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Learn · Full-field reduced-order prediction

Reduced-order models that predict the whole field and show where they are wrong

A scalar surrogate says the pressure drop went down. It cannot say the separation moved or the peak stress migrated to the fillet, so every promising design waits for a full solve before anyone sees its field. The TensorLynx platform learns the whole field from designs you have already solved, and every prediction arrives with its error map, a baseline it had to beat, and a refusal when it cannot.

Scored on held-out designs, near-twins held out together Refused wherever a simpler baseline scores lower Declines outside its trained range and names the input

A stress field assembled mode by mode Schematic: a clamped plate with a cut-out. Its predicted field forms as the mean and three modes are added; the singular values below show which modes are kept, and the error map fades as each mode arrives. predicted field · whole plate x̄ mean + a₁φ₁ + a₂φ₂ + a₃φ₃ singular values σₖ energy ≥ 0.999 kept r = 3 rest → band error map schematic

The cost of the old way

One number hides where the design will fail

Design studies end in scalars: pressure loss, peak stress, mass. Scalars rank designs, but judgement lives in the field: where separation sits, which fillet carries the load, how evenly a manifold feeds its branches. Two designs can share a scalar and fail in different places.

So teams open fields only for the few designs they could afford to solve. Field predictors promise to close that gap, and industry is rightly cautious. In a 2026 NAFEMS × Teratec consultation, 47 % of respondents named trust and validation of results as a barrier Survey · source 1. In a 2026 survey of 350 engineering leaders, 92 % had deployed surrogate models, but only 8 % extensively Survey · source 2.

A field prediction that cannot show its own error is a picture, not evidence. The question is not “can a model draw a field?” but “where, and by how much, is this field wrong?”

Same scalar, different field Schematic: two plate designs report the same scalar result, but in design A the stress peaks at the cut-out and in design B it has moved to the clamped root. Design A peak at cut-out Design B peak moved to root ≠ scalar result scalar result = A ranking on the scalar alone treats these two designs as one. schematic
Two designs, one scalar, two different failure locations.Schematic

How TensorLynx does it

Snapshots in, a judged field out

The method is the one model reduction has refined for decades: proper orthogonal decomposition of solved snapshots, then a regression from design parameters to mode coefficients. TensorLynx wraps it in a workflow that scores and gates every field before it is offered.

01 · Snapshots

Every converged design becomes a column

Each converged evaluation contributes its whole field on a shared mesh, with run, study fingerprint, solver settings and units attached. Failed and unconverged evaluations stay in the corpus, labelled unusable with their reason, never used to train.

02 · Modes

A few modes carry the field

The snapshots are centred and decomposed. The rank is the smallest that keeps 99.9 % of the snapshot energy Method, capped at n − 1 and at 32 modes. The energy left out enters the model’s band.

03 · Coefficients

Design parameters map to mode weights

A Gaussian process maps design parameters to each mode’s coefficient. The kernel, Matérn 5/2, Matérn 3/2 or squared exponential, is chosen by the closed-form leave-one-out residual over the whole field, never left at a default.

04 · Field

The whole field, rebuilt for a new design

Predicted coefficients rebuild the full field: the mean plus weighted modes, every node, every quantity, one band per quantity. For flow fields the predicted velocity is projected so that it conserves mass.

05 · Score

Scored the way a sceptic would

Every fold refits basis, rank, kernel and hyperparameters. Near-duplicate designs are held out together, so an infill point cannot borrow accuracy from its twin. The score is judged against a field-error bar fixed before any measurement, and against simpler baselines on the same folds.

06 · Serve or decline

Served, refused, or declined, with the reason

If a baseline scores lower on any split, the model is refused for that field, its numbers kept as evidence. Outside its trained region it declines and names the coordinate responsible. What is served stays labelled a prediction until a solver confirms it.

