Bulletin of the American Physical Society
62nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 54, Number 19
Sunday–Tuesday, November 22–24, 2009; Minneapolis, Minnesota
Session PQ: Industrial Applications |
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Chair: Suman Muppidi, University of Minnesota Room: 200E |
Tuesday, November 24, 2009 11:40AM - 11:53AM |
PQ.00001: Study of the turbulent wake behind a tidal turbine through different numerical models Amir Teymour Javaherchi Mozafari, Alberto Aliseda, Sylvain Antheaume, Joseph Seydel, Brian Polagye As developing sources of renewable energy becomes a critical priority, research in this field become more essential. A novel method to produce clean renewable energy is extraction from ocean tides via a turbine. Although energy generation from tidal currents has many similarities to wind, the balance between kinetic and potential energy is a key element in tidal channels that invalidates ``Betz's'' limit. Other practical differences arise from the concentrated nature of tidal resources which impose very close turbine spacing for economic reasons. These, together with the potential influence of geometric constraints imposed by free surface and tidal channel walls, makes the study of the turbulent wake in tidal energy extraction a very important problem in development of this technology from economical and environmental aspects. We will present numerical simulations of turbulent wake behind a well characterized two-bladed turbine using a hierarchy of different models: Actuator Disk, Virtual Blade, the Single and Multiple Reference Frame and Sliding Mesh model with various boundary conditions and inlet velocity profiles. We will compare the results, discuss the differences among these models and the potential for each one to answer questions about optimization of energy extraction and environmental impacts. [Preview Abstract] |
Tuesday, November 24, 2009 11:53AM - 12:06PM |
PQ.00002: Wind energy conversion affected by turbulent wind conditions Joachim Peinke, Matthias Waechter, Patrick Milan Wind turbines are put up into the turbulent boundary layer of windy regions. The standard operational description is mainly based on simple statistical quantities like averaged wind speeds and turbulence degree (standrad deviation). Short time fluctuations are expected to be Gaussian. In this contribution we show that the intermittent - non Gaussian structure of small scale wind turbulence plays an important role for the working condition of a wind turbine and leads to additional mechanical loads as well as to fluctuations of the power production with many short time extreme events. [Preview Abstract] |
Tuesday, November 24, 2009 12:06PM - 12:19PM |
PQ.00003: Flow structure and induction factor of a lightly loaded wind turbine model in a wind-turbine array boundary layer Jose Lebron, Raul Bayoan Cal, Hyung Suk Kang, Luciano Castillo, Charles Meneveau Wind-tunnel experiments are carried out in order to study the structure of the flow within a 3 by 3 array of lightly loaded wind turbine models operating inside of a boundary layer. Particle-Image-Velocimetry measurements are performed in a volume surrounding a wind turbine model located on the center of the last row. Data gathered is used to compute time-averaged mean velocity and turbulence quantities in 18 planes surrounding the wind turbine model, and missing data are obtained through bilinear interpolation in space. The induction factor is estimated by computing the volumetric flux and mean velocities through circles centered at hub-height both upstream and downstream of the wind turbine model. Computation and visualization of the streamtube is performed by tracking the evolution of (virtual) fluid particles that pass through the (interpolated)~rotor disk location. The effects of wall blockage, mean velocity shear, and turbulence stresses and mixing on the streamtube geometry are considered. [Preview Abstract] |
Tuesday, November 24, 2009 12:19PM - 12:32PM |
PQ.00004: Laboratory model of the airborne jet-ski train riding on a soft porous track Parisa Mirbod, Yiannis Andreopoulos, Sheldon Weinbaum A small laboratory scale prototype of the airborne jet train and its track has been designed and constructed to measure the pressure signals as the planfrom passes over a particular location. We considered a lift weight W of 1 kg fully supported when airborne by a planform that is 65 cm long and 10 cm wide symmetrically positioned beneath the prototype. Our prototype model used the same porous media, described in Mirbod et al. (2009) J. Fluid Mech. 619:127 for the full scale AJT, where the Darcy permeability Kp, is 3.4x10$^{-9}$ m$^2$. We have performed a parametric study to estimate the primary lift-off velocity U as a function of compression ratio, k for this value of Kp and W. We considered the simpler case where both the variation of Kp with compression and the small lift force due to the fiber phase are neglected in predicting the pressure distribution on the planform. One then integrated this pressure distribution over the surface of the planform and sets F in the expression for the dimensionless force F = F Kp(H)/$\mu$L2Uw equal to the weight W of the prototype model. This solution, which provided an expression for U as a function of k, is used to predict primary lift off velocity for a laboratory model and to obtain an initial estimate for the pressure distribution beneath the planform. [Preview Abstract] |
Tuesday, November 24, 2009 12:32PM - 12:45PM |
PQ.00005: Stress transfer through fibrous materials in wicking experiments Daria Monaenkova, Taras Andrukh, Konstantin Kornev Due to the recent progress in preparation of fibers and nanofibers with different properties, the idea of smart textiles attracts much attention. In many situations the probes and sensors are designed for bio fluid detection. The liquid penetration in fibrous materials causes their deformations including stretching, twisting, wrinkling, buckling etc. The most of researches on wicking properties of textiles are focused on determination of media permeability and ignore the specific features of fibrous materials. On the other hand the theoretical works on quantitative analysis of the deformation effects in porous materials filled with liquids are mostly focused on deformation of fully saturated samples. The fundamental understanding of the stress transfer through the fiber network is crucial for sensors development, but to the best of our knowledge, the stress analysis in the fibrous materials absorbing liquids has never been discussed in the literature. This paper sets a physical basis for analysis of absorption processes in nanotubular and nanofibrous materials. We study absorption of droplets by yarns and webs made of fibers, develop a theory which explains the stress distribution in fibrous materials and checked this theory on wicking experiments. The reported theory and experiments propose a new area of research on absorption-induced deformations of fibrous materials. [Preview Abstract] |
