MECHANICAL — CFD AND ENERGY · CASE STUDY
Data Centre CFD Analysis — Evidence
NOT ENGINEERING VALIDATED — native CFD converged; validation gates partly failed
Evidence
Evidence folders
| Folder | Status | SHA256SUMS sha256 |
|---|---|---|
| cfd-DC00-20261024-r2 | final DC-00 evidence; 1,758 files; checksums re-verified 2026-10-25 (0 failures) | 6e1715a8d12990e0831d3fd20054b76cd0cf5bf40951d0349172967f6af21e7c |
| cfd-DC00-20261024 | SUPERSEDED by r2 (SUPERSEDED.txt present); 212 files | 6911696e9521f536d35129ed7a6a223dbf4542ad42ab3cbfc0b89249e3b514dd |
| cfd-DC01-N1-DSM-20261024 | DC-01 annual simulation; 219 files | 8a000b9d6b210592a6337c43ae110183f029c73ff626f50419c89e1f79491cf9 |
| cfd-review-20261024 | independent review package | 64a0d0bea8d8a9a81128fcfc2a6bce173ddc7600567246ca734144af79a9f2b5 |
Derivative pack
This pack is a sanitised derivative: crops of native viewer screenshots, Hexanta plots and a report. Native project files and raw solver outputs stay in the evidence store.
Native evidence and completeness matrix
| Result | Origin | Software · date | Verdict | Status | Source · evidence hash | Engineering approval |
|---|---|---|---|---|---|---|
| DC00B-R6 baseline CFD (final)CFD runFinal baseline: DC00B-R5 field resumed with the same boundaries; all 7 residuals at the 1e-5 termination residual after 2,599 outer iterations; rack inlets 19.09-21.62 °C (max 21.62 °C), within 0.02 K of R5. Convergence only - the study is NOT ENGINEERING VALIDATED. | Native tool output | IESVE (MicroFlo CFD) 2026 (trial licence, internal evaluation)2026-10-24 | PASS | exploratory | cfd-DC00-20261024-r2/cfd/DC00B-R6/HX_DC00_M1.logsha256 b03ee3d19604… | OUTSTANDING — no engineer review or approval recorded |
| DC00O-R1 optimised CFD (final)CFD runFinal optimised design (supply 1.05 x IT airflow, two hot-aisle extracts): all 7 residuals at 1e-5 after 653 outer iterations. Convergence only - not engineering validated. | Native tool output | IESVE (MicroFlo CFD) 2026 (trial licence, internal evaluation)2026-10-24 | PASS | exploratory | cfd-DC00-20261024-r2/cfd/DC00O-R1/HX_DC00_MO.logsha256 5f26864180c4… | OUTSTANDING — no engineer review or approval recorded |
| DC00O-R1b rack-inlet monitor read-outCFD runConverged DC00O field resumed 1 iteration with 11 cell monitors: rack inlets 19.02-21.49 °C (max 21.49 °C); represented rack heat 9.85-9.97 kW per 10 kW rack. Values are the converged state; no stability window. | Native tool output | IESVE (MicroFlo CFD) 2026 (trial licence, internal evaluation)2026-10-24 | PASS | exploratory | cfd-DC00-20261024-r2/cfd/DC00O-R1b/HX_DC00_MO.logsha256 6c564f5ac841… | OUTSTANDING — no engineer review or approval recorded |
| DC00O-F1 refined-mesh CFDMesh studyRefined grid 0.075 m (80 x 63 x 39 = 196,560 cells) converged after 830 iterations; rack inlets within +0.08 K of the base grid; max inlet 21.53 °C. | Native tool output | IESVE (MicroFlo CFD) 2026 (trial licence, internal evaluation)2026-10-24 | PASS | exploratory | cfd-DC00-20261024-r2/cfd/DC00O-F1/HX_DC00_MOF.logsha256 86bc4b430b60… | OUTSTANDING — no engineer review or approval recorded |
| DC00O-C1 coarse-mesh CFDMesh studyCoarse grid 0.133 m (44 x 35 x 22 = 33,880 cells, aspect 2:1) converged after 517 iterations; third grid for the GCI study. | Native tool output | IESVE (MicroFlo CFD) 2026 (trial licence, internal evaluation)2026-10-24 | PASS | exploratory | cfd-DC00-20261024-r2/cfd/DC00O-C1/HX_DC00_MOC.logsha256 a6ed0cc09169… | OUTSTANDING — no engineer review or approval recorded |
