Streamlining: Student Success CriteriaI can describe factors affecting laminar flow,

and explain how the design of an item or organism responds to these factors.

SPH4C

DragThe frictional forces that act on an

object’s motion through a fluid are called drag.

StreamliningTo reduce drag, a technique called

streamlining is used. Streamlining is the process of reducing

turbulence by altering the design (shape and surface features) of an object that moves rapidly relative to a fluid.

StreamliningStreamlined flow is the same as laminar

flow.

The turbulent wake behind the non-streamlined object is a low pressure region, pulling the object backwards.

Streamlining in NatureStreamlining is found in nature in animals that

move quickly though water or the air. Scientists study this streamlining and try to model it in technology.

TestingModels are tested in computer simulations

and in wind tunnel and water tank tests.

A scale model in a wind tunnel

Drag Coefficients Scientists communicate the amount of drag

something has with a number referred to as the drag coefficient (Cd).

The lower the drag coefficient the less drag there is.

Drag Coefficients E.g.: A highly streamlined airplane wing is around

Cd = 0.050 while an open parachute designed for maximum drag is around Cd = 1.35.

Drag CoefficientsIn the 1930’s, when gas was inexpensive, most

cars had a drag coefficient of Cd = 0.70; today most cars have a coefficient of about Cd = 0.40 and some have coefficients as low as 0.15.

Shapes and Drag

Which shapes have the highest drag coefficients?

Which shapes have the lowest?

Fluid Dynamics AssignmentDescribe the types of features used on

a particular vehicle (e.g. a sport bike, a locomotive, or a bobsled) to reduce drag.

ExamplesE.g.: Air dams, tapered light covers and

hood, concealed windshield wipers, low profile windshield, flush pillars, flush door handles, flush wheel openings, aerodynamic mirrors. . .