From solved snapshots to a judged field prediction Schematic in six states: snapshots form a matrix; the decomposition yields singular values and modes; a regression maps design parameters to mode coefficients with a band; the field is rebuilt; the field is scored and served, refused or flagged; requests outside the trained region are declined with the input named. 1 · snapshots e01 e02 e03 e04 e05 e06 e07not converged: kept, labelledunusable, never used to train X = [ x₁ x₂ … xₙ ] one column per converged design, whole field 2 · modes 99.9 % energy σ₁ … σᵣ kept dropped energy → band φ₁ φ₂ φ₃ X − x̄ = U Σ Vᵀ 3 · coefficients aₖ(μ) design parameter μ ● solved design — regression mean ▒ band aₖ(μ) ~ GP(m, k) 4 · whole field x̂(μ) = x̄ + Σ aₖ(μ) φₖ flow fields: velocity projected to conserve mass every node, every quantity, one band per quantity 5 · scored on held-out designs per-node error map field APASS field BCAUTION field C · baseline lowerREFUSED PASS ≤ 0.05 CAUTION ≤ 0.25 · beyond: FAIL relative L2, physical units, area weighted bar fixed before measurement, never moved near-twin designs held out together 6 · serve or decline μ₁ μ₂ Predictioninside the trained region Declinednames μ₂ as the cause confirmed only by an independent solver re-run schematic

Move the design. Watch the whole field, and its error.

Five snapshots of an analytic plate field are decomposed in your browser and the mode coefficients interpolated between them. The hot spot travels with the design parameter, the hard case for a linear basis, and the error map shows where the reconstruction falls short. Drag beyond the trained range and the model declines.

Synthetic field reconstruction with its error map Synthetic demonstration: on the left, the field rebuilt from the kept modes for the chosen design parameter; on the right, the absolute error against the exact analytic field; below, both along the centreline. The readouts under the figure give the numbers. predicted field error against the exact field low → high 0 → 0.25+ centreline exactreconstruction clamped root free end

Dots: the five solved snapshots, t = 0.10 to 0.90 (the trained range).

Modes kept
Snapshot energy kept
100.0 %
Relative L2 error, exact field
0.150
Status
Prediction (between snapshots)
Analytic field, five snapshots, computed in your browser. It illustrates the method; it is not a measured result.Synthetic demonstration

Inside the engine

Three errors, one honest score

Grouped leave-out: near-twin designs are held out together Schematic design space with sixteen evaluated designs in normalised coordinates. Designs closer than the distance delta are linked; linked chains form groups, and each group is held out as one fold, so a design is never scored while its near-twin stays in training. u₁ u₂ held out together evaluated design link: ‖uᵢ − uⱼ‖ < δ group = one fold radius δ δ = ½ · s(n, d) s: mean nearest-neighbour spacing of n random points in the unit d-cube every fold refits basis, rank, kernel and hyperparameters schematic
Hover or focus a design to see its fold. A plain leave-one-out would score evaluation 07 while its twin 08 stays in training.Schematic

Designs placed by an optimiser cluster, so a plain leave-one-out scores a design with its near-twin still in training and reads optimistic. TensorLynx makes the grouped leave-out the headline: designs closer than half the expected nearest-neighbour spacing are linked, chains form groups, and each group is held out as one fold. The plain leave-one-out sits beside it with its own verdict.

The grouping rule and the bars were fixed before any score was computed.

X = [x1 − x̄, …, xn − x̄] = U Σ VT

r = min { k : Σi≤k σi2 / Σi σi2 ≥ 0.999 }, r ≤ min(n − 1, 32)

x̂(μ) = x̄ + Σk≤r ak(μ) φk, ak ~ GP

Every score is weighted by nodal volume or cell area, so boundary-layer clustering does not dominate the error. The band combines each mode’s variance with that of the truncated modes: a model band reported with its measured coverage, not a calibrated interval. Hyperparameters come from maximum marginal likelihood with seeded restarts, the seed recorded. Method

A model that reports one error number cannot be debugged. TensorLynx splits it into three parts, because each has a different fix.

  • Truncation what the reduction threw away. Fixed by a higher rank.
  • Pre-image how well the inverse rebuilds a snapshot it was trained on: a floor. Fixed by a different inverse or a linear reduction. For nonlinear reductions it is reported, never hidden.
  • Coefficient leave-one-out per mode over the design parameters. Fixed by a different regressor or more cases.

