AA W1 - BL Thickness

The viscosity of a fluid is:

• The mass of the fluid per unit volume.
• A measure of the fluid’s resistance to flow.
• The force exerted by a fluid on a surface per unit area.
• A measure of the kinetic energy of the fluid molecules.

The units of dynamic viscosity are:

• kg/s
• kg/m³

• m²/s

• kg/ms

A boundary layer forms at a surface due to:

• Shear stresses in the fluid.
• Normal pressures acting on the surface.

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.

As viscous flow transitions from laminar to turbulent, the boundary layer thickness will:

• Stay the same.
• Increase.
• Decrease.

The effects of viscosity are often negligible outside the boundary layer.

• True
• False

The edge of the boundary layer is defined as the point at which the fluid velocity equals what % of the freestream velocity?

• 100%

• 90%

• 99%

• 95%

The boundary layer displacement thickness is related to:

• The drop in momentum due to the boundary layer.
• The drop in mass flow rate due to the boundary layer.

Which do you think is larger?

• the displacement thickness
• the momentum thickness

A shape factor is used in boundary layer flow to help to differentiate laminar and turbulent flow.

• True
• False