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Richard D Sandberg - One of the best experts on this subject based on the ideXlab platform.
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direct numerical simulation of turbulent premixed jet flames influence of Inflow Boundary conditions
Combustion and Flame, 2020Co-Authors: Mohsen Talei, Richard D SandbergAbstract:Abstract Direct Numerical Simulations (DNS)s of a low Karlovitz number turbulent premixed round jet flame are performed to determine the impact of the turbulence Inflow conditions on the flame characteristics. This is accomplished by providing the first flame with a fully developed turbulent Inflow via simulation of the upstream pipe and the coflow region, while the Inflow Boundary condition in the second flame is generated with a digital filter-based method without including the upstream region. The two databases are then thoroughly compared to reveal any differences resulting from the different Inflow Boundary conditions. The turbulence kinetic energy is observed to drop shortly downstream of the synthetic Inflow, which results in a higher jet momentum and a longer flame compared to the flame with the fully developed turbulent Inflow. The distributions of the flame front orientation in the near field are observed to differ between the two flames but differences decrease quickly downstream as distributions tend towards isotropy. The flame structure is largely affected by tangential straining close to the Inflow while further downstream, the flame structure is similar to that in an unstrained laminar flame. While the difference between the Inflow boundaries had a significant effect on global parameters such as flame length, the influence of the Inflow conditions on local statistics related to turbulence-flame interaction appear to be limited to the near Inflow region.
Julio Ortega - One of the best experts on this subject based on the ideXlab platform.
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On the importance of spiral‐flow Inflow Boundary conditions when using idealized artery geometries in the analysis of liver radioembolization: A parametric study.
International Journal for Numerical Methods in Biomedical Engineering, 2020Co-Authors: Julio Ortega, Raúl Antón, Juan Carlos Ramos, Alejandro Rivas, Gorka S. Larraona, Bruno Sangro, José Ignacio Bilbao, Jorge AramburuAbstract:In the last decades, the numerical studies on hemodynamics have become a valuable explorative scientific tool. The very first studies were done over idealized geometries, but as numerical methods and the power of computers have become more affordable, the studies tend to be patient specific. We apply the study to the numerical analysis of tumor-targeting during liver radioembolization (RE). RE is a treatment for liver cancer, and is performed by injecting radiolabeled microspheres via a catheter placed in the hepatic artery. The objective of the procedure is to maximize the release of radiolabeled microspheres into the tumor and avoid a healthy tissue damage. Idealized virtual arteries can serve as a generalist approach that permits to separately analyze the effect of a variable in the microsphere distribution with respect to others. However, it is important to use proper physiological Boundary conditions (BCs). It is not obvious, the need to account for the effect of tortuosity when using an idealized virtual artery. We study the use of idealized geometry of a hepatic artery as a valid research tool, exploring the importance of using realistic spiral-flow Inflow BC. By using a literature-based cancer scenario, we vary two parameters to analyze the microsphere distribution through the outlets of the geometry. The parameters varied are the type of microspheres injected and the microsphere injection velocity. The results with realistic inlet velocity profile showed that the particle distribution in the liver segments is not affected by the analyzed injection velocity values neither by the particle density. NOVELTY STATEMENT: In this article, we assessed the use of idealized geometries as a valid research tool and applied the use of an idealized geometry to the case of an idealized hepatic artery to study the particle-hemodynamics during radioembolization (RE). We studied three different Inflow Boundary conditions (BCs) to assess the usefulness of the geometry, two types of particle injection velocities and two types of commercially available microspheres for RE treatment. In recent years, the advent in computational resources allowed for more detailed patient-specific geometry generation and discretization and hemodynamics simulations. However, general studies based on idealized geometries can be performed in order to provide medical doctors with some basic and general guidelines when using a given catheter for a given cancer scenario. Moreover, using an idealized geometry can be a reasonable approach which allows us to isolate a given parameter and control other parameters, so that parameters can be independently assessed. Even though an idealized geometry does not match any patient's geometry, the use of an idealized geometry can be valid when drawing general conclusions that may be useful in patient-specific cases. However, we believe that even if an idealized hepatic artery geometry is used for the study, it is necessary to account for the upstream and downstream tortuosity of vessels through the BCs. In this work, we highlighted the need of modeling the tortuosity of upstream and downstream vasculatures through the BCs.
