Application of a Dual Beam Laser Velocimeter to Turbulent Flow Measurements

1974 ◽  
Author(s):  
V. A. Cline ◽  
H. T. Bentley ◽  
III
Keyword(s):  
Turbulent Flow ◽  
Flow Measurements ◽  
Beam Laser ◽  
Dual Beam

Highly resolved experimental results of the separated flow in a channel with streamwise periodic constrictions

2016 ◽  
Vol 796 ◽  
pp. 257-284 ◽  
Author(s):  
Christian J. Kähler ◽  
Sven Scharnowski ◽  
Christian Cierpka
Keyword(s):  
Turbulent Flow ◽  
Flow Separation ◽  
Flow Direction ◽  
Separated Flow ◽  
Mean Flow ◽  
Complex Flow ◽  
Flow Measurements ◽  
Flow Features ◽  
Wall Flow ◽  
Near Wall

The understanding and accurate prediction of turbulent flow separation on smooth surfaces is still a challenging task because the separation and the reattachment locations are not fixed in space and time. Consequently, reliable experimental data are essential for the validation of numerical flow simulations and the characterization and analysis of the complex flow physics. However, the uncertainty of the existing near-wall flow measurements make a precise analysis of the near-wall flow features, such as separation/reattachment locations and other predicted near-wall flow features which are under debate, often impossible. Therefore, the periodic hill experiment at TU Munich (ERCOFTAC test case 81) was repeated using high resolution particle image velocimetry and particle tracking velocimetry. The results confirm the strong effect of the spatial resolution on the near-wall flow statistics. Furthermore, it is shown that statistically stable values of the turbulent flow variables can only be obtained for averaging times which are challenging to realize with highly resolved large eddy simulation and direct numerical simulation techniques. Additionally, the analysis implies that regions of correlated velocity fluctuations with rather uniform streamwise momentum exist in the flow. Their size in the mean flow direction can be larger than the hill spacing. The possible impact of the correlated turbulent motion on the wake region is discussed, as this interaction might be important for the understanding and control of the flow separation dynamics on smooth bodies.

Temperature and Stress Analysis of Dual-Beam Laser Cladding on Gray Cast Iron Surface

Applied laser ◽  
2014 ◽  
Vol 34 (4) ◽  
pp. 288-293
Author(s):  
刘衍聪 Liu Yancong ◽  
范常峰 Fan Changfeng ◽  
尹晓丽 Yin Xiaoli ◽  
杨光辉 Yang Guanghui ◽  
许鹏云 Xu Pengyun
Keyword(s):  
Cast Iron ◽  
Stress Analysis ◽  
Laser Cladding ◽  
Gray Cast Iron ◽  
Iron Surface ◽  
Gray Cast ◽  
Beam Laser ◽  
Dual Beam

Effect of Energy Ratio on Dual Beam Laser Welding Characteristics

2017 ◽  
Vol 44 (3) ◽  
pp. 0302003
Author(s):  
马国龙 Ma Guolong ◽  
李俐群 Li Liqun ◽  
陈彦宾 Chen Yanbin
Keyword(s):  
Laser Welding ◽  
Energy Ratio ◽  
Beam Laser ◽  
Dual Beam

Influence of Temperature Distribution of Ceramic Coating Using Top-Hat Assistant Laser Beam in Dual-Beam Laser Cladding

2014 ◽  
Vol 41 (7) ◽  
pp. 0703012
Author(s):  
吴东江 Wu Dongjiang ◽  
褚洋 Chu Yang ◽  
牛方勇 Niu Fangyong ◽  
马广义 Ma Guangyi ◽  
庄娟 Zhuang Juan
Keyword(s):  
Temperature Distribution ◽  
Laser Beam ◽  
Laser Cladding ◽  
Ceramic Coating ◽  
Influence Of Temperature ◽  
Beam Laser ◽  
Dual Beam

Investigation of Fluid Flow and Heat Transfer in 3D Dual-Beam Laser Keyhole Welding

2010 ◽  
Author(s):  
Jun Zhou ◽  
Hai-Lung Tsai
Keyword(s):  
Heat Transfer ◽  
Laser Welding ◽  
Welding Process ◽  
Solidification Process ◽  
Melt Flow ◽  
Single Beam ◽  
Keyhole Welding ◽  
Beam Laser ◽  
Dual Beam ◽  
Laser Keyhole Welding

Dual-beam laser welding has become an emerging joining technique. Studies have demonstrated that it can provide benefits over conventional single-beam laser welding, such as increasing keyhole stability, slowing down cooling rate and delaying the humping onset to a higher welding speed. It is also reported to be able to improve weld quality significantly. However, due to its complexity the development of this promising technique has been limited to the trial-and-error procedure. In this study, mathematical models are developed to investigate the heat transfer, melt flow, and solidification process in three-dimensional dual-beam laser keyhole welding. Effects of key parameters, such as laser-beam configuration on melt flow, weld shape, and keyhole dynamics are studied. Some experimentally observed phenomena, such as the changes of the weld pool shape from oval to circle and from circle to oval during the welding process are analyzed in current study.

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