臺灣博碩士論文加值系統

本文係以實驗的方法來探討:在固定之自由流下,高攻角之 75°後掠角三
角翼搭接不同的外掛載後,其翼上方之基本流場特性。實驗是在循環水槽
中進行。為清楚瞭解流場之基本物理現象,在定性方面是應用流場可視化
法作流場觀察;包括採用染液注射法以固定座標觀察流場中煙線變化;並應
用雷射光頁法觀察渦度場特性。在定量分析方面則運用一維光纖雷射都普
勒測速儀偵測渦流平行翼根弦方向之平均速度分佈及渦漩垂直自由流方向
之平均速度分佈。為達到研究目的,本實驗設計了五種不同幾何尺寸之外
掛載,每種外掛載具有特徵長度、特徵高度及特徵厚度等三個參數,再配合
攻角之改變,以分析這些參數與流場變化之關係。結果顯示：渦流潰散之
位置隨著攻角的增加而愈往上游提前發生。若將三角翼加上外掛載,則會
因為前緣渦流之環流速度減少、渦漩尺寸變大、及渦流核心之軸向速度突
然減速等,導致渦流潰散的提前發生。且外掛載之特徵長度愈長、特徵高
度愈高、及特徵厚度愈厚,均更容易使渦流潰散往上游發生。

An experimental study of the leading edge vortices over a 75°
swept delta wing with external stores is presented. A com-
bination of flow visualization technique and fiber-optic laser
doppler velocimeter measurements were used to study the leading
edge vortex formation and breakdown for the delta wing with a
set of external stores. The external stores had characteristic
incidence angles of 20°,45°,90°;characteristic width of 15
or 30 mm. The flow structure was examined for angles of attack
from 25°to 40°at Reynolds number of 1.75×10 based on the
root chard. Vortex breakdown was observed on all the tests of
the wing with external stores. The visualization and velocity
field survey data shows that the external stores made vortex
breakdown occur early and the core flow transform abruptly from
a jet-like flow to a wake-like flow. The result also revealed
the external stores induced vortex breakdown was more steady
than the natural breakdown.