scholarly journals Measurement of the Flow Field Generated by Multicopter Propellers

Sensors ◽  
2020 ◽  
Vol 20 (19) ◽  
pp. 5537
Author(s):  
Zbigniew Czyż ◽  
Paweł Karpiński ◽  
Wit Stryczniewicz
Keyword(s):  
Velocity Field ◽  
Particle Image ◽  
Angle Of Attack ◽  
Vertical Plane ◽  
Airflow Velocity ◽  
Field Distributions ◽  
Image Velocimetry ◽  
Plane Passing ◽  
The Impact ◽  
Qualitative Analyses

This paper presents the results of research on the airflow around a multirotor aircraft. The research consisted of the analysis of the velocity field using particle image velocimetry. Based on the tests carried out in a wind tunnel, the distribution of the velocity and its components in the vertical plane passing through the propeller axis were determined for several values of the angle of attack of the tested object for two values of airflow velocity inside the tunnel, i.e., vwt = 0 m/s and vwt = 12.5 m/s. Determining the velocity value as a function of the coordinates of the adopted reference system allowed for defining the range of impact of the horizontal propellers and the fuselage of the research object itself. The tests allowed for quantitative and qualitative analyses of the airflow through the horizontal rotor. Particular attention was paid to the impact of the airflow and the angle of attack on the obtained velocity field distributions.

Analysis of Airflow Velocity Field Characteristics of an Oat Cleaner Based on Particle Image Velocimetry Technology

2019 ◽  
Vol 35 (2) ◽  
pp. 193-201 ◽  
Author(s):  
Xinping Li ◽  
Jialiang Zhang ◽  
Jiangtao Ji
Keyword(s):  
Particle Image Velocimetry ◽  
Velocity Field ◽  
High Speed ◽  
Radial Direction ◽  
Particle Image ◽  
Longitudinal Section ◽  
Airflow Velocity ◽  
Cleaning Performance ◽  
Image Velocimetry ◽  
Cleaning Machine

Abstract.To improve the cleaning performance of oat sorting devices with a single-fan three-cylinder screen system, this study investigated the airflow velocity field of a cleaning machine using particle image velocimetry (PIV) technology. Specifically, an optimal cleaning performance can be described as one with no material idling under the optimal operating parameters of the oat cleaning machine, the measured airflow velocity field space is divided into nine representative longitudinal planes that can reflect airflow velocity characteristics in the longitudinal plane. The results showed that a phenomenon of airflow backflow occurred in the radial direction above the medium cylinder screen, the airflow velocity in each longitudinal section of the airflow velocity field was less uniform in the transverse distribution, a. The movement of oat extracts in the cleaning room was recorded by a high-speed digital video camera. The phenomenon of oat impurities moving along the airflow backflow direction, and a transverse flow irregularity appearing in the radial direction above the medium cylinder screen were observed. The grain loss rate and impurity rate of the oat cleaner were 1.53% and 1.25%, respectively, under optimal conditions. Therefore, to improve the cleaning performance of the cleaner, it is necessary to theoretically analyze the phenomenon of airflow backflow in the cleaner, which can provide a reference for the follow-up design and optimization of the structure of the cleaner. Keywords: Airstream, Analysis, Cleaning, Particle image velocimetry, Test, Velocity field.

scholarly journals Experimental Validation of Falling Liquid Film Models: Velocity Assumption and Velocity Field Comparison

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1205
Author(s):  
Ruiqi Wang ◽  
Riqiang Duan ◽  
Haijun Jia
Keyword(s):  
Experimental Data ◽  
Particle Image Velocimetry ◽  
Velocity Field ◽  
Experimental Validation ◽  
Particle Image ◽  
Velocity Fields ◽  
Number Range ◽  
Comparison Results ◽  
Image Velocimetry ◽  
Experimental Particle

This publication focuses on the experimental validation of film models by comparing constructed and experimental velocity fields based on model and elementary experimental data. The film experiment covers Kapitza numbers Ka = 278.8 and Ka = 4538.6, a Reynolds number range of 1.6–52, and disturbance frequencies of 0, 2, 5, and 7 Hz. Compared to previous publications, the applied methodology has boundary identification procedures that are more refined and provide additional adaptive particle image velocimetry (PIV) method access to synthetic particle images. The experimental method was validated with a comparison with experimental particle image velocimetry and planar laser induced fluorescence (PIV/PLIF) results, Nusselt’s theoretical prediction, and experimental particle tracking velocimetry (PTV) results of flat steady cases, and a good continuity equation reproduction of transient cases proves the method’s fidelity. The velocity fields are reconstructed based on different film flow model velocity profile assumptions such as experimental film thickness, flow rates, and their derivatives, providing a validation method of film model by comparison between reconstructed velocity experimental data and experimental velocity data. The comparison results show that the first-order weighted residual model (WRM) and regularized model (RM) are very similar, although they may fail to predict the velocity field in rapidly changing zones such as the front of the main hump and the first capillary wave troughs.

Analysis of Particle Image Velocimetry Measurements of Natural Convection in an Enclosure Using Proper Orthogonal Decomposition

2015 ◽  
Vol 137 (12) ◽  
Author(s):  
Nirmalendu Biswas ◽  
Souvick Chatterjee ◽  
Mithun Das ◽  
Amlan Garai ◽  
Prokash C. Roy ◽  
...  
Keyword(s):  
Particle Image Velocimetry ◽  
Natural Convection ◽  
Velocity Field ◽  
Proper Orthogonal Decomposition ◽  
Particle Image ◽  
Field Measurements ◽  
Orthogonal Decomposition ◽  
Image Velocimetry ◽  
Low Dimensional ◽  
Proper Orthogonal

This work investigates natural convection in an enclosure with localized heating on the bottom wall with a flushed or protruded heat source and cooled on the top and the side walls. Velocity field measurements are done by using 2D particle image velocimetry (PIV) technique. Proper orthogonal decomposition (POD) has been used to create low dimensional approximations of the system for predicting the flow structures. The POD-based analysis reveals the modal structure of the flow field and also allows reconstruction of velocity field at conditions other than those used in PIV study.

