Finite Volume Graph Network(FVGN): Predicting unsteady incompressible fluid dynamics with finite volume informed neural network

In recent years, the development of deep learning is noticeably influencing the progress of computational fluid dynamics. Numerous researchers have undertaken flow field predictions on a variety of grids, such as MAC grids, structured grids, unstructured meshes, and pixel-based grids which have been many works focused on. However, predicting unsteady flow fields on unstructured meshes remains challenging. When employing graph neural networks (GNNs) for these predictions, the message-passing mechanism can become inefficient, especially with denser unstructured meshes. Furthermore, unsteady flow field predictions often rely on autoregressive neural networks, which are susceptible to error accumulation during extended predictions. In this study, we integrate the traditional finite volume method to devise a spatial integration strategy that enables the formulation of a physically constrained loss function. This aims to counter the error accumulation that emerged in autoregressive neural networks during long-term predictions. Concurrently, we merge vertex-center and cell-center grids from the finite volume method, introducing a dual message-passing mechanism within a single GNN layer to enhance the message-passing efficiency. We benchmark our approach against MeshGraphnets for unsteady flow field predictions on unstructured meshes. Our findings indicate that the methodologies combined in this study significantly enhance the precision of flow field predictions while substantially minimizing the training time cost. We offer a comparative analysis of flow field predictions, focusing on cylindrical, airfoil, and square column obstacles in two-dimensional incompressible fluid dynamics scenarios. This analysis encompasses lift coefficient, drag coefficient, and pressure coefficient distribution comparison on the boundary layers

Numerical validation and physical explanation of the universal force theory of three-dimensional steady viscous and compressible flow

In a recent paper, Liu et al. ["Lift and drag in three-dimensional steady viscous and compressible flow", Phys. Fluids 29, 116105 (2017)] obtained a universal theory for the aerodynamic force on a body in three-dimensional steady flow, effective from incompressible all the way to supersonic regimes. In this theory, the total aerodynamic force can be determined solely with the vorticity distribution on a single wake plane locating in the steady linear far field. Despite the vital importance of this result, its validity and performance in practice has not been investigated yet. In this paper, we performed Reynolds-averaged Navier-Stokes simulations of subsonic, transonic, and supersonic flows over a three-dimensional wing. The aerodynamic forces obtained from the universal force theory are compared with those from the standard wall-stress integrals. The agreement between these two formulas confirms for the first time the validity of the theory in three-dimensional steady viscous and compressible flow. The good performance of the universal formula is mainly due to the fact that the turbulent viscosity in the wake is much larger than the molecular viscosity therein, which can reduce significantly the distance of the steady linear far field from the body. To further confirm the correctness of the theory, comparisons are made for the flow structures on the wake plane obtained from the analytical results and numerical simulations. The underlying physics relevant to the universality of the theory is explained by identifying different sources of vorticity in the wake

Causal mechanism behind the stall delay by airfoil’s pitching-up motion

Why the stall of an airfoil can be significantly delayed by its pitching-up motion? Various attempts have been proposed to answer this question over the past half century, but none is satisfactory. In this letter we prove that a chain of vorticity-dynamics processes at accelerating boundary is fully responsible for the causal mechanism underlying this peculiar phenomenon. The local flow behavior is explained by a simple potential-flow model

Toward carbon free by 2060: A decarbonization roadmap of operational residential buildings in China

Restraining the rapid growth of operational carbon emissions from residential buildings is critical to achieve carbon neutrality. To illustrate the future decarbonization roadmap, this study builds an end-use emissions model to analyze past decarbonization efforts and projected emission change in China's residential building operations by mid-century. From 2001 to 2018, residential building operations reduced emissions by 2.77 (±1.61) giga tons of carbon dioxide (GtCO2). Dynamic simulation results of the emission model reveal that residential building operations will peak in 2031 (±3) with 0.95 (±0.06) GtCO2. Energy-related carbon intensity (∼44%) and energy intensity (∼36%) are identified as the primary factors affecting carbon peak status, with heating (∼87%) playing a crucial role in energy intensity. A feasible emission path towards carbon neutrality suggests limiting urban and rural residential building emissions to 0.38 and 0.27 GtCO2 in 2030, respectively, and offsetting only 0.03 and 0.01 GtCO2 in urban and rural regions by 2060, to become carbon free. Overall, the study proposes a stepwise data analysis benchmark to decarbonize the residential building operations of top emitters, contributing to global building decarbonization in the era of carbon neutrality

Idarubicin‐Loaded DEB‐TACE plus Lenvatinib versus Lenvatinib for patients with advanced hepatocellular carcinoma: A propensity score‐matching analysis

Abstract Aims To investigate the efficacy and safety of lenvatinib and idarubicin‐loaded drug‐eluting beads transarterial chemoembolization (IDADEB‐TACE) in primary advanced hepatocellular carcinoma (HCC). Methods This retrospective study included patients with primary advanced HCC who received either lenvatinib monotherapy or lenvatinib plus IDADEB‐TACE as first‐line treatment from September 2019 to September 2020 at three institutes. Overall survival (OS), time to progression (TTP), objective response rate (ORR), and adverse events were compared. Propensity score‐matching was used to reduce the influence of confounding factors on the outcomes. Results The study reviewed 118 patients who received lenvatinib plus IDADEB‐TACE (LIDA group) and 182 who received lenvatinib alone (LEN group). After propensity score‐matching, 78 pairs of patients remained. Compared to patients in the LEN group, those in the LIDA group had better post‐treatment ORR (57.7% vs. 25.6%, p < 0.001, respectively), median OS and TTP (15.7 vs. 11.3 months, hazard ratio [HR] = 0.50, p < 0.001; 8.0 vs. 5.0 months, HR = 0.60, p = 0.003, respectively), 6‐ and 12‐month OS rates (88.5% vs. 71.4%; 67.6% vs. 43.4%, respectively), and progression‐free rates at 6 and 12 months (60.3% vs. 42.3%; 21.1% vs. 10.3%, respectively). Vascular invasion, α‐fetoprotein level, and treatment type were independent OS predictors, and vascular invasion and treatment type were independent TTP predictors. Incidences of nausea/vomiting, fever, abdominal pain, and increased ALT/AST were higher in the LIDA group than in the LEN group. Conclusions Lenvatinib plus IDADEB‐TACE is well‐tolerated and more effective than lenvatinib monotherapy in patients with advanced HCC

Effect of Resveratrol Dry Suspension on Immune Function of Piglets

Resveratrol, a polyphenolic plant antitoxin, has a wide range of pharmacological activities. In this study, we systematically evaluated the effects of resveratrol dry suspension (RDS) on immune function in piglets that were treated with different doses of RDS for 2 weeks. The results showed that the RDS has significant effects on the development, maturation, proliferation, and transformation of T lymphocytes. RDS could regulate humoral immune responses by upregulating the release of IFN-γ and downregulating the release of TNF-α. After piglets were vaccinated against classical swine fever virus and foot-and-mouth disease virus, the antibody titers were significantly increased. RDS treatment showed an excellent resistance to enhance T-SOD activity. Values of blood routine and blood biochemistry showed no toxicity. These results suggested that RDS could be considered as an adjuvant to enhance immune responses to vaccines, as well as dietary additives for animals to enhance humoral and cellular immunity