One reduce-then-regress model with a menu: POD or PCA, kernel PCA and Isomap with an explicit pre-image, paired with radial-basis, Gaussian-process, ridge, polynomial or nearest-case regressors. Beside it sit POD on a canonical domain, Grassmann-manifold interpolation of the basis, operator networks and conditioned neural fields, always next to per-node and do-nothing baselines.

Methods say when they are the wrong choice. On a nine-case test where the modes barely rotated, the Grassmann route reported “probably not worth it here”, and the global basis scored lower. Measured · 9-case test corpus

  • Minimum evidence. At least max(15, 10·d) usable cases for d design variables before a field claim. Method
  • Field-error bar. Relative L2 in physical units: PASS ≤ 0.05, CAUTION ≤ 0.25, beyond that FAIL. Read, never moved. Method
  • Beaten means refused. If any baseline is lower on any split, plain or grouped, the field model is refused for that field, its numbers kept as evidence.
  • Missing is never zero. A snapshot covering less than 90 % of the support is refused with its count; unscored cases read Missing with the reason. Method
  • Bands say what they are. Field bands carry the label “band uncalibrated: coverage shown, not calibrated, not a claim”.

Evidence you can check

Two campaigns on record, scored on designs the models never saw

Campaign-specific measurements on held-out designs, in physical units: not a general accuracy figure, and reported that way.

Measured field error on two campaigns Bar chart of mean relative L2 field error, lower is better, drawn to scale. Pipe-bend flow fields: per-node ridge baseline 0.0147 and POD with interpolation 0.0238 on a mesh both had seen; on unseen meshes the conditioned neural field 0.0358, while mesh-tied models declined. Plate stress field: POD with Gaussian-process coefficients 0.036 leave-one-out and 0.038 grouped leave-out, best baseline 0.123 grouped; the pass bar is 0.05. 0 0.05 0.10 Pipe-bend flow fields ridge baseline · seen mesh 0.0147 POD + interp. · seen mesh 0.0238 neural field · unseen meshes 0.0358 mesh-tied · unseen meshes declined, mismatch named Plate campaign · von Mises stress field PASS bar ≤ 0.05 POD + GP · leave-one-out 0.036 POD + GP · grouped 0.038 · PASS best baseline · grouped 0.123
Mean relative L2 field error, lower is better, drawn to scale.Measured · values below

Pipe-bend flow fields

Steady turbulent flow through 90° circular bends: pressure, velocity and turbulence fields. With three cases held out on a mesh every model had seen, a per-node ridge baseline scored 0.0147 and POD with interpolation 0.0238; the baseline won, and the record says so. On six cases spanning three mesh topologies none had seen, every mesh-tied model declined, naming the mismatch (75,396 training nodes, 46,168 asked), and the mesh-free conditioned neural field answered at 0.0358.

Measured · bend corpus, 13 + 6 cases

Plate campaign, stress field

From 42 solved plate designs, the POD-plus-Gaussian-process field model predicted the von Mises stress field at 0.036 leave-one-out and 0.038 grouped leave-out: PASS against the 0.05 bar, where the best baseline on the same grouped folds scored 0.123. Displacement fields went through the same rules; where a simpler baseline scored lower, the model was refused for that field.

Measured · 42 snapshots, one campaign

A gate that held

In an airfoil study with 9 design variables and 24 usable evaluations, the field model was refused: the rule asks for at least 90. The refusal carries a reason and a fix, and no number.

Measured · refusal on record

What it changes for your programme

See where, not just how much, for every design in the study

Engineering lead

A verdict per field you can accept or reject in review, and a field for every design, not just the few you could afford to open.

Analyst

Field models from the runs you already have, with error maps, baselines and refusal reasons ready to show.

Programme manager

Fewer late surprises from a peak that moved; full solves spent where they matter.

Where engineering teams apply it

Ducts, bends, intakes

Where loss and separation sit as the shape changes.

Brackets and plates

Where the load path concentrates across sizing parameters.