| Mesh sensitivity, optimised design (two-grid and three-grid GCI)Mesh studyTwo-grid comparison (86,400 vs 196,560 cells) within the ASSUMED tolerances (|dT| <= 0.2 K, speed <= 10 %). Three-grid GCI (Celik et al. 2008): low and mid inlets monotonic with GCI <= 0.1 K; top inlets not monotonic (spread <= 0.08 K). The gate check is FAIL. The baseline was solved on one grid only. | Hexanta offline | Hexanta CFD engine (hexanta_api.cfd) branch feat/cfd-dc01-engine2026-10-24 | PARTIAL | exploratory | cfd-DC00-20261024-r2/study-manifest.study.mdsha256 3a1534d76fb3… | OUTSTANDING — no engineer review or approval recorded |
| Room energy balance (sampled at the extract plane)ValidationNOT ESTABLISHED: heat removed vs represented rack heat -7.5 % (optimised, base grid), -6.6 % (refined grid), -25.5 % (baseline, samples inside the impinging jet). Point samples 0.15 m below the extract face; the solver exports no field data. | Hexanta offline | Hexanta CFD engine (hexanta_api.cfd) branch feat/cfd-dc01-engine2026-10-24 | FAIL | exploratory | cfd-DC00-20261024-r2/study-manifest.study.mdsha256 3a1534d76fb3… | OUTSTANDING — no engineer review or approval recorded |
| CFD gate: ConvergenceValidation gateDC00B PASS; DC00O PASS. Residuals and monitors within criteria on both designs. | Hexanta offline | Hexanta CFD engine (hexanta_api.cfd) branch feat/cfd-dc01-engine2026-10-24 | PASS | exploratory | cfd-DC00-20261024-r2/study-manifest.study.mdsha256 3a1534d76fb3… | OUTSTANDING — no engineer review or approval recorded |
| CFD gate: Mass conservationValidation gateDC00B FAIL; DC00O FAIL. Flows are prescribed boundary settings, not a solver flow report: conservation not shown. | Hexanta offline | Hexanta CFD engine (hexanta_api.cfd) branch feat/cfd-dc01-engine2026-10-24 | FAIL | exploratory | cfd-DC00-20261024-r2/study-manifest.study.mdsha256 3a1534d76fb3… | OUTSTANDING — no engineer review or approval recorded |
| CFD gate: Energy balanceValidation gateDC00B FAIL; DC00O FAIL. Extract temperatures sampled, not solver-reported; gaps -25.5 % (DC00B) and -7.5 % (DC00O). | Hexanta offline | Hexanta CFD engine (hexanta_api.cfd) branch feat/cfd-dc01-engine2026-10-24 | FAIL | exploratory | cfd-DC00-20261024-r2/study-manifest.study.mdsha256 3a1534d76fb3… | OUTSTANDING — no engineer review or approval recorded |
| CFD gate: Boundary consistencyValidation gateDC00B FAIL; DC00O FAIL. Model boundary values not read back programmatically. | Hexanta offline | Hexanta CFD engine (hexanta_api.cfd) branch feat/cfd-dc01-engine2026-10-24 | FAIL | exploratory | cfd-DC00-20261024-r2/study-manifest.study.mdsha256 3a1534d76fb3… | OUTSTANDING — no engineer review or approval recorded |
| CFD gate: Rack inlets completeValidation gateDC00B PASS; DC00O PASS. All 4 racks monitored. | Hexanta offline | Hexanta CFD engine (hexanta_api.cfd) branch feat/cfd-dc01-engine2026-10-24 | PASS | exploratory | cfd-DC00-20261024-r2/study-manifest.study.mdsha256 3a1534d76fb3… | OUTSTANDING — no engineer review or approval recorded |
| CFD gate: Physical plausibilityValidation gateDC00B FAIL; DC00O FAIL. Field temperature range not available (no field export). | Hexanta offline | Hexanta CFD engine (hexanta_api.cfd) branch feat/cfd-dc01-engine2026-10-24 | FAIL | exploratory | cfd-DC00-20261024-r2/study-manifest.study.mdsha256 3a1534d76fb3… | OUTSTANDING — no engineer review or approval recorded |
