The Experts below are selected from a list of 25554 Experts worldwide ranked by ideXlab platform
Qingyan Chen - One of the best experts on this subject based on the ideXlab platform.
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optimal design of an indoor environment by the cfd based Adjoint Method with area constrained topology and cluster analysis
Building and Environment, 2018Co-Authors: Xingwang Zhao, Wei Liu, Dayi Lai, Qingyan ChenAbstract:Abstract An indoor environment should be designed to provide occupants with a desirable level of thermal comfort and air quality. The optimal design of an indoor environment can be achieved by using the computational fluid dynamics (CFD)-based Adjoint Method to determine the size, locations, and shape of air supply inlets, and the air supply parameters (i.e., velocity, temperature, and angle). However, the optimal design may involve a large number of air supply inlets, which would be impractical to implement. This investigation developed an area-constrained topology and cluster analysis to consolidate multiple air supply inlets into a limited number and to determine their size and locations. The desired indoor environment can be maintained by further optimizing the air supply inlet shape and parameters. This investigation demonstrated the Method's capability by applying it to a two-person office and a single-aisle, fully-occupied aircraft cabin. The optimal thermal comfort conditions around the occupants can be achieved with a limited number of air supply inlets at appropriate locations.
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development of a fast fluid dynamics based Adjoint Method for the inverse design of indoor environments
Journal of Building Performance Simulation, 2017Co-Authors: Wei Liu, Ruoyu You, Jie Zhang, Qingyan ChenAbstract:The computational fluid dynamics (CFD)-based Adjoint Method may be appropriate for the inverse design of indoor environments, considering both accuracy and efficiency, but a single design still requires tens of hours with the use of a personal computer. To speed up the inverse design process, this study evaluated four fast fluid dynamics (FFD) models in terms of solving the Navier–Stokes equations, integration with turbulence models, and solving the Adjoint equations. This study implemented the FFD solvers in OpenFOAM and validated them for predicting steady-state and transient indoor airflow. This study then validated the FFD solvers for solving the Adjoint equations and the FFD-based Adjoint Method for inverse identification problems and inverse designs in indoor environments. The results showed that FFD was 20 times faster than CFD in predicting transient indoor airflow, and similar computational accuracy could be maintained; the FFD-based Adjoint Method was 4–16 times faster than the CFD-based Adjoint...
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inverse design of the thermal environment in an airliner cabin by use of the cfd based Adjoint Method
Energy and Buildings, 2015Co-Authors: Wei Liu, Qingyan Chen, Ran Duan, Chun Chen, Chaohsin LinAbstract:Abstract The current thermal environments in airliner cabins may not provide satisfactory comfort levels, and the design of these environments should be improved. This study aimed to design a desirable thermal environment for a single-aisle airliner cabin and used the CFD-based Adjoint Method to find the optimal design variables of air supply locations, size, and parameters. The design variables are used as the boundary conditions for solving the Navier–Stokes equations. By setting the occupant region as the design domain with a minimal predicted mean vote for thermal comfort, this study aimed to determine the corresponding air supply conditions for mixing and displacement ventilation systems under summer and winter conditions. The results show that it is possible to find the optimal air supply conditions in fewer than 10 design cycles if the initial conditions for design variables are provided within a reasonable range. This design Method has a high computing efficiency as it takes one hour for a design cycle using a 16-core cluster. In addition, the results show that a displacement ventilation system provides a better thermal comfort level than a mixing ventilation system.
Philip John Binning - One of the best experts on this subject based on the ideXlab platform.
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a split operator approach to reactive transport with the forward particle tracking eulerian lagrangian localized Adjoint Method
Advances in Water Resources, 2004Co-Authors: L S J Bell, Philip John BinningAbstract:Abstract A forward particle tracking Eulerian Lagrangian localized Adjoint Method (ELLAM) is applied to the multicomponent reactive transport problem using a split operator approach. Two split operator algorithms are compared, the Strang algorithm and the sequential non-iterative algorithm (SNIA). The reaction equations are integrated using a coupled predictor corrector algorithm with adaptive time stepping. Reaction time steps are adjusted at the inflow boundary to reflect the actual time of transport inside the solution domain. Results show that split operator ELLAM formulations are competitive with direct or fully coupled ELLAM solutions for reactive transport problems. The SNIA algorithm is more accurate than the Strang splitting algorithm when large time steps are used. The reaction algorithm employed dominates computational effort in runs with large time step sizes. To illustrate the use of the Method in practical problems, the model is fitted to aerobic aniline degradation data from laboratory scale column experiments. Model inversion is achieved using non-linear regression with a shuffled complex evolution optimization algorithm and parameter uncertainty is assessed using a Bayesian uncertainty analysis procedure.
