scholarly journals Investigation of Wheelhouse Flow Interaction and the Influence of Lateral Wheel Displacement

Energies ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 3340
Author(s):  
Eleanor Rajaratnam ◽  
Duncan Walker
Keyword(s):  
Lateral Displacement ◽  
Longitudinal Vortex ◽  
Lower Amount ◽  
Complex Flow ◽  
Longitudinal Edge ◽  
Image Velocimetry ◽  
Potential Benefits ◽  
Lateral Width ◽  
Wheel Arch ◽  
Good Agreement

The aim of this research was to improve the understanding of the complex flow featuresfound around a wheel and wheelhouse and to examine how the lateral displacement of the wheelaffects these features and the production of exhibited pressures and forces. A bespoke rotatingwheel rig and accompanying wheelhouse with a fully-pressure-tapped wheel arch was designedand manufactured at Loughborough University. Wind tunnel tests were performed where force andpressure measurements and Particle Image Velocimetry (PIV) data were obtained. The experimentaldata was used to validate unsteady CFD predictions where a k-! SST Improved Delayed DetachedEddy Simulation (IDDES) turbulence model was used in STAR-CCM+ (10.04.009, Siemens). The CFDshowed good agreement with all trends of the experimental results providing a validated numericalmethodology. For both methodologies, a lower amount of wheelhouse drag was found generatedwhen the wheel was rotating. However, the CFD showed that whilst this was the case, totalconfiguration drag had increased. This was attributed to an increase of the wheel and axle drag,illustrated by the change in separation over the wheel itself when located within a wheelhouseand so overcompensating the reduction in body and stand drag. Differences in vortex locationswhen comparing to previously-attained results were due to differences in housing geometry, suchas blockage in the cavity or housing dimensions. Experimental and computational results showedthat up until a 10 mm displacement outboard of the housing, overall drag decreased. The reductionin housing drag was credited to a reduction in the size of outboard longitudinal vortex structures.This led to the lateral width of the shear layer across the housing side being narrower. Overall, thisstudy identified that there were potential benefits to be gained when offsetting a wheel outboard ofthe longitudinal edge of a model housing.

scholarly journals The seismic performance of steel encased reinforced concrete bridge piles

1983 ◽  
Vol 16 (2) ◽  
pp. 123-140
Author(s):  
R. J. T. Park ◽  
M. J. N. Priestley ◽  
W. R. Walpole
Keyword(s):  
Reinforced Concrete ◽  
Seismic Performance ◽  
Theoretical Investigation ◽  
Axial Load ◽  
Lateral Displacement ◽  
Load Level ◽  
Concrete Bridge ◽  
Reinforced Concrete Bridge ◽  
Outside Diameter ◽  
Good Agreement

An experimental and theoretical investigation into the seismic performance of steel encased reinforced concrete bridge piles is described. Six test units were designed, constructed and tested
under cyclic lateral displacement-controlled loading. The units had
an outside diameter of 360 mm and a steel casing thickness of 5 mm. Variables included the axial load level, inclusion or exclusion of internal reinforcing cages, and the influence of the casing continuity at he critical flexural sections. Sound seismic performance was observed in all of the models and good agreement between predicted and observed ultimate behaviour was obtained.

scholarly journals Accelerated Particle Separation in a DLD Device at Re > 1 Investigated by Means of µPIV

Micromachines ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 768 ◽  
Author(s):  
Jonathan Kottmeier ◽  
Maike Wullenweber ◽  
Sebastian Blahout ◽  
Jeanette Hussong ◽  
Ingo Kampen ◽  
...  
Keyword(s):  
Lateral Displacement ◽  
Fluid Dynamic ◽  
Particle Diameter ◽  
Reynolds Numbers ◽  
Field Pattern ◽  
Cfd Simulations ◽  
Deterministic Lateral Displacement ◽  
Tracer Particles ◽  
Image Velocimetry ◽  
Microparticle Image Velocimetry

