Reconstruction of incomplete flow fields based on unsupervised learning

Abstract

The loss of flow field data is a common challenge in experimental techniques and data transmission processes. Traditional methods often rely on another complete or high-fidelity dataset to compensate for missing information regarding fluid characteristics. However, obtaining such complete data is not always feasible. In this study, we propose an unsupervised learning approach that efficiently, swiftly, and cost-effectively reconstructs the complete flow field by leveraging the inherent properties of the flow field itself, without the need for high-fidelity data integration. Our proposed methods primarily encompass three techniques: Fourier basis function interpolation, the Autoregressive Integrated Moving Average model (ARIMA), and AMF (ARIMA-Median Filter). The first two methods are founded on the temporal evolution characteristics of the flow field and reconstruct the missing fluid information by extrapolating from the available data. The AMF method, building upon the ARIMA reconstruction outcomes, employs a median filtering approach to eliminate noise and outliers introduced by the lack of spatial correlation. All three methods perform well, with the AMF method exhibiting superior performance, particularly in cases involving scatter missing data with higher absence rates. While ARIMA and AMF entail longer computational times, they offer stability and are less prone to overfitting during the reconstruction process, rendering them more suitable for reconstructing flow fields with varying degrees of missing data. The Fourier basis function interpolation method, with its shorter runtime, is better suited for swiftly reconstructing flow fields with lower rates of missing data. However, it is worth noting that improper parameter selection for this method can lead to overfitting. Additionally, the non-stationarity of the flow field has an impact on reconstruction accuracy, with regions exhibiting stronger non-stationarity resulting in more noticeable reconstruction errors. For the ARIMA method, which relies on temporal correlation for reconstruction, the missing structures have a relatively minor effect. However, in the case of flow fields with block missing data, the improvement in reconstruction accuracy when using median filtering compared to ARIMA is not substantial.