|
1
0
.
Shezi formulasi.
Darsi-Veysbax formulasidan oqim o‘rtacha tezligii aniklaymiz
g
R
l
h
l
2
4
2
(4.137)
l
h
R
g
l
8
(4.138)
RJ
C
(4.139)
bunda,
S
=
g
8
Shezi koeffitsienti,
с
м
5
,
0
;
– oqimning o‘rtacha tezligi,
с
м
;
R
– gidravlik radius,
m
;
J
– oqimning tekis harakatida gidravlik
nishablikka mos pezometrik nishablik.
Bu formula Shezi formulasi deb atalishi bizga ma’lum.
2
8
C
g
(4.140)
(4.139) ifodaga asoslanib, gidravlik qarshilik Reynolds soni (Re)ga
bog‘liqligini etiborga olib, Shezi koeffitsientini ham kvadrat qarshiliklar
sohasida faqat g‘adir-budirlikka bog‘liqligini etrof etish kerak.
2
0
.
Shezi formulasiga asosan olingan formulalar
.
l
R
C
Jl
h
l
2
2
(4.142)
RJ
C
Q
(4.143)
Bu formula
tekis harakatining asosiy hisoblanish tenglamasi
deb ataladi,
bunda, –
l
oqim harakatlanayotgan hisobiy soha uzunligi;
3
0
.
Sarf moduli.
~ 322 ~
R
С
K
(4.144)
bunda,
K
–sarf moduli.
Belgilash kiritamiz:
J
K
Q
(4.145)
Bunda tekis harakat uchun:
J
Q
K
(4.146)
Bu formuladan ko‘rinib turibdiki,
J
= 1,0 da
K=Q
,
l
h
J
l
o‘lchov
birliksiz munosabat bo‘lganligi uchun
K
sarf moduli
Q
sarf o‘lchov birligiga
ega.
2
2
K
Q
J
(4.147)
Demak,
l
h
=
l
K
Q
Jl
2
2
(4.148)
4
0
.Tezlik moduli
R
C
W
(4.149)
Belgilash kiritamiz
J
W
(4.150)
Tekis harakat uchun
J
W
(4.151)
Agar
J
= 1,0 bo‘lsa, tezlik moduli tezlik bilan bir xil o‘lchov birlikka ega
bo‘ladi.
2
2
W
J
(4.152)
Demak,
l
W
h
l
2
2
(4.153)
~ 323 ~
Sarf va tezlik modullari quvur va kanallarning gidravlik hisobida keng
qo‘llaniladi.
4.26. SHEZI KOEFFITSIENTINI (
S
) ANIQLASH UCHUN
EMPIRIK FORMULALAR
Shezi tenglamasini (4.139)
S
ga nisbatan yechimini hisoblaymiz:
RJ
С
(4.154)
Har qanday suv oqimi harakatlanayotgan o‘zanda
,
R
,
J
kattaliklarni
o‘lchab (4.111) formula asosida
S
Shezi koeffitsientini hisoblash mumkin.
Ko‘pgina tadqiqotchilar shu tariqa ish tutib, Shezi koeffitsientini
aniqlashga doir empirik formulararni olishgan. Quyida ulardan ayrimlarini
keltirishni Biz, mualliflar maqsadga muvofiq deb topdik.
Gangile
-
Kutter formulasi
R
n
n
С
23
1
/
1
23
(4.155)
bunda,
n
– g‘adir-budirlik koeffitsienti
Manning formulasi
6
/
1
1
R
n
С
(4.156)
Bu formula amaliyotda ko‘p qo‘llanilganligi sababli, keyingi mavzularda,
bu formula asosida tuzilgan o‘zanning berilgan g‘adir budirligi
n
va aniq
parametlar asosda hisoblangan gidravlik radius
R
ga asosan Shezi koeffitsientini
aniqlash jadvali keltirilgan.
Akademik N.N Pavlovskiy formulasi
~ 324 ~
y
R
n
C
1
(4.157)
bunda
)
,
(
n
R
f
y
(4.158)
10
,
0
75
,
0
13
,
0
5
,
2
n
R
n
у
(
м
R
1
bo‘lganda,
n
y
5
,
1
,
м
R
1
bo‘lganda,
n
y
3
,
1
).
Bu formula ham amaliyotda ko‘p qo‘llanilganligi sababli, keyingi
mavzularda bu formula asosida tuzilgan o‘zanning berilgan g‘adir budirligi
n
va
aniq parametlar asosda hisoblangan gidravlik radius
R
ga asosan Shezi
koeffitsientini aniqlash jadvali keltirilgan.
Baxmetov va boshqalarning yarim impirik formulasi
(
1943 y.
)
R
n
С
lg
72
,
17
1
(4.159)
I.I. Agroskin formulasi
(
1949 y.
