Problem with Bernoulli calculation

[gen x]

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?

 

[Lnewqban]

V2 can't reach ten times the value of V1 in the smallest diameter section of the Venturi because it would be way over the speed of sound.
You are stepping into the field of supersonic flow, in which the theorem of Bernoulli can't be applied.

 

[FactChecker]

V2 can't reach ten times the value of V1 in the smallest diameter section of the Venturi because it would be way over the speed of sound.
You are stepping into the field of supersonic flow, in which the theorem of Bernoulli can't be applied.

Good catch.

 

[gen x]

V2 can't reach ten times the value of V1 in the smallest diameter section of the Venturi because it would be way over the speed of sound.
You are stepping into the field of supersonic flow, in which the theorem of Bernoulli can't be applied.

What is solution to find pressure P2?

 

[jack action]

Use the isentropic nozzle flow equations which consider compressibility effects.