A Combined Experimental and Theoretical Investiation of Fluid Sheets Flow generated by Obliquely Colliding Laminar Water Jets
Date Issued
2007
Date
2007
Author(s)
Yu, Chuan-Chun
DOI
zh-TW
Abstract
The objective of this investigation is study the principle of classic atomization engineering of the impinge type of liquid sheet in great depth .and the attempts would be made to introduce the collide condition of new form in micro scale of liquid jets. Our aim is to examine the applicability of the classic theory of fluid sheets in the above condition, and discuss the formation condition of a new type of flow named fishbones. And the works is a combined experimental and theoretical investigation of fluid sheets flow generated by obliquely colliding laminar water jets in atmosphere environment. This investigation is mainly divided into three parts:
(1) The characteristics of fluid sheet flows formed by symmetric collision:
(i) fluid sheet types
The works is using method of dimensional analysis(Rej、Wej) to study the characteristics of fluid sheet types. In addition to several classic fluid sheet types, we discover a new type of fluid sheets called unclosed fluid chain with meta-stable rim. In addition , this research have provided the flow pattern of oscillating stream , despite the flow has been proposed by Bush and Hasha【24】in 2004. But they only had word statement without any flow pattern presented in their report.
(ii)dynamic analysis of fluid sheet flows:
The research is firstly introduce the aspect of the momentum of liquid jet to study
the characteristic of fluid sheet formation. And the results clearly demonstrate that the hypothesis of fluid sheet formation can be examined by experiment which has been proposed by Taylor【7】in 1960.
(iii) fluid sheet geometry
In these section, the classic fluid sheet shape theory in the micro-scale liquid jet impingement condition has been investigated. And the results have been demonstrated that the agreement of classical fluid sheet shape theory is conditional accuracy. And it has confirmed that the theoretical fluid sheets length to width ratio only vary with impingement angle, and the reality fluid sheets length to width ratio well vary with liquid jet velocity and jet diameter.
(2) The characteristics of fluid sheet flows formed by asymmetric collision:
(i) fluid sheets types
In an asymmetric collision, the fishbone flow has been observed .The limited parameter regine( 2θ=90∘, 250<Wej<1200、800<Rej<1500) in which the fishbones exist is reasonable.
(ii) fluid sheets flow with periodic property
Our results indicate that the frequency of fishbones can reach several thousand Hz which is much different to that reported by Bush and Hasha【24】. The later indicates that the frequency should be only in 150~250Hz. The possible reasons will be explaned later in this paper.
(3) The instability of fluid sheet flows
(i)rim-driven instabilities
In the section, after using Rayleigh-Plateau instability to examine the possible mechanism of instabilities of fisbones flow. We find that major mechanism of instabilities of fisbones should be Rayleigh -Plateau instability can be confirmed.
(ii)the relationship between fishbones and periodic drops.
It appears that the flow characteristics between periodic drops and fishbones are similar. It indicates that the formation principle between this two type flows might be similar too.
Subjects
液頁
液頁長寬比
液頁型態
軸對稱碰撞
非軸對稱碰撞
fluid sheets
fluid sheets length to width ratio
symmetric collision
asymmetric collision
types of fluid sheets
Type
thesis
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