scholarly journals Blade Tip-Vortices of a Four-Bladed Rotor with Axial Inflow

2020 ◽  
Vol 65 (4) ◽  
pp. 1-13
Author(s):  
Andreas Goerttler ◽  
Johannes N. Braukmann ◽  
C. Christian Wolf ◽  
Anthony D. Gardner ◽  
Markus Raffel
Keyword(s):  
Particle Image ◽  
Test Facility ◽  
Vortex System ◽  
Tip Vortices ◽  
Image Velocimetry ◽  
Swirl Velocity ◽  
Blade Tip ◽  
Velocity Circulation ◽  
Bladed Rotor ◽  
German Aerospace

The vortex system of four rotating and pitching DSA-9A blades was examined numerically and experimentally. Numerical computations were performed using German Aerospace Center (DLR)'s finite-volume solver TAU and were validated against experimental data gathered using particle image velocimetry carried out at the rotor test facility (RTG) in Göttingen. Algorithms deriving the vortex position, swirl velocity, circulation, and core radius were implemented. Hover-like conditions with a fixed blade pitch were analyzed giving further physical insights of the static vortex system. These results are used to understand the vortex development for the unsteady pitching conditions, which can be described as a superpositioning of static vortex states. The use of a zonal detached-eddy simulations approach improved physical modeling of the vortex development by resolving finer scales than URANS. Trimmed cases agree well with differences less than 0.5% in the circulation and swirl velocity.

scholarly journals Combining simultaneous density and velocity measurements of rotor blade tip vortices under cyclic pitch conditions

2021 ◽  
Vol 62 (9) ◽  
Author(s):  
Johannes N. Braukmann ◽  
Andreas Goerttler ◽  
C. Christian Wolf ◽  
Clemens Schwarz ◽  
Markus Raffel
Keyword(s):  
Velocity Data ◽  
Tip Vortices ◽  
Related Data ◽  
Isentropic Flow ◽  
Image Velocimetry ◽  
Measurement Plane ◽  
Swirl Velocity ◽  
Blade Tip ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Variables

Abstract An investigation into blade tip vortices of a sub-scale rotor under cyclic pitch conditions is carried out. Background oriented schlieren (BOS), particle image velocimetry (PIV), and computational fluid dynamics (CFD) are applied to the same test cases. This approach allows to combine the velocity data from PIV in a measurement plane, the density related data from BOS in a measurement volume, and the comprehensive set of flow variables provided by unsteady detached eddy simulations. Vortices up to an age of $$\varPsi _{{\text {v}}}= {70}^\circ$$ Ψ v = 70 ∘ in case of PIV and CFD, and up to $$\varPsi _{{\text {v}}}= {200}^\circ$$ Ψ v = 200 ∘ in case of BOS are considered. The vortex locations are obtained through all three techniques. The unsteadiness of the vortices was obtained by the experimental results, whereas CFD provides an average solution. An increased position scatter was observed during the downstroke of the pitch cycle with both experimental methods and was found to be in good agreement. In the second part, the PIV velocity data are compared to common vortex models. An approach to link the density distribution and the swirl velocity is applied to the measured data. Based on the CFD results, it is shown that the assumption of isothermal flow yields better agreement between velocity and density than isentropic flow. Graphic abstract

scholarly journals Measurement of Velocity and Temperature Profiles in the 1/40 Scaled-Down CANDU-6 Moderator Tank

2015 ◽  
Vol 2015 ◽  
pp. 1-9
Author(s):  
Hyoung Tae Kim ◽  
Jae Eun Cha ◽  
Han Seo ◽  
In Cheol Bang
Keyword(s):  
Particle Image ◽  
Laser Induced Fluorescence ◽  
Test Facility ◽  
Temperature Profiles ◽  
Cfd Analysis ◽  
Tank Model ◽  
Piv Technique ◽  
Image Velocimetry ◽  
Potential Problems ◽  
Accident Conditions

In order to simulate the CANDU-6 moderator circulation phenomena during steady state operating and accident conditions, a scaled-down moderator test facility has been constructed at Korea Atomic Energy Institute (KAERI). In the present work an experiment using a 1/40 scaled-down moderator tank has been performed to identify the potential problems of the flow visualization and measurement in the scaled-down moderator test facility. With a transparent moderator tank model, a flow field is visualized with a particle image velocimetry (PIV) technique under an isothermal state, and the temperature field is measured using a laser induced fluorescence (LIF) technique. A preliminary CFD analysis is also performed to find out the flow, thermal, and heating boundary conditions with which the various flow patterns expected in the prototype CANDU-6 moderator tank can be reproduced in the experiment.

scholarly journals The complex aerodynamic footprint of desert locusts revealed by large-volume tomographic particle image velocimetry

2015 ◽  
Vol 12 (108) ◽  
pp. 20150119 ◽  
Author(s):  
Per Henningsson ◽  
Dirk Michaelis ◽  
Toshiyuki Nakata ◽  
Daniel Schanz ◽  
Reinhard Geisler ◽  
...  
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Aerodynamic Force ◽  
Helmholtz Instability ◽  
Tip Vortices ◽  
Left Behind ◽  
Image Velocimetry ◽  
Secondary Vortices ◽  
Animal Flight ◽  
Wing Tip

