Water Rocket
Computer Model Problems
Here is the fourth Water
Rocket Computer Model Problem.
The screen shot below is from the 3D optimisation of
the default 2 litre water rocket.
Again I have included the file details so that you can
reproduce it yourself to investigate the peculiar maxima
displayed in the screen shot on the right.
It is a plot of Flight Time as the output variable
with Pressure in Vessel (18psi to 131psi) on the Y axis
and Mass of Water (212g to 1487g) on the X axis with a
post-thrust integration interval of 10ms and a model time
limit of 1 second.
The graph shows a number of lines that run all of the
way across the display.
| Variables |
| Water Rocket Computer Model Problem 04 |
|
|
| Rocket |
| Mass of Rocket Empty |
120 |
|
g |
| Capacity of Pressure Vessel |
2050 |
|
cm3 |
| Rocket Diameter |
9.5 |
|
cm |
| Rocket Coeff of Drag |
0.56 |
|
|
| Nozzle Diameter |
21.5 |
|
mm |
| Constant K for nozzle |
0.16 |
|
|
| [ ] Launch Tube in use |
Not Used |
|
|
| Duration of air impulse |
50 |
|
ms |
| [ ] Parachute in use |
Not Used |
|
|
| Launch
Tube |
| Length |
20 |
|
cm |
| External
Diameter |
21 |
|
mm |
| [X] Hollow
Launch Tube |
Used |
|
|
| Wall Thickness |
2 |
|
mm |
| Length of Tube
Empty |
25 |
|
cm |
| Distance of
Vent from End |
0 |
|
cm |
| [ ] T-Nozzle
in use |
Not Used |
|
|
| T-Nozzle
Diameter |
4.75 |
|
mm |
| Parachute |
| Diameter
opened out flat |
1.2 |
|
m |
| Parachute
Coeff of Drag |
0.9 |
|
|
| Deploy ()
Apogee.( ) Timer |
4 |
|
s |
| Delay in
opening |
5 |
|
m |
| Initial |
| Mass of Water |
850 |
|
g |
| Pressure in Vessel |
75 |
|
psi |
| Height |
1.5 |
|
feet |
| Angle of Elevation |
88 |
|
° |
| Speed at Angle of Elevation |
0 |
|
m/s |
| Temperature |
10 |
|
C |
| Environmental |
| Gamma of Gas in Rocket |
1.402 |
|
|
| Density of Gas in Rocket |
1.293 |
|
kg/m3 |
| Density of Liquid in Rocket |
998 |
|
kg/m3 |
| Acceleration due to Gravity |
9.81 |
|
m/s2 |
| Atmospheric Pressure |
1013 |
|
mBar |
| Density of Air at STP |
1.293 |
|
kg/m3 |
| The problem here
is . . . |
| 1. |
to
find an explanation for the curiously shaped
lines. |
The variables are in the table on the left...
If you give up or you think you know what is going on,
look at the answers.
|
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