)
R
n
С
lg
72
,
17
1
(4.160)
Bundan tashqari, amaliyotda keng qo‘llaniladigan, oqimning turbulent
tartibdagi harakatining har uchala tekis o‘zanlar, kvadrat qarshilikkacha, kvadrat
qarshiliklar sohalari uchun o‘rinli bo‘lgan A.D.Altshulning umumlashtirilgan
formulasini ham keltirish mumkin:
6
1
6
025
,
0
80
25
RJ
n
R
С
(4.161)
Shezi koeffitsienti
S
ni quyidagi Manning formulasi asosida tuzilgan
jadval yoki N.N.Pavlovskiy maxsus grafigi yordamida ham aniqlash mumkin
~ 325 ~
Manning formulasiga asosan aniqlangan Shezi koeffitsientining
qiymatlari,
6
1
1
R
n
С
с
м
5
,
0
4.5-jadval
R, m
n
0,011
0,013 0,014 0,017 0,020 0,025 0,030 0,035 0,045 0,050
0,30
74,38
62,94 58,44 48,13 40,91 32,73 27,27 23,38 18,18 16,36
0,32
75,19
63,62 59,07 48,65 41,35 33,08 27,57 23,63 18,38 16,54
0,34
75,95
64,26 59,67 49,14 41,77 33,42 27,85 23,87 18,57 16,71
0,36
76,68
64,88 60,25 49,61 42,17 33,74 28,11 24,10 18,74 16,87
0,38
77,37
65,47 60,79 50,06 42,55 34,04 28,37 24,32 18,91 17,02
0,40
78,03
66,03 61,31 50,49 42,92 34,33 28,61 24,52 19,07 17,17
0,42
78,67
66,57 61,81 50,90 43,27 34,62 28,85 24,73 19,23 17,31
0,44
79,28
67,09 62,29 51,30 43,61 34,88 29,07 24,92 19,38 17,44
0,46
79,87
67,58 62,76 51,68 43,93 35,14 29,29 25,10 19,52 17,57
0,48
80,44
68,07 63,20 52,05 44,24 35,39 29,50 25,28 19,66 17,70
0,50
80,99
68,53 63,64 52,41 44,54 35,64 29,70 25,45 19,80 17,82
0,55
82,29
69,63 64,65 53,24 45,26 36,21 30,17 25,86 20,11 18,10
0,60
83,49
70,65 65,60 54,02 45,92 36,74 30,61 26,24 20,41 18,37
0,65
84,61
71,59 66,48 54,75 46,54 37,23 31,02 26,59 20,68 18,61
0,70
85,66
72,48 67,31 55,43 47,11 37,69 31,41 26,92 20,94 18,85
0,75
86,65
73,32 68,08 56,07 47,66 38,13 31,77 27,23 21,18 19,06
0,80
87,59
74,11 68,82 56,68 48,17 38,54 32,12 27,53 21,41 19,27
0,85
88,48
74,87 69,52 57,25 48,66 38,93 32,44 27,81 21,63 19,47
0,90
89,33
75,58 70,19 57,80 49,13 39,30 32,75 28,07 21,84 19,65
0,95
90,14
76,27 70,82 58,32 49,57 39,66 33,05 28,33 22,03 19,83
1,00
90,91
76,92 71,43 58,82 50,00 40,00 33,33 28,57 22,22 20,00
1,10
92,36
78,15 72,57 59,77 50,80 40,64 33,87 29,03 22,58 20,32
1,20
93,71
79,30 73,63 60,64 51,54 41,23 34,36 29,45 22,91 20,62
1,30
94,97
80,36 74,62 61,45 52,23 41,79 34,82 29,85 23,22 20,89
1,40
96,15
81,36 75,55 62,22 52,88 42,31 35,26 30,22 23,50 21,15
1,50
97,26
82,30 76,42 62,94 53,50 42,80 35,66 30,57 23,78 21,40
~ 326 ~
R, m
n
0,011
0,013 0,014 0,017 0,020 0,025 0,030 0,035 0,045 0,050
1,60
98,32
83,19 77,25 63,62 54,07 43,26 36,05 30,90 24,03 21,63
1,70
99,32
84,04 78,03 64,26 54,62 43,70 36,42 31,21 24,28 21,85
1,80
100,27 84,84 78,78 64,88 55,15 44,12 36,76 31,51 24,51 22,06
1,90
101,17 85,61 79,49 65,47 55,65 44,52 37,10 31,80 24,73 22,26
2,00
102,04 86,34 80,18 66,03 56,12 44,90 37,42 32,07 24,94 22,45
2,20
103,68 87,73 81,46 67,08 57,02 45,62 38,01 32,58 25,34 22,81
2,40
105,19 89,01 82,65 68,06 57,85 46,28 38,57 33,06 25,71 23,14
2,60
106,60 90,20 83,76 68,98 58,63 46,91 39,09 33,50 26,06 23,45
2,80
107,93 91,32 84,80 69,84 59,36 47,49 39,57 33,92 26,38 23,74
3,00
109,18 92,38 85,78 70,64 60,05 48,04 40,03 34,31 26,69 24,02
3,50
112,02 94,78 88,01 72,48 61,61 49,29 41,07 35,21 27,38 24,64
4,00
114,54 96,92 89,99 74,11 63,00 50,40 42,00 36,00 28,00 25,20
4,50
116,81 98,84 91,78 75,58 64,24 51,40 42,83 36,71 28,55 25,70
5,00
118,88 100,59 93,40 76,92 65,38 52,31 43,59 37,36 29,06 26,15
~ 327 ~
4.33-rasm. N.N.Pavlovskiy maxsus grafigi
~ 328 ~
Do'stlaringiz bilan baham: |
