MECH 3410 Semester 2, 2014

You will be given 30 minutes to complete these problems.

Week 10 In-class problem: External Viscous Flow Part 2

Q1:

Flow in turbulent boundary layers is generally described by the

power velocity profile.

(

) (

)

Perturbed flow arrives at a flat plate as shown in the figure below. A pitot tube positioned

10mm above the surface measures a pressure difference (Pstagnation Pstatic) of 165.5Pa.

What is the distance X between the leading edge and the pitot tube?

The following properties and equations may be used-

Air at 200C: density = 1.2 kg/m

3, kinematic viscosity () = 1.5 x 10-5 m2/s

Natural transition to turbulence occurs where Rex = 5 x 105

Pstagnation Pstatic

U = 20 m/s

X = ?

H = 10mm

MECH 3410 Semester 2, 2014

Q2 Wings, Lift, and Drag

A glider with a mass of 250kg, a wingspan of 16m and a wing area of 12m2 is being towed by

an aircraft. The gliders wing has a NACA0009 profile and is attached at an angle of 4

relative to the glider centerline.

(a) If the glider is oriented horizontally, at what speed does the aircraft need to pull the glider in order to main level flight?

(b) What is the Lift to Drag ratio for this flight condition?

(c) What is the tension in the cable used to pull the glider?

(For all calculations assume that the glider main wing is the only contributor to lift and drag)

The following properties and equations may be used-

Air at 200C: density = 1.2 kg/m

3, kinematic viscosity () = 1.8 x 10-5 m2/s; Retrans = 5 x 10

5.

;

;

;

;

;

4L

D

0

0

Characteristics of NACA0009 airfoil with infinite span: (for =4 assume, CD=0.0075)