Universidad Autónoma de Nuevo León

Facultad de Ingeniería Mecánica y Eléctrica

Mecánica de Fluidos N3

Dr. Román Nava

Aug 2016-Dec 2016

Actividad 1. (Fecha de entrega: examen de medio curso)

1. Elaborate an essay about the concept of pressure and compose a diagram with the different devices available to measure it (essay and diagram, maximum length: 2 pages).

2. Neglecting the pressure upon the Surface and the compressibility of water, what is the pressure in pounds per square inch at a depth of 15,000 ft below the Surface of the ocean? The specific weight of the ocean water under ordinary conditions is 64.0 lb/ft3. Report in SI units too.

3. A pressure gage at elevation 8.0 m on the side of a tank containing a liquid reads 57.4 kN/m2. Another gage at elevation 5.0 reads 80.0 kN/m2. Compute the specific weight and density of the liquid. Convert results to technical units (mks).

4. Repeat Prob. 1, but consider the effects of compressibility (Ev=300,000 psi). Neglect changes in density caused by temperature variations (Hint: As a starting point, express ∆vv

=−∆ pE v

in terms of γ and integrate to determine γ as a function of y.)

5. The tire of an airplane is inflated at sea level to 60 psi. Assuming the tire does not expand, what is the pressure within the tire at elevation 30,000 ft? Assume standard atmosphere. Express the answer in psi and psia.

6. Compute the pressure of 0.6 kg/cm2 in: mm Hg m H20 m CHBr2CHBr2 (acetylene bromide)

The specific gravity of CHBr2CHBr2 is 2.94.

7. Calculate the density, specific weight, and specific volume of chlorine gas at 25°C and pressure of 600 kN/m2, abs. (Hint: Molecular weight of chlorine, Cl2=71)

8. In the figure, originally there is a 4 in manometer reading. Atmospheric pressure is 14.7 psia. If the absolute pressure at A is doubled, what then would be the manometer reading? Report values in SI and English units.

9. A mercury manometer is connected to a pipeline carrying water at 66°C and located in a room where the temperature is also 66°C. If the elevation of point B is 3.05 m above A and the mercury reading is 122 cm, what is the pressure in the pipe in kg/m², kg/cm² and Pa? Repeat, assuming all temperatures are 20°F. Be as precise as possible, and note the effect of the temperature. Perform the analysis by addition of forces (pressure) and by columns obtaining m of H2O.

10. In the sketch below, assume the following: atmospheric pressure = 850 mbars, abs; vapor pressure of the alcohol = 160 mbars, abs; x=2.80 m and y=2.0 m. Compute the reading on the pressure gauge and on the manometer. Report in kg/m², Pa and mbars.

11. In the figure of problem 11, atmospheric pressure is 14.7 psia; the gauge reading is 5.0 psi; the vapor pressure of the alcohol is 1.7 psia. Compute x and y.

12. Compute FR and its localization in the section AB. Consider:a. Triangular section of 1.2 x 1.8 m with vertex in A.b. Consider section a circular section between AB and gate angle of 50°.c. Consider a square section between AB and gate angle of 90°.

d. Consider a square section between AB and gate angle of 30°.e. Conduct a discussion between the obtained results.

13. A tank with vertical ends contains water and is 8 m long normal to the plane of the figure shown. The sketch shows a portion of its cross section where MN is one-quarter of an ellipse with semiaxes b and d. If b = 4 m, d = 6 m, and a = 1.5 m, find for the surface represented by MN the magnitude and position of the line of action of (a) the horizontal component of force; (b) the vertical component of force; (c) the resultant force and its direction with the horizontal.

Table 1. Physical properties of wáter (SI units)