Browsing by Author "Aliseda, Alberto"

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    Experimental and Numerical Analysis of a Scale-Model Horizontal Axis Hydrokinetic Turbine
    Javaherchi, Teymour; Seydel, Joseph; Stelzenmuller, Nick; Aliseda, Alberto (2014-04)
    This paper presents an experimental/numerical study of a scale-model Horizontal Axis Hydrokinetic Turbine (HAHT). The model turbine is based on the DOE Reference Model 1 (DOE RM1), with a modified geometry to reproduce performance at the flume scale Reynolds numbers. These modifications were necessary to overcome the strong Reynolds number effect on the NACA–6 airfoil family used on the design, and therefore on the device performance in experimental analysis. The performance and wake structure of a single turbine was analyzed with measurements conducted on a 45:1 scale physical model of the modified design of the DOE RM1 rotor. The details of the rotor flow field and wake evolution are analyzed from numerical solution of the RANS equations solved around a computational model of the scale-model turbine. A comparison between the experimental and numerical results is presented. These comparisons highlight the strengths as well as limitations of the experimental and numerical analysis for these types of HAHT characterizations. On a more general sense, these comparisons provide useful guidelines for developing a set of experimental flume scale data and to use it to validate numerical tools, and as pilot projects start to go in the water in the US, to perform a similar type of analysis and design validation of full scale devices.
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    Simulation of Hydrokinetic Turbines in Turbulent Flow Using Vortex Particle Methods
    Sale, Danny; Aliseda, Alberto; Li, Ye (2014-04)
    This work presents the development of computational models that capture vorticity generation and turbulent diffusion within wind and hydrokinetic turbine farms. The use of vortex methods is examined as an alternative for modeling turbulent wakes and rotor-wake interaction. The vorticity-velocity formulation of the Navier-Stokes equations are simulated by a hybrid Lagrangian-Eulerian method involving both fluid particles that carry vorticity and mesh discretizations which enable an efficient solution to N-body vorticity dynamics. A "mesh free" particle-strength-exchange (PSE) algorithm and a "particle-mesh" vortex-in-cell (VIC) algorithm are implemented for a series of benchmarks to verify the simulation method for low Reynolds number flows, including: vortex ring dynamics, flow over bluff bodies, and a 3D wing. These examples are presented on a variety of computer architectures, with support for distributed-memory parallelism, multi-core, and GPGPU computing. The scalability and stability of these proposed vortex methods shows potential for modeling the large range of scales present between rotor-scale and farm-scale hydrodynamics. The desired feature of this methodology is faithful prediction of unsteady phenomenon, capture of vortex shedding, and tracking the evolution of vortical structures as they evolve and interact with immersed structures and ambient turbulent flow.