fluent unit計算單位和設(shè)計單位、網(wǎng)格單位、縮放單位的關(guān)系

2016-09-20 by:CAE仿真在線來源:互聯(lián)網(wǎng)

fluent 里頭有幾個單位概念unit,如:計算單位和設(shè)計單位、網(wǎng)格單位、縮放單位的關(guān)系

1、Define Units 通過菜單 define-》units設(shè)置,這里面的值是計算的單位,這個單位必須與網(wǎng)格尺寸的單位、udf代碼、參數(shù)輸入中的所有數(shù)值的單位保持一致

2、設(shè)計單位:即設(shè)計CAD模型時候使用的單位,這個單位極為原始模型單位,后面fluent中必須與之保持實質(zhì)長度上的一致即可,比如創(chuàng)建的時候時1cm,則對應(yīng)于fluent默認的1e-2m

3、網(wǎng)格單位:其實就是設(shè)計單位,因為劃分網(wǎng)格時候使用的單位同樣基于CAD實際模型的尺寸。但是這個要與網(wǎng)格放縮單位相互區(qū)別。

4、fluent網(wǎng)格單位放縮

這是個容易混淆的概念,很多人認為這就是fluent的單位,其實不是。

我們可以參考下面的fluent的幫助文件來進行原汁原味的說明:

#5.8.14. Scaling the Mesh

Internally, ANSYS Fluent stores the computational mesh in meters, the SI unit of length. When mesh information is read, it is assumed that the mesh was generated in units of meters. If your mesh was created using a different unit of length (inches, feet, centimeters, and so on), you must scale the mesh to meters. To do this, you can select from a list of common units to convert the mesh or you can supply your own custom scale factors. Each node coordinate will be multiplied by the corresponding scale factor.

Scaling can also be used to change the physical size of the mesh. For instance, you could stretch the mesh in the direction by assigning a scale factor of 2 in the direction and 1 in the and directions. This would double the extent of the mesh in the direction. However, you should use anisotropic scaling with caution, since it will change the aspect ratios of the cells in your mesh.

翻譯為:fluent內(nèi)部使用的是SI國際單位,即m,kg,s,N,這個在讀取網(wǎng)格mesh數(shù)據(jù)時是默認的,即一個單位就是1m

下面是解釋:

為啥fluent提供一個Scaling the Mesh這樣一個明顯的功能呢?