Dimensional Dynamic Model Research Articles

Lump Kink interactional and breather-type waves solutions of (3+1)-dimensional shallow water wave dynamical model and its stability with applications

The shallow water equations are used to describe the behavior of water waves in various shallow regions such as coastal areas, lakes, rivers, etc. These equations are derived by making simplifying assumptions about the water depth relative to the wavelength of the waves. In this paper, the generalized exponential rational function method (gERFM) is used to construct novel wave solutions of the (3+1)-dimensional shallow water wave ((3+1)-dSWW) dynamical model. These solutions encompass distinct kinds of waves, such as solitary waves, solitons, Kink and anti-kink solitons, lump Kink interactional waves, traveling breathers-type waves and multi-peak solitons. The dynamical behavior of these wave solutions is discussed, examining the influence of free parameters on the resulting wave shapes. Furthermore, to provide a scientific elucidation of the obtained results, the solutions are presented graphically, making it easy to distinguish the dynamical features, which have practical implications in different areas of applied sciences and engineering. The stability of this dynamical model is revealed via modulational instability analysis, signifying that all analytical results are stable. The obtained results show that the given technique is universal and efficient. Through comparing the projected technique with the existing techniques, the obtained results demonstrate that the given technique is universal, pithy and efficient.

A Model for Predicting Physical Health of College Students Based on Semantic Web and Deep Learning Under Cloud Edge Collaborative Architecture

A model for predicting physical health of college students based on semantic web and deep learning under cloud edge collaborative architecture is proposed to address the issue of most physical health prediction models being unable to fully describe the characteristics of sports performance changes and having large prediction errors. Firstly, the authors design a measurement data analysis system based on cloud edge collaboration architecture to improve data analysis efficiency. Then, they preprocess the data on the edge side, such as missing samples, and extract data features using an equal dimensional dynamic GOM model. Finally, they deploy the RBFNN-SSA model in the cloud center, input the characteristics of each indicator into the model for predictive analysis, and obtain the physical health status of college students. Based on the physical health test data of Hohai University from 2018 to 2021, an experimental analysis was conducted. The results showed that all three intervention measures had significant effects on maintaining and improving the physical health level of college students.

Volume and function changes of left atrium and left ventricle in patients with ejection fraction preserved heart failure measured by a three dimensional dynamic heart model.

The accurate diagnosis of HFpEF is still challenging and controversial. In this study, we used 3D-DHM technology to compare the differences of cardiac structure and function between HFpEF patients and healthy controls, as well as the differences of two-dimensional and three-dimensional cardiac function in HFpEF patients. Echocardiography with 3D-DHM and conventional two-dimensional (2D) methods were applied to measure the volume and function parameters of left atrium and ventricle of patients with HFpEF and healthy controls. Significant differences of 3D cardiac function indexes including LVESV, 3D-LVEF, ESL, SV, CI, EDmass, LAVmax, LAVmin, LAEF, and LAVI were observed between patients with HFpEF and controls (P < 0.05). However, no significant difference of LVEDV and EDL were observed (P > 0.05). In addition, we found no significant between-group difference in 2D cardiac function indexes such as LVDD and 2D-LVEF (P > 0.05), but the LAD, LVSD, LVPW, IVS, E, E/A, and E/e ' were significantly different between groups (P < 0.05). There was no significant difference between 3D-LVEF and 2D-LVEF in the control group (P > 0.05), while 3D-LVEF in the HFpEF group was lower than 2D-LVEF(P < 0.05). Among the two-dimensional and three-dimensional parameters of HFpEF patients, the parameters related to diastolic function changed more significantly than those of the normal group, and the three-dimensional LVEF of HFpEF patients decreased. The three-dimensional cardiac function parameters analyzed by DHM can provide more information regarding myocardial mechanics.

The dynamical study and analysis of diverse bright-dark and breathers wave solutions of nonlinear evolution equations and their applications

In this work, we establish novel solitary wave solutions of three nonlinear evolution dynamical models, namely, Boussinesq model, [Formula: see text]-dimensional generalized shallow water wave (SWW) and [Formula: see text]-dimensional Fokas dynamical models by applying two-variable [Formula: see text]- expansion technique. The SWW equations are usually appropriate when the fluid is in a state where the vertical length scale is significantly smaller than the length of horizontal scale. In computer simulations for ocean engineering, Boussinesq-type models are frequently used to represent water waves in harbors and shallow seas. In order to understand the physical processes of waves inside and on the surface of water, the Fokas dynamical model plays a crucial part in wave theory. Analytical solutions in different forms such as solitons, solitary waves, trigonometric, hyperbolic, rational function solutions, breathers-type waves and more wave solutions are devised through using the proposed method. The exact solutions are also presented in graphical form having applications in engineering and other areas of applied sciences. The obtained results show that the given technique is universal and efficient. In addition, this technique can also be applied on lots of other nonlinear dynamical wave models occurring in many scientific real-world application domains, including engineering sciences, mathematics physics, and many more.

