吉林大学学报(工学版) ›› 2019, Vol. 49 ›› Issue (4): 1034-1042.doi: 10.13229/j.cnki.jdxbgxb20180369

• • 上一篇    

基于浸入单元法和延迟分离涡模型的Ahmed车模尾流涡旋结构

陈鑫(),李铭,阮新建,王宁,王佳宁   

  1. 吉林大学 汽车仿真与控制国家重点实验室,长春 130022
  • 收稿日期:2018-04-18 出版日期:2019-07-01 发布日期:2019-07-16
  • 作者简介:陈鑫(1974-),男,教授,博士生导师. 研究方向:汽车空气动力学及NVH控制. E-mail:cx@jlu.edu.cn
  • 基金资助:
    国家重点研发计划项目(2016YFB0101601-7)

Investigation of vortical structures in wake of Ahmed body by delayed detached⁃eddy simulation turbulence model using immersed boundary method

Xin CHEN(),Ming LI,Xin⁃jian RUAN,Ning WANG,Jia⁃ning WANG   

  1. State Key Laboratory of Automotive Simulation and Control, Jilin University, Changchun 130022, China
  • Received:2018-04-18 Online:2019-07-01 Published:2019-07-16

摘要:

在浸入单元法(IBM)和PISO算法的基础上,实现了IBM?PISO求解算法,利用延迟分离涡(DDES)湍流模型,实现了对汽车外流场涡旋结构的准确模拟。以2D圆柱绕流算例,从流场的时均特性和涡脱特性验证了IBM?PISO求解算法的准确性。在此基础上,应用DDES湍流模型对Ahmed整车模型的流场进行仿真,得到不同斜背倾角对尾部流场时均特性和瞬态特性的影响规律,同时研究了尾部流场主要涡旋结构输送和演化规律。结果表明:IBM?PISO求解算法能够在外流场分离区得到较为准确的结果,解析出包括回流涡旋、顶部λ涡旋、C柱尾涡、头部马蹄涡以及侧壁涡在内的主要涡旋结构;C柱尾涡和侧壁涡在尾流输送过程中进一步增强湍流强度并主导尾场后部流场;斜背倾角决定了斜背处的分离特性,从而直接影响斜背表面和尾流前部的流场特性。

关键词: 车辆工程, 浸入单元法, 延迟分离涡湍流模型, Ahmed车模, 涡旋结构

Abstract:

A new solver is implemented based on immersed boundary method (IBM) and pressure implicit with splitting of operators (PISO) algorithm. By this IBM-PISO solver, the external flow of Ahmed body is simulated using the delayed detached-eddy (DDES) turbulence model. First, the time-averaged features and shedding frequency of 2D cylinder cases are used for the verification of the IBM module and IBM-PISO solver. Then the instantaneous flow field, time-averaged features, and vortical flow structures of Ahmed body are investigated. The effect of slant angle and the transport of vortical structures are compared. The results show that the IBM-PISO solver produces accurate results at separation zone and main vortical flow structures including recirculation vortices, horse-shoe vortices at the upper surface and at the foot of the front surface, C-pillar vortices, and lateral vortices. The transport in the wake enhances the turbulence of C-pillar vortices and renders their domination over the far-wake flow field. The effect of slant angle is based on controlling the flow separation at the slant and confined to the near-wake region.

Key words: vehicle engineering, immersed boundary method(IBM), delayed detached?eddy simulation (DDES) turbulence model, Ahmed body, vortical structures

中图分类号: 

  • U461.1

图1

圆柱绕流时均尾流(ReD = 30)"

表1

尾流结构参数的比较(ReD =30)"

L/D Lx/D Ly/D φ/(°)
当前算例 1.56 0.53 0.52 48.00
实验[13] 1.55 0.54 0.54 50.00
IBM仿真[14] 1.70 0.56 0.52 48.05

图2

圆柱绕流瞬时尾流及旋度瞬态图(ReD = 185)"

图3

Ahmed整车模型"

图4

Ahmed整车外流场计算域"

图5

尾场的时均速度曲线(θ = 25°)"

图6

纵截面流线谱(θ = 25°)"

图7

水平截面流线谱(θ = 25°,Z’ = Z?C,C为车底与地面间距)"

图8

车尾横截面流线谱(θ = 25°)"

图9

瞬时涡旋结构(Q = 0.5)"

图10

纵截面瞬时涡量图(θ = 25°)"

图11

横截面瞬时涡量图(θ = 25°)"

图12

湍动能k/u2 ∞ (θ = 25°)"

图13

斜背倾角对时均涡旋结构的影响"

图14

斜背倾角对瞬时涡旋结构的影响"

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