Helical strake type thermowells are replacing standard thermowells according to ASME PTC 19.3 TW-2016 in various industrial sectors. It is because the helical strakes can suppress the flow-induced vibration by Kármán vortex street over a thermowell. However, the ASME PTC 19.3 TW-2016 does not regulate the helical strakes because their design rules are too complicated to be specified.
This study attempts to characterize the effect of helical strakes on the thermowell vibrations by measuring pressure and strain signals at the same time. The pressure signal is expected to give information on the Kármán vortex street while the strain signal gives the flow-induced vibration on the thermowells. Relative vibration energy or relative vibration amplitude is defined to calculate the efficiency of suppressing the Kármán vortex street around the thermowells.