Overview of selected measurement techniques for aerodynamics testing in the NASA Langley Unitary Plan Wind Tunnel

2000 ◽  
Author(s):  
Gary Erickson
Keyword(s):  
Wind Tunnel ◽  
Measurement Techniques

scholarly journals Quantitative evaluation of seven optical sensors for cloud microphysical measurements at the Puy-de-Dôme Observatory, France

2015 ◽  
Vol 8 (10) ◽  
pp. 4347-4367 ◽  
Author(s):  
G. Guyot ◽  
C. Gourbeyre ◽  
G. Febvre ◽  
V. Shcherbakov ◽  
F. Burnet ◽  
...  
Keyword(s):  
Optical Properties ◽  
Wind Tunnel ◽  
Optical Sensors ◽  
Wind Direction ◽  
Total Concentration ◽  
Measurement Techniques ◽  
Ambient Air ◽  
Number Concentration ◽  
Effective Diameter ◽  
Particle Volume

Abstract. Clouds have an important role in Earth's radiative budget. Since the late 1970s, considerable instrumental developments have been made in order to quantify cloud microphysical and optical properties, for both airborne and ground-based applications. Intercomparison studies have been carried out in the past to assess the reliability of cloud microphysical properties inferred from various measurement techniques. However, observational uncertainties still exist, especially for droplet size distribution measurements and need to be reduced. In this work, we discuss results from an intercomparison campaign, performed at the Puy de Dôme in May 2013. During this campaign, a unique set of cloud instruments was operating simultaneously in ambient air conditions and in a wind tunnel. A Particle Volume Monitor (PVM-100), a Forward Scattering Spectrometer Probe (FSSP), a Fog Monitor (FM-100), and a Present Weather Detector (PWD) were sampling on the roof of the station. Within a wind tunnel located underneath the roof, two Cloud Droplet Probes (CDPs) and a modified FSSP (SPP-100) were operating. The main objectives of this paper are (1) to study the effects of wind direction and speed on ground-based cloud observations, (2) to quantify the cloud parameters discrepancies observed by the different instruments, and (3) to develop methods to improve the quantification of the measurements. The results revealed that all instruments showed a good agreement in their sizing abilities, both in terms of amplitude and variability. However, some of them, especially the FM-100, the FSSP and the SPP, displayed large discrepancies in their capability to assess the magnitude of the total number concentration of the cloud droplets. As a result, the total liquid water content can differ by up to a factor of 5 between the probes. The use of a standardization procedure, based on data of integrating probes (PVM-100 or visibilimeter) and extinction coefficient comparison substantially enhanced the instrumental agreement. During this experiment, the total concentration agreed in variations with the visibilimeter, except for the FSSP, so a corrective factor can be applied and it ranges from 0.44 to 2.2. This intercomparison study highlights the necessity to have an instrument which provides a bulk measurement of cloud microphysical or optical properties during cloud ground-based campaigns. Moreover, the FM and FSSP orientation was modified with an angle ranging from 30 to 90° angle with wind speeds from 3 to 7 m s−1. The results show that the induced number concentration loss is between 29 and 98 % for the FSSP and between 15 and 68 % for the FM-100. In particular, FSSP experiments showed strong discrepancies when the wind speed was lower than 3 m s−1 and/or when the angle between the wind direction and the orientation of the instruments is greater than 30°. An inadequate orientation of the FSSP towards the wind direction leads to an underestimation of the measured effective diameter.

scholarly journals Design, Construction and Commissioning of the Braunschweig Icing Wind Tunnel

2017 ◽  
Author(s):  
Stephan E. Bansmer ◽  
Arne Baumert ◽  
Stephan Sattler ◽  
Inken Knop ◽  
Delphine Leroy ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Test Section ◽  
Measurement Techniques ◽  
Convective Cloud ◽  
Ice Crystals ◽  
Wind Tunnels ◽  
Comprehensive Overview ◽  
Tropical Regions ◽  
Water Contents ◽  
Design Construction

