雙流體方程模擬高速液滴撞擊壁面之現象探討

液滴的應用如噴墨印刷、油滴注入燃燒室等，特別是高壓水柱清潔、柴油引擎內液滴與壁面的交互作用和飛機飛行穿越雲層水滴撞擊機翼等，使微小液滴衝擊固體表面成為一個重要的物理現象。在本研究中，吾人以 Niu 等人於 2008年發表的 AUSMDV 結合真實黎曼解之通量分離法建立了可壓縮兩項流求解六個方程雙流體模式之數值模擬，用於高速微小液滴以不同的撞擊速度及入射角度撞擊剛性壁面之流體分析。吾人設置撞擊速度 100-500m/s；入射角度 90-30 度，分析其內部壓力變化、震波及擴散波的傳遞以及於壁面產生高速噴流之狀況。模擬結果皆能準確抓到內部物理現象的變化，模擬結果發現，同速度下 2D 的最大壓力比 3D 大；噴流時間也較為延後。液體可壓縮的影響之下，壁面的壓力逐漸上升，其衝擊能量隨初始速度上升而增加；入射角的增加而減少。最大壓力值和文獻的比較發現較為接近一維模型的預測。

關鍵字

雙流體模型；高速液滴；可壓縮液體；計算流體力學

並列摘要

The liquid droplet dynamics are widely seen in the industry application such as inkjet printing, injection in the combustion chamber, high-pressure spray cleaning, droplet-wall interactions in diesel engines, and impact of cloud droplets on airplane wings in which impact of small droplets on a solid surface is a key phenomenon. In this research, the previous numerical codes developed Niu .et al (2008) is combined with the exact Riemann solver scheme as numerical flux splitting to solve the compressible two-fluid six-equation model. We focus on the simulation of high speed micro-droplet impact on a rigid surface by different impact speed and incidence angle. We set 100-500m/s of impact velocity and 30-90 degree of incidence angle to study the related pressure distributions on walls, propagation of shock front and expansion wave inside the droplet and high speed jetting near the surface. The capturing of phenomenon is accurate and robust. Numerical results show that under the same impact condition the maximum pressure simulated by in the 2D case is shown to be bigger than the 3D case; the jet time in the 3D case is relatively delayed. The impact energy increased with high velocity and incidence angle. Numerical validation shows our results is closer to 1D theoretical model.

並列關鍵字

two fluid model ； high speed droplet ； compressible liquid ； CFD

參考文獻

[1] S. Mitra, Breakup process of plane liquid sheets and prediction of initial droplet size and velocity distributions in sprays, PhD thesis (University of Waterloo) (2001).

[2] J. Blaisot and J. Yon, Droplet size and morphology characterization for dense sprays by image processing: application to the Diesel spray, Exp. Fluids 39, 977 (2005).

[3] K.K. Haller, Y. Ventikos, D. Poulikakos, and P. Monkewitz, Computational study of high-speed liquid droplet impact, J. Appl. Phys. 92, 2821 (2002).

[4] A. McDonald, M. Lamontagne, C. Moreau, and S. Chandra, Impact of plasma-sprayed metal particles on hot and cold glass surfaces, Thin Solid Films 514, 212 (2006).

[5] M. Rein, Phenomena of liquid drop impact on solid and liquid surfaces, Fluid Dyn. Res. 12, 61 (1993).

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雙流體方程模擬高速液滴撞擊壁面之現象探討

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