6 research outputs found
A new smoothed particle hydrodynamics method based on high-order moving-least-square targeted essentially non-oscillatory scheme for compressible flows
In this study, we establish a hybrid high-order smoothed particle
hydrodynamics (SPH) framework (MLS-TENO-SPH) for compressible flows with
discontinuities, which is able to achieve genuine high-order convergence in
smooth regions and also capture discontinuities well in non-smooth regions. The
framework can be either fully Lagrangian, Eulerian or realizing
arbitary-Lagrangian-Eulerian (ALE) feature enforcing the isotropic particle
distribution in specific cases. In the proposed framework, the computational
domain is divided into smooth regions and non-smooth regions, and these two
regions are determined by a strong scale separation strategy in the targeted
essentially non-oscillatory (TENO) scheme. In smooth regions, the
moving-least-square (MLS) approximation is used for evaluating high-order
derivative operator, which is able to realize genuine high-order construction;
in non-smooth regions, the new TENO scheme based on Vila's framework with
several new improvements will be deployed to capture discontinuities and
high-wavenumber flow scales with low numerical dissipation. The present
MLS-TENO-SPH method is validated with a set of challenging cases based on the
Eulerian, Lagrangian or ALE framework. Numerical results demonstrate that the
MLS-TENO-SPH method features lower numerical dissipation and higher efficiency
than the conventional method, and can restore genuine high-order accuracy in
smooth regions. Overall, the proposed framework serves as a new exploration in
high-order SPH methods, which are potential for compressible flow simulations
with shockwaves.Comment: 36 pages, 15 figures, accepted by Journal of Computational Physics on
June 1st, 202
Multi-level adaptive particle refinement method with large refinement scale ratio and new free-surface detection algorithm for complex fluid-structure interaction problems
Fluid-Structure Interaction (FSI) is a crucial problem in ocean engineering.
The smoothed particle hydrodynamics (SPH) method has been employed recently for
FSI problems in light of its Lagrangian nature and its advantage in handling
multi-physics problems. The efficiency of SPH can be greatly improved with the
Adaptive Particle Refinement (APR) method, which refines particles in the
regions of interest while deploying coarse particles in the left areas. In this
study, the APR method is further improved by developing several new algorithms.
Firstly, a new particle refinement strategy with the refinement scale ratio of
4 is employed for multi-level resolutions, and this dramatically decreases the
computational costs compared to the standard APR method. Secondly, the
regularized transition sub-zone is deployed to render an isotropic particle
distribution, which makes the solutions between the refinement zone and the
non-refinement zone smoother and consequently results in a more accurate
prediction. Thirdly, for complex FSI problems with free surface, a new
free-surface detection method based on the Voronoi diagram is proposed, and the
performance is validated in comparison to the conventional method. The improved
APR method is then applied to a set of challenging FSI cases. Numerical
simulations demonstrate that the results from the refinement with scale ratio 4
are consistent with other studies and experimental data, and also agree well
with those employing the refinement scale ratio 2. A significant reduction in
the computational time is observed for all the considered cases. Overall, the
improved APR method with a large refinement scale ratio and the new
free-surface detection strategy shows great potential in simulating complex FSI
problems efficiently and accurately.Comment: 47 pages, 26 figures, accepted to be published by Journal of
Computational Physic
Self adaptive global-local feature enhancement for radiology report generation
Automated radiology report generation aims at automatically generating a
detailed description of medical images, which can greatly alleviate the
workload of radiologists and provide better medical services to remote areas.
Most existing works pay attention to the holistic impression of medical images,
failing to utilize important anatomy information. However, in actual clinical
practice, radiologists usually locate important anatomical structures, and then
look for signs of abnormalities in certain structures and reason the underlying
disease. In this paper, we propose a novel framework AGFNet to dynamically fuse
the global and anatomy region feature to generate multi-grained radiology
report. Firstly, we extract important anatomy region features and global
features of input Chest X-ray (CXR). Then, with the region features and the
global features as input, our proposed self-adaptive fusion gate module could
dynamically fuse multi-granularity information. Finally, the captioning
generator generates the radiology reports through multi-granularity features.
Experiment results illustrate that our model achieved the state-of-the-art
performance on two benchmark datasets including the IU X-Ray and MIMIC-CXR.
Further analyses also prove that our model is able to leverage the
multi-grained information from radiology images and texts so as to help
generate more accurate reports