Effects of Wind Environment on Propeller Performance of Multirotor Drone in Hover

The purpose of this study is to understand the effect of cross flow and fluctuating flow on the propeller performance of MAV. This study especially has focused on the propeller performance during hovering flight under several cross flow velocity in actual flight conditions. We investigated four test cases of propellers with different starting point of design. The thrust and the torque of each propeller were experimentally measured by using the force transducer in wind tunnel. Figure of Merit (FM) of each propeller were evaluated based on the thrust and the torque measurement. The results showed that low cross flow velocity reduced FM. However, high cross flow velocity improved FM. Fluctuating flow yielded the change of FM with time. Furthermore, it was found that the starting point of the propeller design had a great effect on FM under wind environments.

Frequency Response Characterization for Dynamic Measurement of Pressure

Transducer requirements for making true dynamic pressure measurements point to a miniature point-level sensing element that is exposed to the flow. Meeting this requirement, however, is often challenged by transducer size constraints, integration at the location of measurement, and packaging, especially when one considers applications in harsh environments where protection of the sensing element may be needed. As part of an effort towards the development of a high frequency pressure measurement device for use in harsh environments (ultra-high temperature), an investigation was performed to evaluate the effect of sensing element packaging and geometry at the point of measurement on the dynamic response of a nominal transducer. Frequency and time domain calculations were performed to assess variations on the magnitude and phase between an input signal and a “measured” signal at the sensing element location for a range of probe tip parameters. The results offer insights and metrics that can govern transducer sensing element and probe tip implementation for optimum frequency response and strategies for compensation.

Development of a Surface Flow Sensor for Measuring Turbulent Drag Force

A surface flow sensor is needed if turbulent drag force is to be measured over a vehicle, such as a car, a ship, and an airplane. In case of automobile industry, there are no automobile manufacturers which measure surface flow velocity over a car for wind tunnel testing. Instead, they rely on particle image velocimetry (PIV), pressure sensitive paint (PSP), laser Doppler anemometry (LDA), pitot tubes, and tufts to get information regarding the turbulent drag force. Surface flow sensors have not devised yet. This study aims at developing a surface flow sensor for measuring turbulent drag force over a rigid body in a wind tunnel. Two sensing schemes were designed for the fiber-optic distributed sensor and the thermal mass flow sensor. These concepts are introduced in this paper. As the first attempt, a thermal mass flow sensor has been fabricated. It was flush-mounted on the surface of a test section in the wind tunnel to measure the surface flow velocity. The thermal mass flow sensor was operated by either constant current or constant resistance modes. Resistance ratio was changed as the electric current was increased by the constant current mode, while power ratio was saturated as the resistance was increased by the constant resistance mode. Either the resistance ratio or the power ratio was changed with the flow velocity measured by a Pitot tube, located at the center of test section.

Measurements of Dimension and Morphology of Solid Particles Volume With Digital In-Line Holography

Digital in-line holography (DIH) has been applied to measure the 3D position of objects in a variety of applications, including bubbles and droplets in multi-phase flows, tracking particles in turbulence flows, etc. In addition to the 3D position, the morphology and dimension of the individual particles can also be extracted from the recorded hologram. In this study, a lens-less digital in-line holography setup is applied to measure the morphology and size of three kinds of solid particles (Wollastonite Powder, Pearl Mica Powder and Solder Powder), whose sizes range from several to hundreds of micrometers. The statistics of equivalent diameter, aspect ratio and circularity are introduced to describe the morphology and dimension of each kind of particles. Microscopic images of the particles are taken to verify the accuracy of measurements with DIH. The results measured from DIH are in good agreements with results from microscopic images.

Experimental Investigation on the Electrokinetic Motions of Colloidal Particles at an Interfacial Boundary Between Solid and Liquid

We investigate electrokinetic behavior of colloidal particles in the vicinity of a solid-liquid interface. Colloidal liquids are expected to be used as thermal transport media for heat transfer applications such as nanofluids and phase change emulsions. They contain submicrometer-sized particles in liquid, and electrokinetic behavior of the solute particles should play an important role in the heat transfer between solid-liquid interfacing boundaries. However, experimental investigation of the behavior remains difficult due to the required spatial resolution beyond diffraction limit. We developed a measurement system based on laser Doppler principle using an interference of evanescent waves generated at total internal reflections of incident lasers at a solid wall. The system was developed for the measurement of velocities of colloidal particles at an interfacing boundary of colloidal liquid and a solid wall. The system has a unique advantage of a high spatial resolution in the direction perpendicular to the boundary due to the short penetration depth of an evanescent wave in the range of a few hundred nanometers. The principle and performance of the measurement system were investigated using a scanning probe in the measurement volume. We experimentally confirmed the validity of the measurement and characterized the uncertainty of velocity measurement. The system was further applied in a series of measurements of alumina particles dispersed in water in a square-shaped cell under induced electric fields. The measured velocities are proportional to the field strengths at different particle concentrations. The linear relationship is consistent with theoretical predictions, which demonstrates the feasibility of the system for the measurement of velocities of colloidal particles in the near wall region.