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on the importance of spiral flow Inflow Boundary conditions when using idealized artery geometries in the analysis of liver radioembolization a parametric study
International Journal for Numerical Methods in Biomedical Engineering, 2020Co-Authors: Julio Ortega, Raúl Antón, Juan Carlos Ramos, Alejandro Rivas, Gorka S. Larraona, Bruno Sangro, José Ignacio Bilbao, Jorge AramburuAbstract:In the last decades, the numerical studies on hemodynamics have become a valuable explorative scientific tool. The very first studies were done over idealized geometries, but as numerical methods and the power of computers have become more affordable, the studies tend to be patient specific. We apply the study to the numerical analysis of tumor-targeting during liver radioembolization (RE). RE is a treatment for liver cancer, and is performed by injecting radiolabeled microspheres via a catheter placed in the hepatic artery. The objective of the procedure is to maximize the release of radiolabeled microspheres into the tumor and avoid a healthy tissue damage. Idealized virtual arteries can serve as a generalist approach that permits to separately analyze the effect of a variable in the microsphere distribution with respect to others. However, it is important to use proper physiological Boundary conditions (BCs). It is not obvious, the need to account for the effect of tortuosity when using an idealized virtual artery. We study the use of idealized geometry of a hepatic artery as a valid research tool, exploring the importance of using realistic spiral-flow Inflow BC. By using a literature-based cancer scenario, we vary two parameters to analyze the microsphere distribution through the outlets of the geometry. The parameters varied are the type of microspheres injected and the microsphere injection velocity. The results with realistic inlet velocity profile showed that the particle distribution in the liver segments is not affected by the analyzed injection velocity values neither by the particle density. NOVELTY STATEMENT: In this article, we assessed the use of idealized geometries as a valid research tool and applied the use of an idealized geometry to the case of an idealized hepatic artery to study the particle-hemodynamics during radioembolization (RE). We studied three different Inflow Boundary conditions (BCs) to assess the usefulness of the geometry, two types of particle injection velocities and two types of commercially available microspheres for RE treatment. In recent years, the advent in computational resources allowed for more detailed patient-specific geometry generation and discretization and hemodynamics simulations. However, general studies based on idealized geometries can be performed in order to provide medical doctors with some basic and general guidelines when using a given catheter for a given cancer scenario. Moreover, using an idealized geometry can be a reasonable approach which allows us to isolate a given parameter and control other parameters, so that parameters can be independently assessed. Even though an idealized geometry does not match any patient's geometry, the use of an idealized geometry can be valid when drawing general conclusions that may be useful in patient-specific cases. However, we believe that even if an idealized hepatic artery geometry is used for the study, it is necessary to account for the upstream and downstream tortuosity of vessels through the BCs. In this work, we highlighted the need of modeling the tortuosity of upstream and downstream vasculatures through the BCs.
Zhangpeng Sun - One of the best experts on this subject based on the ideXlab platform.
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Optimization Modeling and Simulating of the Stationary Wigner Inflow Boundary Value Problem
Journal of Scientific Computing, 2020Co-Authors: Zhangpeng Sun, Wenqi YaoAbstract:The stationary Wigner Inflow Boundary value problem (SWIBVP) is modeled as an optimization problem by using the idea of shooting method in this paper. To remove the singularity at $$v=0$$ , we consider a regularized SWIBVP, where a regularization constraint is considered along with the original SWIBVP, and a modified optimization problem is established for it. A shooting algorithm is proposed to solve the two optimization problems, involving the limited-memory BFGS (L-BFGS) algorithm as the optimization solver. Numerical results show that solving the optimization problems with respect to the SWIBVP with the shooting algorithm is as effective as solving the SWIBVP with Frensley’s numerical method (Frensley in Phys Rev B 36:1570–1580, 1987). Furthermore, the modified optimization problem gets rid of the singularity at $$v=0$$ , and preserves symmetry of the Wigner function, which implies the optimization modeling with respect to the regularized SWIBVP is successful.
