臺灣博碩士論文加值系統

利用數值方法模擬紊流流場時, 通常需要引入紊流模式,其中以雙方程式
k-e 紊流模式,較為廣用,其大致可分為(一)傳統紊流模式結合邊牆函數(
二)低雷諾數紊流模式。 在近牆區域通常以低雷諾數紊流模式所預測結果
較為準確,在考慮邊牆具有熱傳質傳發生時以低雷諾數紊流模式較為適合
。謝與張,針對諸位學者所提出之低雷諾數紊流模式進行模擬, 其結論中
提到部份低雷諾數紊流模式之模式函數Fm與F2,採用邊牆剪應力為參數,造
成再接觸點附近產生奇異點問題。因此進而發展一強健式低雷諾數紊流模
式, 改善過去學者提出的模式所產生奇異點問題,同時能夠準確模擬紊流
近牆的極限行為。本研究以有限體積法， QUICK scheme 在交錯格點系統
解Navier- Stokes方程式，將此一強健式低雷諾數紊流模式應用至背向階
梯流場。模擬並探討邊牆具有熱傳、傳質現象發生,驗證適用性。

In calculating turbulent flow，the turbulent closure mod- els
are often adopted by investigstors。It is well-known that the
performances of low-Reynolds-number turbulence models are
better than those of the conventional turbulence models incor-
porated with the wall function formulas which bridge the no s-
lip boundary condition at solid wall to flow region。 As a
result，the low-Reynolds-number models have been wid- ely
applied to simulate the problems of wall heat，mass trans- fer
and so on。However these low-Reynolds-number models have been
developed which can yield good predictions in boundary ayer
flows，channels flows，fulley developed pipe flows 。 Hsieh and
Chang，these low-Reynolds-number models are investigated。
Results show that these low-Reynolds-number mod- els fail to
predict accurstedly in the neighborhood of reatta- chment points
，because these models adopted wall shear stress as a parameter
Fm and F2。They are to develop a robust low-Re- ynolds-number
turbulence model which can give correct predict- ion in the
recirculating flow。 The influence of the eddy viscosity may be
seriously on nonisothermal flow in heat or mass transfer
predictions。 In the neighborhood of reattachment points where
invariably produce hot spots。 Therefore ， an accurate
prediction of in the near wall region for turbulent flows is
required。 The numerical program is written on a staggered grid
s- ystem。 The Navier-Stokes equation are approximated via the
finite volume methods， SIMPLER algorithm and the convect- ive
terms are treated by QUICK scheme of Hayase，and emplo- yed
robust low-Reynolds-number turbulent model applied to
Backword facing step flows。Simulation and discuss heat and
mass transfer in the near wall regions。