Open Access. Powered by Scholars. Published by Universities.®
- Keyword
-
- Isogeometric analysis (6)
- NURBS (6)
- Fluid-structure interaction (4)
- Turbomachine blades (4)
- Heat transfer (3)
-
- Wind turbine rotor (3)
- Aerodynamic torque (2)
- Anisotropy (2)
- Buoyancy (2)
- Cooling (2)
- Finite elements (2)
- Mathematical models (2)
- NREL Phase Vi (2)
- Reynolds number (2)
- Rotation-free shells (2)
- Shear flow (2)
- Stratified flow (2)
- Turbulence modeling (2)
- Turbulence models (2)
- Turbulent flow (2)
- Wind turbine aerodynamics (2)
- ALE-VMS formulation (1)
- ALE-VMS methood (1)
- ALI_VMS (1)
- Adiabatic effectiveness (1)
- Advecion-diffusion equation (1)
- Bifurcation (mathematics (1)
- Bifurcation analyses (1)
- Blade pre-bending (1)
- Blade-tower interaction (1)
- Publication Year
Articles 1 - 22 of 22
Full-Text Articles in Mechanical Engineering
Aerodynamic Simulation Of Vertical-Axis Wind Turbines, A. Korobenko, Ming-Chen Hsu, I. Akkerman, Y. Bazilevs
Aerodynamic Simulation Of Vertical-Axis Wind Turbines, A. Korobenko, Ming-Chen Hsu, I. Akkerman, Y. Bazilevs
Ming-Chen Hsu
Full-scale, 3D, time-dependent aerodynamics modeling and simulation of a Darrieus-type vertical-axis wind turbine (VAWT) is presented. The simulations are performed using a moving-domain finite-element-based ALE-VMS technique augmented with a sliding-interface formulation to handle the rotor-stator interactions present. We simulate a single VAWT using a sequence of meshes with increased resolution to assess the computational requirements for this class of problems. The computational results are in good agreement with experimental data. We also perform a computation of two side-by-side counterrotating VAWTs to illustrate how the ALE-VMS technique may be used for the simulation of multiple turbines placed in arrays.
Finite Element Simulation Of Wind Turbine Aerodynamics: Validation Study Using Nrel Phase Vi Experiment, Ming-Chen Hsu, Ido Akkerman, Yuri Bazilevs
Finite Element Simulation Of Wind Turbine Aerodynamics: Validation Study Using Nrel Phase Vi Experiment, Ming-Chen Hsu, Ido Akkerman, Yuri Bazilevs
Ming-Chen Hsu
A validation study using the National Renewable Energy Laboratory (NREL) Phase VI wind turbine is presented. The aerodynamics simulations are performed using the finite element arbitrary Lagrangian–Eulerian–variational multiscale formulation augmented with weakly enforced essential boundary conditions. In all cases, the rotor is assumed to be rigid and its rotation is prescribed. The rotor-only simulations are performed for a wide range of wind conditions, and the computational results compare favorably with the experimental findings in all cases. The sliding-interface method is adopted for the simulation of the full wind turbine configuration. The full-wind-turbine simulations capture the blade–tower interaction effect, and the …
Blended Isogeometric Shells, D. J. Benson, S. Hartmann, Y. Bazilevs, Ming-Chen Hsu, T.J.R. Hughes
Blended Isogeometric Shells, D. J. Benson, S. Hartmann, Y. Bazilevs, Ming-Chen Hsu, T.J.R. Hughes
Ming-Chen Hsu
We propose a new isogeometric shell formulation that blends Kirchhoff–Love theory with Reissner–Mindlin theory. This enables us to reduce the size of equation systems by eliminating rotational degrees of freedom while simultaneously providing a general and effective treatment of kinematic constraints engendered by shell intersections, folds, boundary conditions, the merging of NURBS patches, etc. We illustrate the blended theory’s performance on a series of test problems.
