Unsteady flow-field forecasting leveraging a hybrid deep-learning architecture

With the rapid development of data-driven technology, deep learning has been widely used to study unsteady flow phenomena, owing to its high-dimensional, nonlinear, and excellent big-data processing capabilities. Rapidly and accurately predicting unsteady flow fields has been a major challenge in fluid mechanics. Therefore, we designed a new U-shaped hybrid deep neural network (UDNN) framework using a multilayer convolution. Through the multilayer learning interaction of high-dimensional flow-field data, the temporal and spatial characteristics of the flow-field flow are captured, and the flow-field characteristics are predicted in an end-to-end form. The UDNN comprises a convolutional neural layer, deconvolutional layer, convolutional long-term and short-term layers, and attention-mechanism layer. First, based on computational fluid dynamics, we generated unsteady flow-field datasets of the flow around fixed and rotating cylinders at different Reynolds numbers, which were used as training samples for the network framework. Second, we designed a U-shaped convolutional layer, added horizontal time-series feature processing and attention-mechanism units, and fused the deep feature information predicted by the model with shallow semantic information to predict the flow-field features. In addition, we compared the UDNN, proper orthogonal decomposition – long short-term memory, and traditional convolutional autoencoder – long short-term memory models in terms of the flow-field prediction error, model training time, and inference speed. The final results showed that the proposed UDNN framework achieved high accuracy and strong robustness in predicting unsteady flow fields.