic Acoustic Modes (GAMs) and ZFs in rotating tokamak plasmas. While previous studies have linked centrifugal convection to plasma toroidal rotation, they often overlook the Coriolis effects or inconsistently incorporate non-inertial terms into magneto-hydrodynamic (MHD) equations. In this work, we derive self-consistent drift-ordered two-fluid equations from the collisional Vlasov equation in a non-inertial frame, and we modify the Hermes cold ion code to simulate the impact of rotation on GAMs and ZFs. Our simulations reveal that toroidal rotation enhances ZF amplitude and GAM frequency, with Coriolis convection playing a critical role in GAM propagation and the global structure of ZFs. Analysis of simulation outcomes indicates that centrifugal drift drives parallel velocity growth, while Coriolis drift facilitates radial propagation of GAMs. This work may provide valuable insights into momentum transport and flow shear dynamics in tokamaks, with implications for turbulence suppression and confinement optimization. Full article