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a forward particle tracking eulerian lagrangian localized Adjoint Method for solution of the contaminant transport equation in three dimensions
Advances in Water Resources, 2002Co-Authors: Philip John Binning, Michael A CeliaAbstract:Abstract The contaminant transport equation is solved in three dimensions using the Eulerian–Lagrangian Localized Adjoint Method (ELLAM). Trilinear and finite volume test functions defined by the characteristics of the governing equation are employed and compared. Integrations are simplified by forward tracking of integration points along the characteristics. The resulting equations are solved using a preconditioned conjugate gradient Method. The algorithm is coupled to a block-centered finite difference approximation of the groundwater flow equation similar to that used in the popular MODFLOW code. The ELLAM is tested by comparison with 1D and 3D analytic solutions. The Method is then applied with random, spatially correlated hydraulic conductivities in a simulation of a tracer experiment performed on Cape Cod, Massachusetts. The linear test function ELLAM was found to perform better than the finite volume ELLAM. Both ELLAM formulations were found to be robust, computationally efficient and relatively straightforward to implement. When compared to traditional particle tracking and characteristics codes commonly used with MODFLOW, the ELLAM retains the computational advantages of traditional characteristic Methods with the added advantage of good mass conservation.
Wei Liu - One of the best experts on this subject based on the ideXlab platform.
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optimal design of an indoor environment by the cfd based Adjoint Method with area constrained topology and cluster analysis
Building and Environment, 2018Co-Authors: Xingwang Zhao, Wei Liu, Dayi Lai, Qingyan ChenAbstract:Abstract An indoor environment should be designed to provide occupants with a desirable level of thermal comfort and air quality. The optimal design of an indoor environment can be achieved by using the computational fluid dynamics (CFD)-based Adjoint Method to determine the size, locations, and shape of air supply inlets, and the air supply parameters (i.e., velocity, temperature, and angle). However, the optimal design may involve a large number of air supply inlets, which would be impractical to implement. This investigation developed an area-constrained topology and cluster analysis to consolidate multiple air supply inlets into a limited number and to determine their size and locations. The desired indoor environment can be maintained by further optimizing the air supply inlet shape and parameters. This investigation demonstrated the Method's capability by applying it to a two-person office and a single-aisle, fully-occupied aircraft cabin. The optimal thermal comfort conditions around the occupants can be achieved with a limited number of air supply inlets at appropriate locations.
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development of a fast fluid dynamics based Adjoint Method for the inverse design of indoor environments
Journal of Building Performance Simulation, 2017Co-Authors: Wei Liu, Ruoyu You, Jie Zhang, Qingyan ChenAbstract:The computational fluid dynamics (CFD)-based Adjoint Method may be appropriate for the inverse design of indoor environments, considering both accuracy and efficiency, but a single design still requires tens of hours with the use of a personal computer. To speed up the inverse design process, this study evaluated four fast fluid dynamics (FFD) models in terms of solving the Navier–Stokes equations, integration with turbulence models, and solving the Adjoint equations. This study implemented the FFD solvers in OpenFOAM and validated them for predicting steady-state and transient indoor airflow. This study then validated the FFD solvers for solving the Adjoint equations and the FFD-based Adjoint Method for inverse identification problems and inverse designs in indoor environments. The results showed that FFD was 20 times faster than CFD in predicting transient indoor airflow, and similar computational accuracy could be maintained; the FFD-based Adjoint Method was 4–16 times faster than the CFD-based Adjoint...
