Introducing New Relationship Between High-order Moments In the Turbulent Plain Wake Behind a Circular Cylinder

In this paper, the existence of statistical relationship between high- order velocity moments as flatness and skewness in the plain wake behind a circular cylinder were studied. Hot- wire anemometer was used to measure turbulent parameters in various situations downstream the flow behind the cylinder. Turbulence intensity of wind tunnel’s free line is 0.1 precent which in this sense, it has high accuracy. In these experiments, the Reynolds number is 28000. Non- dimensional values of mean velocity, skewness S and flatness F in various x/d’s has been plotted. By comparing existent relationship for predicting flatness values (which are demonstrated for turbulent boundary layer and free jet) with actual values, it has been found that new relationship can be found which can have much more agreement with their actual cases. Considering this point, and by using fitting method, in this paper some new relationship from which was can predict high- order moments with much more accuracy was provided. Therefore for further accuracy, two polynomial of orders 2 and 3 were used to fit the data which has taken in a wind tunnel. Though the accuracy of these estimations in larger x/d’s reduses significantly.