Experimental Investigation of a Prandtl Probe Fabricated Using Desktop Stereolithography Technology

A Prandtl probe is one of the standard instruments used for flow characterization in wind tunnel facilities. The convectional fabrication method of this instrument requires skilled artisanship, precision drilling, lathing and soldering of its several parts. This reflects into high costs of production in turn making wind energy studies expensive. With the adoption of additive manufacturing, the tooling costs, skills required and design to manufacture constraints can be addressed. This research presents a Prandtl probe that was designed using NX™ software, fabricated by desktop stereolithography additive manufacturing platform and validated in a wind tunnel for velocity range of 0 m/s to 51 m/s. This research attested the option of fabricating relatively cheap functional Prandtl probe with desktop stereolithography technology which can be used for accurate determination of flow quality in wind tunnels experiments. This provides various learning and research institution in developing countries that have already invested in additive desktop manufacturing technology certainty and a cheaper option to fabricate wind research instruments for use at their laboratories. Moreover, fabrication and validation of a 5-hole Prandtl probe can also be examined.

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Accurate determination of reference wind speed and reference static pressure in wind tunnel tests

Advances in Structural Engineering ◽

10.1177/1369433219875302 ◽

2019 ◽

Vol 23 (3) ◽

pp. 578-583

Author(s):

YC He ◽

JCK Cheung ◽

QS Li ◽

JY Fu

Keyword(s):

Boundary Layer ◽

Wind Speed ◽

Wind Tunnel ◽

Measurement Method ◽

Static Pressure ◽

Accurate Determination ◽

Indirect Measurement ◽

Measurement Methods ◽

Wind Tunnel Experiments

The reference wind speed and reference static pressure are two key parameters for determining the testing results of wind tunnel experiments. Traditionally, the values of these parameters can be determined using direct measurement methods. However, such methods may suffer from less accuracy and inconvenience of operations. This article documents an indirect measurement method which, compared to the traditional methods, has the merits of higher accuracy and greater operational convenience. Examples are presented to demonstrate the main procedures of the method and typical findings by using the method in a boundary layer wind tunnel.

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The kata-thermometer as a measure of ventilation

Proceedings of the Royal Society of London. Series B, Containing Papers of a Biological Character ◽

10.1098/rspb.1922.0014 ◽

1922 ◽

Vol 93 (651) ◽

pp. 198-206 ◽

Cited By ~ 10

Keyword(s):

Wind Tunnel ◽

Experimental Work ◽

National Physical Laboratory ◽

Wind Tunnels ◽

Kind Permission ◽

Physical Laboratory ◽

Engineering Department ◽

Wind Velocities ◽

Large Wind

In two papers previously published, one by Leonard Hill, O. W. Griffiths and M. Flack, and the other by Leonard Hill and D. Hargood-Ash, the kata-thermometer was described in detail, and formulæ were given connecting the heat loss with temperature, wind velocity and vapour pressure. Various discrepancies were found to occur, however, and seeing that the kata-thermometer has become recognised as a measure of ventilation the whole matter has now been carefully reinvestigated. Large wind tunnels such as those at the National Physical Laboratory, which were not available during the war, owing to the urgency of aeroplane work, were now at our disposal. Experimental Work. To obtain known wind velocities for the experimental work two methods were adopted, that of the “wind tunnel” where the air is drawn through a long tunnel by means of a propellar at one end, and that of the “whirling arm” where the “kata” is made to move through the air on a revolving arm. The wind tunnel work was carried out in the engineering department at the National Physical Laboratory by kind permission of Dr. T. E. Stanton, where Miss D. Marshall gave us valuable assistance in the determination of wind velocities; also at East London College, where Dr. N. A. V. Piercy was good enough to allow us the use of the tunnel and to help us in determining the wind velocities.

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Turbulence investigation in the VTI’s experimental aerodynamics laboratory

Thermal Science ◽

10.2298/tsci160130187r ◽

2017 ◽

Vol 21 (suppl. 3) ◽

pp. 629-647 ◽

Cited By ~ 1

Author(s):

Slavica Ristic ◽

Suzana Linic ◽

Marija Samardzic

Keyword(s):

Wind Tunnel ◽

Test Section ◽

Flow Direction ◽

Technical Information ◽

Low Flow ◽

Wind Tunnels ◽

Main Requirement ◽

Measurement Results ◽

Experimental Aerodynamics ◽

Flow Quality

Wind tunnels are the aerodynamic laboratories which task is to enable high quality and stabile airflow in controlled volume, a test section, during run time, in order to study the effects of streaming around various aeronautical or nonaeronautical models (airfoils and bluff bodies with complex motorized or robotic constructions). The main requirement that leads to quality and reliable measurement results is a high flow quality in the test section: uniformity of the velocity and pressure fields along and across the test section, low turbulence level and low flow direction angularities or swirling. The knowledge of low parameters enables the exchange of the scientific and technical information, comparison of the experimental results from different wind tunnels and data scaling of the model to the real scale. The turbulence intensity TI significantly affects the wind tunnel results and reduction of turbulence is of the highest importance for the quality measurements. This paper presents the Experimental Aerodynamics Laboratory of the VTI in Belgrade, the equipment and methods of turbulence measurements in the test section stream and around different test models. Wind tunnel facilities maintain equipment and devices for sampling, acquisition and data reduction for various test types, from forces and moment measurements, over the pressure distribution measurements to the advanced measurements, followed with the appropriate flow visualization techniques. The modern instrumentation enables determine flow quality and its influence on tests and measurement results of static and dynamic model characteristics.