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inverse design of the thermal environment in an airliner cabin by use of the cfd based Adjoint Method
Energy and Buildings, 2015Co-Authors: Wei Liu, Qingyan Chen, Ran Duan, Chun Chen, Chaohsin LinAbstract:Abstract The current thermal environments in airliner cabins may not provide satisfactory comfort levels, and the design of these environments should be improved. This study aimed to design a desirable thermal environment for a single-aisle airliner cabin and used the CFD-based Adjoint Method to find the optimal design variables of air supply locations, size, and parameters. The design variables are used as the boundary conditions for solving the Navier–Stokes equations. By setting the occupant region as the design domain with a minimal predicted mean vote for thermal comfort, this study aimed to determine the corresponding air supply conditions for mixing and displacement ventilation systems under summer and winter conditions. The results show that it is possible to find the optimal air supply conditions in fewer than 10 design cycles if the initial conditions for design variables are provided within a reasonable range. This design Method has a high computing efficiency as it takes one hour for a design cycle using a 16-core cluster. In addition, the results show that a displacement ventilation system provides a better thermal comfort level than a mixing ventilation system.
Perolof Persson - One of the best experts on this subject based on the ideXlab platform.
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an Adjoint Method for a high order discretization of deforming domain conservation laws for optimization of flow problems
Journal of Computational Physics, 2016Co-Authors: Matthew J Zahr, Perolof PerssonAbstract:The fully discrete Adjoint equations and the corresponding Adjoint Method are derived for a globally high-order accurate discretization of conservation laws on parametrized, deforming domains. The conservation law on the deforming domain is transformed into one on a fixed reference domain by the introduction of a time-dependent mapping that encapsulates the domain deformation and parametrization, resulting in an Arbitrary LagrangianEulerian form of the governing equations. A high-order discontinuous Galerkin Method is used to discretize the transformed equation in space and a high-order diagonally implicit RungeKutta scheme is used for the temporal discretization. Quantities of interest that take the form of spacetime integrals are discretized in a solver-consistent manner. The corresponding fully discrete Adjoint Method is used to compute exact gradients of quantities of interest along the manifold of solutions of the fully discrete conservation law. These quantities of interest and their gradients are used in the context of gradient-based PDE-constrained optimization.The Adjoint Method is used to solve two optimal shape and control problems governed by the isentropic, compressible NavierStokes equations. The first optimization problem seeks the energetically optimal trajectory of a 2D airfoil given a required initial and final spatial position. The optimization solver, driven by gradients computed via the Adjoint Method, reduced the total energy required to complete the specified mission nearly an order of magnitude. The second optimization problem seeks the energetically optimal flapping motion and time-morphed geometry of a 2D airfoil given an equality constraint on the x-directed impulse generated on the airfoil. The optimization solver satisfied the impulse constraint to greater than 8 digits of accuracy and reduced the required energy between a factor of 2 and 10, depending on the value of the impulse constraint, as compared to the nominal configuration. Globally high-order discretization of deforming domain PDE (DG-in-space, RK-in-time).Solver-consistent integration of quantities of interest ensures globally high-order.Derived corresponding fully discrete Adjoint equation/Method for computing gradients.Enables gradient-based optimal control, shape, time-morphed geometries of PDEsEnergetically optimal time-morphed geometry and control for foil in viscous flow.
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high order time dependent aerodynamic optimization using a discontinuous galerkin discretization of the navier stokes equations
54th AIAA Aerospace Sciences Meeting, 2016Co-Authors: Matthew J Zahr, Perolof PerssonAbstract:The fully discrete Adjoint Method, corresponding to a globally high-order accurate discretization of the compressible Navier-Stokes equations on deforming domains, is introduced. A mapping-based Arbitrary Lagrangian-Eulerian description transforms the governing equations to a fixed reference domain. A high-order discontinuous Galerkin spatial discretization and diagonally implicit Runge-Kutta temporal discretization are employed to obtain the globally high-order discretization of the Navier-Stokes equations. Relevant quantities of interest, to be used as the objective function in aerodynamic trajectory optimization problems, are discretized in a solver-consistent manner. Gradients of these quantities of interest are computed via the Adjoint Method and verified against a secondorder finite difference approximation. The proposed fully discrete Adjoint Method is coupled with state-of-the-art, gradient-based numerical optimization software to solve aerodynamic trajectory optimization problems. The first example is an inverse design problem with a known, global optimum that the solver is able to recover in fewer than 20 iterations. In a second problem, a trajectory is determined that successfully completes a prescribed mission while harvesting energy from the flow.
