为什么我做的自然对流加有辐射模式和不加辐射模式，温度场算出的结果是一样的

stoneegg

在恒壁温条件下，开始时改变黑度，算出的结果是一样的，后来索性把辐射模式关了，居然也一样。我作的是一竖直平板，边界都用了outlet。
在计算中，spot 的T3项值很快就稳定不变，但error 也变成常值不收敛。
改变黑度后T3值有同样表现
是由T3值来计算辐射换热的吧，如何才能让T3值收敛那，改变网格，好象不行呀，
是不是immersol 中的设置不对，还望指教

phoenics

你的model有问题,平板对谁辐射?
另外,你是什么版本的程序?新版本多immersol有了一点改进.

stoneegg

3.4版的，我再改一改，不过比较麻烦

phoenics

Question: - How to accelerate the convergence of T3 for IMMERSOL radiation model ?

Answer:
Convergence of the energy (TEM1 or H1) and T3 equations can be strongly influenced by the PIL real variable RSG41.
RSG41 is a multiplier to the coefficient which is used to link the radiation temperature T3 to TEM1 in solids. The default value is unity, but this can be overwritten by setting RSG41>0 in the Q1 file.
A value of RSG41 equal to unity means that the term linking T3 and TEM1 in the solid is comparable with the surrounding conduction terms in the solid.
A value of RSG41>1 makes a stronger link between T3 and TEM1 than that of the surrounding conductive links. Thus sufficiently large values of RSG41 will achieve the desired effect of fixing T3 to TEM1. However, if the radiative contribution is large, slow and/or difficult convergence can be encountered.
Experience has shown that although smaller values of RSG41 promote convergence, they can artifically reduce the effects of radiation. This is because T3 and TEM1 will not be linked tightly together, and so most of the radiation will remain in the T3 equation and not be transferred to the TEM1 equation via the linking term.
The advice is to use a value of RSG1 in the range 1 to 100, or more generally as large a value as can be used to reasonably link T3 to TEM1 in the solid without preventing convergent behaviour.
In PHOENICS V3.4 onwards RSG41 is no longer required because a Partial-Elimination Algorithm (PEA) has been introduced whereby changes to temperature as a result of radiation fluxes are anticipated by the IMMERSOL model. The benefit is that the T3 and TEM1 values in solids are linked more efficiently, avoiding the conflict between accuracy and speed of convergence in earlier implementations of IMMERSOL. Experience with the PEA has shown that large temperature fluctuations can sometimes occur during early sweeps. There are various steps you can take to control this effect: (a) switch ISOLX, ISOLY and ISOLZ to zero (under 'Numerics', 'Iteration control'), (b) introduce VARMIN and VARMAX values for TEM1 and T3, (c) use FALSDT for TEM1 and T3, rather than LINRLX.

stoneegg

试过了，只有该最值有点用，其他看不到效果，多谢

phoenics

再告诉你一个秘密:老版本的IMMERSOL MODEL是有BUG的.计算不收敛
后来改正了.
你可以与CHAM上海联系.

stoneegg

不会把，3。4版也有bug,我晕

stoneegg

今天受到CHAM的回复了，说确实有，PHEONICS大哥，是否还有其他的BUG，望告知，也好一起升级

phoenics

你应该早点要求升级程序。呵呵

stoneegg

才学了四个月，那知道还有这等事，也没有人通知呀，
呵呵可苦了俺这两个月的辛苦劳动，
再次感谢你，要不毕不了业都可能。

bahbahbah

3。3有问题吗？？