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Parity-decomposition and moment analysis for stationary Wigner equation with Inflow Boundary conditions
Frontiers of Mathematics in China, 2017Co-Authors: Zhangpeng SunAbstract:We study the stationary Wigner equation on a bounded, one-dimensional spatial domain with Inflow Boundary conditions by using the parity decomposition of L. Barletti and P. F. Zweifel [Transport Theory Statist. Phys., 2001, 30(4-6): 507–520]. The decomposition reduces the half-range, two-point Boundary value problem into two decoupled initial value problems of the even part and the odd part. Without using a cutoff approximation around zero velocity, we prove that the initial value problem for the even part is well-posed. For the odd part, we prove the uniqueness of the solution in the odd L 2-space by analyzing the moment system. An example is provided to show that how to use the analysis to obtain the solution of the stationary Wigner equation with Inflow Boundary conditions.
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Stationary Wigner Equation with Inflow Boundary Conditions: Will a Symmetric Potential Yield a Symmetric Solution?
SIAM Journal on Applied Mathematics, 2014Co-Authors: Zhangpeng SunAbstract:Based on the well-posedness of the stationary Wigner equation with Inflow Boundary conditions given in [A. Arnold, H. Lange, and P.F. Zweifel, J. Math. Phys., 41 (2000), pp. 7167--7180] we prove without any additional prerequisite conditions that the solution of the Wigner equation with Inflow Boundary conditions will be symmetric only if the potential is symmetric. This improves the result in [D. Taj, L. Genovese, and F. Rossi, Europhys. Lett., 74 (2006), pp. 1060--1066], which depends on the convergence of the solution formulated in the Neumann series. By numerical studies, we present the convergence of the numerical solution to the symmetric profile for three different numerical schemes. This implies that the upwind schemes can also yield a symmetric numerical solution, contrary to the argument given in [D. Taj, L. Genovese, and F. Rossi, Europhys. Lett., 74 (2006), pp. 1060--1066].
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Stationary Wigner Equation with Inflow Boundary Conditions: Will a Symmetric Potential Yield a Symmetric Solution?
arXiv: Mathematical Physics, 2013Co-Authors: Zhangpeng SunAbstract:Based on the well-posedness of the stationary Wigner equation with Inflow Boundary conditions given in (A. Arnold, H et al. J. Math. Phys., 41, 2000), we prove without any additional prerequisite conditions that the solution of the Wigner equation with symmetric potential and Inflow Boundary conditions will be symmetric. This improve the result in (D. Taj et al. Europhys. Lett., 74, 2006) which depends on the convergence of solution formulated in the Neumann series. By numerical studies, we present the convergence of the numerical solution to the symmetric profile for three different numerical schemes. This implies that the upwind schemes can also yield a symmetric numerical solution, on the contrary to the argument given in (D. Taj et al. Europhys. Lett., 74, 2006).
Chiara Manzini - One of the best experts on this subject based on the ideXlab platform.
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An Analysis of a Quantum Kinetic Two-band Model with Inflow Boundary Conditions
2007Co-Authors: Chiara Manzini, Omar MorandiAbstract:We present a well-posedness study of a two-band envelope function model in the Wigner formalism. It is obtained from a multiband Schrodinger-like system for the conduction and the valence band envelope functions, derived by O.Morandi and M.Modugno, and describes the mixed-states of an open quantum system. It consists of four coupled equations for the unknown quasi-distribution functions. We include a non-linearly coupling with the Poisson equation and consider the unknown functions defined in a one-dimensional, bounded spatial domain with time-dependent ``Inflow'' Boundary conditions. We will prove the existence and uniqueness of a global-in-time, classical solution. [ DOI : 10.1685/CSC06107] About DOI
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On the three-dimensional Wigner–Poisson problem with Inflow Boundary conditions
Journal of Mathematical Analysis and Applications, 2006Co-Authors: Chiara ManziniAbstract:Abstract We study the Wigner–Poisson problem in a bounded spatial domain, with non-homogeneous and time-dependent “Inflow” Boundary conditions. This system is a quantum model of charge transport in a semiconductor device coupled with reservoirs, in presence of a self-consistent potential and of an external one. We state a local-in-time well-posedness result for the problem. The main difficulty is proving in the three-dimensional case that the non-linear potential term is a Lipschitz perturbation of the “affine” streaming operator, in an appropriately weighted L 2 -space.
