挖溝機雙噴嘴沖擊射流的數值研究

摘" " 要：海底射流式挖溝機或疏浚設備的使用過程中涉及到雙噴嘴沖擊射流問題，揭示射流流場的演化規律有望對工程問題提供理論支持。使用CFD方法對二維雙噴嘴淹沒條件下射流沖擊固體壁面問題進行建模并求解，分析在不同射流靶距、噴嘴間距以及射流流速下流速場、沖擊區壓力及剪應力的分布特性。驗證算例表明，CFD方法可以獲得較好的預測結果。計算結果表明，噴嘴間距越小，沖擊區壓力分布越大；射流靶距減小時，射流壓力驟增，且在雙噴嘴之間會形成振蕩效應，讓沖擊區壓力及剪應力大小和位置發生波動。在實際工程中，應注意這種振蕩效應對機械運動穩定性的影響。

關鍵詞：雙噴嘴；沖擊壓力特性；流場特性；CFD

Numerical study on double-nozzle impinging jet of trencher

ZHENG Qiuming YU Yinhai XUAN Yingjie LYU Weijun LAN Xuejie FAN Zeren

1. Offshore Oil Engineering Co.， Ltd.， Tianjin 300461， China

2. School of Infrastructure Engineering， Dalian University of Technology， Dalian 116024， China

Abstract：Double-nozzle impingingjet is involved in the use of underwater jet trenching machines or dredging equipment. Therefore，theoretical support for engineering problems could be provided if the evolution law of the jet flow field is revealed.In this study， a model was made and solved by the CFD method for the problem of jet impingement on solid walls in the condition of the two-dimensional double nozzle in submergence.This paper analyzed the effect of different impinging distances， nozzle spacing， and jet velocity on the flow velocity field as well as pressure and shear stress distribution in the impact area. The verified result shows that the proposed CFD methodcan achieve good prediction results. The calculation results indicate that pressure distribution in the impact area becomes greater if the nozzle spacing is smaller. When the impinging distance gets closer， the jet pressure suddenly increases.At the same time， an oscillation effect is formed between the two nozzles， causing fluctuations in the magnitude and position of pressure and shear stress in the impact area. In practical engineering， attention should be paid to the impact of this oscillation effect on the stability of mechanical motion.

Keywords：double-nozzle; impinging pressure; flow field; CFD

射流沖擊固體表面的現象在許多工程中廣泛出現，例如油漆噴涂、射流干燥工藝、電弧焊接以及飛機的垂直起降等[1]。在土木與水利領域，淹沒式水射流沖擊固體的問題也受到重視。一方面，水射流會導致結構物或土體的沖刷與侵蝕，這會讓結構物遭受短期或長期的失穩威脅；另一方面，射流可被用于清淤、開溝等工程活動，這使得射流在航道疏浚、埋設管道等方面創造了極大的工程價值[2]。為此，學者們對沖擊射流流場結構開展了深入研究。比較早的研究可以追溯到上世紀六七十年代，Beltaos[3]以空氣為研究介質，開展了二維平面及三維圓形噴嘴的沖擊射流試驗，對自由射流區及壁面射流區的流場分布、沖擊區壓力及剪應力分布進行測量并推導了相關預測公式。……