Page 25 - NUZUL_Buku Kerja Pengujian Hidrolika_Denny Yatmadi, Nuzul Barkah Prihutomo & Wahyuni Susilowati

Pengujian Hidrolika II. Venturimeter

Persamaan Bernoulli pada irisan A, B, dan n adalah :

V 2 P V 2 P Vn 2 Pn
Z + 1 + 1 = Z + 2 + 2 = Zn + +
1 2g γ 2 2g γ 2g γ .................................. (1)

Karena garis datum diambil melalui sumbu pipa mendatar, maka :
Z = Z = Z = Zn ..................................................................................................... (2)
1 2

V 2 P V 2 P 2
1 + 1 = 2 + 2 = Vn + Pn
2g γ 2g γ 2g γ ......................................... (3)

Persamaan Kontinuitas :
Q = Q = Q = Q ....................................................................... (4)
n
2
1
Maka :
A1 . V1 = A2 . V2 = An . Vn ............................................................................ (5)

An . Vn An 2 . Vn 2
2
V 1 = → V 1 =
A 1 A 1 2 .......................................... (6)

Persamaan (6) disubsitusikan ke persamaan (3)
An 2 . Vn 2 + P1 = Vn 2 + Pn

2 γ 2g γ ............................................................... (7)
A1 . 2g

P1 − Pn = Vn 2 − An 2 . Vn 2
γ 2g A1 2 . 2g ................................................................ (8)

P1 − Pn = h
γ → Perbedaan tinggi tekanan antara irisan 1 dan n

Maka :

Vn 2 An 2 . Vn 2
h = − ................................................................................. (9)
2g A1 2 . 2g

Vn 2  An 2  Vn 2  A 1 2 − An 2 




h = 1 − =
2g  A 2  2g  A 2  .............................. (10)
 1   1 
2
A1 2 . 2g ⋅ h = Vn 2 (A1 − An 2 ) ........................................................... (11)

Jurusan Teknik Sipil
Politeknik Negeri Jakarta 14