The Experts below are selected from a list of 61584 Experts worldwide ranked by ideXlab platform
Mariya Iv Trukhanova - One of the best experts on this subject based on the ideXlab platform.
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quantum Hydrodynamics of the spinor bose einstein condensate at non zero temperatures
Physics of Fluids, 2021Co-Authors: Pavel A Andreev, Mariya Iv Trukhanova, I N MosakiAbstract:A finite temperature Hydrodynamic model is derived for the spin-1 ultracold bosons by the many-particle quantum Hydrodynamic Method. It is presented as the two fluid model of the Bose–Einstein condensate (BEC) and normal fluid. The continuity, Euler, spin evolution, and nematic tensor evolution equations are derived for each fluid. The linear and quadratic Zeeman effects are included. Scalar and spin–spin like short-range interactions are considered in the first order by the interaction radius. Obtained Hydrodynamic equations are also represented as the set of two nonlinear Pauli equations. The spectrum of the bulk collective excitations is considered for the ferromagnetic phase in the small temperature limit. The spin wave is not affected by the presence of the small temperature in the described minimal coupling model, where the thermal part of the spin-current of the normal fluid is neglected. The two sound waves are affected by the spin evolution in the same way as the change of spectrum of the single sound wave in BEC, where speed of sound is proportional to g 1 + g 2 with gi as the interaction constants.
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quantum Hydrodynamics of the spinor bose einstein condensate at non zero temperatures
arXiv: Quantum Gases, 2021Co-Authors: Pavel A Andreev, Mariya Iv Trukhanova, I N MosakiAbstract:Finite temperature Hydrodynamic model is derived for the spin-1 ultracold bosons by the many-particle quantum Hydrodynamic Method. It is presented as the two fluid model of the BEC and normal fluid. The linear and quadratic Zeeman effects are included. Scalar and spin-spin like short-range interactions are considered in the first order by the interaction radius. It is also represented as the set of two nonlinear Pauli equations. The spectrum of the bulk collective excitations is considered for the ferromagnetic phase in the small temperature limit. The spin wave is not affected by the presence of the small temperature in the described minimal coupling model, where the thermal part of the spin-current of the normal fluid is neglected. The two sound waves are affected by the spin evolution in the same way as the change of spectrum of the single sound wave in BEC, where speed of sound is proportional to $g_{1}+g_{2}$ with $g_{i}$ are the interaction constants.
Donald E Burton - One of the best experts on this subject based on the ideXlab platform.
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a high order lagrangian discontinuous galerkin Hydrodynamic Method for quadratic cells using a subcell mesh stabilization scheme
Journal of Computational Physics, 2019Co-Authors: Nathaniel R Morgan, Donald E BurtonAbstract:Abstract We present a Lagrangian discontinuous Galerkin (DG) Hydrodynamic Method that is up to third-order accurate using subcell mesh stabilization (SMS) for compressible flows on quadratic meshes in two-dimensional (2D) Cartesian coordinates. Similar to the second-order accurate Lagrangian DG Method with linear meshes, the physical evolution equations for the specific volume, velocity, and specific total energy are discretized using a modal DG Method with Taylor series polynomials. The Riemann velocity at the vertices of a curvilinear cell, and the corresponding surface forces, are calculated by solving a multidirectional approximate Riemann problem. Curvilinear cells (e.g., quadratic quadrilateral meshes in this work) have many deformational degrees of freedom, and with these cells, they can deform in unphysical ways. Likewise, the Riemann solution at an edge vertex differs from the one at the corner of a cell. With SMS, each quadratic quadrilateral cell is decomposed into four quadrilateral subcells, that move in a Lagrangian manner. The edge vertex is surrounded by four subcells so that it is similar to the vertex at the cell corner. SMS can detect inconsistent density fields between the cell and subcells. The difference between these two density fields is used to correct the stress (pressure) input to the Riemann solver. This SMS scheme enables stable mesh motion and accurate solutions in the context of a Lagrangian high-order DG Method that is up to third-order with quadratic cells. We also present effective limiting strategies that ensure monotonicity of the primitive variables with the high-order DG Method. This Lagrangian DG Hydrodynamic Method with SMS conserves mass, momentum, and total energy. A suite of test problems are calculated to demonstrate the designed order of accuracy (up to third-order accurate) of this Method, and that the Lagrangian DG Method using SMS preserves cylindrical symmetry on 1D radial flow problems with an equal-angle polar quadratic mesh.
