Numerical analysis of MHD flow and nanoparticle migration within a permeable space containing Non-equilibrium model
Truong Khang Nguyen; Muhammad Usman; M. Sheikholeslami; Rizwan Ul Haq; Ahmad Shafee; Abdul Khader Jilani; I. Tlili;
This article deals with the numerical simulation to examine the significant effects of MHD flow and nanoparticle migration inside a permeable space including two temperature model. For more physical situation, thermal radiation influence is considered. Viable transformation is assumed to alter the governing set of PDEs into dimensionless form. CVFEM was adopted to model this article. Impacts of radiation parameter, Rayleigh number (10 3 < Ra < 10 4 ), nanofluid–solid interface factor (10 < Nhs <1000), Hartmann number (0 < Ha < 20) and nanoparticles’ shape (3 < m < 5.7) on nanofluid behavior were demonstrated. Outcomes depict that stronger convection can be obtained with augmenting in shape factor. Average Nusselt number increases as enhancing the buoyancy and radiation effect whereas decreases as enhancing nanofluid–solid interface factor and Hartmann number. Comparison of the numerical outputs achieved by means of CVFEM with published data was also deliberated. It is evident that the applied approach is very accurate to investigate solution of the discussed problem.
Truong Khang Nguyen; Muhammad Usman; M. Sheikholeslami; Rizwan Ul Haq; Ahmad Shafee; Abdul Khader Jilani; I. Tlili.Numerical analysis of MHD flow and nanoparticle migration within a permeable space containing Non-equilibrium model, Physica A: Statistical Mechanics and its Applications, Volume 537,10.1016/j.physa.2019.122459.
Interaction between shock wave and a movable sphere with cavitation effects in shallow water
Wu, WB; Zhang, AM; Liu, YL; Liu, MB；
In this paper, we establish a fluid-structure interaction (FSI) model to investigate the dynamic interactions between the underwater explosion (UNDEX) shock wave and a movable sphere near the free surface. We utilize the local discontinuous Galerkin (LDG) method to capture the propagation of the shock wave in the fluid domain and employ the pressure cutoff model to calculate cavitation effects. The fluid elements at the fluid-structure interface are directly coupled to the structural dynamic model, and the structural transient dynamic responses are coupled with fluid acoustic pressure at the fluid-structure interface in the governing equation. The validity of the present FSI model is verified by comparing with the continuous Galerkin method. Due to the advantage of the LDG method in capturing the discontinuous wave, the present model shows better properties than the traditional coupled acoustic-structural model. With the present FSI model, we investigate the interaction between the UNDEX shock wave and a submerged and floated sphere. Under the combined effects of the free surface and structure, the UNDEX shock and cavitation loading characteristics are analyzed, and the influences of complicated cavitation effects on dynamic responses of the sphere are discussed. Published under license by AlP Publishing.
Wu, WB; Zhang, AM; Liu, YL; Liu, MB. Interaction between shock wave and a movable sphere with cavitation effects in shallow water, PHYSICS OF FLUIDS, Volume 32, DOI:
Performance Improvement of Dual-Pulse Heterodyne Distributed Acoustic Sensor for SoundDetection
He, XG; Zhang, M; Gu, LJ; Xie, SR; Liu, F; Lu, HL;
Phase fading is fatal to the performance of distributed acoustic sensors (DASs) influencing its capability of distributed measurement as well as its noise level. Here, we report the experimental observation of a strong negative correlation between the relative power spectrum density (PSD) at the heterodyne frequency and the noise floor of the detected phase for the heterodyne demodulated distributed acoustic sensor (HD-DAS) system. We further propose a weighted-channel stack algorithm (WCSA) to alleviate the phase fading noise via an enhancement of the relative PSD at the heterodyne frequency. Experimental results show that the phase noise of the demodulated signal can be suppressed by 13.7 dB under optimal condition. As a potential application, we exploited the improved HD-DAS system to retrieve a piece of music lasted for 205 s, demonstrating the reliability of detecting wideband sound signal without distortion.