Thomas F. Russell - One of the best experts on this subject based on the ideXlab platform.
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solution of the advection dispersion equation in two dimensions by a finite volume eulerian lagrangian localized Adjoint Method
Advances in Water Resources, 1998Co-Authors: Richard W Healy, Thomas F. RussellAbstract:We extend the finite-volume Eulerian-Lagrangian localized Adjoint Method (FVELLAM) for solution of the advection-dispersion equation to two dimensions. The Method can conserve mass globally and is not limited by restrictions on the size of the grid Peclet or Courant number. Therefore, it is well suited for solution of advection-dominated ground-water solute transport problems. In test problem comparisons with standard finite differences, FVELLAM is able to attain accurate solutions on much coarser space and time grids. On fine grids, the accuracy of the two Methods is comparable. A critical aspect of FVELLAM (and all other ELLAMs) is evaluation of the mass storage integral from the preceding time level. In FVELLAM this may be accomplished with either a forward or backtracking approach. The forward tracking approach conserves mass globally and is the preferred approach. The backtracking approach is less computationally intensive, but not globally mass conservative. Boundary terms are systematically represented as integrals in space and time which are evaluated by a common integration scheme in conjunction with forward tracking through time. Unlike the one-dimensional case, local mass conservation cannot be guaranteed, so slight oscillations in concentration can develop, particularly in the vicinity of inflow or outflow boundaries.
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eulerian lagrangian localized Adjoint Method the theoretical framework
Numerical Methods for Partial Differential Equations, 1993Co-Authors: Ismael Herrera, Richard E. Ewing, Michael A Celia, Thomas F. RussellAbstract:This is the second of a sequence of papers devoted to applying the localized Adjoint Method (LAM), in space-time, to problems of advective-diffusive transport. We refer to the resulting Methodology as the Eulerian-Lagrangian localized Adjoint Method (ELLAM). The ELLAM approach yields a general formulation that subsumes many specific Methods based on combined Lagrangian and Eulerian approaches, so-called characteristic Methods (CM). In the first paper of this series the emphasis was placed in the numerical implementation and a careful treatment of implementation of boundary conditions was presented for one-dimensional problems. The final ELLAM approximation was shown to possess the conservation of mass property, unlike typical characteristic Methods. The emphasis of the present paper is on the theoretical aspects of the Method. The theory, based on Herrera's algebraic theory of boundary value problems, is presented for advection-diffusion equations in both one-dimensional and multidimensional systems. This provides a generalized ELLAM formulation. The generality of the Method is also demonstrated by a treatment of systems of equations as well as a derivation of mixed Methods. © 1993 John Wiley & Sons, Inc.
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a finite volume eulerian lagrangian localized Adjoint Method for solution of the advection dispersion equation
Water Resources Research, 1993Co-Authors: Richard W Healy, Thomas F. RussellAbstract:A new mass-conservative Method for solution of the one-dimensional advection-dispersion equation is derived and discussed. Test results demonstrate that the finite-volume Eulerian-Lagrangian localized Adjoint Method (FVELLAM) outperforms standard finite-difference Methods, in terms of accuracy and efficiency, for solute transport problems that are dominated by advection. For dispersion-dominated problems, the performance of the Method is similar to that of standard Methods. Like previous ELLAM formulations, FVELLAM systematically conserves mass globally with all types of boundary conditions. FVELLAM differs from other ELLAM approaches in that integrated finite differences, instead of finite elements, are used to approximate the governing equation. This approach, in conjunction with a forward tracking scheme, greatly facilitates mass conservation. The mass storage integral is numerically evaluated at the current time level, and quadrature points are then tracked forward in time to the next level. Forward tracking permits straightforward treatment of inflow boundaries, thus avoiding the inherent problem in backtracking, as used by most characteristic Methods, of characteristic lines intersecting inflow boundaries. FVELLAM extends previous ELLAM results by obtaining mass conservation locally on Lagrangian space-time elements. Details of the integration, tracking, and boundary algorithms are presented. Test results are given for problems in Cartesian and radial coordinates.