A boundary layer often forms near the pipe wall that can be many hundreds of degrees cooler than the main exhaust flow temp. I did some testing on my insert with flex pipe several years ago using my VOM w/K type thermocouple attached. It confirmed that temps near the the wall are much cooler than toward the center of the pipe. I even inserted the thermocouple at an angle to prevent air being drawn into the probe hole from influencing the results.
Here's a paper about laminar and turbulent flow in pipes, which might answer additional questions or simply put one to sleep:
(broken link removed to http://www.uio.no/studier/emner/matnat/math/MEK4450/h11/undervisningsmateriale/modul-5/Pipeflow_intro.pdf)
Here's a paper about laminar and turbulent flow in pipes, which might answer additional questions or simply put one to sleep:
(broken link removed to http://www.uio.no/studier/emner/matnat/math/MEK4450/h11/undervisningsmateriale/modul-5/Pipeflow_intro.pdf)
