Bernoulli principle - negative pressure

I will write a program about principle bernoulli, but i have a problem.

My input data:

Pressure(p1) = 1000
Cross-section(A1) = 1
Velocity(V1) = 1

Cross-section(A2) = 0.5

Velocity(v2)= (V1A1)/A2

to simplify: h1=h2

i'm counting the pressure p2 : p2 = p1 + 0.5*v1*v1 - 0.5*v2*v2 , so i getting negative pressure..

This is a problem (negative pressure)

I'm trying to add atmospheric pressure, but it doesn't solve my problem.

Is a mathematical formula is good? Is there any other relationship?

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SteamKing
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AlephZero
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i'm counting the pressure p2 : p2 = p1 + 0.5*v1*v1 - 0.5*v2*v2 , so i getting negative pressure..
Your equations look OK. You correctly calculated V2 = 2, so you must have made a mistake in the code.

My calculator says 1000 + 0.5*1*1 - 0.5*2*2 = 998.5 whcih isn't negative.

Your equations look OK. You correctly calculated V2 = 2, so you must have made a mistake in the code.

My calculator says 1000 + 0.5*1*1 - 0.5*2*2 = 998.5 whcih isn't negative.
My mistake. I forgot write the density of liquid.

Should : p2 = p1 + 0.5*v1*v1*ro - 0.5*v2*v2*ro

ro=density=1000,

so:
p2 = 1000 + 0.5*1*1*1000 - 0.5*2*2*1000 = -500 .

I replace Paskal to kPa, but it didn't help

AlephZero