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October 2016 - present
January 2015 - September 2016
Publications
Publications (52)
This work focuses on the heat flux prediction in hypersonic flow regimes using the finite-element based Streamline-Upwind Petrov–Galerkin formulation enhanced with a discontinuity-capturing operator and weak enforcement of the Dirichlet boundary condition. The numerical formulation is validated on several benchmark cases including Mach 14 compressi...
The High Fidelity CFD Workshop was held on January 8-9, 2022, and covered a range of test cases focused on verification. The present paper contains a summary of the test case focused on smooth body separation prediction using wall-modeled large eddy simulation, to which 11 participant teams submitted blind predictions.
The superior accuracy isogeometric analysis (IGA) brought to computations in fluid and solid mechanics has been yielding higher fidelity in computational aerodynamics. The increased accuracy we achieve with the IGA is in the flow solution, in representing the problem geometry, and, when we use the IGA basis functions also in time in a space–time (S...
A numerical study of the free-surface flow over a vertical-axis hydrokinetic turbine with different blade-strut configurations is presented in this paper. The set of equations governing this multi-fluid flow consists of the Navier–Stokes equations and an advection equation of the signed distance function which describes the motion of the air–water...
This work presents a strongly-coupled fluid–structure interaction (FSI) formulation for compressible flows that is developed based on an augmented Lagrangian approach. The method is suitable for handling problems that involve nonmatching fluid–structure interface discretizations. In this work, the fluid is modeled using a stabilized finite element...
Numerical modeling of stratified boundary layer over complex terrain has been an ongoing challenge in the field of environmental fluid dynamics. In this work, we present a computational framework aiming to tackle that challenge. The key components of the framework are residual-based variational multiscale method, isogeometric analysis, and weak imp...
In this work, we propose and validate a new stabilized compressible flow finite element framework for the simulation of aerospace applications. The framework is comprised of the streamline upwind/Petrov–Galerkin (SUPG)-based Navier–Stokes equations for compressible flows, the weakly enforced essential boundary conditions that act as a wall function...
This study investigates the performance and near-wake characteristics of a full-scale vertical-axis hydrokinetic turbine under a uniform inflow and turbulent inflow with a 5% and 10% turbulence intensity. The governing equations of the flow field are the incompressible Navier–Stokes equations expressed within an arbitrary Lagrangian–Eulerian framew...
This work presents a Streamline-Upwind Petrov–Galerkin (SUPG) framework with finite elements discretization for the prediction of non-ionized hypersonic flows in thermal non-equilibrium. The formulation is enhanced with a residual-based discontinuity-capturing (DC) operator. The numerical framework solves the set of Navier–Stokes equations for the...
View Video Presentation: https://doi.org/10.2514/6.2022-3347.vid Verification and validation of computational fluid dynamics (CFD) and a quasi 1D ejector-ramjet (ERAM) solver are presented for the analysis of an ejector-ramjet. A custom OpenFOAM computational fluid dynamics solver, pimpleCentralFOAM, with extended capabilities is shown to be able t...
The formation of recirculation zones in confined jet flows was investigated numerically using large eddy simulation (LES) with the wall-adapting local eddy-viscosity (WALE) subgrid model and Reynolds-Averaged Navier-Stokes (RANS) simulations with a k-ω shear stress transport (SST) turbulence model. Accuracy and robustness of the turbulence closure...
View Video Presentation: https://doi.org/10.2514/6.2022-1077.vid The objective of this work is to investigate and validate a new stabilized compressible flow finite element framework for the simulation of aerospace applications. The framework is comprised of the streamline upwind/Petrov–Galerkin (SUPG)-based Navier–Stokes equations for compressible...
Small supersonic vehicle concepts used as research platforms to test new aerospace technologies, such as advanced propulsion systems or large sensor payloads, require major modifications to conventional, large-scale, manned, supersonic airframe design. High-fidelity numerical simulation of these concepts in academic settings often requires the use...
Modelling the dispersion and deposition of expelled particles in an indoor environment is presented in this paper. The airflow is described by the incompressible Navier–Stokes equations, and the dispersion of a group of particles is modelled through an Eulerian transport equation coupled to the system of Navier–Stokes equations. The turbulent airfl...