Isogeometric Fluid–Structure Interaction Analysis With Emphasis On Non-Matching Discretizations, And With Application To Wind Turbines, Y. Bazilevs, Ming-Chen Hsu, M. A. Scott
Isogeometric Fluid–Structure Interaction Analysis With Emphasis On Non-Matching Discretizations, And With Application To Wind Turbines, Y. Bazilevs, Ming-Chen Hsu, M. A. Scott
Ming-Chen Hsu
In this paper we develop a framework for fluid–structure interaction (FSI) modeling and simulation with emphasis on isogeometric analysis (IGA) and non-matching fluid–structure interface discretizations. We take the augmented Lagrangian approach to FSI as a point of departure. Here the Lagrange multiplier field is defined on the fluid–structure interface and is responsible for coupling of the two subsystems. Thus the FSI formulation does not rely on the continuity of the underlying function spaces across the fluid–structure interface in order to produce the correct coupling conditions between the fluid and structural subdomains. However, in deriving the final FSI formulation the interface …
Wind Turbine Aerodynamics Using Ale–Vms: Validation And The Role Of Weakly Enforced Boundary Conditions, Ming-Chen Hsu, Ido Akkerman, Yuri Bazilevs
Wind Turbine Aerodynamics Using Ale–Vms: Validation And The Role Of Weakly Enforced Boundary Conditions, Ming-Chen Hsu, Ido Akkerman, Yuri Bazilevs
Ming-Chen Hsu
In this article we present a validation study involving the full-scale NREL Phase VI two-bladed wind turbine rotor. The ALE–VMS formulation of aerodynamics, based on the Navier–Stokes equations of incompressible flows, is employed in conjunction with weakly enforced essential boundary conditions. We find that the ALE–VMS formulation using linear tetrahedral finite elements is able to reproduce experimental data for the aerodynamic (low-speed shaft) torque and cross-section pressure distribution of the NREL Phase VI rotor. We also find that weak enforcement of essential boundary conditions is critical for obtaining accurate aerodynamics results on relatively coarse boundary layer meshes. The proposed numerical …
Ale-Vms And St-Vms Methods For Computer Modeling Of Wind-Turbine Rotor Aerodynamics And Fluid–Structure Interaction, Yuri Bazilevs, Ming-Chen Hsu, Kenji Takizawa, Tayfun E. Tezduyar
Ale-Vms And St-Vms Methods For Computer Modeling Of Wind-Turbine Rotor Aerodynamics And Fluid–Structure Interaction, Yuri Bazilevs, Ming-Chen Hsu, Kenji Takizawa, Tayfun E. Tezduyar
Ming-Chen Hsu
We provide an overview of the Arbitrary Lagrangian–Eulerian Variational Multiscale (ALE-VMS) and Space–Time Variational Multiscale (ST-VMS) methods we have developed for computer modeling of wind-turbine rotor aerodynamics and fluid–structure interaction (FSI). The related techniques described include weak enforcement of the essential boundary conditions, Kirchhoff–Love shell modeling of the rotor-blade structure, NURBS-based isogeometric analysis, and full FSI coupling. We present results from application of these methods to computer modeling of NREL 5MW and NREL Phase VI wind-turbine rotors at full scale, including comparison with experimental data.
