Using numerical results for the Blasius exact solution for laminar boundary-layer flow on a flat plate, (Section 9.2 on the web) plot the dimensionless velocity profile, u / U (on the abscissa), versus dimensionless distance from the surface, y / δ (on the ordinate). Compare with the approximate parabolic velocity profile of Problem 9.8. 9.8 Velocity profiles in laminar boundary layers often are approximated by the equations Linear : u U = y δ Sinusoidal : u U = sin ( π 2 y δ ) Parabolic : u U = 2 ( y δ ) − ( y δ ) 2 Compare the shapes of these velocity profiles by plotting y / δ (on the ordinate) versus u / U (on the abscissa).
Using numerical results for the Blasius exact solution for laminar boundary-layer flow on a flat plate, (Section 9.2 on the web) plot the dimensionless velocity profile, u / U (on the abscissa), versus dimensionless distance from the surface, y / δ (on the ordinate). Compare with the approximate parabolic velocity profile of Problem 9.8. 9.8 Velocity profiles in laminar boundary layers often are approximated by the equations Linear : u U = y δ Sinusoidal : u U = sin ( π 2 y δ ) Parabolic : u U = 2 ( y δ ) − ( y δ ) 2 Compare the shapes of these velocity profiles by plotting y / δ (on the ordinate) versus u / U (on the abscissa).
Using numerical results for the Blasius exact solution for laminar boundary-layer flow on a flat plate, (Section 9.2 on the web) plot the dimensionless velocity profile, u/U (on the abscissa), versus dimensionless distance from the surface, y/δ (on the ordinate). Compare with the approximate parabolic velocity profile of Problem 9.8.
9.8 Velocity profiles in laminar boundary layers often are approximated by the equations
Linear
:
u
U
=
y
δ
Sinusoidal
:
u
U
=
sin
(
π
2
y
δ
)
Parabolic
:
u
U
=
2
(
y
δ
)
−
(
y
δ
)
2
Compare the shapes of these velocity profiles by plotting y/δ (on the ordinate) versus u/U (on the abscissa).
The standard sea level value of viscosity coefficient for air is μ = 1.7894×10−5 kg/(m · s) = 3.7373 × 10−7 slug/(ft · s).
The wing on a Piper Cherokee general aviation aircraft is rectangular, witha span of 9.75 m and a chord of 1.6 m. The aircraft is flying at cruisingspeed (141 mi/h) at sea level. Assume that the skin-friction drag on thewing can be approximated by the drag on a flat plate of the samedimensions. Calculate the skin-friction drag:a. If the flow were completely laminar (which is not the case in real life)b. If the flow were completely turbulent (which is more realistic)Compare the two results.
Air at 20°C flows at V = 80.0 m/s over a smooth flat plate of length L = 17.5 m. Plot the turbulent boundary layer profile in physical variables (u as a function of y) at x = L. Compare the profile generated by the one-seventh-power law, the log law, and Spalding’s law of the wall, assuming that the boundary layer is fully turbulent from the beginning of the plate.
A Savonius rotor can be approximatedby the two open half-tubes in Fig mounted ona central axis. If the drag of each tube is similar to thatin Table 7.2, derive an approximate formula for therotation rate Ω, as a function of U, D, L, and the fluidproperties (ρ, μ).
Chapter 9 Solutions
Fox and McDonald's Introduction to Fluid Mechanics
Thinking Like an Engineer: An Active Learning Approach (3rd Edition)
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