He, XG; Zhang, M; Gu, LJ; Xie, SR; Liu, F; Lu, HL. Performance Improvement of Dual-Pulse Heterodyne Distributed Acoustic Sensor for SoundDetection, SENSORS, Volume
CFD based parameter tuning for motion control of robotic fish
Tian, RY; Li, L; Wang, W; Chang, XH; Ravi, S; Xie, GM;
After millions of years of evolution, fishes have been endowed with agile swimming ability to accomplish various behaviourally relevant tasks. In comparison, robotic fish are still quite poor swimmers. One of the unique challenges facing robotic fish is the difficulty in tuning the motion control parameters on the robot directly. This is mainly due to the complex fluid environment robotic fish need to contend with and endurance limitations (i.e. battery capacity limitations). To overcome these limitations, we propose a computational fluid dynamics (CFD) simulation platform to first tune the motion control parameters for the computational robotic fish and then refine the parameters by experiments on robotic fish. Within the simulation platform, the body morphology and gait control of the computational robotic fish are designed according to a robotic fish. The gait control is implemented by a central pattern generator (CPG); The CFD model is solved by using a hydrodynamic-kinematics strong-coupling method. We tested our simulation platform with three basic tasks under active disturbance rejection control (ADRC) and try-and-error-based parameter tuning. Trajectory comparisons between the computational robotic fish and robotic fish verify the effectiveness of our simulation platform. Moreover, power costs and swimming efficiency under the motion control are also analyzed based on the outputs from the simulation platform. Our results indicate that the CFD based simulation platform is powerful and robust, and shed new light on the efficient design and parameter optimization of the motion control of robotic fish.
Tian R , Li L , Wang W , et al. CFD based parameter tuning for motion control of robotic fish, Bioinspiration & Biomimetics, Volume
Observer-Based Event-Triggered Circle Formation Control for First- and Second-Order Multiagent Systems
Xu, P; Xie, GM; Tao, J; Xu, MY; Zhou, Q;
This paper proposes an observer-based event-triggered algorithm to solve circle formation control problems for both first- and second-order multiagent systems, where the communication topology is modeled by a spanning tree-based directed graph with limited resources. In particular, the observation-based event-triggering mechanism is used to reduce the update frequency of the controller, and the triggering time depends on the norm of the state function and the trigger threshold of measurement errors. The analysis shows that sufficient conditions are established for achieving the desired circle formation, while there exists at least one agent for which the next interevent interval is strictly positive. Numerical simulations of both first- and second-order multiagent systems are also given to demonstrate the effectiveness of the proposed control laws.
Xu, P; Xie, GM; Tao, J; Xu, MY; Zhou, Q. Observer-Based Event-Triggered Circle Formation Control for First- and Second-Order Multiagent Systems, COMPLEXITY, Volume 2020, 10.1155/2020/4715315.
Comprehensive study and comparison of equilibrium and kinetic models in simulation of hydratereaction in porous media
Teng, YH; Zhang, DX;
Coupling hydrate reaction in fluid transport in porous media is essential for simulation of gas hydrate production, as well as carbon sequestration in deep-sea sediments. It can be conceptualized as multiphase, multicomponent, and non-isothermal reactive transport. Two types of models have been developed for the description of hydrate reaction in numerical models. The equilibrium model (EM) assumes instantaneous chemical equilibrium among species, and thus ignores reaction kinetics. The kinetic model (KM) incorporates reaction kinetics by introducing a term of reaction rate dependent on fugacity difference. Although KM achieves a more accurate description of the reaction, it is potentially more computationally intensive due to the increased degree of freedom in the nonlinear equation system. Although several previous studies have investigated the similarities and differences between these two models, inconsistencies exist in their studies, and the mechanisms to distinguish these two models are still not well understood. In our study, in order to identify the reasons for these inconsistencies and elucidate the mechanisms that control the differences between the two reaction models, we provide a comprehensive investigation and comparison of these two models via theoretical analysis and numerical experiments. Through comparing the basic assumptions, mathematical model and the equation systems, we pointed out the basic difference of these two models, which results from the different calculations of physical parameters. Dimensionless analysis of the governing equations of KM yields several characteristic numbers, representing the relative strength of different physical processes. We performed numerical experiments to investigate the effect of characteristic numbers on the difference between the two models, and the results indicate that there exist critical values for these characteristic numbers, lower than which lead to an obvious gap between the results of EM and KM. It turns out that the relative strength of the hydrate reaction and other physical processes controls the magnitude of difference between these two models. EM is essentially a special case of KM when the time scale of the hydrate reaction is sufficiently smaller than other physical processes, such as convective and diffusive transport of mass and heat. Comparison between the time and iteration steps in the two reaction models provides insights into the computational efficiency of the two models. (C) 2019 Elsevier Inc. All rights reserved.