3d Simulation Of Wind Turbine Rotors At Full Scale. Part Ii: Fluid–Structure Interaction Modeling With Composite Blades, Y. Bazilevs, Ming-Chen Hsu, J. Kiendel, R. Wuchner, K. U. Bletzigner
3d Simulation Of Wind Turbine Rotors At Full Scale. Part Ii: Fluid–Structure Interaction Modeling With Composite Blades, Y. Bazilevs, Ming-Chen Hsu, J. Kiendel, R. Wuchner, K. U. Bletzigner
Ming-Chen Hsu
In this two-part paper, we present a collection of numerical methods combined into a single framework, which has the potential for a successful application to wind turbine rotor modeling and simulation. In Part 1 of this paper we focus on: 1. The basics of geometry modeling and analysis-suitable geometry construction for wind turbine rotors; 2. The fluid mechanics formulation and its suitability and accuracy for rotating turbulent flows; 3. The coupling of air flow and a rotating rigid body. In Part 2, we focus on the structural discretization for wind turbine blades and the details of the fluid–structure interaction computational …
High-Performance Computing Of Wind Turbine Aerodynamics Using Isogeometric Analysis, Ming-Chen Hsu, Ido Akkerman, Yuri Bazilevs
High-Performance Computing Of Wind Turbine Aerodynamics Using Isogeometric Analysis, Ming-Chen Hsu, Ido Akkerman, Yuri Bazilevs
Ming-Chen Hsu
In this article we present a high-performance computing framework for advanced flow simulation and its application to wind energy based on the residual-based variational multiscale (RBVMS) method and isogeometric analysis. The RBVMS formulation and its suitability and accuracy for turbulent flow in a moving domain are presented. Particular emphasis is placed on the parallel implementation of the methodology and its scalability. Two challenging flow cases were considered: the turbulent Taylor–Couette flow and the NREL 5 MW offshore baseline wind turbine rotor at full scale. In both cases, flow quantities of interest from the simulation results compare favorably with the reference …
3d Simulation Of Wind Turbine Rotors At Full Scale. Part I: Geometry Modeling And Aerodynamics, Y. Bazilevs, Ming-Chen Hsu, I. Akkerman, S. Wright, K. Takizawa, B. Henicke, T. Spielman, T. E. Tezduyar
3d Simulation Of Wind Turbine Rotors At Full Scale. Part I: Geometry Modeling And Aerodynamics, Y. Bazilevs, Ming-Chen Hsu, I. Akkerman, S. Wright, K. Takizawa, B. Henicke, T. Spielman, T. E. Tezduyar
Ming-Chen Hsu
In this two-part paper we present a collection of numerical methods combined into a single framework, which has the potential for a successful application to wind turbine rotor modeling and simulation. In Part 1 of this paper we focus on: 1. The basics of geometry modeling and analysis-suitable geometry construction for wind turbine rotors; 2. The fluid mechanics formulation and its suitability and accuracy for rotating turbulent flows; 3. The coupling of air flow and a rotating rigid body. In Part 2 we focus on the structural discretization for wind turbine blades and the details of the fluid–structure interaction computational …
The Bending Strip Method For Isogeometric Analysis Of Kirchhoff–Love Shell Structures Comprised Of Multiple Patches, J. Kiendel, Y. Bazilevs, Ming-Chen Hsu, R. Wuchner, K. U. Bletzigner
The Bending Strip Method For Isogeometric Analysis Of Kirchhoff–Love Shell Structures Comprised Of Multiple Patches, J. Kiendel, Y. Bazilevs, Ming-Chen Hsu, R. Wuchner, K. U. Bletzigner
Ming-Chen Hsu
In this paper we present an isogeometric formulation for rotation-free thin shell analysis of structures comprised of multiple patches. The structural patches are C1- or higher-order continuous in the interior, and are joined with C0-continuity. The Kirchhoff–Love shell theory that relies on higher-order continuity of the basis functions is employed in the patch interior as presented in Kiendl et al. [36]. For the treatment of patch boundaries, a method is developed in which strips of fictitious material with unidirectional bending stiffness and zero membrane stiffness are added at patch interfaces. The direction of bending stiffness is chosen to be transverse …
Improving Stability Of Stabilized And Multiscale Formulations In Flow Simulations At Small Time Steps, Ming-Chen Hsu, Y. Bazilevs, V. M. Calo, T. E. Tezduyar, T.J.R. Hughes
Improving Stability Of Stabilized And Multiscale Formulations In Flow Simulations At Small Time Steps, Ming-Chen Hsu, Y. Bazilevs, V. M. Calo, T. E. Tezduyar, T.J.R. Hughes
Ming-Chen Hsu
