Experimental investigations of Strouhal number for flows past dual triangulate bluff bodies

Experimental studies were carried out on the Strouhal number for flow past dual triangulate bluff bodies in a circular pipe 50 mm in diameter. Results are presented of an experience instrument evaluation of the Strouhal number of nine dual combinations based on triangulate bluff body geometries of different size for a range of separations between 35 and 65 mm. The Reynolds number varies in the range of 6.62×103–1.99×105. The vortex shedding frequency was obtained on the basis of measured fluctuating pressure on the lateral side of the vortex shedder by a piezoelectric press sensor. Those results led to the following conclusions: (1) the linearity of Strouhal numbers of dual triangulate bluff body combinations varies with the opening length of two bluff bodies and diameters of the bluff bodies. The best linearity is the same as that of a single bluff body. (2) The best size of a dual triangulate bluff body was found as: If the pipe diameter is DD, the diameters of the first and second bluff body are 0.26D0.26D and the height of the bluff bodies is 0.34D0.34D. (3) For a dual triangulate bluff body, the optimal opening length is equal to the distance between consecutive vortices of flow over single bluff body. Our results will be valuable in the flow measurement and instrument design of vortex flowmeters in industries.