The essence of wind-blown sand movement is a particle movement system driven by high Reynolds number wall turbulence in the atmospheric surface layer (ASL). Understanding this phenomenon is crucial as the law and mechanism of sand movement have not been effectively revealed at present. In this study, we utilize the high-frequency time series data from the Oceano site, a renowned location for such studies, which includes streamwise wind velocity (u), wall-normal wind velocity (w), temperature (T), and total saltation mass flux (q) to delve deeper into wind-blown sand movement. The results indicate a positive correlation between T and w. Interestingly, this correlation not only escalates with height but also intensifies with the increase of the stratification stability parameters (z/L). Sand influences the intensity ratio of each quadrant to Reynolds stress without altering the time ratio. Both the ejection and sweep processes correlate well with z/L. Similarly, q also exhibits a good correlation with z/L. The buoyancy's impact on the low-frequency fluctuations of q might be through its effect on the low-frequency fluctuations of w, enhancing the sand transport capacity of w. This discovery holds profound implications for the study of two-phase flow in ASL and the precise prediction of surface sediment transport.

Bulk high-temperature superconductors exhibit outstanding electromagnetic properties and are capable of trapping very large magnetic fields. However, bulk superconductors are subjected to a large Lorentz force during field cooling magnetization (FCM), which can cause crack initiation and propagation. Superconducting performance is then limited by the damage to the bulk. In this paper, we study the mechanical behavior and brittle damage of a three-dimensional (3D) bulk GdBCO superconductor during FCM. Firstly, the distribution of electromagnetic field in the bulk is obtained based on the H-formulation with a finite element model. Then, a 3D bond-based peridynamic (PD) model is used to simulate the mechanical behavior and possible brittle damage to the bulk under a given electromagnetic force. The initiation and propagation of cracks can be predicted using the 3D bond-based PD model. The effect of residual stress due to the presence of a reinforcement ring during the cooling process is also discussed. The results show that mechanical stability can be improved by reinforcing the sample.

Single-grain GdBCO bulk superconductors have significant applications potential due to their ability to trap stable and large magnetic fields. The internal fracture of these bulk superconductors caused by Lorentz force and thermal load is a key issue in their practical applications. The aim of this work presented here is to investigate the mechanical behavior of the bulk superconductor during pulsed field magnetization. The H-formulation and heat transfer equation are used to obtain the electromagnetic force and thermal load in the bulk with and without defects. Numerical simulations show strong local enhancement of the electromagnetic load at the crack tips. Moreover, dynamic stress intensity factors at the crack tips are presented based on the two-dimensional state-based peridynamic theory. In addition, the crack propagation path is predicted. Finally, different dynamic crack problems are considered to discuss the influence of crack, void, inclusion, and hole on the mechanical stability of the bulk. Results show that defects increase the risk of damage of superconducting bulks.

Bulk high-temperature superconductors exhibit priority magnetic properties compared to the conventional permanent magnets. Single-grain bulk GdBaCuO superconductors have significant application potential due to higher critical current density (J(c)) and trapped fields. However, bulk superconductors are subject to larger Lorentz forces under high magnetic fields and their performance is limited by damage to the materials. In this paper, a finite element model based on the H-formulation is used to solve for the electromagnetic force in bulk GdBCO containing defects or inclusions under application of a pulsed field. Strong local electromagnetic force enhancement is observed at the crack tip. A bond-based peridynamic (PD) approach is proposed for analysis of the dynamic mechanical behavior and brittle damage of the sample. Crack initiation and propagation paths can be predicted using PD theory. PD is thus shown to be a suitable method for dynamic fracture problem analysis. As a further demonstration of the proposed model's capabilities, the bulk fracture process is simulated. The effect of voids, cross cracks and multiple inclusions are presented. Results show that mechanical stability can be enhanced by the presence of silver particles.

The performance of Nb3Sn cable-in-conduit-conductor (CICC) shows a significant degradation with increasing electromagnetic load in the International Thermonuclear Experimental Reactor (ITER). As the strand is under the compression caused by adjacent strands, the strand damage may occur for high contact force. In this paper, we present a 3D helix model based on the TEMLOP and FEMCAM to simulate the contact force among the strands under transverse load. The maximum linear strain and indentation depth induced by contact stress are calculated with two-dimensional contact model of cylinder. The numerical results are compared with the experimental values. Finally, the indentation depth is discussed for different layers and cross angles based on two models. With the increasing of layer number, the degradation of performance will occur. The short bending wavelength leads to small indentation depth. (C) 2016 Elsevier B.V. All rights reserved.

A theoretical model for calculating the stress and strain states of cabling structures with different loadings has been developed in this paper. We solve the problem for the first- and second-stage cable with tensile or bending strain. The contact and friction forces between the strands are presented by two-dimensional contact model. Several theoretical models have been proposed to verify the results when the triplet subjected to the tensile strain, including contact force, contact stresses, and mechanical loss. It is found that loadings will affect the friction force and the mechanical loss of the triplet. The results show that the contact force and mechanical loss are dependent on the twist pitch. A shorter twist pitch can lead to higher contact force, while the trend of mechanical loss with twist pitch is complicated. The mechanical loss may be reduced by adjusting the twist pitch reasonably. The present model provides a simple analysis method to investigate the mechanical behaviors in multistage-structures under different loads.