# Is supersonic flow not possible in a venturi tube?

I'm trying to design a venturi tube that will have a pressure drop of 91525 Pascals where the inlet pressure is at 1 atm and the throat pressure is at 9800 Pascals. I calculated the minimum throat velocity need to have this drop assuming my inlet velocity is super small by doing the following.

$$p_1-p_2=\frac{ρ}{2}(v_2^2-v_1^2)$$
$$91525=\frac{1.204}{2}(v_2^2-0), v_2>>>v_1$$\

What I get for $$v_2$$ is around 389 m/s.

This is over the speed of sound and I have been told that venturi tubes cant have supersonic flow at the throat. I have also been told that the velocity should stay under mach 0.3 as above mach 0.3 compressibility starts to become a problem.

I guess my question is, Is it possible to have a venturi tube that has a pressure drop of 91525 Pascals, why can't supersonic flow happen in the venturi tube, and if a venturi tube won't work what can I use to drop the pressure.

PS: The fluid in my tube is air

• Hi, when askiing a question, please provide references for "I have been told" or "I read somewhere" so we can evaluate the reliability of your sources. Aug 8, 2022 at 14:57
• engapplets.vt.edu/fluids/CDnozzle/cdinfo.html Aug 8, 2022 at 15:41
• I was told this on Reddit so credibility isn't the best. Aug 9, 2022 at 2:28
• Compressibility is not a problem, the only problem is that theory for incompressible flow starts to be more than a few percent off when the velocity exceeds Mach 0.3. Aug 9, 2022 at 10:40