A Closure for Isotropic Turbulence Based on Extended Scale Similarity Theory in Physical Space

The closure of a turbulence field is a longstanding fundamental problem, while most closure models are introduced in spectral space. Inspired by Chou＇s quasi-normal closure method in spectral space, we propose an analytical closure model for isotropic turbulence based on the extended scale similarity theory of the velocity structure function in physical space. The assumptions and certain approximations are justified with direct numerical simulation. The asymptotic scaling properties are reproduced by this new closure method, in comparison to the classical Batchelor model.

Extending Science Popularization Base Construction and Promoting Meteorological Science Popularization Ability

In recent years,Kaifeng Meteorological Bureau and Kaifeng Municipal Meteorological Society seriously think how to strengthen the construction of science popularization base,and take below measures improving the influence of ＂ national science popularization education base＂ and further increasing the propaganda of meteorological popular science knowledge. Firstly,launching periodical meteorological science popularization into campus,village and community,and holding meteorological science forum; secondly,cooperating with municipal science association and Science and Technology Bureau,and jointly issuing the related documents of carrying out the propaganda of meteorological science popularization;thirdly,co-constructing campus weather station and meteorological science popularization demonstration community; fourthly,setting up special meteorological science lecture and report meeting; fifthly,integrating meteorological science with studies of Chinese ancient civilization based on innovation. In the form of recreation and loved by the masses,the propaganda of meteorological popular science knowledge is done well,and people recognizing,understanding,grasping and applying meteorological science is improved,thereby reaching the target of decreasing the damages of meteorological disaster to social economy and human life and property.

Computational modeling of cavitating flows in liquid nitrogen by an extended transport-based cavitation model

Developing a robust computational strategy to address the rich physical characteristic involved in the thermcdynamic effects on the cryogenic cavitation remains a challenge in research. The objective of the present study is to focus on developing mod- elling strategy to simulate cavitating flows in liquid nitrogen. For this purpose, numerical simulation over a 2D quarter caliber hydrofoil is investigated by calibrating cavitation model parameters and implementing the thermodynamic effects to the Zwart cavitation model. Experimental measurements of pressure and temperature are utilized to validate the extensional Zwart cavi- tation model. The results show that the cavitation dynamics characteristic under the cryogenic environment ale different from that under the isothermal conditions： the cryogenic case yields a substantially shorter cavity around the hydrofoil, and the pre- dicted pressure and temperature inside the cavity are steeper under the cryogenic conditions. Compared with the experimental data, the computational predictions with the modified evaporation and condensation parameters display better results than the default parameters from the room temperature liquids. Based on a wide range of computations and comparisons, the extension- al Zwart cavitation model may predict more accurately the quasi-steady cavitation over a hydrofoil in liquid nitrogen by pri- marily altering the evaporation rate near the leading edge and the condensation rate in the cavity closure region.