A DECOUPLING METHOD WITH DIFFERENT SUBDOMAIN TIME STEPS FOR THE NON-STATIONARY NAVIER-STOKES/DARCY MODEL

A decoupling method with different subdomain time steps for the non-stationary Navier- Stokes/Darcy model is formulated and analyzed. The method has asynchronous time steps, which adopt small time steps in the fluid region and large time steps in the porous region. It saves relatively large amount of CPU time. Stability and convergence of the method are proved. The numerical results are presented to illustrate the features of the proposed method.

NUMERICAL ANALYSIS OF A BDF2 MODULAR GRAD-DIV STABILITY METHOD FOR THE STOKES/DARCY EQUATIONS

In this paper,a BDF2 modular grad-div algorithm for the Stokes/Darcy model is constructed.This method not only effectively avoids solver breakdown,but also increases computational efficiency for increasing parameter values.Herein,complete stability and error analysis are provided.Finally,some numerical tests are proposed to justify the theoretical analysis.

A Broad Range Triboelectric Stiffness Sensor for Variable Inclusions Recognition

With the development of artificial intelligence,stiffness sensors are extensively utilized in various fields,and their integration with robots for automated palpation has gained significant attention.This study presents a broad range self-powered stiffness sensor based on the triboelectric nanogenerator(Stiff-TENG)for variable inclusions in soft objects detection.The Stiff-TENG employs a stacked structure comprising an indium tin oxide film,an elastic sponge,a fluorinated ethylene propylene film with a conductive ink electrode,and two acrylic pieces with a shielding layer.Through the decoupling method,the Stiff-TENG achieves stiffness detection of objects within 1.0 s.The output performance and characteristics of the TENG for different stiffness objects under 4 mm displacement are analyzed.The Stiff-TENG is successfully used to detect the heterogeneous stiffness structures,enabling effective recognition of variable inclusions in soft object,reaching a recognition accuracy of 99.7%.Furthermore,its adaptability makes it well-suited for the detection of pathological conditions within the human body,as pathological tissues often exhibit changes in the stiffness of internal organs.This research highlights the innovative applications of TENG and thereby showcases its immense potential in healthcare applications such as palpation which assesses pathological conditions based on organ stiffness.

Fragility analysis for vehicle derailment on railway bridges under earthquakes

With the rapid development of high-speed railways around the globe,the safety of vehicles running on bridges during earthquakes has been paid more attention to.In the design of railway bridges,in addition to ensuring the safety of the bridge structure in earthquake,the vehicle safety should also be ensured.Previous studies have focused on the detailed analysis of vehicle derailment on bridges,proposing complex numerical algorithms for wheel-rail contact analysis as well as for parametric analysis,but they are inconvenient for designers.Intensity measure(IM)used in performance-based earthquake engineering is introduced in this study.A method to evaluate the vehicle safety on bridges under earthquakes is proposed with respect to the optimal IM.Then,the vehicle derailment case of the Kumamoto earthquake in Japan verifies the decoupling method of vehicle-bridge interaction model.In the assessment of vehicle derailments,eight IMs are systematically compared:the IMs of bridge deck motion are generally better than those of ground motion;the variation coefficient of spectral intensity of the bridge deck is the smallest at different frequencies.Finally,the derailment fragility cloud map is presented to evaluate the vehicle safety on bridges during earthquakes.

Perturbation spectrum method for seismic analysis of non-classically damped systems

Fundamental principles from structural dynamics,random theory and perturbation methods are adopted to develop a new response spectrum combination rule for the seismic analysis of non-classically damped systems,such as structure-damper systems. The approach,which is named the perturbation spectrum method,can provide a more accurate evaluation of a non-classically damped system's mean peak response in terms of the ground response spectrum. To account for the effect of non-classical damping,all elements are included in the proposed method for seismic analysis of structure,which is usually ap-proximated by ignoring the off-diagonal elements of the modal damping matrix. Moreover,as has been adopted in the traditional Complete Quadratic Combination (CQC) method,the white noise model is also used to simplify the expressions of perturbation correlation coefficients. Finally,numerical work is performed to examine the accuracy of the proposed method by comparing the approximate results with exact ones and to demonstrate the importance of the neglected off-diagonal elements of the modal damping matrix. In the examined cases,the proposed method shows good agreement with direct time-history integration. Also,the perturbation spectrum method leads to a more efficient and economical calculation by avoiding the integral and complex operation.

A decoupled method to identify affecting mechanism of crosswind on performance of a natural draft dry cooling tower

The natural draft dry cooling tower(NDDCT)has been increasingly used for cooling in power generation in arid area.As crosswind affects the performance of a NDDCT in a complicated way,and the basic affecting mechanism is unclear,attempts have been made to improve the performance of a NDDCT based on limited experiences.This paper introduces a decoupled method to study the complicated crosswind effects on the inlet and outlet of a NDDCT separately by computational fluid dynamics(CFD)modeling and hot state experiments.Accordingly,the basic affecting mechanism of crosswind on the NDDCT performance is identified.Crosswind changes the inlet flow field of a NDDCT and induces mainstream vortices inside the tower,so as to degrade the ventilation.Besides,low crosswind deflects the upward plume at the outlet to further degrade the ventilation,while high crosswind induces the low pressure area at the outlet to reduce the ventilation degradation.