REVIEW 4 major objections 5 minor 38 references
DeepVIVONet: Using deep neural operators to optimize sensor locations with application to vortex-induced vibrations
T0 review · 4 major / 5 minor · reviewed 2026-08-10 · deepseek-v4-flash
Pith's one-line read DeepVIVONet reconstructs and forecasts the full cross-flow and in-line strain fields of a VIV-excited marine riser from only three observer sensors, and learns the sensor locations that minimize prediction error.
desk verdict A reasonable DeepONet application to VIV reconstruction and sensor placement, but the headline claim about beating POD rests on a single 0.3% MSE gap with no error bars. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The load-bearing object is the DeepONet decomposition $G_\theta(u)(z^*) = \sum_{k=1}^P B_k(u) T_k(z^*) + B_0$, where the branch net $B_k$ consumes the $m$ observer strain values at a time step (or a look-back stack for forecasting) and the trunk net $T_k$ consumes the query location $(t_j, z^*)$. For sensor placement, observer locations are turned into learnable Gaussian distributions $(\mu_i, \sigma_i)$; at each training step $r$ realizations are sampled from each distribution, and the location parameters are optimized alternately with the network weights so the $\sigma_i$ shrink toward the informative positions. The POD baseline supplies three manually selected three-sensor combinations from the first three spatial modes, which the paper both matches and compares against.
What would settle it
Train DeepVIVONet on the test2430 shear case with m=2 observers instead of m=3, keep the same optimization procedure, and measure prediction-window MSE; if the error rises by more than an order of magnitude relative to the reported 1.290e-06, the 'three sensors suffice' claim is specific to that sensor count rather than a general low-dimensional property. A second check is to train on test2430 and test on test2500 (1.50 m/s vs 2.20 m/s) without transfer learning; the transfer claim predicts graceful degradation, while a collapse would bound the generalization to near-neighbor velocities.
Extended reading notes
Core claim
On the paper's terms, the central discovery is that a DeepONet-style operator can learn a map from the m=3 observer strain histories to the entire strain field ε(z,t), and that this map is accurate enough that the prediction window (data never used in training) is matched to the level shown in the time-domain and FFT comparisons. The supporting quantitative comparison is Table 2, where the learned observer locations (4, 67, 92) give prediction-window MSE 1.290e-06, versus 3.745e-05 for the initial guesses and 9.838e-06, 1.294e-06, and 5.410e-06 for three POD-based choices. The learned locations are not uniformly better than every POD choice, but the paper argues POD selection is sensitive to manual choices while the learned locations are produced automatically. The paper also claims transfer learning: a network trained on shear-flow case test2430 (U=1.50 m/s) predicts the neighboring case test2420 (U=1.40 m/s) without retraining.
Load-bearing premise
The load-bearing premise is that three point strain measurements determine the entire riser strain field at that instant, meaning the VIV response is low-dimensional enough for a learned map from three observer values to all spatial locations to generalize across time windows and nearby flow speeds.
Editorial extensions
If this is right
- A three-sensor strain array on a riser can replace denser instrumentation for reconstruction and short-horizon forecasting of both cross-flow and in-line strain.
- Sensor placement can be included in neural-operator training, making the placement problem differentiable rather than a separate heuristic.
- A model trained at one maximum flow speed transfers to a neighboring speed without full retraining, reducing calibration cost when operating conditions drift.
- The trained network acts as a fast surrogate, so monitoring can run in near-real time instead of relying on CFD or dense instrumentation.
- POD-based placement remains a useful initialization but its manual mode-selection step causes large variation in error; the learned locations automate that selection.
Reading between the lines
- Editorial inference: the same differentiable-location optimization could be applied to other sparse-sensing problems, such as temperature or pressure field reconstruction in structures, provided the underlying field is comparably low-dimensional.
- Editorial inference: because the POD analysis in Section 4.2 shows 96.91% of variance in three modes for one shear case, the method's success likely tracks that low-dimensionality; a natural test is to run the same pipeline on a multi-frequency VIV case with richer modal content and check whether three observers still suffice.