Abstract. Beyond its physical importance in both fundamental and climate research, atmospheric icing is considered as a severe operational condition in many engineering applications like aviation, electrical power transmission and wind-energy production. To reproduce such icing conditions in a laboratory environment, icing wind tunnels are frequently used. Creating and maintaining a stable icing cloud in the tunnel test section yields different design constraints compared to conventional wind tunnels. In this paper, a comprehensive overview on the design, construction and commissioning of the Braunschweig icing wind tunnel is given. The tunnel features a test section of 0.5 m x 0.5 m with peak velocities of up to 40 m/s. The static temperature ranges from −25 °C to +30 °C. Supercooled droplet icing with liquid water contents up to 3 g/m³ can be reproduced. Outstanding ability of the tunnel is to simulate ice crystal icing with natural ice crystals for ice water contents up to 20 g/m³. We further show, how current state-of-the-art measurement techniques for particle sizing perform on ice crystals. The data is compared to those of in-flight measurements in mesoscale convective cloud systems in tropical regions. Finally, some applications of the icing wind tunnel are mentioned.

scholarly journals Comparison of different droplet measurement techniques in the Braunschweig Icing Wind Tunnel

2021 ◽  
Vol 14 (2) ◽  
pp. 1761-1781
Author(s):  
Inken Knop ◽  
Stephan E. Bansmer ◽  
Valerian Hahn ◽  
Christiane Voigt
Keyword(s):  
Wind Tunnel ◽  
Mass Flow ◽  
Liquid Water ◽  
Measurement Techniques ◽  
Wind Tunnel Test ◽  
Cloud Droplet ◽  
Liquid Water Content ◽  
Liquid Droplets ◽  
Spray System ◽  
Phase Doppler Interferometry

Abstract. The generation, transport and characterization of supercooled droplets in multiphase wind tunnel test facilities is of great importance for conducting icing experiments and to better understand cloud microphysical processes such as coalescence, ice nucleation, accretion and riming. To this end, a spray system has been developed, tested and calibrated in the Braunschweig Icing Wind Tunnel. Liquid droplets in the size range of 1 to 150 µm produced by pneumatic atomizers were accelerated to velocities between 10 and 40 m s−1 and supercooled to temperatures between 0 and −20 ∘C. Thereby, liquid water contents between 0.07 and 2.5 g m−3 were obtained in the test section. The wind tunnel conditions were stable and reproducible within 3 % standard variation for median volumetric diameter (MVD) and 7 % standard deviation for liquid water content (LWC). Different instruments were integrated in the icing wind tunnel measuring the particle size distribution (PSD), MVD and LWC. Phase Doppler interferometry (PDI), laser spectroscopy with a fast cloud droplet probe (FCDP) and shadowgraphy were systematically compared for present wind tunnel conditions. MVDs measured with the three instruments agreed within 15 % in the range between 8 and 35 µm and showed high coefficients of determination (R2) of 0.985 for FCDP and 0.799 for shadowgraphy with respect to PDI data. Between 35 and 56 µm MVD, the shadowgraphy data exhibit a low bias with respect to PDI. The instruments' trends and biases for selected droplet conditions are discussed. LWCs determined from mass flow calculations in the range of 0.07–1.5 g m−3 are compared to measurements of the bulk phase rotating cylinder technique (RCT) and the above-mentioned single-particle instruments. For RCT, agreement with the mass flow calculations of approximately 20 % in LWC was achieved. For PDI 84 % of measurement points with LWC<0.5 g m−3 agree with mass flow calculations within a range of ±0.1 g m−3. Using the different techniques, a comprehensive wind tunnel calibration for supercooled droplets was achieved, which is a prerequisite for providing well-characterized liquid cloud conditions for icing tests for aerospace, wind turbines and power networks.

scholarly journals MEASUREMENT OF FLUID-STRUCTURE INTERACTION OF WIND TURBINES IN WIND TUNNEL EXPERIMENTS: CONCEPT AND FIRST RESULTS

2019 ◽  
Vol XLII-2/W18 ◽  
pp. 143-149
Author(s):  
S. Nietiedt ◽  
M. Goering ◽  
T. Willemsen ◽  
T. T. B. Wester ◽  
L. Kröger ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Rotor Blade ◽  
Spatial Information ◽  
Measurement Techniques ◽  
Rotor Blades ◽  
Wind Flow ◽  
Wind Tunnel Experiments ◽  
Fluid Structure ◽  
Measurement Concept ◽  
Wind Flows

Abstract. Fluid-structure interactions are crucial for the design of rotor blades of wind power systems. