| |
| For the fluid flow in pipes, when the friction of pipe wall is big enough the velocity near the wall will significantly smaller than the flow velocity in the pipe center. This will cause the material volume elements of fluid rotate along the tangent direction of circular pipe wall. The intrinsic rotation angle of such a local rotation is a function of radium from the pipe center where the viscosity parameter of fluid plays an essential role. This local intrinsic rotation not only produces an additional pressure field, but also produces turbulence when the transportation distance is big enough. This result is gained based on the Chen’s S+R decomposition of deformation gradient theorem. For the fluid flow problem, the related motion equations established on Chen’s rational mechanics theory is used in this paper. The theoretic equations are compared with traditional fluid motion equations. Traditional fluid motion equations (Navier-Stokes equation) are correct for non-symmetric stress fields, but they do not supply reasonable equations for the asymmetric stress fields. This is the essential disadvantage for the tradition fluid dynamics theory to predict the local rotation and the possibility of turbulent flow in the simple case of pipe flow problem. This research shows that the new theoretic formulation may be valuable to explain complex flow phenomena. |
|
| Keywords:turbulence, local rotation, asymmetric stress, motion equation, velocity gradient decomposition |
|
