Fluid Mechanics - External Flow HW

2.

The cables that hold up the road deck of a large suspension bridge are 15 cm in diameter. If the wind is blowing at 42 km/hour, what is the side force on a cable that is 26 meters long? Assume that the cables are perfectly cylindrical. Use ρ=1.2kg/m3. 

Solution:

출처: Yunus Çengel,  John M. Cimbala - Fluid Mechanics Fundamentals and Applications-McGraw-Hill College (2017)

3.

A fluids student decides to take up skydiving. The student and gear mass 115 kg, and the parachute has a drag coefficient of 1.3 and a diameter of 12 m. Neglect the drag force on the student. Use ρ=1.2kg/m3$\mathrm{<span\; style="background-color:\; rgb(255,\; 255,\; 255);\; color:\; rgb(0,\; 0,\; 0);">\rho </span>}<span\; style="background-color:\; rgb(255,\; 255,\; 255);\; color:\; rgb(0,\; 0,\; 0);">=</span>\mathrm{<span\; style="background-color:\; rgb(255,\; 255,\; 255);\; color:\; rgb(0,\; 0,\; 0);">1.2</span>}\mathrm{<span\; style="background-color:\; rgb(255,\; 255,\; 255);\; color:\; rgb(0,\; 0,\; 0);">k</span>}\mathrm{<span\; style="background-color:\; rgb(255,\; 255,\; 255);\; color:\; rgb(0,\; 0,\; 0);">g</span>}<span\; style="background-color:\; rgb(255,\; 255,\; 255);\; color:\; rgb(0,\; 0,\; 0);">/</span>{\mathrm{<span\; style="background-color:\; rgb(255,\; 255,\; 255);\; color:\; rgb(0,\; 0,\; 0);">m</span>}}^{\mathrm{<span\; style="background-color:\; rgb(255,\; 255,\; 255);\; color:\; rgb(0,\; 0,\; 0);">3</span>}}$. What is the steady-state fall speed for our bold skydiver?

4.

An important part of industrial wastewater treatment is allowing particulate matter to settle out of the water. This is done in large settling ponds, through which water moves slowly, allowing gravity to pull particles to the bottom. For a mean flow velocity of 0.28 meters per second along the length of the pond, a pond depth of 1.1 meters, and spherical particles with a specific gravity of 2.6, how long must the settling pond be for particles 105 microns in diameter to all fall to the bottom of the pond?