892’ - fakultet strojarstva i brodogradnje · 0(+$1,.$)/8,’$ 892’ 892’...
TRANSCRIPT
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( , , , ) ( , , , ) ( , , , )x y z
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d( , , , ) ( , , , ) ( , , , )x y z
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Strujna površina je sastavljena od strujnica koje SUROD]H�WRþNDPD�QHNH�NULYXOMH�&��9HNWRU� EU]LQH� MH� WDQJHQFLMDODQ na površinu 0v n⋅ =G G
, pa kroz strujnu površinu nema protoka
d 0S
Q v n S= ⋅ =∫G G ��
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Ako je krivulja C zatvorena, strujna površina prelazi u plašt strujne cijevi, kroz kojeg nema SURWRND� IOXLGD�� NDR� L� NUR]� SODãW� QHNH� IL]LþNH�FLMHYL��$NR� MH� SRYUãLQD� SRSUHþQRJ� SUHVMHND� FLMHYL� dS �LQILQLWH]LPDOQD�� JRYRUL� VH� R� HOHPHQWDUQRM�VWUXMQRM� FLMHYL�� 8� JUDQLþQRP� SULMHOD]X� d 0S → �HOHPHQWDUQD�VWUXMQD�FLMHY�SUHOD]L�X�VWUXMQLFX���
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EU]LQD� JLEDQMD� þHVWLFD� IOXLGD� X� RGQRVX� QD� SRYUãLQX� w v u= −G G G �� D� SURWRN� Q � MH� GHILQLUDQ�L]UD]RP� �� ( )d d
S S
Q w n S v u n S= ⋅ = − ⋅∫ ∫G G G G G ��
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S
Q v n S= ⋅∫G G ��
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G G� ¸ �� 9ROXPHQ�
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G G� ¸ � ¸ ¸ ��
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dd = d
d
VQ v n S
t
G G� ¸ , a ukupni protok kroz površinu 6�
jednak je zbroju svih elementarnih protoka, što se opisuje integralom dS
Q v n S= ⋅∫G G ��
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d dA A
Q v n A v A= ⋅ =∫ ∫G G �
vdA
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A
Q v A vA= =∫ �vA
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dS
Q u n S= − ⋅∫G G ��
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G �� D� YROXPHQ�d d dV u n S t
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G prolazile kroz površinu. Zato je protok GHILQLUDQ�L]UD]RP� d
S
Q u n S= − ⋅∫G G ��
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SIMT , kg/sm m−= =� � �� =D� VOXþDM�PLUXMXüH�
površine: dS
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S
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SIMLT , N/sG G− = =
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S
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k kQ Q− = = ��
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d d
V t t V tV
t t
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Vu n S u V
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tV t V t V t t V t
V t V t t V t V
df dV f r t t dV f r t dV
dt t
f r t t dV f r t dV f r t t dV f r t t dVt
f fdV f r t t dV dV
t t
φ∆ →
+∆
∆ →+∆
+∆ −
= + ∆ − =
∆
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∫ ∫ ∫
∫ ∫ ∫ ∫
∫ ∫
G G
G G G G
G
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dd d d d
d V V S V
f ff V V fu n S fu V
t t t
∂ ∂ = + ⋅ = + ∇ ⋅ ∂ ∂ ∫ ∫ ∫ ∫G G G
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d Dt t→ ��
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Dd d d d
D V V S V
f ff V V fv n S fv V
t t t
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na fluid
dd d d d
d u i w
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v V gk V v v n S St
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n
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d KV KP KV KP
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r v V r v v n S r f V r St
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moment sile moment sile fluida na plašt WHåLQH
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