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on the three dimensional wigner poisson problem with Inflow Boundary conditions
Journal of Mathematical Analysis and Applications, 2006Co-Authors: Chiara ManziniAbstract:Abstract We study the Wigner–Poisson problem in a bounded spatial domain, with non-homogeneous and time-dependent “Inflow” Boundary conditions. This system is a quantum model of charge transport in a semiconductor device coupled with reservoirs, in presence of a self-consistent potential and of an external one. We state a local-in-time well-posedness result for the problem. The main difficulty is proving in the three-dimensional case that the non-linear potential term is a Lipschitz perturbation of the “affine” streaming operator, in an appropriately weighted L 2 -space.
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An analysis of the Wigner–Poisson problem with Inflow Boundary conditions
Nonlinear Analysis: Theory Methods & Applications, 2005Co-Authors: Chiara Manzini, Luigi BarlettiAbstract:Abstract We present a study of the Wigner–Poisson problem in a bounded spatial domain with non-homogeneous and time-dependent “Inflow” Boundary conditions. This system of nonlinearly coupled equations is a mathematical model for quantum transport of charges in a semiconductor with external contacts. We prove well-posedness of the linearized n -dimensional problem as well as existence and uniqueness of a global-in-time, regular solution of the one-dimensional nonlinear problem.
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an analysis of the wigner poisson problem with Inflow Boundary conditions
Nonlinear Analysis-theory Methods & Applications, 2005Co-Authors: Chiara Manzini, Luigi BarlettiAbstract:Abstract We present a study of the Wigner–Poisson problem in a bounded spatial domain with non-homogeneous and time-dependent “Inflow” Boundary conditions. This system of nonlinearly coupled equations is a mathematical model for quantum transport of charges in a semiconductor with external contacts. We prove well-posedness of the linearized n -dimensional problem as well as existence and uniqueness of a global-in-time, regular solution of the one-dimensional nonlinear problem.
Jorge Aramburu - One of the best experts on this subject based on the ideXlab platform.
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On the importance of spiral‐flow Inflow Boundary conditions when using idealized artery geometries in the analysis of liver radioembolization: A parametric study.
International Journal for Numerical Methods in Biomedical Engineering, 2020Co-Authors: Julio Ortega, Raúl Antón, Juan Carlos Ramos, Alejandro Rivas, Gorka S. Larraona, Bruno Sangro, José Ignacio Bilbao, Jorge AramburuAbstract:In the last decades, the numerical studies on hemodynamics have become a valuable explorative scientific tool. The very first studies were done over idealized geometries, but as numerical methods and the power of computers have become more affordable, the studies tend to be patient specific. We apply the study to the numerical analysis of tumor-targeting during liver radioembolization (RE). RE is a treatment for liver cancer, and is performed by injecting radiolabeled microspheres via a catheter placed in the hepatic artery. The objective of the procedure is to maximize the release of radiolabeled microspheres into the tumor and avoid a healthy tissue damage. Idealized virtual arteries can serve as a generalist approach that permits to separately analyze the effect of a variable in the microsphere distribution with respect to others. However, it is important to use proper physiological Boundary conditions (BCs). It is not obvious, the need to account for the effect of tortuosity when using an idealized virtual artery. We study the use of idealized geometry of a hepatic artery as a valid research tool, exploring the importance of using realistic spiral-flow Inflow BC. By using a literature-based cancer scenario, we vary two parameters to analyze the microsphere distribution through the outlets of the geometry. The parameters varied are the type of microspheres injected and the microsphere injection velocity. The results with realistic inlet velocity profile showed that the particle distribution in the liver segments is not affected by the analyzed injection velocity values neither by the particle density. NOVELTY STATEMENT: In this article, we assessed the use of idealized geometries as a valid research tool and applied the use of an idealized geometry to the case of an idealized hepatic artery to study the particle-hemodynamics during radioembolization (RE). We studied three different Inflow Boundary conditions (BCs) to assess the usefulness of the geometry, two types of particle injection