CFD Analysis of a Savonius Rotor in a Confined Test Section and in Open Field

2011 ◽  
Author(s):  
Marco Torresi ◽  
Bernardo Fortunato ◽  
Giuseppe Pascazio ◽  
Sergio Mario Camporeale
Keyword(s):  
Open Field ◽  
Test Section ◽  
Stokes Equations ◽  
Experimental Tests ◽  
Field Testing ◽  
Numerical Approach ◽  
Wind Tunnels ◽  
Savonius Rotor ◽  
Turbine Performance ◽  
Fundamental Information

Aim of this paper is to provide a deep insight into the dynamic behavior of the flow through a Savonius rotor by means of computational fluid dynamics (CFD). The analysis is carried out solving the incompressible Unsteady Reynolds Averaged Navier-Stokes equations, providing fundamental information concerning the complex unsteady flow field in and around the rotor. The motivation for employing a numerical approach relies on the consideration that detailed analysis of wind turbines, aiming to improve their design, cannot be easily performed by means of experimental full-scale field-testing due to the lack of control on the test conditions. At the same time, few are the wind tunnels where large turbine prototype testing is possible, so that experimental tests are usually carried out inside wind tunnels having dimensions comparable with those of the prototype. Moreover, if the available wind tunnel has a confined test section, the turbine performance could be quite different from those expected in open field. Therefore, in this paper, the turbine is firstly supposed to operate in open field and then in a bounded test section, in order to analyze the effect of flow confinement and to correlate the turbine performance in open field with experimental results obtained from prototypes tested in small wind tunnels of assigned blockage.

Heat and Mass Transfer Porous Medium Saturated with Compressible Fluid with Boundary Domain Integral Method

2008 ◽  
Vol 273-276 ◽  
pp. 808-813 ◽  
Author(s):  
Janja Kramer ◽  
Renata Jecl ◽  
Leo Škerget
Keyword(s):  
Mass Transfer ◽  
Porous Medium ◽  
Heat And Mass Transfer ◽  
Compressible Fluid ◽  
Integral Method ◽  
Stokes Equations ◽  
Numerical Approach ◽  
Momentum Equation ◽  
Navier Stokes ◽  
Domain Integral

A numerical approach to solve a problem of combined heat and mass transfer in porous medium saturated with compressible fluid is presented. Transport phenomena in porous media is described using the modified Navier-Stokes equations, where for the governing momentum equation the Brinkman extended Darcy formulation is used. Governing equations are solved with the Boundary Domain Integral Method, which is an extension of classical Boundary Element Method.

Theoretical and Experimental Investigation on the Flow Induced Vibrations of a Centrifugal Pump

2004 ◽  
Author(s):  
Friedrich-Karl Benra ◽  
Hans Josef Dohmen
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Transient Flow ◽  
Stokes Equations ◽  
Computer Code ◽  
Numerical Approach ◽  
Experimental Investigations ◽  
Pump Operation ◽  
Pump Rotor ◽  
Wide Range

The transport of fluids which include a lot of impurities is often done by special single-stage pumps. In order to avoid clogging of the pumps, the impellers have only one blade. This minimum blade number brings strong disadvantages during the pump operation. The rotation of the impeller in the pump casing produces a strongly uneven pressure field along the perimeter of the casing. The resulting periodically unsteady flow forces affect the impeller and produce radial deflections of the pump shaft which can be recognized as vibrations at the bearing blocks or at the pump casing. These vibrations will also be transferred to the pump casing and attached pipes. In a numerical approach the hydrodynamic excitation forces of a single-blade pump were calculated from the time dependent flow field. The flow field is known from the numerical simulation of the three-dimensional, viscous, unsteady flow in the pump by using a commercial computer code determining the Reynolds averaged Navier-Stokes equations (URANS). The periodically unsteady flow forces were computed for a complete impeller revolution. This forces affect the rotor of the pump and stimulate it to oscillations. The computed forces were defined as external forces and applied as the load on the rotor for a structural analysis. The resulting oscillations of the rotor were calculated by a transient analysis of the rotors structure using a commercial FEM-Method. To verify the calculated results, experimental investigations have been performed. The deflections of the pump rotor were measured with proximity sensors in a wide range of pump operation. Measurements of the vibration accelerations at the pump casing showed the visible effects of the transient flow. To minimize the vibration amplitudes the energizing forces have been reduced by attaching a compensation mass at the impeller. This procedure can be used as “operational balancing” of the pump rotor for a certain point of operation.

Motion Decay Simulations of a Moored Wave Energy Converter

2020 ◽  
Author(s):  
Changqing Jiang ◽  
Ould el Moctar ◽  
Thomas E. Schellin ◽  
Guilherme Moura Paredes
Keyword(s):  
Wave Energy ◽  
Stokes Equations ◽  
Numerical Approach ◽  
Offshore Structures ◽  
Primary Role ◽  
Viscous Effects ◽  
Restoring Force ◽  
System A ◽  
Cost Reductions ◽  
Catenary System