- Editorial inference: the paper's comparison does not include robustness of the learned locations to sensor failure; a testable extension is to retrain with one observer randomly dropped at test time and measure error degradation.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript proposes DeepVIVONet, a DeepONet-based surrogate that maps time histories from m=3 observer strain sensors on a marine riser to the full CF/IL strain field, and uses the trained network in an outer-loop optimization to learn sensor locations. Experiments use NDP VIV field data for three shear-flow cases (U=0.50, 1.50, and 2.20 m/s) for reconstruction and forecasting, one transfer-learning case (U=1.5 to U=1.4 m/s), and a sensor-placement comparison against three manually selected POD-based location sets. The paper claims that DeepVIVONet provides accurate reconstruction and forecasting and that its learned sensor locations are more precise and cost-effective than POD-based placements.
Significance. If the claims held, the paper would offer a practical sparse-sensing framework for riser monitoring and a data-driven alternative to POD-based sensor placement. The use of real experimental NDP data, the direct comparison to POD, and the clear description of the DeepONet input/output structure are strengths. However, the central quantitative evidence is thin: the reconstruction/forecasting and transfer-learning claims are supported mainly by qualitative plots, and the sensor-placement superiority claim rests on a 0.3% MSE difference with no statistical characterization. The contribution is primarily empirical, and the conclusions need stronger quantitative support before they can be relied upon.
major comments (4)
- [Section 4.4, Table 2] The claim that DeepVIVONet's learned observer locations are "more precise and cost-effective" than POD-based placement rests on a single MSE pair: learned locations (4,67,92) give 1.290e-06, while the best POD placement (29,43,81) gives 1.294e-06, a difference of about 0.3%. No seeds, error bars, or statistical comparison are reported, and the POD placements are chosen manually from Figure 12 rather than by an automated criterion. The observed gap is smaller than the run-to-run variation expected after 500,000 stochastic training iterations, so the practical superiority claim is not established by the evidence presented.
- [Section 3.1, Figures 5-8] The reconstruction and forecasting results for the CF cases and the IL case are reported only as qualitative time-series and FFT plots; no quantitative error metric (MSE, relative L2, or similar) is given for the test window, and no confidence intervals are provided. This makes it impossible to assess the abstract's claims of "accurately reconstructing" and "accurate predictions" across the tested velocity regimes. The only quantitative numbers in the paper appear in Table 2 for the sensor-placement study.
- [Section 3.2] The transfer-learning demonstration uses a single near-neighbor case (U=1.5 m/s to U=1.4 m/s) and reports no quantitative metric or comparison with a model trained directly on the target case, so the abstract's claim of generalization to other flow conditions via transfer learning is not supported. At minimum, the authors should report the prediction-window error for the transferred model and compare it with a model trained directly on the target case.
- [Section 4.1] The sensor-placement optimization is performed on a "reconstructed dataset" discretized at 500 equidistant points, but the construction of this dense field is never described. If it relies on interpolation or on the same surrogate family as DeepVIVONet, the MSE values in Table 2 may not reflect performance on the original 23-sensor field data. The construction should be specified, and the final evaluation should be reported on the original sensor locations as well.
minor comments (5)
- [Section 4.2] The definition of the matrix E is inconsistent: the text says "with 100 spatial elements, and 100 time samples," but the displayed matrix has 250 rows and the preceding sentence mentions 250 time samples. Please clarify the number of time samples used in the POD analysis.
- [Section 4.4] The sentence "The observer locations optimized by DeepVIVONet consistently delivered superior results" is misleading given that POD placement (29,43,81) achieves an MSE of 1.294e-06, nearly identical to the learned placement's 1.290e-06; a more precise wording would acknowledge that the two are statistically indistinguishable on the reported evidence.
- [Section 4.1] The text says "we use our DeepVIVONet model as a surrogate" and describes sampling r realizations from the location distributions, but the number r and the method for obtaining strain values at non-instrumented sampled locations are not specified. Please state r and explain how the strain at those sampled points is obtained from the discrete sensor data.
- [Section 3.1] The choice m=3 is not justified beyond the POD variance argument; no experiments with other sensor counts are shown, so it is unclear how sensitive the method is to the number of observers. A brief sensitivity study or at least a discussion of the choice would strengthen the paper.
