--- title: Insights - CFD and scale-down notes | p4b | CFD description: "CFD | CFD and scale-down notes from p4b: mixing times, gradients and what cells experience in large bioreactors - and how to bring production-scale conditions into the lab." image: https://www.p4b.io/hubfs/raw_assets/public/p4b/images/og-default.png --- [![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 Insights # Notes from the simulation lab What we learn while simulating and scaling down bioreactors - mixing, gassing, validation and the occasional surprise. [All](https://www.p4b.io/insights) [CFD](https://www.p4b.io/insights/tag/cfd)[Case study](https://www.p4b.io/insights/tag/case-study)[DREAM-bio](https://www.p4b.io/insights/tag/dream-bio)[Events](https://www.p4b.io/insights/tag/events)[Scale-down](https://www.p4b.io/insights/tag/scale-down) ### [![](https://www.p4b.io/hubfs/website/insights/slides/eleven-2.webp) CFD23 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.](https://www.p4b.io/insights/eleven-mixing-times-one-reactor) ### [![](https://www.p4b.io/hubfs/website/insights/slides/kla-5.webp) CFD23 Oct 2026 Validation first: can CFD rank stirrer positions by kLa? In a demanding 2 L kLa comparison at 1.5 vvm and 1400 rpm, we changed only the stirrer position and compared CFD against experimentally measured kLa. Even though the values were close, the simulation ranked the configurations in the right order and found a stirrer position that performed better than the standard setup.](https://www.p4b.io/insights/cfd-validation-kla-stirrer-position) ### [![](https://www.p4b.io/hubfs/website/video/xcellerex-2000l-rpm.webp) CFD23 Oct 2026 We expected 100 rpm to mix fastest. It didn't. A gas-liquid CFD study of a 2000 L single-use bioreactor similar to a Cytiva XCellerex setup showed the fastest mixing at ~80 rpm and the slowest at 100 rpm. In this design, the impeller's main job is to control how far the gas plume spreads.](https://www.p4b.io/insights/faster-stirring-not-faster-mixing) ![pDS inserts next to Ambr 250 vessels](https://www.p4b.io/hubfs/website/pds-family.webp) White paper · CHO demonstration case ## Large-scale conditions in a 1 L lab bioreactor How a reactor designed by generative AI recreates the gradients of a 10,000 L scale in a 1 L vessel - and what they do to lactate and mAb titer in a CHO process. 4 pages, free. [Download the white paper](https://share-eu1.hsforms.com/1Iz-e9dcFQYax4uBfRa8fiw2dmt7m) 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. [Request a quote](https://www.p4b.io/contact#quote)[Book a 30-min call](https://www.p4b.io/contact#meeting) ![Lena Achleitner](https://www.p4b.io/hs-fs/hubfs/website/team/lena-avatar.webp?width=84&height=84&name=lena-avatar.webp) **Lena Achleitner**Senior Bioprocess Engineer, Key Account Manager[lena.achleitner@p4b.io](mailto:lena.achleitner@p4b.io) ### Get new insights by email CFD results, case studies and new insert systems when we publish them. Unsubscribe any time. ![p4b](https://www.p4b.io/hubfs/raw_assets/public/p4b/images/p4b-logo-white.svg) Scale reliably. Develop faster. Digital and 3D-printed technologies for bioprocessing. 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