Multi-scale analysis on cavitation damage and its mitigation for the spallation neutron source

Impact of injecting microbubbles on the thermal expansion due to the nuclear spallation reaction were examined numerically. Since the mercury density is higher than the density of solid wall, the interaction between mercury and solid wall must be taken into account. Our approach is to solve the momentum and energy conservation equations and the time development of elastic stress for both bubbly fluid and elastic solid. The Keller equation is employed to reproduce the nonlinear oscillation of bubble with considering the thermal dumping effect by the reduced order model. The continuum phase of liquid mercury is coupled with the discrete phase of microbubbles using the Euler-Lagrange method. As the results, the bubble cloud develops around the center of inertia of motion induced by the thermal expansion. The elasticity of the wall affects on the migration of the center of inertia away from the wall. The injection of microbubbles is effective to decrease the pressure rise due to thermal expansion for both rigid and elastic wall conditions when the void fraction of microbubbles is higher than the volume rate of thermal expansion of liquid mercury

Vibrational Relaxation of Diatomic Molecules in Rarefied Gas Flows

Abstract. The direct simulation Monte Carlo (DSMC) method is widely used for simulations of rarefied gas flows. To make a vibrational relaxation model of diatomic molecules for the DSMC method, the collisions of diatomic molecules are investigated numerically. The collision cross section for vibrational relaxation can be described as a function of the relative translational energy, the rotational energy and the vibrational energy level of each colliding molecule. Thus the collision cross section could be evaluated with the Monte Carlo integration for these parameters. To achieve this idea, a lot of collisions with appropriate initial conditions should be calculated and analyzed statistically. A collision is simulated with the Semiclassical approach in which the vibrational energy is treated quantum mechanically and the rotational and the relative translational energies are treated classically. For the comparison of methods, the Quasiclassical approach is applied. The simulation by this method is the same as that by the classical method, and the obtained vibrational energy is discretized to the quantum level. The intermolecular potential is also compared between two different types that are the site-to-site Lennard-Jones and the Billing-Fisher potential

Sclerosing angiomatoid nodular transformation of the spleen masquerading as a sarcoma metastasis

We report a case of sclerosing angiomatoid nodular transformation (SANT) of the spleen presenting as an incidental splenic mass in a patient with a history of retroperitoneal spindle cell sarcoma. Imaging studies and preoperative fine needle biopsy failed to differentiate this lesion from other vascular splenic lesions or a metastatic focus of a prior sarcoma. The patient was treated with splenectomy, which has proved both diagnostic and therapeutic in this and other cases of SANT. Although histology can lead to the diagnosis of vascular tumor, immunohistochemistry is the only way to confirm the diagnosis of SANT. The etiology of SANT is unknown. SANT of the spleen is a benign lesion that does not recur after splenectomy

