以Lagrangian方式模擬探討定溫熱源下平面熱羽流之流場特性

Investigations on the Flow Properties of Planar Thermal Plume under Isothermal Heating Source by a Lagrangian Approach

許掙強(Cheng-Chiang Hsu) ； 洪振益(Chen-I Hung) ； 蔡朝安(Choa-An Shia)

《航空太空及民航學刊.系列B》 41卷1期 (2009/04) Pp. 25-33

https://doi.org/10.6124/JAAA.200904_41(1).04

摘要

本文以引入虛擬熱粒子方式，提出一個以Lagrangian數值方式處理能量方程式，並結合離散渦流法執行流熱耦合計算及應用隨機走步方式模擬動量與能量之分子擴散效應。模擬探討無初始速度及定溫熱源下二維平面熱羽流之空間與時間發展特性。在數值上，除對提出之Lagrangian運算方式處理能量方程做一詳細探討外，並提出一個合適的的壁面定溫熱源Lagrangian虛擬熱粒子產生機制；在物理上，則針對熱羽流之不穩定特性及紊流態統計特性做探討，由模擬的結果可知在高Rayleigh數下平面熱羽流不穩定機制由脹縮、搖擺與合併等三個過程所主導，在下游之統計特性顯示與紊流區域不變分析結果一致。

關鍵字

渦流法 ； 熱流耦合 ； 平面定溫熱羽流 ； 不穩定機制

並列摘要

A new Lagrangian approach is proposed to simulate the development of plane thermal plume. In the present studies, the virtual thermal particles are introduced to transport energy from thermal source; the discrete vortex method is adopted to calculate the convective effect of flow field; the molecular diffusive transportations of momentum and energy are done by random walk approach. The approaches on the flow-thermal coupling are clearly illustrated. A proper generation mechanism of virtual thermal particle on isothermal heating source is also presented. Both instability mechanism and turbulent statistical flow properties are studied carefully. Not only reasonable flow patterns but also interesting statistical flow properties are obtained. The instability mechanisms of plane thermal plume at high Rayleigh number, including vortex phase lag, flapping and merging, are observed; the statistical properties of flow and thermal fields are consistent surprisingly well with the predictions from the local invariant analysis of turbulence theory.

並列關鍵字

Lagrangian numerical approach ； Thermal-flow coupling ； Plane thermal plume ； Instability