Teng, YH; Zhang, DX. Comprehensive study and comparison of equilibrium and kinetic models in simulation of hydratereaction in porous media, JOURNAL OF COMPUTATIONAL PHYSICS, Volume 404, 10.1016/j.jcp.2019.109094.
Investigations on sloshing mitigation using elastic baffles by coupling smoothed finite elementmethod and decoupled finite particle method
Zhang, ZL; Khalid, MSU; Long, T; Chang, JZ; Liu, MB;Abstract:
Liquid sloshing in partially filled containers is widely observed in various engineering systems where the forces exerted by the liquid on tank walls may result in the instability of tank or even a structural failure. To enhance the hydrodynamic damping ratio and consequently decrease the sloshing forces, baffles have been designed as effective internal components inside containers in most of the practical engineering problems. In this work, we numerically investigate the sloshing mitigation using elastic baffles through our recently developed methodology based on the coupling strategy of smoothed finite element method (SFEM) and an improved version of smoothed particle hydrodynamics (SPH) offering better accuracy. First, we simulate a benchmark problem of sloshing flow interacting with an elastic baffle installed in a container, and the numerical results agree well with the experimental data. Further, various cases are conducted to study the sloshing mitigation by using deformable baffles with different configurations and elasticities. Our current observations and findings based on the simulation results demonstrate that the impact pressure on the tank wall is significantly influenced by the geometric orientations and complex configurations of elastic baffles. The timing of sloshing flow impacting on the container wall can be passively controlled by adequately choosing the baffle elasticity. The damping performances of different elastic baffles are quantified by the numerically obtained Pressure-E-baffle lines. The relevant analysis in this paper can greatly help explore the effective solutions to mitigate the liquid sloshing in engineering systems. (C) 2020 Elsevier Ltd. All rights reserved.
Zhang, ZL; Khalid, MSU; Long, T; Chang, JZ; Liu, MB. Investigations on sloshing mitigation using elastic baffles by coupling smoothed finite elementmethod and decoupled finite particle method, JOURNAL OF FLUIDS AND STRUCTURES, Volume
Novel operational matrices-based method for solving fractional-order delay differential equationsvia shifted Gegenbauer polynomials
Usman, M; Hamid, M; Zubair, T ; Haq, RU; Wang, W ; Liu, MB;
Accurate solutions of nonlinear multi-dimensional delay problems of fractional-order arising in mathematical physics and engineering recently have been found to be a challenging task for the research community. This paper witnesses that an efficient fully spectral operational matrices-based scheme is developed and successfully applied for stable solutions of time-fractional delay differential equations (DDEs). Monomials are introduced in order to proposed the novel operational matrices for fractional-order integration I-nu and derivative D-nu by means of shifted Gegenbauer polynomials. Some ordinary and partial delay differential equations of fractional-order are considered to show reliability, efficiency and appropriateness of the proposed method. In order to approximate the delay term in DDEs a novel delay operational matrix Theta(a)(b) is introduced with the help of shifted Gegenbauer polynomials. The proposed algorithm transform the problem understudy into a system of algebraic equations which are easier to tackle. Analytical solutions of the mentioned problem are effectively obtained, and an inclusive comparative study is reported which reveals that the proposed computational scheme is effective, accurate and well-matched to investigate the solutions of aforementioned problems. Error bound analysis is enclosed in our investigation to reveal the consistency and support the mathematical formulation of the algorithm. This proposed scheme can be extended to explore the solution of more dervisfy problem of physical nature in complex geometry. (C) 2019 Elsevier Inc. All rights reserved.
Usman, M; Hamid, M; Zubair, T ; Haq, RU; Wang, W ; Liu, MB. Novel operational matrices-based method for solving fractional-order delay differential equationsvia shifted Gegenbauer polynomials, APPLIED MATHEMATICS AND COMPUTATION, Volume