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a lagrangian discontinuous galerkin Hydrodynamic Method
Computers & Fluids, 2018Co-Authors: Xiaodong Liu, Nathaniel R Morgan, Donald E BurtonAbstract:Abstract We present a new Lagrangian discontinuous Galerkin (DG) Hydrodynamic Method for solving the two-dimensional gas dynamic equations on unstructured hybrid meshes. The physical conservation laws for the momentum and total energy are discretized using a DG Method based on linear Taylor expansions. Three different approaches are investigated for calculating the density variation over the element. The first approach evolves a Taylor expansion of the specific volume field. The second approach follows certain finite element Methods and uses the strong mass conservation to calculate the density field at a location inside the element or on the element surface. The third approach evolves a Taylor expansion of the density field. The nodal velocity, and the corresponding forces, are explicitly calculated by solving a multidirectional approximate Riemann problem. An effective limiting strategy is presented that ensures monotonicity of the primitive variables. This new Lagrangian DG Hydrodynamic Method conserves mass, momentum, and total energy. Results from a suite of test problems are presented to demonstrate the robustness and expected second-order accuracy of this new Method.
Sangwoo Kim - One of the best experts on this subject based on the ideXlab platform.
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evaluation of bird strike induced damages of helicopter composite fuel tank assembly based on fluid structure interaction analysis
Composite Structures, 2019Co-Authors: Donghyeop Kim, Sangwoo KimAbstract:Abstract We numerically investigated the structural behaviors and damage of a bird strike on a composite fuel tank assembly of a commercial KUH-1 Surion utility helicopter based on a fluid-structure interaction analysis. A coupled Eulerian–Lagrangian Method and a smoothed particle Hydrodynamic Method were applied to consider the sloshing of fuel and replicate the impact behaviors of a bird strike, respectively. In addition, the Hashin failure criteria considering four composite damage modes was applied in the simulation. We found that not only the increase in the amount of fuel but also the curved geometry had a negative effect on the structural safety of the composite fuel tank during the impact. These findings will be used as reference data and guidelines for bird strike tests and airworthiness certification in the future.
Xiaosheng Gao - One of the best experts on this subject based on the ideXlab platform.
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Bird Strike on a Flat Plate: Experiments and Numerical Simulations
International Journal of Impact Engineering, 2014Co-Authors: Jun Liu, Xiaosheng GaoAbstract:Abstract In this study, experiments of bird impact with a flat plate are conducted at different striking velocities and simulated using an explicit finite element software PAM-CRASH with three bird material models. The predicted displacement and strain in the plate and impact reaction force on the clamping fixture are compared with experimental measurements. The results suggest that the elastic–plastic material model with a defined failure strain is best suited for bird strike simulation at low impact velocities, the isotropic elastic–plastic Hydrodynamic solid model is best suited for bird strike simulation at intermediate impact velocities, and the SPH (smooth particle Hydrodynamic) Method with the Murnaghan EOS (equation of state) for solid element is best suited for bird strike simulation at high impact velocities. Using the appropriate bird material model, the simulation results agree very well with experimental data.
Takayoshi Nakano - One of the best experts on this subject based on the ideXlab platform.
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quantitative regulation of bone mimetic oriented collagen apatite matrix structure depends on the degree of osteoblast alignment on oriented collagen substrates
Journal of Biomedical Materials Research Part A, 2015Co-Authors: Aira Matsugaki, Yoshihiro Isobe, Taro Saku, Takayoshi NakanoAbstract:Bone tissue has a specific anisotropic morphology derived from collagen fiber alignment and the related apatite crystal orientation as a bone quality index. However, the precise mechanism of cellular regulation of the crystallographic orientation of apatite has not been clarified. In this study, anisotropic construction of cell-produced mineralized matrix in vitro was established by initiating organized cellular alignment and subsequent oriented bone-like matrix (collagen/apatite) production. The oriented collagen substrates with three anisotropic levels were prepared by a Hydrodynamic Method. Primary osteoblasts were cultured on the fabricated substrates until mineralized matrix formation is confirmed. Osteoblast alignment was successfully regulated by the level of substrate collagen orientation, with preferential alignment along the direction of the collagen fibers. Notably, both fibrous orientation of newly synthesized collagen matrix and c-axis of produced apatite crystals showed preferential orientation along the cell direction. Because the degree of anisotropy of the deposited apatite crystals showed dependency on the directional distribution of osteoblasts cultured on the oriented collagen substrates, the cell orientation determines the crystallographic anisotropy of produced apatite crystals. To the best of our knowledge, this is the first report demonstrating that bone tissue anisotropy, even the alignment of apatite crystals, is controllable by varying the degree of osteoblast alignment via regulating the level of substrate orientation.
