NUMERICAL ANALYSIS FOR TWO-FLUID BOUNDARY LAYER AND ITS DRAG REDUCTION CHARACTERISTICS

Drag-Reduction is always one of the most interesting problem Generally drag forces consist of shape and skin parts. Nowadays with optimised shape design its drag could vastly be reduced. The factor for constituting of skin drag really formation of boundary layer due to viscosity of fluid. The aim is to design physical models to reduce skin drag by considering the effects of molecular viscosity of fluid (u) and velocity gradient (dudy on the wall. Consideration is given to coexisting two-fluid boundary-layers which occur when ۱۱ secondary fluid is injected at the surface of the wall into a free stream main flow or ۲) secondary fluid is along with free stream main flow and constant discharge. It is postulated that secondary fluid forms a continuous film the wall in both physical models. The problem can be formulated within the framework of the laminar boundray-layer theory Numerical analysis of the designed physical system demonstrate that skin drag forces are much smaller than those for the single-fluid flow. For example, for a blowing velocity which is ۰.۰۰۱ of the free-stream velocity and secondary Reynolds number of ۱۰۵, the over-all drag calculation yields a value which is ۰۲۰۵ of the single fluid drag force. Hydrodynamics flow analysis is necessary to find relation between physical properties of interfacial fluids for keeping stability of flow configuration