--- title: Same reactor, same speed, eleven mixing times description: In a CFD study of an Eppendorf DASGIP vessel, we released eleven tracers into the same running flow and measured mixing times anywhere between 20.3 and 23.5 seconds. This is why one mixing time per reactor is not enough to compare two reactors. image: https://www.p4b.io/hubfs/website/insights/slides/eleven-2.webp --- [![p4b](https://www.p4b.io/hubfs/raw_assets/public/p4b/images/p4b-logo-white.svg) ![p4b](https://www.p4b.io/hubfs/raw_assets/public/p4b/images/p4b-logo-navy.svg)](https://www.p4b.io/) Products [**pDS inserts**Large-scale conditions in your lab bioreactor](https://www.p4b.io/pds) [**Advanced CFD**Gradients, lifelines and cell experiences](https://www.p4b.io/cfd) [**DREAM-bio**Find the best geometry for your bioreactor](https://www.p4b.io/dream-bio) [**Ambr 250 vs. 2,000 L**Interactive CFD comparison of the mixing](https://www.p4b.io/compare) [Case studies](https://www.p4b.io/case-studies) [Insights](https://www.p4b.io/insights) [Events](https://www.p4b.io/events) [About](https://www.p4b.io/about) [Contact](https://www.p4b.io/contact) [Request a quote](https://www.p4b.io/contact#quote) [Home](https://www.p4b.io/) / [Insights](https://www.p4b.io/insights) CFD · 23 Oct 2026 # Same reactor, same speed, eleven mixing times In a CFD study of an Eppendorf DASGIP vessel, we released eleven tracers into the same running flow and measured mixing times anywhere between 20.3 and 23.5 seconds. This is why one mixing time per reactor is not enough to compare two reactors. ![Tracer spreading in the vessel after 0.5, 1, 5 and 20 seconds](https://www.p4b.io/hs-fs/hubfs/website/insights/slides/eleven-2.webp?width=900&height=900&name=eleven-2.webp) Mixing time is usually measured by releasing a tracer into the running flow and following how it spreads. Once the tracer concentration is within ±5 % of the average concentration, the vessel is considered mixed. In the Eppendorf DASGIP vessel we simulated, this takes around 20 seconds. Then we did it again, eleven times. A fresh tracer went in every five seconds: same tank, same stirrer speed, same simulation. The only thing that changed was the moment the tracer was added. The results ranged from 20.3 s for the fastest tracer to 23.5 s for the slowest, with a mean of 22.2 s. That is a spread of around ±7 % about the mean, even in a perfect simulation. In the lab, measurement error comes on top. This matters when reactors are compared. If the same vessel gives anything from 20.3 to 23.5 seconds, two designs that are less than 3 seconds apart can easily come out in the wrong order. So we measure many times in one condition and report the range: how fast, how reproducible, and where the slow spots are. Every CFD run now injects a series of tracers into the running flow automatically, at no extra calculation effort. The report gives the mean, spread and confidence interval for every run (here 22.2 ± 0.9 s at 95 %), so designs can be compared side by side on numbers with error bars. Differences are tested, not guessed. ![Same reactor, same speed, eleven mixing times - CFD study of an Eppendorf DASGIP vessel](https://www.p4b.io/hs-fs/hubfs/website/insights/slides/eleven-1.webp?width=900&height=900&name=eleven-1.webp)![Tracer spreading in the vessel after 0.5, 1, 5 and 20 seconds](https://www.p4b.io/hs-fs/hubfs/website/insights/slides/eleven-2.webp?width=900&height=900&name=eleven-2.webp)![Eleven tracers: fastest 20.3 s, slowest 23.5 s, about ±7 % around the mean of 22.2 s](https://www.p4b.io/hs-fs/hubfs/website/insights/slides/eleven-3.webp?width=900&height=900&name=eleven-3.webp)![Eleven CoV curves of the tracer concentration crossing the 5 % line between 20.3 and 23.5 s](https://www.p4b.io/hs-fs/hubfs/website/insights/slides/eleven-4.webp?width=900&height=900&name=eleven-4.webp)![Why it matters: one mixing time per reactor is not enough to compare two reactors](https://www.p4b.io/hs-fs/hubfs/website/insights/slides/eleven-5.webp?width=900&height=900&name=eleven-5.webp) Slides from the LinkedIn post - swipe through [← All insights](https://www.p4b.io/insights) Get in touch ## Let's find out how your process reacts to scale Tell us your system and target scale - we come back with a proposal for your insert set. 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