Multi-objective optimization of thermodynamic and dynamic performance of free-piston Vuilleumier heat pump using NSGA-II

Free-piston Vuilleumier heat pump (FVHP) is a heat pump driven by thermal energy such as the combustion of natural gas. Thus, it is a more energy-efficient way for heating than boilers. In this work, one dimensional computational fluid dynamic model is developed for FVHP with dwell motion. Structural design parameters of FVHP are optimized for higher COPtotal based on the coupling of developed model and NSGA-II (Non-dominated Sorting Genetic Algorithm-II) under the condition of given heating capacity. 8 structural parameters are optimized for dynamic performance. The results show that free stroke is improved by 78% and COPtotal is improved by 2.61%. Then, based on the obtained optimal 8 structural parameters, 9 structural parameters for thermodynamic performance are further optimized. The results show COPh is increased by 3.04% while the heating output power is only reduced by 3.15%

Robust control of rubber–tyred gantry cranes with structural elasticity

A gantry crane holds strict underactuation and elastic multibody structure, and thus faces challenges in control system design. For model–based control, we develop a three–dimensional dynamic model of rubber–tyred gantry cranes considering the distributed mass and bending deformation of gantry. Such modelling hybridises the lumped model of trolley–bridge–payload motions and continuous model of gantry vibration. We consider a complex operation in which three motors composed of travelling trolley, pushing bridge and hoisting container run simultaneously. We propose two versions of the robust controller, namely, dynamic sliding mode and fast terminal sliding mode for tracking the three motions, eliminating swings of container, and reducing the bending vibration of elastic gantry. Simulation and experiment reveal precision and effective application of our crane modelling to control approaches. The control system effectively tracks and stabilises all outputs and achieves robustness when a crane suffers from the structural and parametric uncertainties.

Flow synthesis of poly(acrylamide-co-acrylic acid) microspheres in a microreactor: Experimental and CFD studies

A microfluidic platform to synthesize monodispersed and spherical hydrogel beads (microspheres) of poly(acrylamide-co-acrylic acid) (p(AM-co-AA)) is reported. An aqueous phase consisting of monomer, cross-linker, functional moiety and initiator, all dissolved in water, is dispersed as uniform drops of desired size into a carrier phase (dodecane) at an opposed T-junction. The chemical and physical properties of the microspheres are systematically studied. Effects of operating parameters like velocity and O/A (oil to aqueous phase flow ratio) ratio on the average size, polydispersity and shape of microspheres are investigated. Microspheres within a size range of 960 to 502 microns can be synthesized. A comparison of two different mixing techniques namely in-situ and ex-situ mixing is also presented. A two dimensional computational fluid dynamic (2 D CFD) model is also developed to quantify and validate drop formation phenomena at the T junction at extreme O/A ratios. Detailed numerical insights on the velocity and pressure field at the junction have been provided.

Recurrent neural networks enable design of multifunctional synthetic human gut microbiome dynamics.

Predicting the dynamics and functions of microbiomes constructed from the bottom-up is a key challenge in exploiting them to our benefit. Current models based on ecological theory fail to capture complex community behaviors due to higher order interactions, do not scale well with increasing complexity and in considering multiple functions. We develop and apply a long short-term memory (LSTM) framework to advance our understanding of community assembly and health-relevant metabolite production using a synthetic human gut community. A mainstay of recurrent neural networks, the LSTM learns a high dimensional data-driven non-linear dynamical system model. We show that the LSTM model can outperform the widely used generalized Lotka-Volterra model based on ecological theory. We build methods to decipher microbe-microbe and microbe-metabolite interactions from an otherwise black-box model. These methods highlight that Actinobacteria, Firmicutes and Proteobacteria are significant drivers of metabolite production whereas Bacteroides shape community dynamics. We use the LSTM model to navigate a large multidimensional functional landscape to design communities with unique health-relevant metabolite profiles and temporal behaviors. In sum, the accuracy of the LSTM model can be exploited for experimental planning and to guide the design of synthetic microbiomes with target dynamic functions.

