Multiscale Analysis of Concrete Damage and Crack Propagation Under High Cycle Loading

Concrete is a typical multiphase composite material in which the initiation and propagation of cracks under fatigue load are mainly determined by its mesoscopic structure. In this paper, a concrete multiphase mesoscopic model which considers thickness of interfacial transition zone (ITZ) varying with aggregate’s size is established by the integrated scripting method. The model comprehensively contains the stochastic characteristics of concrete mesoscopic structure. According to the fatigue crack propagation characteristics in different stages, a multiscale method is proposed by establishing the interactive mesoscopic and macroscopic models to targetedly analyze the whole process of fatigue crack initiation, propagation and failure of concrete specimen. Based on the technique of cycle block, concurrent simulation of concrete damage and crack propagation under high-cycle fatigue load is realized. The analysis results show that fatigue cracks in concrete mainly born near the ITZ and gradually enter into the cement mortar matrix to formulate the cracks with finite size. These cracks influence each other until the dominant crack appears and insatiably propagates to result in the failure of specimen.

A New Vertical Grid Nesting Capability in the Weather Research and Forecasting (WRF) Model

Mesoscale atmospheric models are increasingly used for high-resolution (<3 km) simulations to better resolve smaller-scale flow details. Increased resolution is achieved using mesh refinement via grid nesting, a procedure where multiple computational domains are integrated either concurrently or in series. A constraint in the concurrent nesting framework offered by the Weather Research and Forecasting (WRF) Model is that mesh refinement is restricted to the horizontal dimensions. This limitation prevents control of the grid aspect ratio, leading to numerical errors due to poor grid quality and preventing grid optimization. Herein, a procedure permitting vertical nesting for one-way concurrent simulation is developed and validated through idealized cases. The benefits of vertical nesting are demonstrated using both mesoscale and large-eddy simulations (LES). Mesoscale simulations of the Terrain-Induced Rotor Experiment (T-REX) show that vertical grid nesting can alleviate numerical errors due to large aspect ratios on coarse grids, while allowing for higher vertical resolution on fine grids. Furthermore, the coarsening of the parent domain does not result in a significant loss of accuracy on the nested domain. LES of neutral boundary layer flow shows that, by permitting optimal grid aspect ratios on both parent and nested domains, use of vertical nesting yields improved agreement with the theoretical logarithmic velocity profile on both domains. Vertical grid nesting in WRF opens the path forward for multiscale simulations, allowing more accurate simulations spanning a wider range of scales than previously possible.

Substantiation of the Possibility to Use Dikes for Flood Regulation.

Effect of the flood regulation with the river floodplains was discussed, and a mechanism of the flood wave transformation with the basin channel network in the natural regime and during the floodplain banking was characterized. The possibility of dikes’ capacity use for cutting off the flood peak in extreme situations was substantiated and the relevant Chinese experience was analyzed. Theoretical basis for the channel network capacity management with pre-planned flooding of the “protected” floodplain areas was presented. The appropriated methods were developed; they included plotting of the maximal runoff calculated hydrographs, concurrent simulation of the flood wave passage and dikes capacities filling, more precise definition of parameters of the water-passing facilities in the dike body. Proposals on the designing of floodplain volumes and dikes intended for the flood runoff regulation were formulated. The Ingoda River (Transbaikal Kray) was taken as a study case. It was characterized by the flood maximal flows passage in different reaches due to the regulating impact of the bed and floodplain. Comparison of the real flood passage with the simulation results with the use of floodplain regulating capacities for this river was presented. Tentative results were the evidence of the principal possibility of the dikes capacity use in extreme conditions.

The M2 Internal Tide Simulated by a 1/10° OGCM

Using a concurrent simulation of the ocean general circulation and tides with the ° Max Planck Institute Ocean Model (MPI-OM), known as STORMTIDE, this study provides a near-global quantification of the low-mode M2 internal tides. The quantification is based on wavelengths and their near-global distributions obtained by applying spectral analysis to STORMTIDE velocities and on comparisons of the distributions with those derived by solving the Sturm–Liouville eigenvalue problem. The simulated wavelengths, with respect to both their magnitudes and their geographical distributions, compare well with those obtained by solving the eigenvalue problem, suggesting that the STORMTIDE internal waves are, to a first approximation, linear internal waves satisfying local dispersion relations. The simulated wavelengths of modes 1 and 2 range within 100–160 and 45–80 km, respectively. Their distributions reveal, to different degrees for both modes, a zonal asymmetry and a tendency of a poleward increase with stratification N and the Coriolis parameter f being responsible for these two features, respectively. Distributions of mode 1 wavelengths are found to be determined by both N and f, but those of mode 2 are mainly controlled by variations in N. Larger differences between the STORMTIDE wavelengths and those of the eigenvalue problem occur, particularly for mode 2, primarily in high-latitude oceans and the Kuroshio and Gulf Stream and their extensions.

Reaction kinetics of the electrochemical oxidation of CO and syngas fuels on a Sr2Fe1.5Mo0.5O6−δ perovskite anode

Concurrent simulation of chemical and electro-chemical processes on Sr2Fe1.5Mo0.5O6−δ predicted a higher activity for CO/syngas fuels for a surface with higher Mo content.

An Ultrasonic Through-Wall Communication (UTWC) System Model

Ultrasonic waves at 1 MHz are used to send information across solid walls without the needs for through wall penetrations. A communication channel is established by attaching a set of three ultrasonic transducers to the wall. The first transducer transmits a continuous ultrasonic wave into the wall. The second transducer is mounted on the opposite side of the wall (inside) and operates as a receiver and signal modulator. The third transducer, the outside receiving transducer, is installed on the same side as the first transducer where it is exposed to the signal reflected from the blended interface of the inside wall and inside transducer. Inside sensor data is digitized and the bit state is used to vary in time the electrical load connected to the inside transducer, changing its acoustic impedance in accordance with each data bit. These impedance changes modulate the amplitude of the reflected ultrasonic signal. The modulated signal is detected at the outside receiving transducer, where it is then demodulated to recover the data. Additionally, some of the ultrasonic power received at the inside transducer is harvested to provide energy for the communication and sensor system on the inside. The entire system (ultrasonic, solid wall, and electronic) is modeled in the electrical domain by means of electro-mechanical analogies. This approach enables the concurrent simulation of the ultrasonic and electronic components. A model of the communication system is implemented in an electronic circuit simulation package, which assisted in the analysis and optimization of the communication channel. Good agreement was found between the modeled and experimental results.