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The application of high speed air flow in the textile field represents the frontier development direction in this field. However, the coupling mechanism between air flow and fiber is extremely complicated which greatly limits the development and application of new textile technologies. For this reason, this research study is intended to focus on the common cutting-edge basic scientific problem of the air-flow-fiber coupling mechanism, the vortex spinning technology is taken as a breakthrough point for research. Three-dimensional numerical models of air flow in vortex spinning nozzle and a free-end fiber were established. The hybrid grids including the structured hexahedral grids and the unstructured tetrahedral grids were used to divide the air-flow computational region, the realizable κ - ε model was used to solve the turbulent characteristics of air flow, and the wall function method was used to solve the air flow in the near wall region. The displacement and deformation of a single free-end fiber under the action of the air-flow force was solved by the second-order nonlinear double asymptotic method and interpolation method. The dynamic twist process of a free-end fiber was simulated in three-dimensional space by taking into account the fiber characteristics, such as straightening, bending, and torsion. In addition, a high magnification microscope was used to observe the free-end fiber motion during the spinning process. The results show that the numerical simulation is consistent with the experimental observation, proving that dynamic numerical simulation can solve difficult problems in the unobserved dynamic twisting process, and this deepens the understanding of the spinning mechanism in vortex spinning. [ABSTRACT FROM AUTHOR]

In order to study the stability of power generation in reverse of a pumping station unit, the computational fluid dynamics simulation and finite element analysis of the whole passage has been carried out, to study the pressure pulsation and stress distribution law under the condition of power generation in reverse, and compared with them in pump mode. The simulation results showed that, under the condition of power generation in reverse, the pressure pulsation of each monitoring point in front and at back of the runner were higher than that under pump mode. The most amplitude of pressure pulsation was about twice as large as the pump mode, increased gradually from hub to rim. The flow was seriously affected by the rotating runner. The internal frequency of pressure pulsation was blade frequency. The results of fluid–solid coupling showed that the stress mainly concentrated on the root of the pressure side and the suction side of the blade, and the maximum equal stress appeared on the suction side of the blade. The maximum stress and strain value under the condition of power generation in reverse were 20% higher than that under pump mode, and the maximum stress was about twice. [ABSTRACT FROM AUTHOR]

The reciprocating piston seals are crucial parts in hydraulic system, which are widely used in aerospace and military industry. A direct fluid–structure coupling method with high efficiency is proposed for solving the transient Elaso-Hydrodynamic-Lubrication problem in float piston series seal system of hydropneumatic suspension. The method is validated by theory solution of a simple pad-bearing film model. Detailed three-dimensional fluid–structure coupling model of the seal system is built using finite element discretization. Rubber material tests are carried out to obtain parameters of the third-order Ogden constitutive model for the O-ring seal. The sealing performance and friction force of the complicated series seal system are analyzed with direct fluid–structure dynamic coupling simulation in high pressure and high speeds conditions. The critical speed from mixed lubrication to full film lubrication is obtained. The fluid velocity and pressure distribution in the sealing gap along axial direction is compared. The outlet volume flux leakage in different piston speeds and inlet pressures is calculated to evaluate the sealing performance. The friction force experiment for the float piston system is carried out in various speeds. The friction force from direct fluid–structure interface simulation coincides well with the test result. [ABSTRACT FROM AUTHOR]

A fast dynamic mesh technology by our research group has been applied in the time synchronized fluid-structure coupling. It is found that flow mesh update after the convergent calculation of the flow will induce excessive iterations in the computation of flow increasing the computing time of fluid-structure coupling. To reduce the computing time, a time-space synchronized fluid-structure coupling algorithm was developed in this paper based on the pre-existing time synchronized method and the fast dynamic mesh technology. The wing vibration and flow mesh deformation were computed using the fast dynamic mesh technology after each iteration in the calculation of the flow. Namely, the flow and the wing vibration were solved in space synchronization. The calculating convergence of the flow and the wing vibration were both achieved through iterations every time step. Namely, the flow and the wing vibration were solved in time synchronization. Thus, the flow and the wing vibration are coupled both in time and space synchronization. The flutter boundary of wing 445.6 was predicted using the present algorithm. The calculated results compare well with the experimental data and the computing time was almost reduced by 75%. [ABSTRACT FROM AUTHOR]

As a form of passive control, padding rubber layers onto the most heavily deformed zones of a system can improve the dynamic behavior and the acoustic comfort of a vehicle system. This paper proposes an extensive hybrid modal synthesis method in order to study coupled fluid-structure systems, in retaining a few degrees of freedom. Modal criteria, corresponding to noise transmission paths between substructures in the system, have been derived to characterize the dynamic phenomenon from a modal view. These criteria were then substituted by Kriging interpolation models to avoid prohibitive simulation steps during optimization of the complex system. Once the mathematical models of the investigated modal criteria were established and the multi-objective functions for rubber characteristics defined, an approximate optimal solution leading to superior dynamic performance could be obtained based on a genetic algorithm. The analytical results and numerical experiments conducted have also justified the efficiency of our proposed strategy. [ABSTRACT FROM AUTHOR]

This article presents a novel calculation method for the bearing performance of the aerostatic thrust bearing. This method is provided while taking the fluid-structure coupling effect into account. High pressure air film leads to the structure deformation, thus the bearing clearance after deformation is utilized to estimate the real bearing performance. Furthermore, the influencing factors on the bearing performance, the thrust plate’s thickness, and the orifices’ location, are investigated on the basis of the fluid-structure coupling effect. The calculation method of the best gas film thickness is deduced and presented. Experimental results for validation highlight the reliability of this method. [ABSTRACT FROM AUTHOR]

This study focuses on the dynamic characteristics of the containers with fuel consumption. With fuel consumption, the fuel container system vibrates with decreasing mass, which is a typical variable mass system. In order to investigate the influences of the time-varying liquid on vibration of the containers, this fluid–structure coupling system with time-varying mass is modeled combining finite element method, used to model the structure, and virtual mass method representing the fluid. The dynamic responses and time–frequency analysis of the time-varying mass system are presented based on the numerical simulations. From the results, it is shown that decrease of the mass results in increase of the vibration frequencies of the system and induces an additional negative damping. The additional negative damping is proportional to the rate of mass change and causes the vibration to decay slowly. The results also suggest that the time–frequency analysis possess appealing advantages in processing nonstationary signals and thus are able to provide reliable time–frequency domain information for time-varying mass systems. [ABSTRACT FROM AUTHOR]

In this paper, a methodology for coupled fluid–structure model reduction is proposed. The overall objective of the method is to reduce the numerical computational costs without affecting the accuracy level of the prediction. This methodology is organized according to the three following steps. In the first step, this method uses a reliable criterion for selecting the number of the kept modes for the fluid and the structure in vacuo subsystems. In the second step, this basis will be enriched through static residual responses taking into account the fluid–structure coupling effects. These responses are selected according to an energetic criterion. Finally, the enriched basis is extended by introducing some residual static responses due to the error forces considered as structural modifications forces.In the context of the finite element method (FEM), the performances of the proposed method are established through a comparative study with other strategies that are proposed in the literature. Thus, the computational cost (CPU time) and the accuracies of the different methods are discussed and compared with a reference method. The validation of the proposed method and the comparative study are performed through two numerical simulation examples. The first one concerns a parallelepiped acoustic cavity with a simply supported plate. The method can handle both weak and strong couplings; as illustrated in the examples. The second one consists of a pipe with a strong coupling and a larger model size. [ABSTRACT FROM PUBLISHER]