| CFD gate: Grid qualityValidation gateDC00B PASS; DC00O PASS. Within limits (60 x 48 x 30, aspect 1:1). | Hexanta offline | Hexanta CFD engine (hexanta_api.cfd) branch feat/cfd-dc01-engine2026-10-24 | PASS | exploratory | cfd-DC00-20261024-r2/study-manifest.study.mdsha256 3a1534d76fb3… | OUTSTANDING — no engineer review or approval recorded |
| CFD gate: Mesh sensitivityValidation gateDC00B FAIL; DC00O FAIL. DC00B: no refined-grid comparison; DC00O: top inlets not monotonic over three grids. | Hexanta offline | Hexanta CFD engine (hexanta_api.cfd) branch feat/cfd-dc01-engine2026-10-24 | FAIL | exploratory | cfd-DC00-20261024-r2/study-manifest.study.mdsha256 3a1534d76fb3… | OUTSTANDING — no engineer review or approval recorded |
| Computed study statusValidation gateNOT ENGINEERING VALIDATED - computed from the gates (validation/gate.py + verdict.py); a manifest cannot claim more. Both designs fail 5 of 8 gate checks. | Hexanta offline | Hexanta CFD engine (hexanta_api.cfd) branch feat/cfd-dc01-engine2026-10-24 | FAIL | exploratory | cfd-DC00-20261024-r2/study-manifest.study.mdsha256 3a1534d76fb3… | OUTSTANDING — no engineer review or approval recorded |
| DC00B annual energy simulationAnnual energyBuild, Apache input (.der) and physics gates PASS. Cooling-system electricity 141,449 kWh/yr (chillers 97,867 + fans 43,582) with ASSUMED SEER 4.0 and SFP 1.5 W/(l/s); room held at 28 °C. | Native tool output | IESVE (ApacheSim) 2026 (trial licence, internal evaluation)2026-10-24 | PASS | exploratory | cfd-DC00-20261024-r2/dsm/DC00B/export-DC00B.jsonsha256 111c064c2e42… | OUTSTANDING — no engineer review or approval recorded |
| DC00O annual energy simulationAnnual energyBuild, .der and physics gates PASS. Cooling-system electricity 123,467 kWh/yr (chillers 94,270 + fans 29,197); fan power from the ASSUMED fan law n = 3. | Native tool output | IESVE (ApacheSim) 2026 (trial licence, internal evaluation)2026-10-24 | PASS | exploratory | cfd-DC00-20261024-r2/dsm/DC00O/export-DC00O.jsonsha256 ea9e18412b0c… | OUTSTANDING — no engineer review or approval recorded |
| DC00O vs DC00B modelled energy difference (independent recalculation)Annual energyRecalculation matches IESVE. Modelled difference 17,982 kWh/yr (12.7 % of cooling-system electricity), GBP 4,495/yr at an ASSUMED 0.25 GBP/kWh. SIMULATED WITH ASSUMED EQUIPMENT MODEL - not a validated saving; upper bound (fan law n = 2 gives 12,768 kWh/yr). Apache total difference (32,368 kWh/yr) excluded: it double-counts fans. | Hexanta offline | Hexanta CFD engine (hexanta_api.cfd) branch feat/cfd-dc01-engine2026-10-24 | PARTIAL | exploratory | cfd-DC00-20261024-r2/study-manifest.study.mdsha256 3a1534d76fb3… | OUTSTANDING — no engineer review or approval recorded |
| DC-01 annual simulation N1F (100 kW hall)Annual energyACCEPTED as the DC-01 dynamic-simulation baseline at software/automation level: build, .der and physics gates PASS; room 28.0 °C all year; cooling load 973,525 kWh; cooling-system electricity 352,337 kWh/yr (ASSUMED SEER 4.0, SFP 1.5). No CFD was run for DC-01. | Native tool output | IESVE (ApacheSim) 2026 (trial licence, internal evaluation)2026-10-24 | PASS | exploratory | cfd-DC01-N1-DSM-20261024/out/export-DC01N1F.jsonsha256 b19d2111554a… | OUTSTANDING — no engineer review or approval recorded |
| DC-01 annual simulation N1EAnnual energyREJECTED by the physics gate: the Apache system airflow was outdoor air, flushing the hall (mean 21.1 °C instead of 28 °C). | Native tool output | IESVE (ApacheSim) 2026 (trial licence, internal evaluation)2026-10-23 | FAIL | exploratory | cfd-DC01-N1-DSM-20261024/out/export-DC01N1E.jsonsha256 a39cc869a062… | OUTSTANDING — no engineer review or approval recorded |
