I have been having several issues with fix ave/chunk, temp/profile and temp/chunk:
When I use ‘fix ave/chunk’ to print the spatial temperature profile, I would expect that the spatial average over the bins would give the same result as the instantaneous temperature printed in the thermo file. This is not the case. The attached input script, in.test, illustrates this. I realize that I would need to normalize by the bin population in the spatial average to get the exact instantaneous temperature, but this is not the issue, because the test script runs for 0 steps, so all the bins are still equally populated.
When I use both temp/profile and ‘temp/chunk com yes’ to compute the temperature in a simulation, I would expect the result to be the same, if the binning is the same. This does not seem to be the case. The attached input script demonstrates this. See the thermo output, which gives the two temperatures. This is a simulation with no flow, but I would expect the two commands to give identical output regardless of what is going on. Also, you can check that the binning is the same in the files tempMapNoBias and tempMapNoBiasChunk.
Similarly, when I use ‘fix ave/chunk’ to output the spatial temperature profile. The relevant files that are output are: tempMap, which contains the temperature profile with no bias removed, tempMapNoBias, which contains the temperature profile with the bias from temp/profile removed, and tempMapNoBiasChunk, which contains the temperature profile with the bias from ‘temp/chunk com yes’ removed. It seems that ‘temp/chunk com yes’ is not compatible with the feature to remove a bias in ‘fix ave/chunk temp’, as the output in tempMap is identical with that in tempMapNoBiasChunk. This is fine. The issue is that the spatial average of the temperature in tempMapNoBias over all the bins is not the same as the instantaneous value of c_myTp, as I would expect it to be. Instead, the spatial average of tempMapNoBias is the same as the instantaneous value of ‘temp/compute com yes’
I’ve attached the input files, as well as some of the output files I mentioned above. Below are some of the averages I talk about (in LJ units):
instantaneous data (from thermo file):
Step Temp myTp(profile) myTc(chunk)
0 2 2.0284802 1.8700052
spatial average of temp/profile: 1.87 (from file tempMapNoBias)
spatial average of raw temperature: 1.97 (from file tempMap)
If anyone has some ideas about what’s going on, I would be grateful. Let me know if any of the above is not clear.
in.test (895 Bytes)
tempMap (210 Bytes)
tempMapNoBias (211 Bytes)
tempMapNoBiasChunk (211 Bytes)