Manifolds, process equipment

Flow distribution across branches, not one averaged outlet value.

Aero surfaces

Pressure distributions across shape parameters, beside the study they came from.

Typical field workflow compared with the TensorLynx workflow
QuestionTypical workflowWith TensorLynx
What you see per designA scalar; fields only for solved designsThe whole field, with a per-node error map
How accuracy is judgedTraining fit or a few spot checksGrouped leave-out, refit per fold, bar fixed in advance
When the model is weakA field is drawn anywayRefused per field, numbers and reason kept
Outside the dataSilent extrapolationDeclined, with the input that caused it named
The design you take forwardRead off the predictionThe best evaluated design, confirmed by an independent re-run

Where it sits in the loop. Field models extend the trust-aware scalar surrogates to whole fields, under the same rule: a weak model stays silent. They are fitted as an analysis of a multidisciplinary optimisation run’s own kept fields: the run itself is never changed, and every value is labelled a prediction, never a solver result. Next, multi-fidelity optimisation decides where expensive solves go, and designs you take forward pass through high-fidelity reassessment. The whole loop is on the TensorLynx overview.

FAQ

Questions engineers ask first

How many solved designs does a field model need?

At least max(15, 10·d) usable, converged cases for d design variables before any field claim: 30 for a three-parameter study. Below that the model is refused, with the count and the reason.

Which fields can it predict?

Fields written on a shared mesh support. On record are pressure, velocity and turbulence fields of a pipe-bend family and the von Mises stress field of a plate campaign. Each field is judged on its own: one can pass while another is refused.

Can it predict on a new geometry or a different mesh?

Mesh-tied models such as POD decline a mesh they were not trained on and name the mismatch. The mesh-free conditioned neural field is the route to new topologies: on the bend corpus it answered on three it had never seen. A shape outside the trained family calls for new solves.

How do I know a predicted field is good enough to use?

Read the grouped leave-out score against the field-error bar, the best baseline on the same folds, and the per-node error map. Bands carry their measured coverage and the label uncalibrated. Any design you take forward is confirmed by an independent solver re-run.

Does a reduced-order model replace the solver or physical testing?

No. It explores between solved designs and shows where to look. Recommendations rest on solver-evaluated designs; required tests and sign-off stay where they are.

How does OLTRION help us get started?

OLTRION engineers plan the snapshot campaign with you, set up the field model, review error maps and refusals with your team, and hand over a documented workflow.

One loop, not twelve tools

Where full-field rom sits in the TensorLynx loop

Every capability hands its result to the next on the same model, the same units and the same record: geometry feeds physics, physics feeds sensitivities and learning, optimisation proposes, verification confirms, and the history keeps every step reproducible.

The TensorLynx loop: Design exploration, Coupled multiphysics, Mesh verification, Adjoint optimisation, Gradient verification, Trust-aware surrogates, Full-field ROM, Multi-fidelity, MDAO, Pareto selection, High-fidelity reassessment, Provenance. TensorLynx one model · one record DefineSimulateImproveLearnOptimiseDecideVerifyRecord Design exploration Coupled multiphysics Mesh verification Adjoint optimisation Gradient verification Trust-aware surrogates Full-field ROM Multi-fidelity MDAO Pareto selection High-fidelity reassessment Provenance
Schematic of the platform workflowSchematic
Work with OLTRION

Bring us the design question. Leave with a verified answer and the record behind it.

TensorLynx is built and run by the engineers who use it on client work. You can start small, with one geometry and one question, and grow into a workflow your own team owns.

Feasibility review

Send a geometry, the objective and the constraints. We tell you which TensorLynx route answers it, what it needs from you, and what you will get back.

We run the study

Our engineers run the loop on your problem: physics, sensitivities, optimisation and full-model verification, handed over with every setting on record.

A workflow built for your product

A TensorLynx workflow, surrogate and verification gates set up around your product family, so the next design cycle starts where the last one ended.

Platform access and handover

Your team on TensorLynx, trained on your own cases, with OLTRION engineers behind it for the questions that need a specialist.