| DC-01 annual simulation N1DAnnual energyREJECTED by the input and physics gates: the Apache input held no internal-gain records (mean 13.3 °C, zero cooling). | Native tool output | IESVE (ApacheSim) 2026 (trial licence, internal evaluation)2026-10-23 | FAIL | exploratory | cfd-DC01-N1-DSM-20261024/out/export-DC01N1D.jsonsha256 359613614c0f… | OUTSTANDING — no engineer review or approval recorded |
| DC00B-R5 baseline CFD (32 °C exhaust)CFD runNOT CONVERGED to the strict target (t 1.73e-5, e 1.65e-5 vs 1e-5) at 2,500 iterations; monitors steady. Source field of the baseline figures; numbers superseded by R6. | Native tool output | IESVE (MicroFlo CFD) 2026 (trial licence, internal evaluation)2026-10-24 | PARTIAL | superseded | cfd-DC00-20261024-r2/cfd/DC00B-R5/HX_DC00_M1.logsha256 413274e10830… | OUTSTANDING — no engineer review or approval recorded |
| DC00B-R4 baseline CFD (resumed)CFD runConverged, but the edited 32 °C exhaust was not applied (a resumed run keeps the old boundaries); superseded. | Native tool output | IESVE (MicroFlo CFD) 2026 (trial licence, internal evaluation)2026-10-24 | FAIL | superseded | cfd-DC00-20261024-r2/cfd/DC00B-R4/HX_DC00_M1.logsha256 4c6fda4725f9… | OUTSTANDING — no engineer review or approval recorded |
| DC00B-R3 baseline CFD (regenerated)CFD runNOT CONVERGED at 1,500 iterations; airflow orientation verified; represented rack heat -16 % at 30 °C exhaust, which led to the 32 °C exhaust iteration. | Native tool output | IESVE (MicroFlo CFD) 2026 (trial licence, internal evaluation)2026-10-24 | FAIL | superseded | cfd-DC00-20261024-r2/cfd/DC00B-R3/HX_DC00_M1.logsha256 eb1e153f6a32… | OUTSTANDING — no engineer review or approval recorded |
| DC00B-R2 baseline CFDCFD runNOT CONVERGED (iteration limit; resumed the aborted R1 field; 30 °C exhaust). Its early figures are not used. | Native tool output | IESVE (MicroFlo CFD) 2026 (trial licence, internal evaluation)2026-10-24 | FAIL | superseded | cfd-DC00-20261024-r2/cfd/DC00B-R2/HX_DC00_M1.logsha256 cae7587d6d5f… | OUTSTANDING — no engineer review or approval recorded |
| DC00B-R1 baseline CFDCFD runABORTED after about 270 iterations by an automation fault (the watcher locked the solver log). Led to the rule: never read solver files during a solve. | Native tool output | IESVE (MicroFlo CFD) 2026 (trial licence, internal evaluation)2026-10-24 | FAIL | exploratory | raw solver output store (not in the sealed evidence folder) | OUTSTANDING — no engineer review or approval recorded |
Evidence folders
| Folder | Date | Purpose | Status | Manifest SHA-256 |
|---|---|---|---|---|
| cfd-DC00-20261024-r2 | 2026-10-24 | Final DC-00 CFD and annual-energy evidence (solver outputs, exports, figures, study) | final; NOT ENGINEERING VALIDATED | 6e1715a8d12990e0… |
| cfd-DC00-20261024 | 2026-10-24 | First DC-00 evidence | SUPERSEDED by cfd-DC00-20261024-r2 | 6911696e9521f536… |
| cfd-DC01-N1-DSM-20261024 | 2026-10-24 | DC-01 annual dynamic simulation (N1 attempts and accepted N1F) | N1F accepted at software level; N1D and N1E rejected | 8a000b9d6b210592… |
| cfd-review-20261024 | 2026-10-24 | Independent review package (handover, review guide, checksum manifests) | review package | 64a0d0bea8d8a9a8… |
Engineering findings
- Both final CFD runs converged natively: DC00B-R6 after 2,599 iterations and DC00O-R1 after 653, all 7 residuals at 1e-5.
