Y4 Boundary Layer Quiz

A boundary layer forms at a surface due to:

• Shear stresses in the fluid.

• Normal pressures acting on the surface.

The distance normal to the wall to a point where the flow velocity has essentially 0.99 of the freestream velocity is called the:

• displacement thickness

• momentum thickness

• boundary layer thickness

• friction thickness

Which do you think is larger?

• the displacement thickness

• the momentum thickness

Ignoring viscous effects will result in:

• Inaccurate predictions of pressure drag only.

• Inaccurate predictions of skin friction drag only.

• Inaccurate predictions of skin friction drag, pressure drag, and lift.

• Inaccurate predictions of lift only.

This expression applies for _____ boundary layers.

• laminar

• turbulent

For flow over a flat plate, the transition region is large compared with the laminar and turbulent regions.

• True

• False

Which thickness is representative of the friction force experienced by the fluid in the boundary layer?

• The physical boundary layer thickness.

• The displacement thickness.

• The momentum thickness.

This expression for skin-friction coefficient is applicable for:

• laminar flow.

• turbulent flow.

• transitional flow.

• inviscid flow.

The velocity profile shown is for a ____ boundary layer.

• laminar

• turbulent

When transition occurs, we can assume that the ____ remains constant.

• displacement thickness

• momentum thickness

• physical boundary layer thickness