Spurious oscillation in heat transfer analysis
Spurious oscillation in heat transfer analysis
(OP)
I've met a problem with ABAQUS.
In fully coupled thermal-stress analysis (or just simple heat transfer analysis), there's a phenomenon called
"Spurious oscillation", which is stated in ABAQUS/Doc as below:
Spurious oscillations due to small time increments
In transient analysis with second-order elements there is a relationship between the minimum usable time increment and the element size. If time increments smaller than this value are used in a mesh of second-order elements, spurious oscillations can appear in the solution, in particular in the vicinity of boundaries with rapid temperature changes. These oscillations are nonphysical and may cause problems if temperature-dependent material properties are present. In transient analyses using first-order elements the heat capacity terms are lumped, which eliminates such oscillations but can lead to locally inaccurate solutions for small time increments. If smaller time increments are required, a finer mesh should be used in regions where the temperature changes rapidly.
I frequently encountered this problem and because my model is for 3D-fully coupled thermal-stress analysis, the mesh size can't be too small in consideration of computation cost.
Anyone can help me?
Thanks a lot!
In fully coupled thermal-stress analysis (or just simple heat transfer analysis), there's a phenomenon called
"Spurious oscillation", which is stated in ABAQUS/Doc as below:
Spurious oscillations due to small time increments
In transient analysis with second-order elements there is a relationship between the minimum usable time increment and the element size. If time increments smaller than this value are used in a mesh of second-order elements, spurious oscillations can appear in the solution, in particular in the vicinity of boundaries with rapid temperature changes. These oscillations are nonphysical and may cause problems if temperature-dependent material properties are present. In transient analyses using first-order elements the heat capacity terms are lumped, which eliminates such oscillations but can lead to locally inaccurate solutions for small time increments. If smaller time increments are required, a finer mesh should be used in regions where the temperature changes rapidly.
I frequently encountered this problem and because my model is for 3D-fully coupled thermal-stress analysis, the mesh size can't be too small in consideration of computation cost.
Anyone can help me?
Thanks a lot!





RE: Spurious oscillation in heat transfer analysis
(also the restrictions on the time increment)
If you're using ABAQUS/Explicit, then you might be interested in changing to ABAQUS/Standard ...
RE: Spurious oscillation in heat transfer analysis
Acutally I'm using Standard.
Tianle
RE: Spurious oscillation in heat transfer analysis
You might want to try first-order elements and with the time savings of the simpler elements use a tighter mesh to get the accuracy you need. Hope this helps.
Robert Stupplebeen
RE: Spurious oscillation in heat transfer analysis
What I used is S4T in Abaqus which is fully coupled
thermal-stress shell elements(with 4 nodes). "with time savings of simpler elements"? Would you please make me clearer?
ABAQUS/Doc suggests me to user finer mesh, but my problem
is, I think it already very fine. Because it's a fully coupled thermal-stress analysis with contact, the computation is quite complicated and time-consuming, if I refine the mesh, the computation time might be unbearable...
RE: Spurious oscillation in heat transfer analysis
corus
RE: Spurious oscillation in heat transfer analysis
Your first message made me think that you were using second order elements but apparently you are using first order. I think corus is getting you down the right path.
Rob
RE: Spurious oscillation in heat transfer analysis
Did you mean you meet the same problem by finite difference method? I'm not sure if what I met is akin to
the instability to FDM. However, my model is fully coupled thermal-stress analysis with contact and geometrically nonlinearity, the considerable spurious oscillation may be not very significant at the beginning but it may cause significant difference at the end due to the high nonlinearity.
Actually the oscillation is caused by forced convection on a surface (modeled by shell elements S4T). Someone told me that I could find the theoretical description on this topic in some advanced finite element books while I've not got it so far. Maybe I would follow your suggestion, to setup a smaller model and then to examine the effects on the oscillation.
RE: Spurious oscillation in heat transfer analysis
corus
RE: Spurious oscillation in heat transfer analysis
I am surprised that ABAQUS says it is a function of of the order of the element. A transient solution should show the same problems element-element if you violate the rules. If the solver can't relax a solution in the time intervals demanded, it won't.
Sinda G manual or TAK manuals have good explanations.
or see Carslaw and Jaeger
or the Handbook of Heat Transfer.
Sorry I can't provide detail but my HT books are elsewhere and I've been working stress/structure for the last 3 years. It's like cleaning your desk between jobs.
Gerry Starkeson
Principal Mechanical Engineer
Aerospace - Stress/Thermal
RE: Spurious oscillation in heat transfer analysis
time increment 'Delta t' should be
Delta t > (Density*Specific heat)*(Delta L)^2/6k
where k is the thermal conductivity. ^2 means power law of 2
Delta L stands for the typical element size.
Also, it's stated that for 1st order element, this formula
might not fit, and the only thing is that the time increment can't be too small or the result will be inaccurate.
I know my problem is. I just face to how to solve it. It's said the upwinding scheme might be effective but I'm not sure, either do I know how to implement it in ABAQUS.