A pressure resistant and optically accessible deterministic lateral displacement (DLD) device was designed and microfabricated from silicon and glass for high-throughput fractionation of particles between 3.0 and 7.0 µm comprising array segments of varying tilt angles with a post size of 5 µm. The design was supported by computational fluid dynamic (CFD) simulations using OpenFOAM software. Simulations indicated a change in the critical particle diameter for fractionation at higher Reynolds numbers. This was experimentally confirmed by microparticle image velocimetry (µPIV) in the DLD device with tracer particles of 0.86 µm. At Reynolds numbers above 8 an asymmetric flow field pattern between posts could be observed. Furthermore, the new DLD device allowed successful fractionation of 2 µm and 5 µm fluorescent polystyrene particles at Re = 0.5–25.

scholarly journals Experimental Research and Numerical Analysis of Flow Phenomena in Discharge Object with Siphon

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3330
Author(s):  
Milan Sedlář ◽  
Pavel Procházka ◽  
Martin Komárek ◽  
Václav Uruba ◽  
Vladislav Skála
Keyword(s):  
Experimental Research ◽  
Turbulence Models ◽  
Free Surface Flow ◽  
Stationary Flow ◽  
Surface Flow ◽  
Flow Structures ◽  
Complex Flow ◽  
Flow Topology ◽  
Image Velocimetry ◽  
Flow Phenomena

This article presents results of the experimental research and numerical simulations of the flow in a pumping system’s discharge object with the welded siphon. The laboratory simplified model was used in the study. Two stationary flow regimes characterized by different volume flow rates and water level heights have been chosen. The study concentrates mainly on the regions below and behind the siphon outlet. The mathematical modelling using advanced turbulence models has been performed. The free-surface flow has been carried out by means of the volume-of-fluid method. The experimental results obtained by the particle image velocimetry method have been used for the mathematical model validation. The evolution and interactions of main flow structures are analyzed using visualizations and the spectral analysis. The presented results show a good agreement of the measured and calculated complex flow topology and give a deep insight into the flow structures below and behind the siphon outlet. The presented methodology and results can increase the applicability and reliability of the numerical tools used for the design of the pump and turbine stations and their optimization with respect to the efficiency, lifetime and environmental demands.

Analytical Solution of Sidewise Buckling of Two-Hinged Circular Arch under Concentrated Force

2013 ◽  
Vol 676 ◽  
pp. 170-174
Author(s):  
Ju Tao Kuang ◽  
Ai Rong Liu ◽  
Qi Ca Yu ◽  
Jiang Dong Deng
Keyword(s):  
Finite Element ◽  
Analytical Solution ◽  
Lateral Displacement ◽  
Displacement Function ◽  
Buckling Load ◽  
The Finite Element Method ◽  
Concentrated Force ◽  
Critical Buckling Load ◽  
Circular Arch ◽  
Good Agreement

By the setting torsional and lateral displacement function of sidewise buckling of two-hinged circular arch under concentrated force, the single-arch structure's bending, torsional deformation and external force potential can be constructed. An analytical solution for the lateral critical buckling load of two-hinged arch is first deduced by using the energy method; the results are also compared and analyzed by the finite element method. The results show that the analytical solution of single arch’s lateral critical buckling load is in good agreement with the finite element numerical solution, and the validity of the formula is proven.

scholarly journals Inundation of the Ziltendorfer Lowland during the Odra flood 1997 and its impact on the main river – a numerical study

2006 ◽  
Vol 8 (3) ◽  
pp. 181-192 ◽  
Author(s):  
Hilmar Messal ◽  
Heinz-Theo Mengelkamp
Keyword(s):  
Water Level ◽  
Hydrodynamic Model ◽  
Numerical Study ◽  
Complex Flow ◽  
Dam Breach ◽  
Main River ◽  
Flooding Event ◽  
Odra River ◽  
Flooding Period ◽  
Good Agreement

The inundation of the Ziltendorfer Lowland, a farmland polder with some villages, during the major flooding event in July 1997 in the Odra watershed, is simulated with the two-dimensional hydrodynamic model TRIM2D. Inflow and outflow through three consecutive embankment breaches make up a complex flow regime which governs the inundation and the water level in the Odra river. With reasonable assumptions for the dam breach genesis the inundation and depletion are simulated in good agreement with the observed flooding front positions. Simulations with a one-dimensional hydrodynamic model for “dam breach” and “no dam breach” scenarios confirm analytical considerations of an increase of the water level downstream in the main river for the “dam breach” scenario because of an outflow from the Ziltendorfer Lowland into the Odra river during the peak flooding period.