Multiphysics modeling of thermal behavior, melt pool geometry, and surface topology during laser additive manufacturing

Metal additive manufacturing (AM) processes regularly experience high temperatures, quick velocities and rapid solidification taking place in a small volume melt pool. Accurate capturing of data from the melt pools is very difficult and can require expensive equipment. Physics based numerical models can be used to simulate the AM process. However, there are many thermal and fluid dynamics models that have been developed each with their own sets of physical models and assumptions. In this work, a three dimensional multiphysics computational fluid dynamics model was used to obtain thermal behavior, geometry and surface topology from the melt pool of single laser scan tracks on a bare Inconel 625 substrate. The simulation results were compared with the highly controlled AMB2018-02 series of benchmark tests performed by the National Institute of Standards and Technology (NIST). The complex physics involved in the simulations, including heat and mass transfer, fluid flow, evaporation, and Marangoni convection enabled accurate prediction of the melt pool geometry, thermal behavior and the surface topology. The simulation results for the thermal behavior were mostly within the standard deviation of the experimental results. Simulation results from surface topography were able to capture the peak and valley trends. Overall, the underlying physics involved produced good results in a reasonable amount of time and were accurate enough to form a basis that can be coupled with other models to predict microstructure and other material properties.

Adaptive fuzzy backstepping control of flexible marine riser with uncertain parameters and input saturation constraint

To suppress the vibration of a flexible riser system with input saturation and uncertain parameters under the influence of unknown external disturbances, an adaptive fuzzy backstepping boundary control algorithm was designed. First, the backstepping method and Lyapunov function are used to analyze the subsystem and design the virtual control law. On this basis, the adaptive fuzzy system was designed to approximate the unknown nonlinear term in the design process, and the smooth hyperbolic tangent function and the auxiliary system based on Nussbaum function were introduced to limit control input. The stability and uniform boundedness of the closed-loop control system are proved by the Lyapunov stability theory without simplifying or discretizing the infinite dimensional dynamic model. Finally, the effectiveness of the proposed control algorithm is verified by comparing the control effect with proportional–integral–derivative control and the previous adaptive backstepping control by MATLAB simulation. The simulation results show that the proposed control algorithm can overcome the uncertainty of system parameters and effectively suppress the riser vibration under input constraints, and its control effect is better than proportional–integral–derivative control and adaptive backstepping control.

Natural characteristic and vibration analysis of nonlinear articulated multi-beam ring structure for modeling ring truss antenna under base excitation

The investigation of natural characteristic and dynamic response of the ring truss antenna is essential for its design and vibration control since its high flexibility and nonlinearity. This paper investigates the dynamic properties of the articulated multi-beam ring structure for modeling the ring truss antenna under base excitation. The mathematical model of the multi-beam ring structure is established based on the global mode method. The matching conditions of force and displacement at connected points and boundary conditions of the ring structure are obtained. The global mode method and separation of variables method are applied to derive the analytical characteristic equation. Then natural frequency and global mode of the system are obtained. The orthogonality of global modes is proved. Based on the Galerkin procedure, the global modes which are explicitly functions are truncated to be substituted into the nonlinear partial differential equations of the system to yield the low dimensional discrete dynamic model with high accuracy described by ODEs which is useful for designing active vibration controllers. Afterwards the validity of the dynamic model is verified by comparing natural frequencies and mode shapes with those obtained by FEM. Finally, the effects of system parameters including external excitation, linear stiffness, third-order nonlinear stiffness, damping and friction torque on natural characteristic and dynamic response for the first resonance are analyzed. The results show that parameters of the structure have a significant effect on the whole system. The dynamic analysis in the paper is meaningful for design and vibration control of the antenna for the future study.

Generalized Multiphase Dynamic Modeling and Precision Interaction Force Control of a Walking Lower Limb Hydraulic Exoskeleton.

