Turbulence Model Investigations on the Boundary Layer Flow with Adverse Pressure Gradients

In this paper, a numerical study of flow in the turbulence boundary layer with adverse and pressure gradients （APGs） is conducted by using Reynolds-averaged Navier-Stokes （RANS） equations. This research chooses six typical turbulence models, which are critical to the computing precision, and to evaluating the issue of APGs. Local frictional resistance coefficient is compared between numerical and experimental results. The same comparisons of dimensionless averaged velocity profiles are also performed. It is found that results generated by Wilcox （2006） k-co are most close to the experimental data. Meanwhile, turbulent quantities such as turbulent kinetic energy and Reynolds-stress are also studied.

Numerical Investigation on Two-dimensional Boundary Layer Flow with Transition

As a basic problem in many engineering applications, transition from laminar to turbulence still remains a difficult problem in computational fluid dynamics （CFD）. A numerical study of one transitional flow in two-dimensional is conducted by Reynolds averaged numerical simulation （RANS） in this paper. Turbulence model plays a significant role in the complex flows＇ simulation, and four advanced turbulence models are evaluated. Numerical solution of frictional resistance coefficient is compared with the measured one in the transitional zone, which indicates that Wilcox （2006） k-ω model with correction is the best candidate. Comparisons of numerical and analytical solutions for dimensionless velocity show that averaged streamwise dimensionless velocity profiles correct the shape rapidly in transitional region. Furthermore, turbulence quantities such as turbulence kinetic energy, eddy viscosity, and Reynolds stress are also studied, which are helpful to learn the transition＇s behavior.

Preparation,properties,and applications of Bi_(2)O_(2)Se thin films:A review

Two-dimensional materials have shown great application potential in high-performance electronic devices because they are ultrathin,have an ultra-large specific surface area,high carrier mobility,efficient channel current regulation,and extraordinary integration.In addition to graphene,other types of 2D nanomaterials have also been studied and applied in photodetectors,solar cells,energy storage devices,and so on.Bi_(2)O_(2)Se is an emerging 2D semiconductor material with very high electron mobility,modest bandgap,near-ideal subthreshold swing,and excellent thermal and chemical stability.Even in a monolayer structure,Bi_(2)O_(2)Se has still exhibited efficient light absorption.In this mini review,the latest main research progresses on the preparation methods,electric structure,and the optical,mechanical,and thermoelectric properties of Bi_(2)O_(2)Se are summarized.The wide rang of applications in electronics and photoelectronic devices are then reviewed.This review concludes with a discussion of the existing open questions/challenges and future prospects for Bi_(2)O_(2)Se.