ANSI/HI 9.8.4.1 provides a great checklist for physical modeling, and section 9.8.7 provides guidance for using CFD. As of 2012 (that's the version I have on my desk), the standard states that CFD can be used for understanding general approach flow to the sump, but more simulating complex phenomena at the intake (free and submerged vortices and pre-swirl) was still not to a point that it could be standardized.
CFD has evolved a lot in the last few years, so a more recent version of the HI may have more refined guidance on using CFD for detailed intake hydraulics.
Without listing each bullet in the HI here:
- On the upper end, if your total station flow exceeds 144 mgd, or flow-per-pump exceeds 57 mgd, HI requires a physical modeling study
- On the lower end (for more specific sump arrangements), if flow-per-pump exceeds 7 mgd, HI requires a physical modeling study
- There is a great exhaustive list for specific requirements in HI 9.8.4.1
This does not address your question about cost, but the standard should help you answer the question about what degree of modeling is required for your size of project.
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Brandon Billing P.E., M.ASCE
Water Resources Engineer
Coeur D Alene ID
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Original Message:
Sent: 04-10-2017 16:25
From: John Weiland
Subject: Hydraulic Modeling
I'm looking for some guidance on when the cost of performing physical hydraulic modeling of pump stations is considered justified, versus computer models or hand calculations. Obviously, this is dependent on the judgement of the Engineer and Owner, but I'd like to hear about some different experiences on this.
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John Weiland P.E., M.ASCE
Project Manager
Wade Trim
Eureka MO
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