HOMEWORK ASSIGNMENT #6

ME 303 FLUID DYNAMICS/ WESTPHAL/ WSU/ FALL 2000

• Follow the Homework Guidelines for preparing your submission.
• You are encouraged to work together with other students, but the work you submit cannot be a machine-produced duplication of another student's work - it must be an original, but can represent your version of a collaborative effort.
• Late work not accepted!
• Remember to check your PIs.
• Identify each of the problems involving Hydraulic/ Mechanical Conservation of Energy as "Type I" (rating), "TYPE II" (performance), or "TYPE III" (sizing) BEFORE you try to solve.

The assignment consists of the problems given below.

1. 8.32 DISCUSSION: What wind tunnel velocity would be appropriate if the model was 1/2 scale?
   
   
2. A one-third scale model test of an automobile is to be performed in a wind tunnel. The test is to satisfy Reynolds number similarity. The prototype conditions are to be 25 m/s speed, with air at 100 kPa (abs) and 20 deg C.
   
   • What wind tunnel test air speed should be used if the wind tunnel operates at 100 kPa (abs) and 20 deg C?
     
   • Now, suppose that the wind tunnel test was conducted at 200 kPa (abs) and 20 deg C. What test airspeed would be needed?
   DISCUSSION: Will Mach number similarity be obtained for either case? Why or why not? What changes to wind tunnel air temperature or model scale would allow the test and prototype Mach numbers to be more closely matched?
   
   
3. 8.47 omit discussion
   
   
4. 8.62 NOTE: Wave resistance is governed by Froude number only. DISCUSSION: Assuming that the model test and prototype conditions both involve water at the same temperature, what would be the ratio (Re-prototype)/(Re-model test)?
   
   
5. 8.55 omit discussion
   
   
6. The South Columbia Basin Irrigation District incorporates a HUGE concrete-lined "wasteway", which is a canal that carries unused irrigation water and other drainage water to be returned to the Columbia River. The channel cross-sectional shape is that of a "V" with a 120 degree included angle, and its slope is 2 feet per mile. Use Manning's equation to calculate the discharge that this channel can carry at a water depth of 15 feet. omit discussion
   
   
7. 10.9 DISCUSSION: Is the flow LAMINAR or TURBULENT? Why does it matter?
   
   
8. 10.33 omit discussion
   
   
9. 10.64 On your EGL/HGL sketch, label the pump head and frictional head losses... the sketch need only be qualitative... also, calculate "NPSHA" -- Net Positive Suction Head Available -- for the pump, assuming that the oil's vapor pressure is 2 psia. omit discussion
   
   
10. 10.67 Neglect entrance and exit losses, and all "minor" losses. omit discussion
    
    
11. 10.87 Neglect entrance and exit losses, and all "minor" losses. HINT: assume a volume flowrate, then calculate the system head requirement at that flow, to create a curve of system head requirement vs. volume flowrate ("system curve"). Plot this on the same graph as the pump curve, and determine the operating point as the intersection of these. DISCUSSION: Describe how the discharge would change if TWO pumps with the identical pump curves as given were used IN SERIES, or IN PARALLEL... which configuration would result in the higher discharge?
    
    
12. 10.97 Assume that you have square-edged inlet and outlet, and the "minor" and pipe friction losses as indicated on the diagram. omit discussion
    
    
13. 10.116 HINT: use hydraulic diameter for non-round ducts. omit discussion