Abstract Significant cost reductions are required for marine renewable energy to become competitive. Aside from the deployment of arrays, one key area that has been identified as having potential for cost reductions is the mooring system. A challenge, therefore, is to design mooring systems which can satisfy their primary role of station keeping while being affordable and durable. This paper presents the effects of three different mooring configurations on the motion behavior of a buoy type wave energy convertor, considering nonlinear mooring-induced fluid-structure interactions, such as the associated viscous effects. To simulate motion decay, an overset mesh method that coupled a dynamic mooring model with the Navier-Stokes equations flow solver OpenFOAM was adopted. The mooring configurations comprised an all catenary system, a catenary system with buoys, and a catenary system with buoys and clump weights. The favorable agreement between the simulations and experimental measurements validated the coupled numerical approach for simulating different mooring configurations. The mooring systems influenced not only restoring force characteristics, but also total damping of the system, which demonstrated the importance of considering mooring-induced damping when investigating moored offshore structures.

scholarly journals Transplanted Human Neural Progenitor Cells Attenuate Motor Dysfunction and Lengthen Longevity in a Rat Model of Ataxia

2020 ◽  
Vol 29 ◽  
pp. 096368972092027
Author(s):  
Wesley M. Tierney ◽  
Toni L. Uhlendorf ◽  
Aaron J.J. Lemus ◽  
Bianca A. Ortega ◽  
Jesse Magaña ◽  
...  
Keyword(s):  
Progenitor Cells ◽  
Open Field ◽  
Neural Progenitor Cells ◽  
Field Testing ◽  
Neural Progenitor ◽  
Motor Dysfunction ◽  
Cresyl Violet ◽  
Control Group ◽  
Presenting Symptoms ◽  
Human Neural Progenitor Cells

The spastic Han Wistar (sHW) rat serves as a model for human ataxia presenting symptoms of motor deterioration, weight loss, shortened lifespan, and Purkinje neuron loss. Past studies revealed that human neural progenitor cells (NPCs) improved ataxic symptoms at 20 d posttransplantation in sHW rats. In this study, we investigated the fate and longer-term effectiveness of these transplanted NPCs. Rats were placed into four treatment groups: an untreated normal control group ( n = 10), an untreated mutant rat control ( n = 10), a mutant group that received an injection of dead NPCs ( n = 9), and a mutant group that received live NPCs ( n = 10). Bilateral cerebellar injections containing 500,000 of either live or dead NPCs were performed on mutant sHW rats at 40 d of age. Motor activity for all mutant rats started to decline in open field testing around day 35. However, at day 45, the live NPC-treated mutants exhibited significant improvements in open field activity. Similar improvements were observed during rotarod testing and weight gain through the completion of the experiments (100 d). Immunohistochemistry revealed few surviving human NPCs in the cerebella of 80- and 100-d-old NPC-treated mutants; while cresyl violet staining revealed that live NPC-treated mutants had significantly more surviving Purkinje neurons compared to mutants that were untreated or received dead NPCs. Direct stereotactic implantation of NPCs alleviated the symptoms of ataxia, acting as a neuroprotectant, supporting future clinical applications of these NPCs in the areas of ataxia as well as other neurodegenerative diseases.

scholarly journals Squeal Frequency of a Railway Disc Brake Evaluation by FE Analyses

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
F. Cascetta ◽  
F. Caputo ◽  
A. De Luca
Keyword(s):  
Sensitivity Analysis ◽  
Finite Element ◽  
Experimental Tests ◽  
Numerical Approach ◽  
System Stability ◽  
Brake System ◽  
Physical Parameters ◽  
Disc Brake ◽  
Complex Eigenvalues ◽  
The Stability

This paper deals with the development of a numerical model, based on the Finite Element (FE) theory for the prediction of the squeal frequency of a railway disc brake. The analytical background has been discussed and presented, as well as the most efficient methods for evaluating the system stability; the attention has been paid particularly to the complex eigenvalues method, which has been adopted within this paper to investigate the railway disc brake system. Numerical results have been compared with measurements from experimental tests in order to validate the proposed numerical approach. At the end of this work, a sensitivity analysis, aimed at understanding the effects of some physical parameters influencing the stability of the brake system and the squeal propensity, has been carried out.

A Combined Experimental and Numerical Study of Flow Past a Single Step Cylinder

2010 ◽  
Author(s):  
Chris R. Morton ◽  
Serhiy Yarusevych
Keyword(s):  
Vortex Shedding ◽  
Numerical Study ◽  
Experimental Tests ◽  
Numerical Approach ◽  
Single Step ◽  
Wake Flow ◽  
Cylinder Wake ◽  
Flow Topology ◽  
Single Vortex ◽  
Flow Past

The current study investigates flow past a step cylinder for ReD = 1050 and D/d = 2 using both experimental and numerical methods. The focus of the study is on the vortex shedding and vortex interactions occurring in the step cylinder wake. Flow visualization with hydrogen bubble technique and planar Laser Induced Fluorescence has shown that three distinct spanwise vortex cells form: a single vortex shedding cell in the wake of the small cylinder and two vortex shedding cells in the wake of the large cylinder. Vortex connections form between the spanwise vortices in these cells downstream of the step, and vortex dislocations occur at cell boundaries. Complementary to the experimental tests, an LES-RANS hybrid numerical simulation is used to model the flow development. A comparison of the experimental and numerical results indicates that the numerical approach adequately models vortex dynamics in the wake of a step cylinder and, thus, may be used to analyze time dependent, three-dimensional flow topology which is difficult to characterize quantitatively using experimental methods.

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