Slide 1

Pressure, Drag and Lift for Uniform Flow Over a Cylinder

a2 = 1Pressure, Drag and Lift for Uniform Flow Over a Cylinder

Along the cylinder, r = a, the velocity components become:

u is maximum at = /2 and 3 /2; zero at = 0 and = The pressure distribution can be obtained using Bernoullis equation:

dimensionless pressure coefficient Cp

The drag on the cylinder may be calculated through integration of the pressure over the cylinder surface:

The drag on the cylinder acts parallel to the flow.

The lift is perpendicular to the flow:FxFy

Along the cylinder, r = a, the velocity components become:

Pressure, Drag and Lift for Uniform Flow Over a Rotating CylinderThe pressure distribution can be obtained using Bernoullis equation:

dimensionless pressure coefficient CpThe drag and lift can be obtained by integrating the pressure over the cylinder surface pc :

Still no drag for a rotating cylinderThere is lift proportional to density, upstream velocity, and strength of vortex-- Kutta Jukowski lawLifting effect for rotating bodies in a free stream is called Magnus effect

Example of Pressure, Drag and Lift for Uniform Flow Over a Cylinder3 mu = 20 m/s

The drag on the cylinder may be calculated through integration of the pressure over half the cylinder surface, from 0 to . Thatll be with the outside pressure, inside pressure p0 should also be considered:

3 mu = 20 m/s

3 mu = 20 m/s

The lift on the object may be calculated through integration of the pressure over half the cylinder surface, from 0 to .

3 mu = 20 m/s

Lift for half-cylinder, 3 m high, influenced by wind (air density) hurricanetropical stormtropical depres-sionGale Force

Lift for half-cylinder, 1 m high, influenced by flow (water density)