velocities and two types of commercially available microspheres for RE treatment. In recent years, the advent in computational resources allowed for more detailed patient-specific geometry generation and discretization and hemodynamics simulations. However, general studies based on idealized geometries can be performed in order to provide medical doctors with some basic and general guidelines when using a given catheter for a given cancer scenario. Moreover, using an idealized geometry can be a reasonable approach which allows us to isolate a given parameter and control other parameters, so that parameters can be independently assessed. Even though an idealized geometry does not match any patient's geometry, the use of an idealized geometry can be valid when drawing general conclusions that may be useful in patient-specific cases. However, we believe that even if an idealized hepatic artery geometry is used for the study, it is necessary to account for the upstream and downstream tortuosity of vessels through the BCs. In this work, we highlighted the need of modeling the tortuosity of upstream and downstream vasculatures through the BCs.
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on the importance of spiral flow Inflow Boundary conditions when using idealized artery geometries in the analysis of liver radioembolization a parametric study
International Journal for Numerical Methods in Biomedical Engineering, 2020Co-Authors: Julio Ortega, Raúl Antón, Juan Carlos Ramos, Alejandro Rivas, Gorka S. Larraona, Bruno Sangro, José Ignacio Bilbao, Jorge AramburuAbstract:In the last decades, the numerical studies on hemodynamics have become a valuable explorative scientific tool. The very first studies were done over idealized geometries, but as numerical methods and the power of computers have become more affordable, the studies tend to be patient specific. We apply the study to the numerical analysis of tumor-targeting during liver radioembolization (RE). RE is a treatment for liver cancer, and is performed by injecting radiolabeled microspheres via a catheter placed in the hepatic artery. The objective of the procedure is to maximize the release of radiolabeled microspheres into the tumor and avoid a healthy tissue damage. Idealized virtual arteries can serve as a generalist approach that permits to separately analyze the effect of a variable in the microsphere distribution with respect to others. However, it is important to use proper physiological Boundary conditions (BCs). It is not obvious, the need to account for the effect of tortuosity when using an idealized virtual artery. We study the use of idealized geometry of a hepatic artery as a valid research tool, exploring the importance of using realistic spiral-flow Inflow BC. By using a literature-based cancer scenario, we vary two parameters to analyze the microsphere distribution through the outlets of the geometry. The parameters varied are the type of microspheres injected and the microsphere injection velocity. The results with realistic inlet velocity profile showed that the particle distribution in the liver segments is not affected by the analyzed injection velocity values neither by the particle density. NOVELTY STATEMENT: In this article, we assessed the use of idealized geometries as a valid research tool and applied the use of an idealized geometry to the case of an idealized hepatic artery to study the particle-hemodynamics during radioembolization (RE). We studied three different Inflow Boundary conditions (BCs) to assess the usefulness of the geometry, two types of particle injection velocities and two types of commercially available microspheres for RE treatment. In recent years, the advent in computational resources allowed for more detailed patient-specific geometry generation and discretization and hemodynamics simulations. However, general studies based on idealized geometries can be performed in order to provide medical doctors with some basic and general guidelines when using a given catheter for a given cancer scenario. Moreover, using an idealized geometry can be a reasonable approach which allows us to isolate a given parameter and control other parameters, so that parameters can be independently assessed. Even though an idealized geometry does not match any patient's geometry, the use of an idealized geometry can be valid when drawing general conclusions that may be useful in patient-specific cases. However, we believe that even if an idealized hepatic artery geometry is used for the study, it is necessary to account for the upstream and downstream tortuosity of vessels through the BCs. In this work, we highlighted the need of modeling the tortuosity of upstream and downstream vasculatures through the BCs.