Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/1750
標題: 具阻塊之三維高溫紊流雙噴射撞擊流場分析
The Flowfield Analysis of 3-D Hot and Turbulent Flow of Impinging Twin-Jet on Rough Ground
作者: 黃奇課
Hwang, Cheey-Kuo
關鍵字: three-dimensional turbulent;三維紊流;block;crossflow;upwash fountain;circulating flow;塊狀阻物;橫向流;上沖噴泉;迴流
出版社: 機械工程學系
摘要: 
摘要本文研究模擬垂直起降飛機(VTOL)在凹凸
不平地表從事起降的流場分析。數值模擬採用PHOENICS軟體來進行分析運
算。因為噴射撞擊流場具有紊流的特性,所以採用 紊流模式,並以控制
體積法建立差分方程式。接著利用SIMPLEST計算程序求解,藉以模擬三維
、高溫、高壓氣體之矩形噴口雙噴射撞擊流場。本文分別就阻塊的數目與
位置、橫向流的有無、兩噴口間距、兩平板間距、噴流角度及噴流速度等
參數變化對流場之速度、溫度和壓力的影響逐一討論。數值分析結果顯示
,噴射主流撞擊阻塊平板後,由於地面效應,在兩噴射主流間將產生上沖
噴泉流。在兩平板高度為0.5公尺下,具阻塊流場之上沖噴泉速度比在沒
阻塊時約減少64%。因流體間的交互作用產生數個迴流。在不具橫向流時
,迴流會隨著高度下降漸漸散開來,並向流場內側移動。當具橫向流時,
上游迴流變窄並隨著高度下降而接近噴射主流,下游迴流則遠離噴射主流
。對橫向流、阻塊、噴嘴角度等參數變化而言,橫向流會使停滯線呈彎區
。當在兩平板高度為0.5公尺下且不具阻塊時,上沖噴泉在一半高度處發
生向下游偏向,且其上游流場約為60 之低溫區。當在兩平板高度為0.3公
尺下且具有阻塊時,阻塊將使上沖噴泉從5.2696 m/s(不具阻塊時)變弱
為1.6906 m/s,比沒有阻塊情況時約減少68%,且其流場壓力下降,溫度
升高50 。又噴流向內斜噴時,上沖噴泉變強為2.427 m/s,流場壓力較小
,溫度較低為350 。當其向外斜噴時,上沖噴泉變弱為1.2072 m/s,流場
壓力變大,溫度較高為530 。總而言之,以上參數變化將影響上沖噴泉的
強弱與流場的性質。關鍵字:三維紊流、塊狀阻物、橫向流、上沖噴泉流
、迴流

ABSTRACTIn this study, the near
flowfield of vertical take-off landing (VTOL) military airplane
working on the rough ground is simulated by numerical
simulation. The computational fluid code, PHOENICS, is used to
calculate the properties of the three-dimensional hot flow of
twin-jet impinging on a rough ground. Owing to the turbulence
possessed by the impinging flowfield, the turbulence model is
adopted and the control-volume integration for finite difference
associated with SIMPLEST algorithm are employed to simulate the
three-dimensional, high-temperature, high-pressure flowfield.
The effect of variation of the parameters including, number and
location of block, crossflow, nozzle-to-nozzle spacing, nozzle-
to-ground spacing, impinging angles and jet-inlet velocity on
the flowfield velocity, pressure and temperature will be
studied.The computed results show that upwash fountain is
generated between the two jets with the effect of the ground.
Compared with upwash fountain without block, 64% decay in
velocity of that with block is found when the distance between
the two plates is within 0.5m. Several induced circulation zones
are formed due to the interaction between jets and fluid
surroundings. The circulation zones will be dispersed when the
height of flowfield is downward with absence crossflow. The left
circulation zones will be narrow and close to the jets when the
height of flowfield is downward with crossflow. But the right
circulation zones will be far to the jets when the height of
flowfield is downward. Significant effects of variation of the
parameters including crossflow, block, and nozzle angle are
detailed discussion as follow. The stagnation line is curved
when the flow is a crossflow. The upwash fountain will change
direction toward the latter part of the stream, and the former
part of the stream becomes a low-temperature region of 60 when
the distance between the two plates is within 0.5m. The velocity
of upwash fountain is decreased from 5.2696 m/s without block 3B
to 1.6906 m/s with block when the distance between the two
plates is within 0.3m, whereby 68% decay in velocity is
obtained. The pressure of the flowfield is decreased, and the
increased temperature is 50 when block exists. The inward jets
will enhance the upwash fountain to 2.427 m/s, and decreasing
the pressure and the temperature decreasing to 350 . The outward
jets will weaken the upwash fountain to 1.2072 m/s, and
increasing the pressure and the temperature increasing to 530 .
In summary, the variation of parameters, such as crossflow,
block, and nozzle angle, is shown to be strongly correlated with
the upwash fountain structure and properties of the flowfield.
Key words: three-dimensional turbulent, block, crossflow, upwash
fountain, circulating flow.
URI: http://hdl.handle.net/11455/1750
Appears in Collections:機械工程學系所

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