How to calculate pressure at mixing point

[Bergamo32]

I have a setup with two positive displacement pumps: Pump 1 delivers about 6 BPM through a 4" pipe at pressure P1, and Pump 2 delivers 0.8 BPM through a 1" pipe at pressure P2. The 2 streams mix and discharge into an open tank at atmospheric pressure. Im trying to figure out the pressure at the mixing point (Pm). Is there an empirical formula or method I can use to estimate Pm? Any guidance would be appreciated.

 

[Distinct-Barnacle65]

For estimating Pm, you might look into momentum balance or use Bernoulli's principle with flow rates and pipe sizes. Since it's mixing into an open tank, pressure drops quickly, so Pm will likely be closer to atmospheric unless there's significant resistance at the junction. Have you considered using CFD software for a more accurate model?

 

[Barb Cole]

Trying to calculate a mixing pressure like that is mostly pointless, those pumps and pipe sizes create chaotic flows. Guessing Pm without CFD or real measurements is just a recipe for error

 

[Bergamo32]

For estimating Pm, you might look into momentum balance or use Bernoulli's principle with flow rates and pipe sizes. Since it's mixing into an open tank, pressure drops quickly, so Pm will likely be closer to atmospheric unless there's significant resistance at the junction. Have you considered using CFD software for a more accurate model?

Thanks. I was mostly looking for a quick hand calculation, but CFD could definitely give a clearer picture. Do you think a simple momentum balance would be accurate enough for low viscosity fluids, or would the junction resistance still throw it off?