Wall-function-based weak imposition of Dirichlet boundary condition (WFWD) has seen success in maintaining numerical accuracy with reduced near-wall resolution for modeling wall-bounded turbulent flows. In this work, we extend the formulation of WFWD to stably stratified flows. The performance of the extended formulation is validated with two canon...
View Video Presentation: https://doi.org/10.2514/6.2021-2415.vid A verification and validation assessment of an open-source framework, the Stanford University Aerospace Vehicle Environment (SUAVE), and its individual modules, for the multidisciplinary design and optimization of small-scale, supersonic, unmanned aerial vehicles (UAVs) was performed....
A numerical approach for modelling cavitating flows over moving hydrodynamic surfaces is presented. The operating fluid is modelled as an isothermal homogeneous mixture of water vapor and liquid phases. The flow field is governed by the Navier–Stokes equations along with a transport equation for the vapor volume fraction. The Arbitrary Lagrangian-E...
A stabilized finite element framework for high-speed compressible flows is presented. The Streamline-Upwind/Petrov–Galerkin formulation augmented with discontinuity-capturing (DC) are the main constituents of the framework that enable accurate, efficient, and stable simulations in this flow regime. Full- and reduced-energy formulations are employed...
A residual-based variational multi-scale (VMS) modeling framework is applied to simulate atmospheric flow over complex environmental terrains. The VMS framework is verified and validated using two test cases using linear finite element (FEM) and quadratic non-uniform rational B-spline (NURBS) discretizations. First, the flow over the 3D, axisymmetr...
Computational flow analysis is now playing a key role in aerospace, energy and transportation technologies, bringing solution in challenging problems such as aerodynamics of parachutes, thermo-fluid analysis of ground vehicles and tires, and fluid–structure interaction (FSI) analysis of wind turbines. The computational challenges include complex ge...
A numerical formulation for the modeling of turbulent cavitating flows is presented. The flow field is governed by the 3D, time-dependent Navier–Stokes equations for a compressible isothermal mixture. The Arbitrary Lagrangian–Eulerian Variational Multiscale (ALE-VMS) formulation is adopted to model the turbulent flow on moving domains with no-slip...
With the recent advances in the variational multiscale (VMS) methods, computational ow analysis in aerospace, energy, and transportation technologies has reached a high level of sophistication. It is bringing solutions in challenging problems such as the aerodynamics ofparachutes, thermo-fluid analysis of ground vehicles and tires, and fluid-struct...
The performance prediction of two counter-rotating vertical axis hydrokinetic turbines is presented in this paper. The flow field is governed by the 3D time-dependent incompressible Navier–Stokes equations. The system of equations is discretized using the Arbitrary Lagrangian-Eulerian Variational Multi-scale formulation for turbulence modeling on m...
The actuator line method is implemented into a residual-based variational multiscale (VMS) fluid modelling framework to simulate airflow around a wind turbine. In the actuator line method, the turbine blades are represented as rotating lines of body force applied to the flow field. The NREL 5MW turbine is simulated first to validate the model for a...
We describe the recent advances made by our teams in ALE-VMS and ST-VMS computational aerodynamic and fluid-structure interaction (FSI) analysis of wind turbines. The ALE-VMS method is the variational multiscale version of the Arbitrary Lagrangian-Eulerian method. The VMS components are from the residual-based VMS method. The ST-VMS method is the V...
This is the first part of a two-part article on computer modeling of wind turbines. We describe the recent advances made by our teams in ALE-VMS and ST-VMS computational aerodynamic and fluid–structure interaction (FSI) analysis of wind turbines. The ALE-VMS method is the variational multiscale version of the Arbitrary Lagrangian–Eulerian method. T...
This article reviews state-of-the-art numerical techniques for fluid–structure interaction (FSI) of full-scale wind-turbine systems. Simulation of floating wind turbines subjected to combined wind-flow and ocean-wave forcing, and modeling of high-cycle fatigue failure of blades due to long-term cyclic aerodynamic loading, are the focal points of th...
Aeroelastic analysis is a major task in the design of long-span bridges, and recent developments in computer power and technology have made Computational Fluid Dynamics (CFD) an important supplement to wind tunnel experiments. In this paper, we employ the Finite Element Method (FEM) with an effective mesh-moving algorithm to simulate the forced-vib...