Wearable lower limb hydraulic exoskeletons can be used to augment the human performance in heavy load transportation. Nonlinear and walking phase-dependent dynamics make the lower limb hydraulic exoskeleton become difficult to be modeled. This paper presents a generalized multiphase dynamic modeling method in which the dynamic model of each walking phase can all be solved based on a general higher dimensional dynamic model and different holonomic constraints. Compared to traditional lower limb exoskeleton modeling methods where the modeling of each walking phase is done independently, the proposed method is simple and applicable to arbitrary walking phases, especially for double leg support phase (closed-chain dynamics). Based on the established dynamic models, MIMO adaptive robust cascade force controllers (ARCFC) are designed both for double leg support phase and single leg support phase to effectively address high-order nonlinearities and various modeling uncertainties in hydraulic exoskeletons. An additional torque allocation method is proposed to deal with the overactuated characteristic in double leg support. Comparative simulations are conducted to verify the excellent human-machine interaction force control performance of the proposed scheme.

Numerical estimation of critical local energy dissipation rate for particle detachment from a bubble-particle aggregate captured within a confined vortex

In flotation, interactions of bubble-particle aggregates with turbulent flow structures in the liquid medium result in particle detachment. This study aims to simulate this phenomenon involving a bubble-particle aggregate (bubble diameter ∼ 3 mm and particle diameter ∼ 314 µm) interacting with a turbulent flow structure manifested as a confined vortex in a square cavity connected to a square cross-section channel. An interface resolved three dimensional (3D) computational fluid dynamics (CFD) model was developed to quantify the bubble-vortex interaction dynamics over a range of channel Reynolds numbers. The CFD model produced a good agreement with the experimentally measured vorticity magnitude, local energy dissipation rate, and bubble motion. It was shown that a bubble-particle aggregate could be captured within the vortex by suitably varying the channel Reynolds number, eventually leading to particle detachment. A separate force balance analysis was performed to determine a criterion for particle detachment utilising the CFD model predicted vorticity and local energy dissipation rate. It was shown that a critical local energy dissipation rate ∼ 1.59 m2/s3 was required for particle detachment to occur, which was also verified experimentally.

Abundant solitary wave structures of the higher dimensional Sakovich dynamical model

In this study, the abundant families of multiwave structures are constructed for (2 + 1)‐dimensional Sakovich model. The single and combined wave structures are observed in shock, complex solitary‐shock, shock‐singular, and periodic‐singular forms. The rational solutions are also emerged during the derivation. The new modified extended direct algebraic (NMEDA) technique and mathematica software are used to obtained the solutions. The obtained results are very useful to study and verify the analytical solutions with numerical and experimental work in nonlinear dynamics. Moreover, the graphics of obtained solutions for the different values of parameters are drawn in three and two dimensions along with their contour diagrams.

Development of dynamic motion models of SPACE code for ocean nuclear reactor analysis

Lately, ocean nuclear power plants have attracted attention as one of diverse uses of nuclear power plants. Because ocean nuclear power plants are movable or transportable, it is necessary to analyze the thermal hydraulics in a moving frame of reference, and computer codes have been developed to predict thermal hydraulics in large moving systems. The purpose of this study is to incorporate a three dimensional dynamic motion model into the SPACE code (Safety and Performance Analysis CodE) so that the code is able to analyze thermal hydraulics in an ocean nuclear power plant. A rotation system that describes three-dimensional rotations about an arbitrary axis was implemented, and modifications were made to the one-dimensional momentum equations to reflect the rectilinear and rotational acceleration effects. To demonstrate the code's ability to solve a problem utilizing a rotational frame of reference, code calculations were conducted on various conceptual problems in the two-dimensional and three-dimensional pipeline loops. In particular, the code results for the three-dimensional pipeline loop with a tilted rotation axis agreed well with the multi-dimensional CFD results.

Spread of virus laden aerosols inside a moving sports utility vehicle with open windows: A numerical study.

A three dimensional Computational Fluid Dynamics (CFD) model to study the dispersion of virus laden aerosols in a car moving with its windows open is reported. The aerosols are generated when a possibly infected passenger speaks. A sports utility vehicle having three rows of seats has been considered. As the vehicle moves forward, its interior will exchange air from the surroundings. The CFD model captures the flow patterns generated both outside and inside the vehicle. This internal aerodynamics will in turn dictate how aerosols will spread across the interior and whether or not they will be transported outside the vehicle. A Lagrangian approach is used to determine the transport of the aerosol particles and the effect of particle size on the simulation result has been studied. Four sets of scenarios of practical interest have been considered. The first set shows the effect of vehicle speed on aerosol transport, and the second set describes what happens when some of the windows are closed, while the third set describes how aerosol transport is affected by the location of the passenger speaking. The fourth set describes how a gush of cross wind affects aerosol transport. Simulation results reveal that when all windows are open, aerosols can go out of one window and then return back to the vehicle interior through another window. Results also reveal that when a passenger sitting in the second row speaks, the aerosols generated span across the entire volume of the car interior before going out through the open windows.

