Learning Forum

[ham]

Hi,

I'm simulating a small arc jet nozzle (hence the high constrictor temperature) and I was experimenting with viscous heating and I'm struggling to understand the results. I'm simulating Hydrogen using a transient pressure-based solver with laminar flow. My understanding of viscous heating is it becomes noticeable in highly compressible flows, which this is. My expectation was that it might increase temperatures near the wall, but it seems to have a big effect on the total flow field.

As can be seen in the contours below, turning on viscous heating appears to result in a cooler near axis flow, channeling the hot gasses around the axis and overall leading to lower exhaust temperatures. This doesn't seem like a physically plausible solution to me, and I haven't seen anything similar in literature.

Any ideas on why viscous heating may cause this strange solution? I would expect it should be on for my simulation, but seeing this result I'm keeping it off for now...

The top row shows solutions with viscous heating off, the bottom row is viscous heating on. The left column shows axial velocity, the right column shows temperature. Scales are the same for each velocity/temperature contour.

[Rob]

Can you zoom into the throat and plot Mach Number? Also density. Knowing what the data scales is would also be useful.
The main theory is covered here, https://ansyshelp.ansys.com/account/Secured?returnurl=/Views/Secured/corp/v212/en/flu_th/flu_th_sec_hxfer_theory.html%23flu_th_sec_hxfer_theory_viscous

[ham]

Thanks for your help, here's all the contour plots of the throat, as well as full geometry ones showing scales.