FLUENT的單精度和雙精度求解器
2016-09-30 by:CAE仿真在線 來源:互聯(lián)網(wǎng)
單精度和雙精度的區(qū)別:
單精度:具有7位精確小數(shù)位。
雙精度:具有15位精確小數(shù)位。
另外,雙精度需要占用兩倍的內(nèi)存空間,需要更長的時(shí)間完成計(jì)算。
看了一遍FLUENT幫助文件中對(duì)如何選擇單精度和雙精度求解器的說明:
**************************************************************************************************
對(duì)大多數(shù)算例來說,單精度求解器已經(jīng)足夠精確。但是對(duì)以下幾種情況,雙精度求解器更適合:
1.流域具有顯著的長度尺度(例如一根細(xì)長的管道),用單精度表示點(diǎn)坐標(biāo)可能不夠精確。
2.流域是幾個(gè)區(qū)域,彼此之間用小尺寸的管道連接起來(例如汽車發(fā)動(dòng)機(jī)歧氣管),其中的一個(gè)區(qū)域的氣壓大大高于整個(gè)流域的平均水平,這種情況有必要用雙精度方案來求解壓差。
3.對(duì)于涉及到高的熱傳導(dǎo)率的共軛問題(共軛問題,我的理解是兩個(gè)區(qū)域的相鄰邊界傳熱或者邊界和區(qū)域內(nèi)流體相互傳熱)、或網(wǎng)格單元的長寬高尺寸比率很大的網(wǎng)格(扁的或狹長的網(wǎng)格),單精度求解器不能有效地傳遞邊界信息,會(huì)導(dǎo)致計(jì)算不收斂和不精確。
4.對(duì)于采用了population balance模式求解particle
size分布可能包含數(shù)個(gè)數(shù)量級(jí)跨度的statistical
moments的的多相流問題,適合用雙精度求解器。(沒用過population
balance模式,完全不知道這一條什么意思)
**************************************************************************************************
另外,我個(gè)人的經(jīng)驗(yàn),當(dāng)計(jì)算瞬態(tài)問題的時(shí)間步長很小時(shí),用雙精度求解器可以獲得更好的收斂性。
附:FLUENT幫助文件原文:
Single-Precision and Double-Precision Solvers
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
(e.g., 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 (e.g., 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.
開放分享:優(yōu)質(zhì)有限元技術(shù)文章,助你自學(xué)成才
相關(guān)標(biāo)簽搜索:FLUENT的單精度和雙精度求解器 Fluent培訓(xùn) Fluent流體培訓(xùn) Fluent軟件培訓(xùn) fluent技術(shù)教程 fluent在線視頻教程 fluent資料下載 fluent分析理論 fluent化學(xué)反應(yīng) fluent軟件下載 UDF編程代做 Fluent、CFX流體分析 HFSS電磁分析
編輯