Particle image velocimetry has been the preferred experimental technique with which to study the aerodynamics of animal flight for over a decade. In that time, hardware has become more accessible and the software has progressed from the acquisition of planes through the flow field to the reconstruction of small volumetric measurements. Until now, it has not been possible to capture large volumes that incorporate the full wavelength of the aerodynamic track left behind during a complete wingbeat cycle. Here, we use a unique apparatus to acquire the first instantaneous wake volume of a flying animal's entire wingbeat. We confirm the presence of wake deformation behind desert locusts and quantify the effect of that deformation on estimates of aerodynamic force and the efficiency of lift generation. We present previously undescribed vortex wake phenomena, including entrainment around the wing-tip vortices of a set of secondary vortices borne of Kelvin–Helmholtz instability in the shear layer behind the flapping wings.

scholarly journals Measurement of Velocity and Temperature Profiles in the Scaled-Down CANDU-6 Moderator Tank

2013 ◽  
Author(s):  
Hyoung Tae Kim ◽  
Jae Eun Cha ◽  
Bo Wook Rhee ◽  
Hwa-Lim Choi ◽  
Han Seo ◽  
...  
Keyword(s):  
Particle Image ◽  
Test Facility ◽  
Temperature Profiles ◽  
Cfd Analysis ◽  
Energy Research ◽  
Tank Model ◽  
Piv Technique ◽  
Steady State Operation ◽  
Image Velocimetry ◽  
Accident Conditions

We are planning to construct a scaled-down moderator test facility to simulate the CANDU-6 moderator circulation phenomena during steady state operation and accident conditions at the Korea Atomic Energy Research Institute. In the present work a preliminary experiment using a 1/40 scaled-down moderator tank has been performed to identify the potential problems of the flow visualization and measurement in the scaled-down moderator test facility. With a transparent moderator tank model, a flow field is visualized with a Particle Image Velocimetry (PIV) technique under an isothermal state, and the temperature field is measured using a Laser Induced Fluorescence (LIF) technique. A preliminary CFD analysis is also performed to find out the flow, thermal, and heating boundary conditions with which the various flow patterns expected in the prototype CANDU-6 moderator tank can be reproduced in the experiment.

Investigation of Blade Tip Interaction With Casing Treatment in a Transonic Compressor: Part 1—Particle Image Velocimetry

2008 ◽  
Author(s):  
M. Voges ◽  
R. Schnell ◽  
C. Willert ◽  
R. Mo¨nig ◽  
M. W. Mu¨ller ◽  
...  
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Light Sheet ◽  
Tip Clearance ◽  
Stall Margin ◽  
Casing Treatment ◽  
Transonic Compressor ◽  
Image Velocimetry ◽  
Flow Phenomena ◽  
Blade Tip

A single-stage transonic axial compressor was equipped with a casing treatment (CT), consisting of 3.5 axial slots per rotor pitch in order to investigate the predicted extension of the stall margin characteristics both numerically and experimentally. Contrary to most other studies the CT was designed especially accounting for an optimized optical access in the immediate vicinity of the CT, rather than giving maximum benefit in terms of stall margin extension. Part 1 of this two-part contribution describes the experimental investigation of the blade tip interaction with casing treatment using Particle image velocimetry (PIV). The nearly rectangular geometry of the CT cavities allowed a portion of it to be made of quartz glass with curvatures matching the casing. Thus the flow phenomena could be observed with essentially no disturbance caused by the optical access. Two periscope light sheet probes were specifically designed for this application to allow for precise alignment of the laser light sheet at three different radial positions in the rotor passage (87.5%, 95% and 99%). For the outermost radial position the light sheet probe was placed behind the rotor and aligned to pass the light sheet through the blade tip clearance. It was demonstrated that the PIV technique is capable of providing velocity information of high quality even in the tip clearance region of the rotor blades. The chosen type of smoke-based seeding with very small particles (about 0.5 μm in diameter) supported data evaluation with high spatial resolution, resulting in a final grid size of 0.5 × 0.5 mm. The PIV data base established in this project forms the basis for further detailed evaluations of the flow phenomena present in the transonic compressor stage with CT and allows validation of accompanying CFD calculations using the TRACE code. Based on the combined results of PIV measurements and CFD calculations of the same compressor and CT geometry a better understanding of the complex flow characteristics can be achieved, as detailed in Part 2 of this paper.

The Application of Particle Image Velocimetry (PIV) in a Short-Duration Transonic Annular Turbine Cascade

1992 ◽  
Vol 114 (3) ◽  
pp. 504-509 ◽  
Author(s):  
P. J. Bryanston-Cross ◽  
C. E. Towers ◽  
T. R. Judge ◽  
D. P. Towers ◽  
S. P. Harasgama ◽  
...  
Keyword(s):  
Particle Image Velocimetry ◽  
Flow Field ◽  
Short Duration ◽  
Particle Image ◽  
Guide Vane ◽  
Three Dimensional ◽  
Film Plane ◽  
Test Facility ◽  
Image Velocimetry

A series of experiments have been performed to demonstrate the application of Particle Image Velocimetry (PIV) to turbomachinery flows. The tests were performed at transonic speeds on a fully annular engine size turbine nozzle guide vane. The vane cascade was installed in a short-duration Isentropic Light Piston Cascade (ILPC) test facility operating with high inlet turbulence levels. The technique has been shown to map the whole flow field with a resolution of 0.5 mm. The quality of the results obtained is not significantly affected by local turbulence rates. The accuracy of the measurements is put at around 4 percent of absolute velocity and is limited by the quality of the image on the film plane. The velocities derived from the PIV images have been compared with predictions from a three-dimensional viscous numerical calculation. It is shown that the experimental and predicted results are in good agreement. It is considered that this technique has considerable potential in application to turbomachinery flow field diagnostics.

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