- [Throughout] There are several typographical and grammatical errors, e.g., "explaind" in Section 4, "the the motion" in the Introduction, and "We find that that" in the Abstract. A careful proofreading pass is needed.
Circularity Check
No significant circularity: held-out prediction windows and an independently computed POD baseline make the main reconstruction, forecasting, and sensor-placement comparisons genuine generalization tests.
full rationale
The derivation chain is not circular. The reconstruction and forecasting results (Section 3) are evaluated on temporally held-out prediction windows defined in Table 1 and shown in Figures 5-8, so the trained network is not being tested on its own training labels. The transfer-learning experiment (Section 3.2) predicts a different flow case (test2420) from a network trained on test2430, which is an external generalization check. The sensor-location optimization (Sections 4.1-4.3) fits the observer locations and network parameters on the training setup, and then Table 2 reports MSE in the prediction window; although the optimization objective and the evaluation metric are both MSE, the evaluation window is temporally distinct, so the comparison is a genuine generalization test rather than a fitted parameter renamed as a prediction. The POD baseline is implemented independently in Section 4.2, with modes computed from the data and the first three modes accounting for 96.91% of the variance; the cited reference [38] is used only as methodological motivation, not as a load-bearing uniqueness claim. Self-citations to DeepONet [31] reference a published architecture whose representation guarantee rests on an external theorem [33]; they are not used to forbid alternatives. The main caveats—unspecified origin of the 'reconstructed dataset' at 500 points in Section 4.1, lack of error bars around Table 2, and the small gap to the best POD placement—are correctness or statistical concerns, not circularity. No step in the claimed derivation is equivalent to its inputs by construction.
Assumptions & free parameters
free parameters (5)
- Observer sensor location means μ_i (m=3) =
4, 67, 92 (discretized spatial indices in test2430)
- Observer location standard deviations σ_i =
Not reported numerically; described as converging to minimal values
- DeepONet architecture (layers/neurons) =
6 hidden layers, 50 neurons for branch and trunk nets
- Data normalization factor =
0.2 * max(ε(z,t))
- Forecasting look-back window lb =
Not reported
assumptions (5)
- standard math Neural networks and DeepONet can approximate the operator mapping observer signals to full-field strain.
- domain assumption VIV strain dynamics follow the linear beam-string equation (2.2).
- domain assumption Three instantaneous point measurements determine the full spatiotemporal strain field (low-rank or spatial-coherence assumption).
- domain assumption Frozen network parameters trained at U=1.5 m/s transfer to U=1.4 m/s without adaptation.
- domain assumption Pinned boundary conditions; two imaginary zero sensors at riser ends.
Cite this review
Pith. "Pith review of DeepVIVONet: Using deep neural operators to optimize sensor locations with application to vortex-induced vibrations." pith.science (2026). https://pith.science/paper/V6WACEMO
@misc{pith2026250104105,
author = {Pith},
title = {Pith review of: DeepVIVONet: Using deep neural operators to optimize sensor locations with application to vortex-induced vibrations},
year = {2026},
howpublished = {\url{https://pith.science/paper/V6WACEMO}},
note = {Machine review of arXiv:2501.04105}
}
read the original abstract
We introduce DeepVIVONet, a new framework for optimal dynamic reconstruction and forecasting of the vortex-induced vibrations (VIV) of a marine riser, using field data. We demonstrate the effectiveness of DeepVIVONet in accurately reconstructing the motion of an off--shore marine riser by using sparse spatio-temporal measurements. We also show the generalization of our model in extrapolating to other flow conditions via transfer learning, underscoring its potential to streamline operational efficiency and enhance predictive accuracy. The trained DeepVIVONet serves as a fast and accurate surrogate model for the marine riser, which we use in an outer--loop optimization algorithm to obtain the optimal locations for placing the sensors. Furthermore, we employ an existing sensor placement method based on proper orthogonal decomposition (POD) to compare with our data-driven approach. We find that that while POD offers a good approach for initial sensor placement, DeepVIVONet's adaptive capabilities yield more precise and cost-effective configurations.
Figures
Figures from the paper (12 more)
Reference graph
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Reviewed August 10, 2026 · model on record in the stance chip above.
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