- #1
gen x
- 21
- 2
When I increase airlfow speed v1, pressure in contraction drop more and more, so at some point fall even below 0 Pa absolute, but this is physically impossible.
I use this numbers just as example, this is not homework question..
Data for pipe:
P1=150 000Pa, absolute pressure
section ratio A1/A2=10
v1=80m/s
ρ=1.2kg/m3
...............................................................
Find pressure P2 in pipe section A2.
P1+1/2 ρ V1^2 = P2 + 1/2 ρ V2^2
A1 V1= A2 V2.........V2=A1/A2 x V1
delta P = P1-P2 = 1/2 ρV1^2 ((A1/A2)^2 -1)
-P2 = 1/2 ρV1^2 ((A1/A2)^2 -1) - P1 /x (-1)
P2= -1/2 ρV1^2 ((A1/A2)^2 -1) + P1
I calculate P2= -230 160Pa, this is imossible because negative absolute pressure dont exist.
How can I caluculate this correctly and up to which speed v1 equation is correct?
I use this numbers just as example, this is not homework question..
Data for pipe:
P1=150 000Pa, absolute pressure
section ratio A1/A2=10
v1=80m/s
ρ=1.2kg/m3
...............................................................
Find pressure P2 in pipe section A2.
P1+1/2 ρ V1^2 = P2 + 1/2 ρ V2^2
A1 V1= A2 V2.........V2=A1/A2 x V1
delta P = P1-P2 = 1/2 ρV1^2 ((A1/A2)^2 -1)
-P2 = 1/2 ρV1^2 ((A1/A2)^2 -1) - P1 /x (-1)
P2= -1/2 ρV1^2 ((A1/A2)^2 -1) + P1
I calculate P2= -230 160Pa, this is imossible because negative absolute pressure dont exist.
How can I caluculate this correctly and up to which speed v1 equation is correct?
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