MHXANIKH ΡΕΥΣΤΩΝ - mie.uth.gr2004-05)Lyseis.pdf · ΠΑΝΕΠΙΣΤΗΜΙΟ...

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  • . &

    ( 2004-2005) : . . : .

    1

    1.2: , :

    A Hg 30cm

    2.1 20cm 10cm H2O 2.2 ( )

    H2O

    1.2

    1121 ghPP = , 2223 ghPP = , 3334 ghPP = kPa3.14ghghghPP 332211aA =+= , kPa6.115PA =

    1.3: , :

    F 0,5m 1m

    3.1 H2O 2m 3.2 ()

    3.3 F A A 1m

    1.3 : h=0.5+1=1.5m, Fp=gh=29.43 kN

    :

    =

    y

    x 'y'x' ,

    =

    y

    y 'x'x'

    m0x0 ''y'x == , m222.0ym667.012bh '43

    'x'x ===

    x=1.5+0.222=1.722m,

    kN25.27FlFlF pp == (lp=2-1.722=0.277m, l=3m)

  • 2

    2.1 3.55 ( Bernoulli) 2.1 (3.55) ( . )

    3 30.00130 30 0.03sec sec secl l mQ

    l= = =

    m,

    2

    0.03 1.6980.15 sec( )2

    Q mVA

    = = =

    hf: 2 210 10(1.698) 1.469

    2 2(9.81)fVh m g

    = = =

    s: 1 1 2 21 22 2 s fP V P Vz z Hg g g g

    h+ + = + + + +

    (P1=P2=Pa, V1=V2=0) => 1 2 16 1.469 17.469s f s fH z z h H H h m= = = =

    : ( n = 80% = 0.8) theoriticalactual

    PnP

    = =>

    1000(9.81)(0.03)(17.469) 16426.408 6426.408 8.6140.8 746

    sgQH HPP Wn W

    W HP= = = = =

    2.2 3.57 ( Bernoulli) 2.2 (3.57) ( . )

    3 3 1120000 120000 33.333600sec sec

    m m hQh h

    = = =3m

    s: 1 1 2 2

    1 22 2 s fP V P Vz z Hg g g g

    h+ + = + + + + ,

    (P1= P2 = Pa, V1 = V2 = 0, hf = 0) =>

    1 2 60s sH z z H H m= = =

    n = 80% = 0.8) actualPntheoriticalP

    = => (

    11000(9.81)(33.33)(60)(0.8) 15694430.4 15694430.4 21038.11746s

    HPP n gQH W W HPW

    = = = = =

    2

  • 2.3 3.88 ( )

    2.3 (3.88)

    ) ( . s/m0555.0Q 31 = , s/m3333.0Q

    31 = , s/m2222.0Q

    31 = ,

    kPa6.68P1 = s/m49.3V1 = , s/m7. 24V2 = , s/m8

    5.12V1 = 2 3. Bernouli (1)-(2): (z1 = z2 = 0)

    +=+VPVP 222

    211

    g2gg2gP2=-63,66kPa

    . Bernouli (1)-(3): (z = 0) 3

    +=+VPVP 233

    211 P =-4,13kPA

    g2gg2g 3

    x: x3

    032

    02 Q60cosVQ45cosV =+

    (F2x = P2A2cos45 , F3x = P3A3cos60) => Fx = 2.9 kN ( )

    y:

    3sin 60oV Q+

    (F1y = P1A1, F2y = P2A2sin45 , F3y = P3A3 sin60)

    ( ) ( ) x3x2 FFF ++ 3

    1 2 3 1 1 2 sin 45o

    y y y yF F F F V Q V Q + + + = + 2 3

    => Fy = 6.21 kN ( ) 2.4 3.114 ( ) 2.4 (3.114)

    ) x:

    u = (V0 u) A u

    u

    :

    1 0

    ( . Fx = (V0 u)2 A => Fx = (V0 u)2 A H W : W = Fx 2 H W u W(u) = u (V0 u)2, W' = (V0 u)(V3u), W'' = 2 (3V0 2u)

    u2 = 03. H V

    V u = V 0

    2 V 0 > 0, 03V

    2 V0 < 0.

    03

    V .

    3

  • 3

    3.1 Vo=8m/s SAE 10. W=0.5m L=1.0m. , :

    1.1 (L=1m) 1.2 () 1.3 1.4 ,

    3.1

    3.1.1 =

    = 40 10x9LV

    Re

    m0183.0Re

    L5.5

    L

    == , 0022.0Re664.0c

    L

    f == , 0044.0c2c fD ==

    3.1.2 N129LWV21c2F 20DD ==

    3.1.3 W1033FVP D0 ==3.1.4 , N183FD = , W1465FVP D0 == 2 Navier-Stokes :

    ( U + V ) = - [ ( ) + ( )]t x y x x x y

    U U U p U Uy

    + + (1)

    ( U + V ) = - [ ( ) + ( )]t x y x x y

    V V V p V Vy y

    + + (2)

    2.1 (=C) . 2.2 , ;

    3.2 3.2.1 (=C) :

    d dU dp ( ) = dy dy dx

    p = 0y

    3.2.2 : U U p(U + V ) = - ( )x y x y

    + Uy

    p = 0y

    : V ~ 0