The objective of this paper is to show that use of the element-vector-based definition of stabilization parameters, introduced in [T.E. Tezduyar, Computation of moving boundaries and interfaces and stabilization parameters, Int. J. Numer. Methods Fluids 43 (2003) 555–575; T.E. Tezduyar, Y. Osawa, Finite element stabilization parameters computed from element matrices and vectors, Comput. Methods Appl. Mech. Engrg. 190 (2000) 411–430], circumvents the well-known instability associated with conventional stabilized formulations at small time steps. We describe formulations for linear advection–diffusion and incompressible Navier–Stokes equations and test them on three benchmark problems: advection of an L-shaped discontinuity, laminar flow in a square …
Inverse Design Of And Experimental Measurements In A Double-Passage Transonic Turbine Cascade Model, G. M. Laskowski, A. Vicharelli, G. Medic, C. J. Elkins, J. K. Eaton, Paul A. Durbin
Inverse Design Of And Experimental Measurements In A Double-Passage Transonic Turbine Cascade Model, G. M. Laskowski, A. Vicharelli, G. Medic, C. J. Elkins, J. K. Eaton, Paul A. Durbin
Paul A. Durbin
A new transonic turbine cascade model that accurately produces infinite cascade flow conditions with minimal compressor requirements is presented. An inverse design procedure using the Favre-averaged Navier-Stokes equations and k-ε turbulence model based on the method of steepest descent was applied to a geometry consisting of a single turbine blade in a passage. For a fixed blade geometry, the passage walls were designed such that the surface isentropic Mach number (SIMN) distribution on the blade in the passage matched the SIMN distribution on the blade in an infinite cascade, while maintaining attached flow along both passage walls. An experimental rig …
Unsteady Effects On Trailing Edge Cooling, G. Medic, Paul A. Durbin
Unsteady Effects On Trailing Edge Cooling, G. Medic, Paul A. Durbin
Paul A. Durbin
It is shown how natural and forced unsteadiness play a major role in turbine blade trailing edge cooling flows. Reynolds averaged simulations are presented for a surface jet in coflow, resembling the geometry of the pressure side breakout on a turbine blade. Steady computations show very effective cooling; however when natural-or even moreso, forced-unsteadiness is allowed, the adiabatic effectiveness decreases substantially. Streamwise vortices in the mean flow are found to be the cause of the increased heat transfer.
A Lagrangian Stochastic Model For Dispersion In Stratified Turbulence, S. K. Das, Paul A. Durbin
A Lagrangian Stochastic Model For Dispersion In Stratified Turbulence, S. K. Das, Paul A. Durbin
Paul A. Durbin
In this paper we discuss the development of a Lagrangian stochastic model (LSM) for turbulent dispersion of a scalar (species). Given any tensorally linear second-moment closure (SMC) turbulence model we show how to derive a mathematically equivalent set of stochastic differential equations (SDEs), i.e., the second-moment equations constructed from these SDEs are exactly the same (within a realizability constraint) as the given SMC. This set of equations forms the LSM. Both turbulence anisotropy and buoyancy effects are incorporated by this method. In order to achieve the correct critical Richardson number and to obtain the simplest Lagrangian formulation, a revised set …
On The Equilibrium States Predicted By Second Moment Models In Rotating, Stably Stratified Homogeneous Shear Flow, Minsuk Ji, Paul A. Durbin
On The Equilibrium States Predicted By Second Moment Models In Rotating, Stably Stratified Homogeneous Shear Flow, Minsuk Ji, Paul A. Durbin
Paul A. Durbin
The structural equilibrium behavior of the general linear second-moment closure model in a stably stratified, spanwise rotating homogeneous shear flow is considered with the aid of bifurcation analysis. A closed form equilibrium solution for the anisotropy tensor aij, dispersion tensor Kij, dimensionless scalar variance q2/k (S/Sθ)2, and the ratio of mean to turbulent time scale ε/Sk is found. The variable of particular interest to bifurcation analysis, ε/Sk is shown as a function of the parameters characterizing the body forces: Ω/S (the ratio of the rotation rate to the mean shear rate) for rotation and Rig (the gradient Richardson number) for …
Toward Improved Film Cooling Prediction, G. Medic, Paul A. Durbin
Toward Improved Film Cooling Prediction, G. Medic, Paul A. Durbin
Paul A. Durbin
Computations of flow and heat transfer for a film-cooled high pressure gas turbine rotor blade geometry are presented with an assessment of several turbulence models. Details of flow and temperature field predictions in the vicinity of cooling holes are examined. It is demonstrated that good predictions can be obtained when spurious turbulence energy production by the turbulence model is prevented.
