Nadia Karima Izzaty 1306369466 Dept. Teknik Sipil
3.3.1. Calculate the terminal terminal velocity of a 0.8-mm raindrop raindrop at standard standard atmospheric atmospheric pressure and air temperature 20 0C. Air density =1.20 kg/m3.
Cd = 0.815;
=1000
= 4.3.. . ( − 1) 0.0008 . (1000 = 4.93..801./815 1.2 − 1) = 3.269269 ⁄
3.3.6. Solve Prob. 3.3.5 3.3.5 for drop sizes of 0.1, 0.5, 1, and 5 mm and and plot a graph showing showing the variation of impact energy with drop size.
= √ .... . − 1 = Rainfall Diameter
Temperature
Air Pressure
0.1 0.5 1 5
20 oC
101.3 Pa
Cd
Vt
Fd
5.47
0.445
5.12E-09
1.365
1.995
6.40E-07
0.671
4.024
5.12E-06
0.66
9.073
6.40E-04
Rainfall Diameter vs. Impact Energy 7.00E-04 6.00E-04 5.00E-04 4.00E-04 3.00E-04 2.00E-04 1.00E-04 0.00E+00 0
1
2
3
4
5
6
-1.00E-04
3.4.4. The following incremental rainfall data were recorded at gage 1-WLN in Austin, Texas, on May 24, 1981. Plot the rainfall hyetograph. Compute and plot the cumulative rainfall hyetograph. Calculate the maximum depth and intensity of rainfall for 5, 10, 30, 60, 90, 120 minutes for this storm. Compare the results for 30, 60, and 120 minutes with the values given in Table 3.4.1 for gage 1-Bee in the same storm. Which gage experienced the more severe rainfall?
Time
Rainfall
Cumulative Rainfall
Running Totals 5
10
30
0
0
0
5
0.09
0.09
0.09
10
0
0.09
0
0.09
15
0.03
0.12
0.03
0.03
20
0.13
0.25
0.13
0.16
25
0.1
0.35
0.1
0.23
30
0.13
0.48
0.13
0.23
0.48
35
0.21
0.69
0.21
0.34
0.6
40
0.37
1.06
0.37
0.58
0.97
60
90
120
45
0.22
1.28
0.22
0.59
1.16
50
0.3
1.58
0.3
0.52
1.33
55
0.2
1.78
0.2
0.5
1.43
60
0.1
1.88
0.1
0.3
1.4
1.88
65
0.13
2.01
0.13
0.23
1.32
1.92
70
0.14
2.15
0.14
0.27
1.09
2.06
75
0.12
2.27
0.12
0.26
0.99
2.15
80
0.16
2.43
0.16
0.28
0.85
2.18
85
0.14
2.57
0.14
0.3
0.79
2.22
90
0.18
2.75
0.18
0.32
0.87
2.27
2.75
95
0.25
3
0.25
0.43
0.99
2.31
2.91
100
0.48
3.48
0.48
0.73
1.33
2.42
3.39
105
0.4
3.88
0.4
0.88
1.61
2.6
3.76
110
0.39
4.27
0.39
0.79
1.84
2.69
4.02
115
0.24
4.51
0.24
0.63
1.94
2.73
4.16
120
0.41
4.92
0.41
0.65
2.17
3.04
4.44
4.92
125
0.44
5.36
0.44
0.85
2.36
3.35
4.67
5.27
130
0.27
5.63
0.27
0.71
2.15
3.48
4.57
5.54
135
0.17
5.8
0.17
0.44
1.92
3.53
4.52
5.68
140
0.17
5.97
0.17
0.34
1.7
3.54
4.39
5.72
145
0.14
6.11
0.14
0.31
1.6
3.54
4.33
5.76
150
0.1
6.21
0.1
0.24
1.29
3.46
4.33
5.73
Max depth Max intensity
0.48
0.48
0.88
2.36
3.54
4.67
5.76
5.76
5.76
5.28
4.72
3.54
3.113333
2.88
Dibandingkan dengan Tabel 3.1.4, maka untuk 60 menit soal ini lebih tinggi intensitas dan kedalamannya, sedangkan untuk 90 dan 120 menit lebih tinggi kedalaman di contoh Tabel 3.1.4.
Rainfall Hyetograph 0.6 0.5 0.4 0.3 0.2 0.1 0 0
10
20
30
40
50
60
70
80
90
100 110 120 130 140 150
Cumulative Rainfall Hyetograph 7 6 5 4 3 2 1 0 0
10
20
30
40
50
60
70
80
90
100 110 120 130 140 150
3.5.2. For Cairo, Egypt, in July, average net radiation is 185 W/m 2, air temperature 28.5°C, relative humidity 55 percent, and wind speed 2.7 m/s at height 2 m. Calculate the open water evaporation rate in millimeters per day using the energy method (E r), the aerodynamic method (Ea), the combination method, and the Priestley-Taylor method. Assume standard atmospheric pressure (101.3 kPa) and Z o = 0.03 cm. Energy Method
Aerodynamic Method
Combination Method
Priestley-Taylor Method
0.102 =0.003552 =0.0353 = =0.0353∗ 185 [ln] =6.5305 / =611.. 17.27 =3075.515 237. 3 + = ℎ =1691.533 = − =4.916 / =178.394 = . ∆+∆ . ∆ = 237.40983+ =6.177 / =6.09 / 3.6.3. The following data (from the American Society of Civil Engineers, 1973) show climatic conditions over a well-watered grass surface in May, July, and September in Davis, California, (latitude 38°N). Calculate the corresponding evapotranspiration rate (mm/day) by the energy balance method, the aerodynamic method, the combination
method, and the Priestley-Taylor method. Assume standard atmospheric pressure. Use Eq. (3.6.1) for the coefficient B.
Evaporation rate (mm/day) Month
Energy Balance
Aerodynamic
Combination
Priestley-Taylor
May
5.9657
8.90122456
15.86692456
5.023492063
July
6.6717
10.68211
18.35381
6.226286591
Sept
4.0242
9.373419424
14.39761942
3.579843562
Energy Balance
Aerodynamic
Combination
May
2.087995
3.115428596
5.553423596
1.758222222
July
2.335095
3.738738501
6.423833501
2.179200307
Sept
1.40847
3.280696798
5.039166798
1.252945247
Evapotranspiration rate (mm/day)
Month
Priestley-Taylor