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Determination of static and dynamic forces for manufacture of corrugated belts for wind tunnel heat exchangers

Omsk Scientific Bulletin Series Aviation-Rocket and Power Engineering ◽

10.25206/2588-0373-2021-5-3-91-98 ◽

2021 ◽

Vol 5 (3) ◽

pp. 91-98

Author(s):

Yu. V. Shchipkova ◽

Keyword(s):

Experimental Study ◽

Stainless Steel ◽

Heat Exchanger ◽

Wind Tunnel ◽

Heat Exchangers ◽

Wind Tunnels ◽

Milling Machine ◽

Machine Model ◽

Dynamic Forces

The article presents the results of an experimental study aimed at determining the required load when rolling a corrugated heat exchanger belt for wind tunnels. The experiments are carried out on a horizontal milling machine model 6H81. The results of the experiment are applied to stainless steel tapes with a thickness of 0,3 to 0,4 mm.

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A quantitative approach to inner shell losses

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010010977x ◽

1978 ◽

Vol 36 (1) ◽

pp. 526-527 ◽

Cited By ~ 2

Author(s):

R.D. Leapman ◽

P. Rez ◽

D.F. Mayers

Keyword(s):

Energy Transfer ◽

Cross Section ◽

Cross Sections ◽

Accurate Determination ◽

Background Intensity ◽

Core Excitation ◽

Quantitative Basis ◽

Cross Section Differential ◽

Bound Electrons

Microanalysis by EELS has been developing rapidly and though the general form of the spectrum is now understood there is a need to put the technique on a more quantitative basis (1,2). Certain aspects important for microanalysis include: (i) accurate determination of the partial cross sections, σx(α,ΔE) for core excitation when scattering lies inside collection angle a and energy range ΔE above the edge, (ii) behavior of the background intensity due to excitation of less strongly bound electrons, necessary for extrapolation beneath the signal of interest, (iii) departures from the simple hydrogenic K-edge seen in L and M losses, effecting σx and complicating microanalysis. Such problems might be approached empirically but here we describe how computation can elucidate the spectrum shape.The inelastic cross section differential with respect to energy transfer E and momentum transfer q for electrons of energy E0 and velocity v can be written as

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Fast calibration of CBED patterns for quantitative analysis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100149209 ◽

1993 ◽

Vol 51 ◽

pp. 674-675

Author(s):

M.A. Gribelyuk ◽

M. Rühle

Keyword(s):

Reciprocal Lattice ◽

Accurate Determination ◽

Incident Beam ◽

Crystal Thickness ◽

Structure Model ◽

Beam Direction ◽

Transmitted Beam ◽

Reciprocal Vector ◽

On Line

A new method is suggested for the accurate determination of the incident beam direction K, crystal thickness t and the coordinates of the basic reciprocal lattice vectors V1 and V2 (Fig. 1) of the ZOLZ plans in pixels of the digitized 2-D CBED pattern. For a given structure model and some estimated values Vest and Kest of some point O in the CBED pattern a set of line scans AkBk is chosen so that all the scans are located within CBED disks.The points on line scans AkBk are conjugate to those on A0B0 since they are shifted by the reciprocal vector gk with respect to each other. As many conjugate scans are considered as CBED disks fall into the energy filtered region of the experimental pattern. Electron intensities of the transmitted beam I0 and diffracted beams Igk for all points on conjugate scans are found as a function of crystal thickness t on the basis of the full dynamical calculation.

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Computer-Assisted High-Re Solution TEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100179567 ◽

1990 ◽

Vol 48 (1) ◽

pp. 162-163

Author(s):

F.A. Ponce ◽

H. Hikashi

Keyword(s):

Signal To Noise Ratio ◽

Accurate Determination ◽

Computer Software ◽

Video Camera ◽

Image Contrast ◽

Objective Lens ◽

Computer Assisted ◽

Optical Parameters ◽

Astigmatism Correction

The determination of the atomic positions from HRTEM micrographs is only possible if the optical parameters are known to a certain accuracy, and reliable through-focus series are available to match the experimental images with calculated images of possible atomic models. The main limitation in interpreting images at the atomic level is the knowledge of the optical parameters such as beam alignment, astigmatism correction and defocus value. Under ordinary conditions, the uncertainty in these values is sufficiently large to prevent the accurate determination of the atomic positions. Therefore, in order to achieve the resolution power of the microscope (under 0.2nm) it is necessary to take extraordinary measures. The use of on line computers has been proposed [e.g.: 2-5] and used with certain amount of success.We have built a system that can perform operations in the range of one frame stored and analyzed per second. A schematic diagram of the system is shown in figure 1. A JEOL 4000EX microscope equipped with an external computer interface is directly linked to a SUN-3 computer. All electrical parameters in the microscope can be changed via this interface by the use of a set of commands. The image is received from a video camera. A commercial image processor improves the signal-to-noise ratio by recursively averaging with a time constant, usually set at 0.25 sec. The computer software is based on a multi-window system and is entirely mouse-driven. All operations can be performed by clicking the mouse on the appropiate windows and buttons. This capability leads to extreme friendliness, ease of operation, and high operator speeds. Image analysis can be done in various ways. Here, we have measured the image contrast and used it to optimize certain parameters. The system is designed to have instant access to: (a) x- and y- alignment coils, (b) x- and y- astigmatism correction coils, and (c) objective lens current. The algorithm is shown in figure 2. Figure 3 shows an example taken from a thin CdTe crystal. The image contrast is displayed for changing objective lens current (defocus value). The display is calibrated in angstroms. Images are stored on the disk and are accessible by clicking the data points in the graph. Some of the frame-store images are displayed in Fig. 4.

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