Toward Improved Prediction Of Heat Transfer On Turbine Blades, G. Medic, Paul A. Durbin
Toward Improved Prediction Of Heat Transfer On Turbine Blades, G. Medic, Paul A. Durbin
Paul A. Durbin
Reynolds averaged computations of turbulent flow in a transonic turbine passage are presented to illustrate a manner in which widely used turbulence models sometimes provide poor heat transfer predictions. It is shown that simple, physically and mathematically based constraints can substantially improve those predictions.
Statistical Modeling Of Sprays Using The Droplet Distribution Function, Shankar Subramaniam
Statistical Modeling Of Sprays Using The Droplet Distribution Function, Shankar Subramaniam
Shankar Subramaniam
The theoretical foundations of a statistical spray modeling approach based on the droplet distribution function ~ddf!, which was originally proposed by Williams @Phys. Fluids 1, 541 ~1958!#, are established. The equation governing the ddf evolution is derived using an alternative approach. The unclosed terms in the ddf evolution equation are precisely defined, and the regime of applicability of current models is discussed. The theory of point processes is used to rigorously establish the existence of a disintegration of the ddf in terms of a spray intensity, which is the density of expected number of spray droplets in physical space, and …
Rough Wall Modification Of Two-Layer K-E, Paul A. Durbin, G. Medic, J.-M. Seo, J. K. Eaton, S. Song
Rough Wall Modification Of Two-Layer K-E, Paul A. Durbin, G. Medic, J.-M. Seo, J. K. Eaton, S. Song
Paul A. Durbin
A formulation is developed to apply the two-layer k-ε model to rough surfaces. The approach involves modifying the ℓv formula and the boundary condition on k. A hydrodynamic roughness length is introduced and related to the geometrical roughness through a calibration procedure. An experiment has been conducted to test the model. It provides data on flow over a ramp with and without surface roughness.
Statistical Representation Of A Spray As A Point Process, Shankar Subramaniam
Statistical Representation Of A Spray As A Point Process, Shankar Subramaniam
Shankar Subramaniam
The statistical representation of a spray as a finite point process is investigated. One objective is to develop a better understanding of how single-point statistical information contained in descriptions such as the droplet distribution function ~ddf!, relates to the probability density functions ~pdfs! associated with the droplets themselves. Single-point statistical information contained in the droplet distribution function ~ddf! is shown to be related to a sequence of single surrogate-droplet pdfs, which are in general different from the physical single-droplet pdfs. It is shown that the ddf contains less information than the fundamental single-point statistical representation of the spray, which is …
Minimum Error Fickian Diffusion Coefficients For Mass Diffusion In Multicomponent Gas Mixtures, Shankar Subramaniam
Minimum Error Fickian Diffusion Coefficients For Mass Diffusion In Multicomponent Gas Mixtures, Shankar Subramaniam
Shankar Subramaniam
Mass diffusion in multicomponent gas mixtures is governed by a coupled system of linear equations for the diffusive mass fluxes in terms of thermodynamic driving forces, known as the generalized Stefan–Maxwell equation. In computations of mass diffusion in multicomponent gas mixtures, this coupling between the different components results in considerable computational overhead. Consequently, simplified diffusion models for the diffusive mass fluxes as explicit functions of the driving forces are an attractive alternative. These models can be interpreted as an approximate solution to the Stefan–Maxwell equation. Simplified diffusion models require the specification of “effective” diffusion coefficients which are usually expressed as …
A Mixing Model To Improve The Pdf Simulation Of Turbulent Diffusion Flames, A. R. Masri, Shankar Subramaniam, S. B. Pope
A Mixing Model To Improve The Pdf Simulation Of Turbulent Diffusion Flames, A. R. Masri, Shankar Subramaniam, S. B. Pope
Shankar Subramaniam
A new mixing model based on Euclidean minimum spanning trees (EMST), which has been developed by Subramaniam and Pope, is used in the PDF simulation of pilot-stabilized turbulent non-premixed flames. a model equation is solved for the joint PDF of velocity composition and turbulence frequency using a particle mesh method.