Investigation of Cross-Sectional Velocity Field Near the Inducer Plane of a Turbocharger Compressor Using 2D Particle Image Velocimetry

2019 ◽  
Author(s):  
Deb Banerjee ◽  
Rick Dehner ◽  
Ahmet Selamet ◽  
Keith Miazgowicz ◽  
Todd Brewer ◽  
...  
Keyword(s):  
Particle Image Velocimetry ◽  
Velocity Field ◽  
Flow Field ◽  
Mass Flow ◽  
Particle Image ◽  
Tangential Velocity ◽  
Cross Sectional ◽  
Flow Rates ◽  
Blade Passage ◽  
Image Velocimetry

Abstract Understanding the velocity field at the inlet of an automotive turbocharger is critical in order to suppress the instabilities encountered by the compressor, extend its map and improve the impeller design. In the present study, two-dimensional particle image velocimetry experiments are carried out on a turbocharger compressor without any recirculating channel to investigate the planar flow structures on a cross-sectional plane right in front of the inducer at a rotational speed of 80 krpm. The objective of the study is to investigate the flow field in front of a compressor blade passage and quantify the velocity distributions along the blade span for different mass flow rates ranging from choke (77 g/s) to deep surge (13.6 g/s). It is observed that the flow field does not change substantially from choke to about 55 g/s, where flow reversal is known to start at this speed from earlier measurements. While the tangential velocity is less than 8 m/s, the radial velocity increases along the span to 17–20 m/s near the tip at high flow rates (55–77 g/s). As the mass flow rate is reduced below 55 g/s, the radial component starts decreasing and the tangential velocity increases rapidly. From about 5 m/s at 55 g/s, the tangential velocity at the blade tip exceeds 50 m/s at 50 g/s and reaches a maximum of about 135 m/s near surge. These time-averaged distributions are similar for different angular locations in front of the blade passage and do not exhibit any substantial azimuthal variation.

scholarly journals Simultaneous Measurement of Free Surface Elevation and Three-Component Velocity Field Around a Translating Surface-Piercing Foil

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
James Schock ◽  
Jason Dahl
Keyword(s):  
Particle Image Velocimetry ◽  
Free Surface ◽  
Velocity Field ◽  
Numerical Methods ◽  
Flow Field ◽  
Particle Image ◽  
Laser Sheet ◽  
Three Dimensional ◽  
Dynamic Mode ◽  
Image Velocimetry

Two methods are investigated to simultaneously obtain both three-dimensional (3D) velocity field and free surface elevations (FSEs) measurements near a surface piercing foil, while limiting the equipment. The combined velocity field and FSE measurements are obtained specifically for the validation of numerical methods requiring simultaneous field data and free surface measurements for a slender body shape. Both methods use stereo particle image velocimetry (SPIV) to measure three component velocities in the flow field and both methods use an off the shelf digital camera with a laser intersection line to measure FSEs. The first method is performed using a vertical laser sheet oriented parallel to the foil chord line. Through repetition of experiments with repositioning of the laser, a statistical representation of the three-dimensional flow field and surface elevations is obtained. The second method orients the vertical laser sheet such that the foil chord line is orthogonal to the laser sheet. A single experiment is performed with this method to measure the three-dimensional three component (3D3C) flow field and free surface, assuming steady flow conditions, such that the time dimension is used to expand the flow field in 3D space. The two methods are compared using dynamic mode decomposition and found to be comparable in the primary mode. Utilizing these methods produces results that are acceptable for use in numerical methods verification, at a fraction of the capital and computing cost associated with two plane or tomographic particle image velocimetry (PIV).

The velocity field under breaking waves: coherent structures and turbulence

2002 ◽  
Vol 454 ◽  
pp. 203-233 ◽  
Author(s):  
W. KENDALL MELVILLE ◽  
FABRICE VERON ◽  
CHRISTOPHER J. WHITE
Keyword(s):  
Velocity Field ◽  
Kinetic Energy ◽  
Reynolds Stress ◽  
Particle Image ◽  
Early Stage ◽  
Breaking Waves ◽  
Video Frame ◽  
Turbulent Kinetic Energy Budget ◽  
Image Velocimetry ◽  
Coherent Vortex

Digital particle image velocimetry (DPIV) measurements of the velocity field under breaking waves in the laboratory are presented. The region of turbulent fluid directly generated by breaking is too large to be imaged in one video frame and so an ensemble-averaged representation of the flow is built up from a mosaic of image frames. It is found that breaking generates at least one coherent vortex that slowly propagates downstream at a speed consistent with the velocity induced by its image in the free surface. Both the kinetic energy of the flow and the vorticity decay approximately as t−1. The Reynolds stress of the turbulence also decays as t−1 and is, within the accuracy of the measurements, everywhere negative, consistent with downward transport of streamwise momentum. Estimates of the mometum flux from waves to currents based on the measurements of the Reynolds stress are consistent with earlier estimates. The implications of the measurements for breaking in the field are discussed. Based on geometrical optics and wave action conservation, we suggest that the presence of the breaking-induced vortex provides an explanation for the suppression of short waves by breaking. Finally, in Appendices, estimates of the majority of the terms in the turbulent kinetic energy budget are presented at an early stage in the evolution of the turbulence, and comparisons with independent acoustical measurements of breaking are presented.

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