ANSYS Fluent单精度与双精度计算差异解析

  ANSYS Fluent的单精度和双精度类型在所有的计算机平台上都可以使用。对大多数情况来说，单精度求解器已经足够精确，但是在一些特定类型的问题上双精度更有好处。以下列出几种情况：

1. 如果你的模型具有非常大的长度尺度（例如一根细长的薄管），用单精度计算来表示点坐标可能不够精确。
   

2. 如果你的模型涉及到多个区域，彼此之间通过小尺寸的管道连接起来（例如汽车阀组），其中的一个区域的气压大大高于整个流域的平均压力水平。因此这种情况有必要用双精度计算来求解这个驱动流体的压力差，同样用于显著低于压力水平的情况。
   

3. 对于涉及到高的热传导率的共轭问题（共轭问题，我的理解是两个区域的相邻边界传热或者边界和区域内流体相互传热）、或长宽高尺寸比率很大的网格（扁的或狭长的网格），由于单精度求解器不能有效地传递边界信息，可能会导致计算不收敛和不精确。
   

4. 对于采用population balance模式求解particle size分布的并包含多个数量级跨度的statistical moments的多相流问题，适合用双精度求解器。

  注意:ANSYS Fluent只允许小数点分隔一个周期。如果您的系统设置是一个使用逗号分隔的欧洲地区(例如德国)，接受数值输入的字段可以接受一个逗号,但是逗号后的一切可能会被忽略。如果您的系统设置是在一个非欧洲地区,数值字段不会接受一个逗号。

  ANSYS Workbench接受逗号代替小数点分隔符。当数据导入到ANSYS Fluent时，这些会被转换成多个周期。

  Both single-precision and double-precision versions of ANSYS Fluent are available on all computer platforms. For most cases, the single-precision solver will be sufficiently accurate, but certain types of problems may benefit from the use of a double-precision version. Several examples are listed below:

• If your geometry has features of very disparate length scales (for example, a very long, thin pipe), single-precision calculations may not be adequate to represent the node coordinates.

• If your geometry involves multiple enclosures connected via small-diameter pipes (for example, automotive manifolds), mean pressure levels in all but one of the zones can be quite large (since you can set only one global reference pressure location). Double-precision calculations may therefore be necessary to resolve the pressure differences that drive the flow, since these will typically be much smaller than the pressure levels.

• For conjugate problems involving high thermal-conductivity ratios and/or high-aspect-ratio meshes, convergence and/or accuracy may be impaired with the single-precision solver, due to inefficient transfer of boundary information.

• For multiphase problems where the population balance model is used to resolve particle size distributions, which could have statistical moments whose values span many orders of magnitude.

  Note:ANSYS Fluent allows only a period to be used as a decimal separator. If your system is set to a European locale that uses a comma separator (for example, Germany), fields that accept numeric input may accept a comma, but may ignore everything after the comma. If your system is set to a non-European locale, numeric fields will not accept a comma at all.

  ANSYS Workbench accepts commas as decimal delimiters. These are translated into periods when data is passed to ANSYS Fluent.

  参考于ANSYS Help和豆瓣网