Water flows past a flat plate that has a length L = 5 m and a width w = 2 m, as shown in Figure Q4. The shear stress at the wall is given by Tw = μ du dy. When the flow is laminar the shear stress at the wall is given by the equation: Tw = 0.0644 pU∞ 2 6 x Where p = 1000 kg/m3 is the water density and U∞ = 5 m/s is the velocity of the water. The height of the boundary layer is d, and can be approximated by 8(x) = 5√ ux pU" The viscosity of water is μ = 1 mPa.s. a) Estimate the drag force on the plate. You may use the expression FD = | TwdA b) When the flow becomes turbulent, we can approximate the velocity gradient at the wall as constant, au ay = A. If the total drag force is 300 N, find A. c) When the fluid is heated to 900C, the density drops slightly and the viscosity decreases a lot, and engineers observe that the equation, Tw = 0.0644pU 2 5 x, becomes less accurate. Explain why this might occur (1-2 sentences). d) In order to visually examine a turbulent boundary layer, engineers release a steady stream of dye from the front of the plate. Does this represent (i) streamlines, (ii) streaklines, (iii) pathlines, (iv) all three.

Elements Of Electromagnetics
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Water flows past a flat plate that has a length L = 5 m and a width w = 2 m, as shown in Figure
Q4.
The shear stress at the wall is given by Tw= μ du dy. When the flow is laminar the shear stress
at the wall is given by the equation: Tw = 0.0644 pU 2 8 x Where p = 1000 kg/m3 is the water
density and U∞ = 5 m/s is the velocity of the water. The height of the boundary layer is 5, and
can be approximated by 8(x) = 5√ ux pU* The viscosity of water is μ = 1 mPa.s.
a) Estimate the drag force on the plate. You may use the expression FD = | TwdA
b) When the flow becomes turbulent, we can approximate the velocity gradient at the wall as
constant, au ay = A. If the total drag force is 300 N, find A.
c) When the fluid is heated to 900C, the density drops slightly and the viscosity decreases a lot,
and engineers observe that the equation, Tw = 0.0644pU 2 6 x, becomes less accurate.
Explain why this might occur (1-2 sentences).
d) In order to visually examine a turbulent boundary layer, engineers release a steady stream of
dye from the front of the plate. Does this represent (i) streamlines, (ii) streaklines, (iii) pathlines,
(iv) all three.
15(x)
Figure Q4: Flow over a long flat plate. The boundary layer is shown by the light grey.
Transcribed Image Text:Water flows past a flat plate that has a length L = 5 m and a width w = 2 m, as shown in Figure Q4. The shear stress at the wall is given by Tw= μ du dy. When the flow is laminar the shear stress at the wall is given by the equation: Tw = 0.0644 pU 2 8 x Where p = 1000 kg/m3 is the water density and U∞ = 5 m/s is the velocity of the water. The height of the boundary layer is 5, and can be approximated by 8(x) = 5√ ux pU* The viscosity of water is μ = 1 mPa.s. a) Estimate the drag force on the plate. You may use the expression FD = | TwdA b) When the flow becomes turbulent, we can approximate the velocity gradient at the wall as constant, au ay = A. If the total drag force is 300 N, find A. c) When the fluid is heated to 900C, the density drops slightly and the viscosity decreases a lot, and engineers observe that the equation, Tw = 0.0644pU 2 6 x, becomes less accurate. Explain why this might occur (1-2 sentences). d) In order to visually examine a turbulent boundary layer, engineers release a steady stream of dye from the front of the plate. Does this represent (i) streamlines, (ii) streaklines, (iii) pathlines, (iv) all three. 15(x) Figure Q4: Flow over a long flat plate. The boundary layer is shown by the light grey.
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