BI TP THY VN1. Hy tnh lu lng nc: Theo ta c cng thc: Q= F.V Trong : Q l lu lng nc ( m2/s ) F l din tch mt ct ngang Bn cnh ta c Q= q BI 1

1)Tnh lu lng nc

i=n

p dng cng thc Q = qii=1

q(I) = f(I) * V(I)

Din tch f(I) = f(1) + f(2)

=

b1*h1 b2(h1+h2) + 2 2

=

6*5 10(6+10) + = 15 + 80 = 95 (m2) 2 2

Tc V(I) = k * V(I)

2 (trong k l h s st b, k = ) 3

=

2 * 1,5 = 1 (m/s) 3

Vy q (I) = f(I) * V(I) = 95 * 1 = 95 (m3/s)

q(II) = f(II) * Vtb(II)

f(II) = f(3) + f(4)

= 187,5 + 350 = 537,5 (m2) 1,5+2,5 = 2 (m/s) 2

Vtb(II) =

Vy q(II) = 537,5 * 2 = 1075 (m3/s)

q(III) = f(III) * Vtb(III) f(III) = f(5) + f(6) = 570 + 330 = 900 (m2)

Vtb(III) =

2,5+1,2 = 1,85 (m/s) 2

Vy q(III) = 900 * 1,85 = 1665 (m3/s) q(IV) = f(IV) * V(IV) f(IV) = f(7) + f(8) + f(9)

= 150 + 112,5 + 50 = 312,5 (m2) 2 = 0,8 (m/s) 3

V(IV) = 1,2 * k = 1,2 *

Vy q(IV) = 312,5 * 0,8 = 250 (m3/s)

Ta tnh c lu lng nc Q = q(I) + q (II) + q(III) + q (IV) = 95 + 1075 + 1665 + 250 = 3085 (m 3/s)

2) c trng thy vn Tc trung bnh Din tch mt ct ngang

= f(I) + f(II) + f(III) + f(IV) = 95 + 537,5 + 900 + 312,5 = 1845 (m2) Tc trung bnh Q 3085 = = 1,67 (m/s) 1845

Vtb =

rng mt ct ngang B = b(1) + b(2) + b(3) + b(4) + b(5) + b (6) + b(7) + b(8) + b(9) = 5 + 10 + 15 +20 + 30 + 20 + 12 +15 +20 = 147 (m) su trung bnh 1845 = = 12,55 (m) 147 B

h=

BI 2 Tnh tng th tch nc do dng chy trc tip sinh ra

i=n

Vd = Qi * Ti=1

trong : Qi l dng chy trc tip th i

T l thi gian tnh ton, tnh t thi im c dng chy trc tip u tin n dng chy cui. Ta tnh c Qi = 1361 (m3) v T = 0,5h = 1800s

Vd = 1361 * 1800 = 2449800 (m3)

Tnh su dng chy trc tip 2449800 Vd = = 0,098 (m) = 98 mm 25000000 F

rd =

c tnh lng tn tht trong n v thi gian do thm v tr nc trn lu vc.

Xc nh cng thm theo cng thc:

i=M

rd =

i=1

( Rm - * t)

(*)

dng phng php th sai

M=1

(*) 98 = 2 - * 0,5

= -192 (v l)

M =2

(*) 98 = (2 +5) - (0,5 * 2)

= -91 ( v l ) M=3

(*) 98 = (2 + 5 + 50) - ( 0,5 * 3)

= -27,3 ( v l) M=4

(*) 98 = (2 + 5 + 50 + 80) - ( 0,5 * 4)

= 19,5 ( hp l)

Bi tp THY VN I CNG