Effect of pressure unsteadiness on vortex shedding frequency from dual bluff body

The present paper investigates a dual equilateral triangle-section bluff body vortex shedding flow meter using oscillating outlet boundary conditions by implementing a user defined function in FLUENT, a commercial CFD software package. The motivation was to analyze the behavior of the flow meter in unsteady flows. During the test procedure the frequency and amplitude of the outlet total pressure was varied. The static pressure fluctuations at the sensor points of the second body were monitored to see if and how the static pressure changed. Afterwards the signal was analyzed by FFT. The results have shown that the vortex shedding was affected in frequency and amplitude when the boundary frequency was higher than the frequency of the undisturbed vortex street using constant conditions. The frequency was shifted to higher values but not equal to the boundary frequency. Even higher frequencies did not increase the vortex street frequency. The explanation of this phenomenon is still outstanding.