This article reviews state-of-the-art numerical techniques for fluid–structure interaction (FSI) of full-scale wind-turbine systems. Simulation of floating wind turbines subjected to combined wind-flow and ocean-wave forcing, and modeling of high-cycle fatigue failure of blades due to long-term cyclic aerodynamic loading are the focal points of thi...
The paper presents aerodynamic and fluid–structure interaction (FSI) simulations of two back-to-back 5 MW horizontal-axis wind turbines (HAWTs) at full scale and with full geometrical complexity operating in a stably-stratified atmospheric boundary layer (ABL) flow. The numerical formulation for stratified incompressible flows is based on the ALE-V...
For geophysical and environmental flows in the high-Reynolds-number regime, stable density stratification strongly affects the turbulent fluid motions. While turbulent flows, due to the presence of a cascade of spatial and temporal scales, present several challenges to accurate numerical approximation, density stratification in these flows exacerba...
In this chapter the numerical challenges of simulating aerodynamics and fluid–structure interaction (FSI) of wind turbines are summarized, and the recently developed computational methods that address these challenges are presented. Several wind-turbine computations at full scale and with full complexity of the geometry and material composition are...
A computational free-surface flow framework that enables 3D, time-dependent simulation of horizontal-axis tidal-stream turbines (HATTs) is presented and deployed using a complex-geometry HATT. Free-surface flow simulations using the proposed framework, without any empiricism, are able to accurately capture the effect of the free surface on the hydr...
This work presents a collection of advanced computational methods, and their coupling, that enable prediction of fatigue-damage evolution in full-scale composite blades of wind turbines operating at realistic wind and rotor speeds. The numerical methodology involves: (1) a recently developed and validated fatigue-damage model for multilayer fiber-r...
In this paper, we propose a computational fluid–structure interaction (FSI) framework for the simulations of the interaction between free-surface flow and floating structures, such as offshore wind turbines. The framework is based on a suitable combination of the finite element method (FEM) and isogeometric analysis (IGA), and has good efficiency,...
In this paper, we combine recent developments in modeling of fatigue-damage, isogeometric analysis (IGA) of thin-shell structures, and structural health monitoring (SHIM) to develop a computational steering framework for fatigue-damage prediction in foil-scale laminated composite structures. The main constituents of' the proposed framework are desc...
A numerical formulation for incompressible flows with stable stratification is developed using the framework of variational multiscale methods. In the proposed formulation, both density and temperature stratification are handled in a unified manner. The formulation is augmented with weakly-enforced essential boundary conditions and is suitable for...
A propulsion system based on tandem hydrofoils is studied experimentally and numerically. An experimen-tal measurement system is developed to extract hydrody-namic loads on the foils and capture their twisting defor-mation during operation. The measured data allowed us to assess the efficiency of the propulsion system as a function of travel speed...
Full-scale, 3D, time-dependent aerodynamics and fluid–structure interaction (FSI) simu-lations of a Darrieus-type vertical-axis wind turbine (VAWT) are presented. A structural model of the Windspire VAWT (Windspire energy, http://www.windspireenergy.com/) is developed, which makes use of the recently proposed rotation-free Kirchhoff–Love shell and...
In this paper, we target more advanced fluid–structure interaction (FSI) simulations of wind turbines than reported previously. For this, we illustrate how the recent advances in isogeometric analysis of thin structures may be used for efficient structural mechanics modeling of full wind turbine structures, including tower, nacelle, and blades. We...
A large-deformation, isogeometric rotation-free Kirchhoff–Love shell formulation is equipped with a damage model to efficiently and accurately simulate progressive failure in laminated composite structures. The damage model consists of Hashin’s theory of damage initiation, a bilinear material model for damage evolution, and an appropriately chosen...
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 us...
A fluid–structure interaction (FSI) validation study of the Micon 65/13M wind turbine with Sandia CX-100 composite blades is presented. A rotation-free isogeometric shell formulation is used to model the blade structure, while the aerodynamics formulation makes use of the FEM-based ALE-VMS method. The structural mechanics formulation is validated b...