Experimental Study On Reynolds Number Effect Of A Sinusoidal Wavy Cylinder

Circular cylinders are widely used in engineering structures,such as piers,structural columns,bridge cables,etc.It has been found that sinusoidal wavy cylinder can reduce drag and suppress vibration compared with smooth cylinder at low Reynolds number.The mechanical properties of sinusoidal wavy cylinder are better than that of smooth cylinder.In practical engineering applications,for example,the Reynolds number of stay-cable is usually 10~5 orders of magnitude.Therefore,it is necessary to study the Reynolds number effect of sinusoidal wavy cylinder.A sinusoidal wavy cylinder with specific geometric parameters is designed.The variation of aerodynamic and flow characteristics with Reynolds number is studied by means of wind tunnel test in the range of Reynolds number 1.1×10~5~4.0×10~5.The main contents of the study are as follows:(1)The variation of aerodynamic characteristics of sinusoidal wavy cylinder with Reynolds was studied.By means of end force measurement and surface pressure measurement,the variation of the whole force coefficient and the force coefficient along different positions along the extension with Reynolds number and the distribution of wind pressure coefficient along the extension with different positions along the circumference are obtained.The results show that in the Reynolds number range of 1.1×10~5~4.0×10~5.the drag of sinusoidal wavy cylinder can not be reduced compared with that of smooth cylinder,on the contrary,the drag of sinusoidal wavy cylinder is larger than that of smooth cylinder.However,there is no large lift in the critical Reynolds number region,and the lift coefficient is near zero.The force coefficients vary with Reynolds number at different locations along the extension direction.The drag coefficient of the minimum diameter decreases considerably in the critical region.The decrease is caused by the decrease of the leeward pressure coefficient and the increase of the minimum wind pressure coefficient at the windward end.(2)The variation of flow characteristics of sinusoidal wave cylinder with Reynolds number.was studied.The boundary layer theory and time history analysis method are used to analyze the flow characteristics and the flow state along the spreading direction at different locations,and the variation of the vortex shedding along the spreading direction at different locations was also studied through the spectrum analysis method.The results show that with the increase of Reynolds number,the separation point moves towards the wake.The flow separation of the minimum diameter is earlier than that of the maximum diameter,and the width of the wake zone is larger.When 1.84×10~5?Re?2.87×10~5,the flow states in different positions show differences,and the unsteady flow characteristics are obvious at the position of maximum diameter.When 1.12×10~5?Re?3.26×10~5,the Strouhal number of sinusoidal corrugated cylinders is about 0.19.There is no obvious predominant frequency after 3.26×10~5.