Numerical Study On Flow Noise In Viscoelastic Fluid

The noise problem caused by the flow around a bluff body is of practical engineering problems are widely used in aviation,marine,offshore platform,wind engineering etc.Many scholars are studying the noise problem of flow around a bluff body,but the study on the viscoelastic fluid flow noise is little,the viscoelastic fluid can be obtained by adding polymer into Newtonian fluid.It is not clear how polymer additions affect the flow noise characteristics of bluff body,so this paper will focus on the influence of polymer additions on flow noise.Based on the previous research work,the flow around a cylinder and airfoil NACA0012 were taken as the research object,It is simulated by FLUENT associated UDF secondary development,the flow field around the bluff body was calculated,and then the sound field was calculated.Firstly,the flow field around a two-dimensional viscoelastic fluid cylinder is calculated,and the simulation results in the literature are compared to verify the rationality and stability of the numerical simulation method in dealing with the flow around a cylinder.Secondly,the two-dimensional flow around a cylinder is numerically simulated,and the near-field and far-field acoustic information are solved respectively.The effects of molecular chain length and Weissenberg number of different polymers on the flow noise around a cylinder are studied,and the results are compared with those of Newtonian fluid.The results show that the addition of polymer can inhibit the flow noise,and the longer the molecular chain length of polymer,the more obvious the inhibiting effect;the greater the Weissenberg number,the more obvious the inhibiting effect.Then the three-dimensional flow around a cylinder is numerically simulated and the far-field acoustic information is solved.The influence of the Weissenberg number of polymer on the flow noise around a cylinder is mainly studied.The results are compared with those of Newtonian fluid.The results are the same as those of two-dimensional flow around a cylinder.The larger the Weissenberg number of polymer,the more obvious the inhibiting effect.Finally,the far-field acoustic field information of flow noise around two-dimensional airfoils is calculated,and the effects of different angles of attack and different polymer Weissenberg numbers on flow noise around airfoils are studied.The results are compared with those of Newtonian fluid.The results show that the sound pressure of the whole acoustic field increases when polymer is added to Newtonian fluid at a smaller angle of attack,but in viscoelastic fluid.With the increase of Weissenberg number,the effect of restraining far-field noise will be enhanced.At larger angle of attack,the sound field characteristics of two-dimensional airfoil flow are similar to those of two-dimensional cylinder flow.Adding polymer can restrain flow noise.The larger Weissenberg number,the more obvious the effect of restraining flow noise is.