Numerical investigation of fluid boundary layer over flat surface

Abstract EN

In present study numerical investigation of two kinds of fluids namely air and water flow on flat surface have been performed to investigate the boundary layer.

Computational fluid dynamics has been used as a numerical technique to solve continuity equation and momentum equation.

The air has been used in this study due to its wide importance in aerodynamics applications.

In addition water has been used for comparison.

A 1 m length flat surface has been used as a base for boundary layer fluid flow.

The altitude of the computational domain which includes the free stream fluid flow was 0.

1 m.

The fluid velocity at the leading edge of the surface was 10 m/s for both air and water.

Flow on smooth surface has been considered.

Viscous fluid flow was used and hence no-slip condition has been adopted for both air and water.

The Reynolds number (Re) was based upon the distance x from the leading edge as a characteristic length.

The boundary layer thickness () has been calculated.

In addition wall shear stress () has been studied for both air and water.

Also some other parameters have been calculated such as displacement thickness (*), momentum thickness ( ) and the coefficient of drag (CD).

The results showed that the Reynolds number of water is bigger than the Reynolds number of air based on the conditions of the current study.

The boundary layer of air is laminar from leading edge until 0.

8 m.

Beyond 0.

8 m up to the surface end, the boundary layer is in the transition region.

Also the boundary layer of water transited to turbulent region at 0.

2 m while the air boundary layer is still laminar.

As expected, the momentum thickness () showed similar behavior as boundary layer thickness ().

The displacement thickness of air is higher than the displacement thickness of water.

The results also showed that the air drag coefficient has less value than water drag coefficient from approximately 0.

2 m up to the downstream.

The results showed that water flow affected the flat surface by bigger wall shear stress than air.