Tuesday, November 24, 2009 12:45PM - 12:58PM |
PQ.00006: A flow intensification model for granular filter applications Zhaohui Qin, Richard Pletcher, Rodney Fox, Shankar Subramaniam a flow intensification model is proposed. We first give an estimation of the flow intensification factor, and then the velocity field in the vicinity of a single granule subject to the intensified flow is obtained. Creeping flow is assumed and Happel's model is used to represent the granular media. Based on the flow field, the initial collector efficiency $\eta _{0}$ is calculated from trajectory analysis and compared with experimental data. The reasonably good agreement between the theory and experiments suggests that the current model might be employed as a starting framework for further theoretical development and numerical modeling for granular filter applications. [Preview Abstract] |
Tuesday, November 24, 2009 12:58PM - 1:11PM |
PQ.00007: Swirling jet nozzle design for seabed excavation J. Ortega-Casanova, N. Campos, R. Fernandez-Feria We have investigated experimentally the seabed excavation performance of several swirling jets, generated by swirl vanes with adjustable angles and different geometries inside a nozzle, impinging against a sand bed for several Reynolds numbers and different impinging distances. The velocity profiles of the swirling jets at the nozzle exit have been measured using LDA, for the different nozzle configurations and Reynolds numbers, and the main features of the generated footprints on the sand bed have been measured by image processing of photographs of the bed illuminated by a laser sheet. Numerical simulations of the flow and visualizations techniques have been used to understand the excavation characteristics of the different swirling jets. It is found that the maximum excavation power is produced, at moderate impinging distances, by jets with a maximum swirl intensity in an annular region surrounding a central core with almost vanishing swirl, and a marked maximum of the axial velocity at the axis. This particular velocity profile of the swirling jet is generated by one of the nozzle configurations considered when the Reynolds number is above a threshold value. [Preview Abstract] |
Tuesday, November 24, 2009 1:11PM - 1:24PM |
PQ.00008: Internal Combustion Engine Flows Amy McCleney, Paul Puzinauskas, Kendrick Gibson An automobile engine's performance can be enhanced by a more complete combustion reaction which results in less fuel consumption and lower emissions. The combustion improvement can be accomplished through an increase in turbulence from tumble flow, a circulatory motion inside the cylinder. In previous research, this increase is created by changing the intake ports on the engine so the flow is more precisely directed in the cylinder. In this study, the following three experiments were conducted: a detailed vane characterization experiment to direct the flow; a study of the effect of the piston shape on the flow; and a seeding settling experiment to determine experimentation quality. These experiments offer insight into the flow structure inside the test cylinder, as observed using particle image velocimetry and impulse swirl meter testing. [Preview Abstract] |
Tuesday, November 24, 2009 1:24PM - 1:37PM |
PQ.00009: Visualization of a cryogenic jet simulating leak from a liquid hydrogen storage tank Tim Rose, Ajay Agrawal Hydrogen is considered an alternative fuel in propulsion and power generation due to fuel economy standards and environmental pollution. However, if an accidental leak were to occur in a hydrogen storage tank, the discharged fuel could find an ignition source and produce an explosion. A barrier wall can be used to contain the leak from the storage tank, therefore protecting equipment and people from the explosion. Past studies have investigated the jet/barrier wall interaction, in a laboratory setting, with fuel stored as a gas. Hydrogen fuel stored as a liquid offers higher energy density. In this work, we have studied the leak at cryogenic conditions due to liquid storage parameters. Jet fluid structure is visualized in a laboratory setting using helium as the supersonic jet fluid. High-speed rainbow schlieren deflectometry (RSD) images are used to show instantaneous flow structure of jet (leakage point) and barrier wall interactions. Results show the jet inlet temperature leads to significant differences in the spread angle and the extent of fuel-air mixture region adjacent to the barrier wall. [Preview Abstract] |
Tuesday, November 24, 2009 1:37PM - 1:50PM |
PQ.00010: Preconditioners for incompressible flows Cornelis Vuik, Mehfooz ur Rehman, Guus Segal We consider solution methods for large systems of linear equations that arise from the finite element discretization of the incompressible Navier-Stokes equations. These systems are of the so-called saddle point type, which means that there is a large block of zeros on the main diagonal. To solve these type of systems efficiently, several block preconditioners have been published. We propose a new block preconditioner MSIMPLER which is a modified version of the SIMPLER solver proposed by Patankar. We compare the performance of the block preconditioners: pressure convection diffusion (PCD), least squares commutator (LSC), and augmented Lagrangian based (AL) preconditioners with the MSIMPLER preconditioner. These preconditioners are first compared for academic problems generated by the IFISS package. Thereafter, we compare the best preconditioners for industrial problems using the SEPRAN FEM package. It appears that the MSIMPLER preconditioner is in general the best method. Finally we also consider the solution of the Stokes problem with variable viscosity. We consider smoothly varying viscosity and jumps in the viscosity. It appears that a special preconditioner is independent of the grid-size and independent of the viscosity variation. Applications from geophysics are used to illustrate the performance. [Preview Abstract] |
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