The minimal flow unit in near-wall turbulence

1991 ◽  
Vol 225 ◽  
pp. 213-240 ◽  
Author(s):  
Javier Jiménez ◽  
Parviz Moin
Keyword(s):  
Wall Stress ◽  
Wall Layer ◽  
Flow Unit ◽  
Wall Turbulence ◽  
Longitudinal Vortex ◽  
Spanwise Direction ◽  
Wall Region ◽  
Low Velocity ◽  
Good Agreement ◽  
Near Wall

Direct numerical simulations of unsteady channel flow were performed at low to moderate Reynolds numbers on computational boxes chosen small enough so that the flow consists of a doubly periodic (in x and z) array of identical structures. The goal is to isolate the basic flow unit, to study its morphology and dynamics, and to evaluate its contribution to turbulence in fully developed channels. For boxes wider than approximately 100 wall units in the spanwise direction, the flow is turbulent and the low-order turbulence statistics are in good agreement with experiments in the near-wall region. For a narrow range of widths below that threshold, the flow near only one wall remains turbulent, but its statistics are still in fairly good agreement with experimental data when scaled with the local wall stress. For narrower boxes only laminar solutions are found. In all cases, the elementary box contains a single low-velocity streak, consisting of a longitudinal strip on which a thin layer of spanwise vorticity is lifted away from the wall. A fundamental period of intermittency for the regeneration of turbulence is identified, and that process is observed to consist of the wrapping of the wall-layer vorticity around a single inclined longitudinal vortex.

Flow in a Co-Axial Control Valve

2003 ◽  
Author(s):  
Hailing An ◽  
Jungsoo Suh ◽  
Michael W. Plesniak ◽  
Steven H. Frankel
Keyword(s):  
Axial Flow ◽  
Control Valve ◽  
Separated Flow ◽  
Flow Coefficient ◽  
Navier Stokes ◽  
Flow Control Valve ◽  
Complex Flow ◽  
Flow Loop ◽  
Image Velocimetry ◽  
Global Performance

An experimental and computational investigation of the complex flow inside a co-axial flow control valve with various piston configurations was performed. A transparent full-scale prototype of a control valve was installed into an instrumented flow loop. The acrylic test article allows optical access for diagnostics, such as flow visualization and Particle Image Velocimetry (PIV). Global performance was assessed in terms of the valve flow coefficient for various piston configurations in the control valve at various flow rates by measuring the pressure drop across the valve using an electronic manometer. These results were compared to those for conventional control valves, and as expected, the co-axial design exhibited considerably lower losses (up to 30 times lower). However, the differences in piston geometry designed for different valve characteristics, such as linear, fast-opening, etc. led to different flow coefficients. Investigation of the mechanisms leading to the differences in the global performance involved PIV measurements of the velocity field in several planes within the valve. Complex piston geometries caused regions of separated flow and vortical structures to form. Companion computational studies were performed for the same valve geometries as installed in the flow loop using a commercial CFD package, FLUENT. A fully 3-D Reynolds Averaged Navier-Stokes (RANS) model employing on the order of 800,000 cells was used with a Renormalized Group theory (RNG) k-ε turbulence model. The computational results were compared qualitatively to the experimental data. The CFD results were then used to investigate details of the flow that were not accessible to the experiments, including streamlines, distributions of the static pressure and turbulent kinetic energy throughout the flow field.

