Experimental Investigation of the Effect of a Semi-Circular Spiral Protrusion on the Turbulent Flow Past a Cylinder
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The effect of semi-circular spirals on a circular cylinder surface to flow structure was experimentally investigated by the particle imaging velocity measurement (PIV) method. Based on the PIV channel, the main body cylinder length was determined as 440 mm. The single coil (p = 440 mm), double coils (p = 220 mm) and quadruple coils (p = 110 mm) structures were formed by changing the number of steps (p) of the semi-circles on the cylinder surface. The flow structure has been examined in six different planes according to the position of the helix. The Reynolds number studied is 10 000, depending on the average fluid velocity in the PIV channel and the main body cylinder diameter (D). The time-averaged streamline 〈ψ〉, the turbulent kinetic energy 〈TKE〉, the root mean square (RMS) of streamwise velocity Urms, the root mean square (RMS) of cross-stream velocity Vrms and the Reynolds shear stress 〈u'v '〉 were obtained. The Strouhal numbers were calculated using the Karman vortex frequencies. It is concluded that the spirals on the cylinder reduce the vibrations caused by the vortex.