A novel Acoustic Fluid Level Estimation Method Based on Evidence Fusion Mechanism

In order to reduce the missed detection error and the systematic error caused by acoustic resonance fluid level detection, liquid level estimation method based on evidence fusion mechanism is designed. It establishes a two dimensional dynamic system model of the standingwavelength. The state evidence of wavelength is obtained through the random set description of evidence, and the extension principle of random set is used to get the observation evidence ofwavelength. The evidential reasoning (ER) rule and dependent evidence fusion are used to fuse those evidence, and the estimation value of fluid level can be calculated from fused result based on pignistic expectation. The corresponding liquid level estimation experiment illustrates the validity and feasibilityof the proposed method.

A new three dimensional dissipative Boussinesq equation for Rossby waves and its multiple soliton solutions

A new three dimensional nonlinear dynamic theoretical model is derived from fluid mechanics system. In this paper, From the quasi-geostrophic barotropic potential vorticity equation, we obtain a three dimensional dissipative Boussinesq equation by the reduced perturbation method, i.e.utt+e1uxx+e2(u2)xx+e3utxy+e4uxxxx+e5uxxyy=0. It is emphasized that the new equation is different from the existing Boussinesq equations, which describe the three dimensional nonlinear Rossby waves in the atmosphere. Moreover, we explore the dispersion relation of the linear wave through the new equation. Using the travelling wave method and simplest equation method, the general solution and soliton solutions of the equation are obtained successfully respectively. Finally, the formation mechanism of Rossby waves is discussed by multiple soliton solutions.

Numerical Studies on Temperature and Material Flow During Friction Stir Welding using Different Tool Pin Profiles

A three dimensional computational fluid dynamics (CFD) model has been developed to study the effect of tool pin profile on the material flow and temperature development in friction stir welding (FSW) of high specific strength AA 7068 alloy. Numerical simulations were carried out using a RNG k-e turbulence model. Three tool pin profiles, viz. cylindrical, conical and straight cylindrical threaded were considered for the simulation. The temperature distribution and material flow pattern obtained from the simulation were compared for different pin profiles. Simulation results predicted Temperature distribution and material maxing was better in straight cylindrical tapered thread pin welds. Weld joints were fabricated using the straight cylindrical threaded pin with the same parametric combinations as in the simulation. Peak temperature measured in the experiment was less than that obtained by simulation. Hardness measurements taken at different weld regions has showed that about 71% of that of the base metal hardness is obtained with the threaded tool pin. The microstructure study revealed a defect free weld joint. Precipitates distributed in the microstructure indicate sufficient heat input to join the material without dissolving precipitates. The developed numerical model is helpful in optimising FSW process parameters.

Numerical optimisation of a micro-wave rotor turbine using a quasi-two-dimensional CFD model and a hybrid algorithm

Wave rotors are unsteady flow machines that exchange energy through pressure waves. This has the potential for enhancing efficiency over a wide spectrum of applications, ranging from gas turbine topping cycles to pressure-gain combustors. This paper introduces an aerodynamic shape optimisation of a power generating non-axial micro-wave rotor turbine and seeks to enhance the shaft power output while preserving the wave rotor’s capacity to function as a pressure-exchanging device. The optimisation considers six parameters including rotor shape profile, wall thickness, and number of channels and is done using a hybrid genetic algorithm that couples an evolutionary algorithm with a surrogate model. The underlying numerical model is based on a transient, reduced-order, quasi-two dimensional computational fluid dynamics model at a fixed operating condition. The numerical results from the quasi-two-dimensional optimisation indicate that the best candidate design increases shaft power by a factor of 1.78 and imply a trade-off relationship between torque generation and pressure exchange capabilities. Further evaluation of the optimised design using three-dimensional computational fluid dynamics simulations confirms the increase in power output at the cost of increased entropy production. It is further disclosed that increased incidence losses during the initial opening of the channel to the high-pressure inlet duct compromise the shock strength of the primary shock wave and account for the decrease in pressure ratio. Finally, the numerical trends are validated using experimental data.