- All monitored rack inlets stayed within 18-27 °C in both designs: maximum 21.62 °C baseline, 21.49 °C optimised, 21.53 °C on the refined mesh.
- The defensible statement is "no degradation with 12.5 % less supply air", not "cooler inlets".
- The baseline flow field shows the floor jet short-circuiting to the ceiling extract above the cold aisle.
- Annual simulations: 141,449 kWh/yr (baseline) vs 123,467 kWh/yr (optimised) cooling-system electricity; modelled difference 17,982 kWh/yr (12.7 %), SIMULATED WITH ASSUMED EQUIPMENT MODEL, upper bound (n = 2 gives 12,768 kWh/yr).
- The independent energy audit matches IESVE and excludes Apache's whole-building difference (32,368 kWh/yr), which counts the fan saving twice.
- DC-01 (synthetic 20 x 12 x 4 m hall, 100 kW): annual simulation N1F accepted at software level, 352,337 kWh/yr cooling-system electricity; N1D and N1E rejected by the gates.
- The computed study status is NOT ENGINEERING VALIDATED.
Conclusions
- As an automation proof of concept the study succeeded: Hexanta drove the CFD set-up, solving, validation gates, annual energy and reporting end to end, and both final native CFD runs converged (DC00B-R6, DC00O-R1).
- With 12.5 % less supply air every monitored rack inlet stayed within 18-27 °C (maximum 21.62 °C baseline, 21.49 °C optimised): the defensible statement is no degradation, not cooler inlets.
- The study is NOT ENGINEERING VALIDATED: the mass, energy-balance, boundary, plausibility and mesh gates failed, and the 12.7 % (17,982 kWh/yr) cooling-energy difference is an upper bound SIMULATED WITH ASSUMED EQUIPMENT MODEL, not a validated saving.
Limitations
- Actual equipment performance curves are not modelled: SEER 4.0, SFP 1.5 W/(l/s) and fan law n = 3 are ASSUMED.
- Racks are 0 W blocks with face boundaries and an imposed exhaust temperature (heat output follows inlet temperature; uniform faces; no bypass or leakage).
- No complete CFD mass and energy balance: no solver flow report or field export; the energy balance is estimated from point samples only.
- Baseline mesh independence not assessed (single grid); optimised top inlets not monotonic over three grids.
- No independent solver benchmark or measured case.
- The annual model is a single zone held at 28 °C and responds to airflow only through fan power; annual cooling energy is not validated.
- Boundary values were read back from screenshots and table cells only, not programmatically.
- The 18-27 °C inlet range comes from a public summary; the licensed current edition is not held.
- The tariff (0.25 GBP/kWh) is an ASSUMED placeholder.
- IESVE 2026 trial licence for internal evaluation only (expired 2026-10-25); commercial use would need a commercial licence and the vendor's written terms.
What this case study does not claim
- Engineering validation, verification, review, approval or sign-off of any result.
- The 17,982 kWh/yr (12.7 %, GBP 4,495/yr) figure as an achieved or validated saving; it is an upper bound with an assumed equipment model and tariff.
- That the optimised design gives cooler rack inlets.
- That mass or energy balance, or full mesh independence, was demonstrated.
- Any CFD for DC-01, or any modelling of a real data centre, client or site: all data are synthetic.
- Compliance with any licensed design guideline or standard.
- A Hexanta CFD solver: the CFD was solved by IESVE MicroFlo; Hexanta prepared inputs, drove the software, parsed outputs and applied the gates.
- Production-scale or commercially licensed automation: the runs were serial GUI automation on one test machine under a trial licence.
- Apache's whole-building total difference (32,368 kWh/yr) as a saving.
Sanitised derivative of preserved evidence (cfd-DC00-20261024-r2, cfd-DC01-N1-DSM-20261024). Nothing was re-simulated. Screenshot crops are static images of the native viewer; plots and the report contain only values read from the evidence. · Pack cfd-data-centre-r2 (built 2026-10-25); every file is checked against its SHA-256 before it is shown.