AJK2011-04001 A FULL EULERIAN FINITE DIFFERENCE METHOD FOR HYPERELASTIC PARTICLES IN FLUID FLOWS

ABSTRACT A full Eulerian finite difference method has been developed for solving a dynamic interaction problem between Newtonian fluid and hyperelastic material. It facilitates to simulate certain classes of problems, such that an initial and neutral configuration of a multi-component geometry converted from voxel-based data is provided on a fixed Cartesian mesh. A solid volume fraction, which has been widely used for multiphase flow simulations, is applied to describing the multicomponent geometry. The temporal change in the solid deformation is described in the Eulerian frame by updating a left Cauchy-Green deformation tensor, which is used to express constitutive equations for incompressible hyperelastic materials. The present Eulerian approach is confirmed to well reproduce the material deformation in the lid-driven flow and the particle-particle interaction in the Couette flow computed by means of the finite element method. It is applied to a Poiseuille flow containing biconcave neo-Hookean particles. The deformation, the relative position and orientation of a pair of particles are strongly dependent upon the initial configuration. The increase in the apparent viscosity is dependent upon the developed arrangement of the particles. INTRODUCTION Numerical simulations of Fluid-Structure Interaction (FSI) problems would make it possible to predict the effect of a medical treatment and help one decide the treatment strategy in clinical practice. In particular, a blood flow simulation is expected to contribute to assisting the surgical planning of a cardiovascular disease and a brain aneurysm. Recently, there are growing expectations for its applications along with a progress in imaging and computational technologies. It is also expected to contribute to the field of life science, such as in the understanding of the very essence of life and the demonstration of pathological mechanisms. It is of great importance to develop numerical techniques suitable for the characteristics of body tissues, which are flexible and complicated in shape, when attempting to rationalize and to generalize the fluidstructure coupled analyses. The expectations include the further understandings of the micro/mesoscopic behavior of the flexibly deformable Red Blood Cells (RBCs) in plasma useful for evaluating the macroscopic blood rheology, and the thrombosis formation as aggregation of platelets, of which th

Pathogenic Roles of Cardiac Fibroblasts in Pediatric Dilated Cardiomyopathy

BACKGROUND: Dilated cardiomyopathy (DCM) is a major cause of heart failure in children. Despite intensive genetic analyses, pathogenic gene variants have not been identified in most patients with DCM, which suggests that cardiomyocytes are not solely responsible for DCM. Cardiac fibroblasts (CFs) are the most abundant cell type in the heart. They have several roles in maintaining cardiac function; however, the pathological role of CFs in DCM remains unknown. METHODS AND RESULTS: Four primary cultured CF cell lines were established from pediatric patients with DCM and compared with 3 CF lines from healthy controls. There were no significant differences in cellular proliferation, adhesion, migration, ap-optosis, or myofibroblast activation between DCM CFs compared with healthy CFs. Atomic force microscopy revealed that cellular stiffness, fluidity, and viscosity were not significantly changed in DCM CFs. However, when DCM CFs were cocultured with healthy cardiomyocytes, they deteriorated the contractile and diastolic functions of cardiomyocytes. RNA sequencing revealed markedly different comprehensive gene expression profiles in DCM CFs compared with healthy CFs. Several hu-moral factors and the extracellular matrix were significantly upregulated or downregulated in DCM CFs. The pathway analysis revealed that extracellular matrix receptor interactions, focal adhesion signaling, Hippo signaling, and transforming growth factor-β signaling pathways were significantly affected in DCM CFs. In contrast, single-cell RNA sequencing revealed that there was no specific subpopulation in the DCM CFs that contributed to the alterations in gene expression. CONCLUSIONS: Although cellular physiological behavior was not altered in DCM CFs, they deteriorated the contractile and diastolic functions of healthy cardiomyocytes through humoral factors and direct cell–cell contact.Tsuru H., Yoshihara C., Suginobe H., et al. Pathogenic Roles of Cardiac Fibroblasts in Pediatric Dilated Cardiomyopathy. Journal of the American Heart Association 12, e029676 (2023); https://doi.org/10.1161/JAHA.123.029676

A full Eulerian finite difference approach for solving fluid-structure coupling problems

A new simulation method for solving fluid-structure coupling problems has been developed. All the basic equations are numerically solved on a fixed Cartesian grid using a finite difference scheme. A volume-of-fluid formulation (Hirt and Nichols (1981, J. Comput. Phys., 39, 201)), which has been widely used for multiphase flow simulations, is applied to describing the multi-component geometry. The temporal change in the solid deformation is described in the Eulerian frame by updating a left Cauchy-Green deformation tensor, which is used to express constitutive equations for nonlinear Mooney-Rivlin materials. In this paper, various verifications and validations of the present full Eulerian method, which solves the fluid and solid motions on a fixed grid, are demonstrated, and the numerical accuracy involved in the fluid-structure coupling problems is examined.Comment: 38 pages, 27 figures, accepted for publication in J. Comput. Phy