The Effect of Blade Lean, Twist and Bow on the Performance of Axial Turbine at Design Point

2011 ◽  
Author(s):  
Hadi Karrabi ◽  
Mohsen Rezasoltani
Keyword(s):  
Stokes Equations ◽  
Numerical Data ◽  
Navier Stokes ◽  
Minor Effect ◽  
Complex Flow ◽  
Navier Stokes Equations ◽  
Axial Turbine ◽  
Twisted Blade ◽  
The Impact ◽  
Good Agreement

An investigation to understand the impact of twisted, leaned and bowed blades on the performance of axial turbine was undertaken. A CFD code, which solves the Reynolds-averaged Navier–Stokes equations, was used to compute the complex flow field of axial turbine. The code was validated against existing Hannover turbine experimental data. Numerical data showed good agreement with measured data. Finally, the effect of geometry changes, focusing on blade lean, twist and bow, on the Avon turbine blade performance, was analyzed. Results show that twisted blade affects performance significantly. Leaned and bowed blade has minor effect on performance.

scholarly journals Vortices, dissipation and flow transition in volatile binary drops

2014 ◽  
Vol 749 ◽  
pp. 649-665 ◽  
Author(s):  
R. Bennacer ◽  
K. Sefiane
Keyword(s):  
Viscous Dissipation ◽  
Flow Structure ◽  
Volatile Component ◽  
Internal Flow ◽  
Reynolds Numbers ◽  
Local Concentration ◽  
Water Mixture ◽  
Concentration Gradients ◽  
Image Velocimetry ◽  
Good Agreement

AbstractDespite its fundamental and practical relevance, flow structure and evolution within volatile mixture drops remains largely unexplored. We study experimentally, using particle image velocimetry (PIV), the evolution of internal flow during the evaporation of ethanol–water mixture drops for different initial concentrations. The investigation revealed the existence of three stages in the evolving flow behaviour within these binary volatile drops. We propose an analysis of the nature of the flow and focus on understanding successive flow stages as well as transition from multiple vortices to a monotonic outward flow. We show that the existence of multiple vortices during the first stage is driven by local concentration gradients along the interface. When the more volatile component (in this case ethanol) is depleted, the intensity of this Marangoni flow abruptly declines. Towards the end of the first stage, ethanol is driven from the bulk of the drop to the interface to sustain weakening concentration gradients. Once these gradients are too weak, the solutal Marangoni number becomes sub-critical and the driving force for the flow switches off. The evolution of flow structure and transition between stages is found to be well correlated with the ratio of Marangoni and Reynolds numbers. Furthermore, we argue that whilst the observed vortices are driven by surface tension shear stress originating at the liquid/vapour interface, the transition in flow and its dynamics is entirely determined by viscous dissipation. The comparison between the analytical expression for vorticity decay based on viscous dissipation and the experimental data shows a very good agreement. The analysis also shows that regardless of the initial concentration, for same sized drops, the transition in flow follows exactly the same trend. This further supports the hypothesis of a viscous dissipation transition of the flow. The last stage is satisfactorily explained based on non-uniform evaporation and continuity-driven flow.

Structure of a stratified tilted vortex

2007 ◽  
Vol 583 ◽  
pp. 443-458 ◽  
Author(s):  
NICOLAS BOULANGER ◽  
PATRICE MEUNIER ◽  
STÉPHANE LE DIZÈS
Keyword(s):  
Particle Image ◽  
Axial Flow ◽  
Stratified Fluid ◽  
Viscous Effects ◽  
Columnar Vortex ◽  
Theoretical Structure ◽  
Image Velocimetry ◽  
Layer Analysis ◽  
Vortex Axis ◽  
Good Agreement

The structure of a columnar vortex in a stably stratified fluid is studied experimentally and theoretically when the vortex axis is slightly tilted with respect to the direction of stratification. When the Froude number of the vortex is larger than 1, we show that tilting induces strong density variations and an intense axial flow in a rim around the vortex. We demonstrate that these characteristics can be associated with a critical-point singularity of the correction of azimuthal wavenumber m = 1 generated by tilting where the angular velocity of the vortex equals the Brunt–Väisälä frequency of the stratified fluid. The theoretical structure obtained by smoothing this singularity using viscous effects (in a viscous critical-layer analysis) is compared to particle image velocimetry measurements of the axial velocity field and visualizations of the density field and a good agreement is demonstrated.

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