An assumed time scale model is applied in the numerical calculation of the turbulenceround jet flow, the results are found to be reasonable. Then, joint-scalar probability densityfunction(pdf) approach together with t...An assumed time scale model is applied in the numerical calculation of the turbulenceround jet flow, the results are found to be reasonable. Then, joint-scalar probability densityfunction(pdf) approach together with the assumed time scale model was employed to computeturbulence diffusion flames, several mixing models were compared. It was suggested thatscalar time scale should be used to improve mixing models.展开更多
Experimental results indicate three regimes for cracking in a ferroelectric double cantilever beam (DCB) under combined electromechanical loading. In the loading, the maximum amplitude of the applied electric field re...Experimental results indicate three regimes for cracking in a ferroelectric double cantilever beam (DCB) under combined electromechanical loading. In the loading, the maximum amplitude of the applied electric field reaches almost twice the coercive field of ferroelectrics. Thus, the model of small scale domain switching is not applicable any more, which is dictated only by the singular term of the crack tip field. In the DCB test, a large or global scale domain switching takes place instead, which is driven jointly by both the singular and non-singular terms of the crack-tip electric field. Combining a full field solution with an energy based switching criterion, we obtain the switching zone by the large scale model around the tip of a stationary impermeable crack. It is observed that the switching zone by the large scale model is significantly different from that by the small scale model. According to the large scale switching zone, the switch-induced stress intensity factor (SIF) and the transverse stress (T-stress) are evaluated numerically. Via the SIF and T-stress induced by the combined loading and corresponding criteria, we address the crack initiation and crack growth stability simultaneously. The two theoretical predictions roughly coincide with the experimental observations.展开更多
文摘An assumed time scale model is applied in the numerical calculation of the turbulenceround jet flow, the results are found to be reasonable. Then, joint-scalar probability densityfunction(pdf) approach together with the assumed time scale model was employed to computeturbulence diffusion flames, several mixing models were compared. It was suggested thatscalar time scale should be used to improve mixing models.
基金supported by the "Sino-German Center for Research Promotion" under a project of "Crack Growth in Ferroelectrics Driven by Cyclic Electric Loading", the National Natural Science Foundation of China (Grant No. 10702071)the China Postdoctoral Science Foundation (Grant No. 201003281)the Shanghai Postdoctoral Scientific Program (Grant No. 10R21415800)
文摘Experimental results indicate three regimes for cracking in a ferroelectric double cantilever beam (DCB) under combined electromechanical loading. In the loading, the maximum amplitude of the applied electric field reaches almost twice the coercive field of ferroelectrics. Thus, the model of small scale domain switching is not applicable any more, which is dictated only by the singular term of the crack tip field. In the DCB test, a large or global scale domain switching takes place instead, which is driven jointly by both the singular and non-singular terms of the crack-tip electric field. Combining a full field solution with an energy based switching criterion, we obtain the switching zone by the large scale model around the tip of a stationary impermeable crack. It is observed that the switching zone by the large scale model is significantly different from that by the small scale model. According to the large scale switching zone, the switch-induced stress intensity factor (SIF) and the transverse stress (T-stress) are evaluated numerically. Via the SIF and T-stress induced by the combined loading and corresponding criteria, we address the crack initiation and crack growth stability simultaneously. The two theoretical predictions roughly coincide with the experimental observations.
