In order to investigate the feasibility of noninvasively detecting blockages in pipelines, experimental research was by designing a facility at the University of Cincinnati to carry out the work. The goal of the work is to ultimately design a facility that can noninvasively detect blockages in arteries, while being able to simultaneously taking flow visualization and pressure measurements. The research primarily dealt with understanding the capabilities of the facility, as well as taking wall pressure and microphone measurements, as well as flow visualization, in order to study the effects of blockages, pulsation frequencies, and pressure head on flow through the pipeline, in hopes of understanding how to improve the facility in the future to achieve the goal of the facility.
The main experimental studies performed on the facility deal with steady flow, which simulates the diastole part of the cardiac cycle, and pulsating flow. These measurements of the steady flow resulted in determining that as the blockage size increases, as well the flow velocity, the pressure drop across the blockage increases. It was also determined that the spectra can be collapsed by the Strouhal number, a non-dimensional parameter based on the blockage, or in case of the largest blockage, the effective blockage, properties. Another way to try and collapse the blockages is to study blockages that have similar flow properties, such as Re or flow rate. It was determined that the most comparable flows come from having both the similar flow properties. For pulsating flows, it was concluded that due to the fact the pressure wave generated from rotating wheel is downstream of the blockage, the wave moves in the opposite direction of the flow, which causes the fundamental pulsation amplitude to be higher downstream of the blockage due to wave energy being reflected back towards the source.
Flow visualization was shown to be an invaluable tool to help visually verify many of the results from the steady and pulsating flow results. Many of the results, such as the fact that the largest blockage (96%) has different fluid dynamic properties than the smaller blockages were confirmed from flow visualization. Flow visualization also helps determine the length of a jet that forms downstream of a blockage. It was shown that as in previous studies as the severity of the blockage increases, the jet length decreases. Also, for pulsating flows, the high the pulsating frequency, the shorter the jet length is due to the decreased amount of time the flow has to travel before the subsequent pressure wave. Microphone measurements were also investigated however due to the transmission loss through the pipe, no conclusive results could be found. Finally, recommendations for future work to improve the current facility were discussed.