Water Rocket
Computer Model Problems
Here is the seventh Water
Rocket Computer Model Problem.
This  is a water rocket with a fairly large T-Nozzle
and uses a fairly high pressure. Otherwise, it is normal.
As always, I have included the file details so that
you can reproduce it yourself to investigate the peculiar
nature of the maxima displayed in the screen shot on the
right.
It is a plot of Flight Time as the output
variable with Mass of water (80g to 1600g) on the Y
axis and Mass of Rocket Empty (30g to 500g) on the X axis with
a post-thrust integration interval of 10ms.
The graph shows two maxima, each with different reasons for being there, one
is at the top left and the other is where the cursor is.
| Variables |
| Water Rocket Computer Model
Problem 07 |
|
|
| 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 |
|
|
| [X] Launch Tube in use |
Used |
|
|
| Duration of air impulse |
200 |
|
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 |
| [X] T-Nozzle in use |
Used |
|
|
| T-Nozzle Diameter |
8 |
|
mm |
| Parachute |
| Diameter
opened out flat |
0.25 |
|
m |
| Parachute
Coeff of Drag |
0.9 |
|
|
| Deploy ()
Apogee.( ) Timer |
4 |
|
s |
| Delay in
opening |
3 |
|
m |
| Initial |
| Mass of Water |
850 |
|
g |
| Pressure in Vessel |
150 |
|
psi |
| Height |
1.3 |
|
feet |
| Angle of Elevation |
90 |
|
° |
| 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 maxima that occur. |
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.
|
Bach to the Computer Model Details
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