计算力学学报
計算力學學報
계산역학학보
CHINESE JOURNAL OF COMPUTATIONAL MECHANICS
2007年
4期
477-481
,共5页
数值模拟%分层大气流动%山体绕流%污染物输移
數值模擬%分層大氣流動%山體繞流%汙染物輸移
수치모의%분층대기류동%산체요류%오염물수이
numerical modeling%stratified flow%atmospheric flow around a mountain%pollutant dispersion
对分层大气山体绕流的流动模式及扩散输移特性进行了数值模拟.采用隐式时间离散方法在贴体网格系统下求解雷诺平均的N-S方程,计算结果描述出大气流动的特征,证实了分层(以Froude数为特征参数,定义为F=U/NH,U为来流风速,N为Brunt-Vaisala频率,H为山体高度)变化对山体绕流流态的影响.数值结果表明:当Froude数大于4.0时,山体绕流的流动不再依赖于大气分层的变化.当Froude数介于4.0和1.0之间时,流场中出现了Lee波,并随着Froude数的进一步减小,流动分离发生及Lee波破碎现象.同时模型也预测了在各种流动模式下大气中夹杂着的污染物绕山体的传输特性,表明大气的分层现象对污染物的分布有着非常重要的影响.
對分層大氣山體繞流的流動模式及擴散輸移特性進行瞭數值模擬.採用隱式時間離散方法在貼體網格繫統下求解雷諾平均的N-S方程,計算結果描述齣大氣流動的特徵,證實瞭分層(以Froude數為特徵參數,定義為F=U/NH,U為來流風速,N為Brunt-Vaisala頻率,H為山體高度)變化對山體繞流流態的影響.數值結果錶明:噹Froude數大于4.0時,山體繞流的流動不再依賴于大氣分層的變化.噹Froude數介于4.0和1.0之間時,流場中齣現瞭Lee波,併隨著Froude數的進一步減小,流動分離髮生及Lee波破碎現象.同時模型也預測瞭在各種流動模式下大氣中夾雜著的汙染物繞山體的傳輸特性,錶明大氣的分層現象對汙染物的分佈有著非常重要的影響.
대분층대기산체요류적류동모식급확산수이특성진행료수치모의.채용은식시간리산방법재첩체망격계통하구해뢰낙평균적N-S방정,계산결과묘술출대기류동적특정,증실료분층(이Froude수위특정삼수,정의위F=U/NH,U위래류풍속,N위Brunt-Vaisala빈솔,H위산체고도)변화대산체요류류태적영향.수치결과표명:당Froude수대우4.0시,산체요류적류동불재의뢰우대기분층적변화.당Froude수개우4.0화1.0지간시,류장중출현료Lee파,병수착Froude수적진일보감소,류동분리발생급Lee파파쇄현상.동시모형야예측료재각충류동모식하대기중협잡착적오염물요산체적전수특성,표명대기적분층현상대오염물적분포유착비상중요적영향.
A series of numerical experiments had been conducted to investigate the flow patterns and dispersion characteristics around a mountain under stably stratified flow. The two-dimensional model equations, based on the time-dependent Reynolds averaged Navier-Stokes equations, were solved numerically using an implicit time integration in body-fitted grid arrangement. The behavior of the flow is clarified to ascertain the effects of changes in the stratification, which is characterized by the Froude number F = U/NH (Where U is speed of the approaching wind, N is the Brunt-Vaisala frequency, and H is the mountain height). The numerical results suggest that the flow structure is independent of stratification when F>4.0. The model predicts lee wave generation as the Froude number is decreased from 4 to 1, then flow splitting, wave breaking phenomena happen as F is further decreased to less than 1.0. Further, the model-predicted concentration fields when the contaminant is coming with the approaching wind show that the stratification of atmospheric flow has significant effects on the dispersion pattern.