Experimental, Numerical and Analytical Evaluation of a Helical-Turbine Performance

A helical wind turbine has been analyzed experimentally and numerically and a novel design protocol has been proposed by means of blade element and momentum theory. The subject of the present analysis is to discuss the effect of low tip speed ratio and high one, respectively. In the low tip speed ratio, the turbine is driven by the torque generated from the flow turning radially after colliding with the runner. On the other hand, in the high tip speed ratio, the turbine is operated by the torque generated from the flow passing through axially the turbine.

Analysis of Characteristics of Bubble on Electrode Surface of Forced Convective Electrolyte Using Image Processing

‘Electrolysis’ is a technology about the transport of electrons caused by placing electrodes in an electrolyte using the difference of electric potential. It has been applied to various industrial fields, e.g., energy storage systems (ESS), fuel cells, and water treatment. Despite the outwardly simple phenomenon of this technology, it has been investigated because of the complex electro-physical process inside the electrolysis system, which can be designed in various ways. Two plate electrodes placed on a bulk of electrolyte is the most common electrolysis system. The electrolysis systems can be identified by the electrolyte flow, such as Forced convection configuration (FCC), Forced convection-induced circulation configuration (FCICC), and No net flow configuration (NNFC). The purpose of the study about the bubbles around the electrodes was to characterize the potential drop induced by the existence of the bubbles in the electric field. The dispersed bubbles, which have less electrical conductivity than does the bulk of the electrolyte, can reduce the efficiency of electrolysis. Therefore, in order to study the relationship between the electrical properties in the channel and the gas layer, the equation was derived with the void fraction and other electrical variables.

Large Scale Wettability Quantification in Porous Media Using Tracers

Tracers are widely used to study physical phenomena taking place inside the porous medium such as hydrodynamics of the reactor by residence time distribution, and characterizing the oil reservoirs for heterogeneity and residual oil saturation. In this work, we use tracer techniques to characterize oil phase tracers to quantify the wettability of a fluid in a multi-phase flow in a porous medium. The wetting fluid will have more contact area with the sediments. The quantification of contact area of a fluid with sediments during flow will give us insights into the wettability and wettability alteration. A two tracer method is used to quantify the wetted area by one fluid in the porous medium. We first find the adsorption characteristics of the tracers for non-aqueous-phase tracers on the sediments. Subsequently flow experiments are performed to conduct residence time distribution (RTD) analysis using single phase flow. The adsorption characteristics during flow are identified for various flow rates. The difference in RTD curves of the two tracers of a phase is used to estimate the area in contact with the fluids with the sediment surface.

The Dynamic Measurement of Impinging Sheet Thickness via Partial Coherent Interferometry

In this work, the thicknesses of a series of impinging sheets formed by two ethanol jets under different jet velocities are measured and compared with the theoretical model via a non-intrusive technique, the partial coherent interferometry. An interferometer with the calibrated partial coherence property is used to record the interference pattern by passing one optical path through the impinging sheet. The thickness is measured by analyzing the change of degree of coherence before and after the sheet insertion. The Reynolds numbers and Weber numbers of this experiment range from 269 to 370 and 35 to 67, respectively. The experimental results show that the jet velocity controls the size of the sheet but not affects the thickness distribution. The measured thicknesses are different from the theoretical predictions and indicate that the velocity inside the sheet may not be a constant along the radial direction.

Erratum: “A Tomographic PIV Study and Comparison of Vortex Identification Methods on NACA 63-215 Hydrofoil Wake Structure” [ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, Volume 4: Fluid Measurement and Instrumentation; Micro and Nano Fluid Dynamics, San Francisco, California, USA, July 28–August 1, 2019, Conference Sponsors: Fluids Engineering Division, ISBN: 978-0-7918-5907-0, Copyright © 2019 by ASME. Paper No. AJKFluids2019-5550, pp. V004T04A014; 12 pages; doi: 10.1115/AJKFluids2019-5550]

This erratum corrects errors that appeared in the paper “A Tomographic PIV Study and Comparison of Vortex Identification Methods on NACA 63-215 Hydrofoil Wake Structure” which was published in Proceedings of the ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, Volume 4: Fluid Measurement and Instrumentation; Micro and Nano Fluid Dynamics, (V004T04A014), July–August 2019, AJKFluids2019-5550, doi: 10.1115/AJKFluids2019-5550.