Computational Fluid Dynamics (CFD) generates high-dimensional spatiotemporal data. The data-driven method approach to extracting physical information from CFD has attracted widespread concern in fluid mechanics. While good results have been obtained for some benchmark problems, the performance on complex flow field problems not extensively studied. In this paper, we use a dimensionality reduction preserve main features of field. Based this, perform unsupervised identification states using...

In the field of fluid mechanics, dimensionality reduction (DR) is widely used for feature extraction and information simplification high-dimensional spatiotemporal data. It well known that nonlinear DR techniques outperform linear methods, this conclusion may have reached a consensus in mechanics. However, derived from an incomplete evaluation techniques. paper, we propose more comprehensive system methods compare evaluate performance differences three methods: principal component analysis...

Water entry is a complex nonlinear behavior that involves the multiphase flow coupling, which exists extensively in various engineering fields. In present work, shear stress transport k − ω turbulence model imported to close governing equations. The air–water interface and six degree-of-freedom motion of cylinder are defined using volume fluid method overlapping grid technology, respectively. A three-dimensional numerical simulate vertical water under wind current velocities carried out....

The presence of structures in the ocean complicates navigation an underwater axisymmetric body. This effect involves special environmental fluid dynamics, such as unsteadiness, strong nonlinearity, cavity multiphase flow, turbulence, and so forth. In this paper, improved delayed detached eddy simulation method is used to investigate ventilated flow body ocean, with intent exploring differences characteristics absence a structure. structure advances deflation tail, shortening length main by...

Supersonic gas jets in conical convergent–divergent nozzles are studied numerically using the OpenFOAM rhoCentralFoam solver. The spatiotemporal evolution of jet flow field is analyzed. influence operating conditions on parametrically, including nozzle pressure ratio (NPR), area ratio, and throat position. behaviors mechanisms double-diamond structure, wave, exit wave interpreted detail. results show that a always generates shock waves. reaches its maximum length during initial stage, then...

The free surface condition of water-entry problems will be significantly modified by the presence an ice sheet on water surface. In this paper, we employ computational fluid dynamics to simulate process a cylinder entering body vertically and validate numerical method comparing cavity evolution with experimental data. Four high-speed cases are considered: ice-free surface, circular holes, minor normal sized petal-shaped holes. evolution, flow field characteristics, motion parameters...

A ventilated vehicle exiting water in a wave environment is complex nonlinear process, and the mechanism by which conditions influence this process remains poorly understood. This paper describes realistic simulations of body under various conditions. Comprehensive analysis conducted for range distinct scenarios, machine learning-based method developed rapid forecasting vehicle-related parameters. three-layer backpropagation neural network constructed, its prediction performance verified....

This paper introduces temporal information shared multi-variable dynamic mode decomposition (TIMDMD), a novel data-driven algorithm for modal decomposition. TIMDMD leverages joint singular value to share across variables, resulting in rather than single-variable optimization. The effectively addresses several common issues with traditional DMD approaches, such as inconsistent physical interpretations, lack of phase consistency between and the mixing frequency components reconstructed flow...

Due to the influence of initial conditions such as tethered velocity, vertically launched underwater vehicles generate large vortex structures in wake after leaving launch platform. This leads an asymmetric surface pressure distribution on second passing through wake, adversely affecting their attitude. The rolling platform is another critical component above conditions. study used Realizable k−ε model, volume-of-fluid multiphase flow and overlapping grid technology numerically simulate...

The motion of a pitching airfoil at low Reynolds number and high angle attack involves nonlinear dynamics unstable characteristics, making it fascinating area for research. In this study, the precise modeling complex fluid flow phenomenon is addressed. By combining manifold learning time delay embedding theory, stable low-dimensional manifolds are successfully extracted from high-dimensional spatiotemporal data system, simplifying representation intricate physical behaviors in space....

The hollow cylinder is a special cylindrical body with through structure in the middle position. A collaborative method based on finite volume and element used to numerically calculate high-speed vertical water entry of cylinder. results show that exhibits unique internal jet phenomenon, height shows an almost linear growth trend. Compared completely sealed cylinder, displacement velocity after entering into are greater, but generated cavities smaller. force stress at bottom smaller than...

When utilizing high-speed gas jet for the propulsion of underwater vehicles, complex flow phenomena such as ventilated cavitation, bubble expansion, and contraction are formed, along with corresponding thrust characteristics. In this paper, an experimental study was conducted on field evolution characteristics vector-deflected jets produced by a Laval nozzle under co-flow conditions. Under conditions study, venting position pulsating foam tail cavity shifts increase in vector angle θ. The...