Interaction between the injected flow from the porous wall and the main flow can reduce drag effectively.The phenomenon is significant to the flight vehicle design.The intensive flux of injection enhances difficulty of numerical simulation and requires higher demands on the turbulence model.A turbulent boundary layer flow with mass injection through a porous wall governed by Reynolds averaged Navier-Stokers(RANS)equations is solved by using the Wilcox′s k-ωturbulence model and the obtained resistance coefficient agrees well with the experimental data.The results with and without mass injection are compared with other conditions unchanged.Velocity profile,turbulent kinetic energy and turbulent eddy viscosity are studied in these two cases.Results confirm that the boundary layer is blowing up and the turbulence is better developed with the aid of mass injection,which may explain the drag reduction theoretically.This numerical simulation may deepen our comprehension on this complex flow.
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.
为减少三体船结构质量以提高三体船总体性能,同时保证结构质量减少后三体船舱壁结构具有足够的结构强度,本文基于《Rules for The Classification of Trimarans》设计了7个三体船结构强度校核工况。应用变密度拓扑优化方法,计算了优化前、后三体船舱壁结构在不同工况下的应力分布。计算及优化结果表明:特定工况不同体积约束条件下,优化后舱壁结构应力最大值与体积减少比例之间不存在正相关关联;通过优化能在保证结构安全的前提下,减少舱壁优化区域内50%的结构重量,实现非水密舱壁结构的轻量化设计;通过与实船舱壁设计对比,优化后舱壁连接材料的分布与实船舱壁的加强筋分布相似,特定工况下按照优化结果进行加强筋布置的舱壁结构强度更好,拓扑优化技术可在特定工况下为舱壁结构的加筋布置提供指导。
应用有限元仿真技术,以我国南海使用的深水半潜式海洋钻井平台为原型建立模型,进行极限工况下波浪参数搜索工作.依据ABS(American Bureau of Shipping)和DNV(Det Norske Veritas)规范,应用随机性设计波法搜索并确定深水半潜式平台两浮体之间分离力最大工况、纵向剪切力最大工况、绕横轴扭矩最大工况以及总纵垂向弯矩最大工况共四种极限工况下的波浪参数,并通过所得波浪参数计算平台表面载荷分布.
