具不同類型顆粒群碰撞之兩相紊流計算分析

Turbulent Flow Computation with Considering Inter-Particle Collisions of Different Particle Groups

張能宗(Neng-Tsung Chang) ； 張克勤(Keh-Chin Chang)

《航空太空及民航學刊.系列B》 40卷1期 (2008/04) Pp. 1-9

https://doi.org/10.6124/JAAA.200804_40(1).01

摘要

應用大尺度渦流法並結合拉氏(Lagrangian)顆粒追蹤法及four-way coupling兩相處理方式來模擬Re(下? r)=644之垂直渠道紊流場，並於流場中放入不同材質顆粒群進行個別紊流統計量之分析。在顆粒與壁面碰撞方面分別使用光滑壁面模式與Sommerfeld與其工作團隊(1999-2003)所提出的壁面粗糙度模式進行模擬計算。
在以往的研究中得知，不同材質顆粒之負載紊流場於光滑壁面模式下，顆粒雖然會受顆粒與顆粒間的碰撞與顆粒碰撞壁面的影響，但顆粒在流場中的運動行為還是主要決定於其St(上? +)值。然而加入了壁面粗糙模式後，壁面粗糙度會造成垂直壁面擾動速度大幅增加而使顆粒往主流中心區移動，降低了St(上? +)較低顆粒在近壁低速區的累積，同時加強了顆粒在垂直壁面方向混合的能力，進而改變顆粒於流場中的分佈狀況。顆粒在流場中的運動行?將不再完全由St(上? +)值主導，還必須考慮壁面粗糙度因素所造成的影響。

關鍵字

紊態顆粒負載流場 ； 顆粒碰撞

並列摘要

Particle-laden turbulent channel flow at Re(subscript r)=644, loaded with binary mixture of particles, is numerically studied using the Lagrangian particle tracking method coupled with large eddy simulation. Turbulence statistics of different particle groups are analyzed. Two particle-wall models are applied to this study with (Sommerfeld and coworkers, 1999-2003) and without considering wall roughness. Taking into considerations of rough wall model, the effect of wall roughness in the computations strengthens the wall-normal particle velocity fluctuations. As a result, particles tend to move from the near-wall region to the central core region. It leads to decrement of particle accumulation in the near-wall region as compared to the case considering the smooth wall model. The wall-normal particle mixing capability is enhanced which results in the redistribution of particles in the channel. The behavior of particle motion in the turbulent channel flow should be, thus, dependent on not only the value of Stokes number but also the wall roughness level.

並列關鍵字

Turbulent particle-laden flow ； Particle collisions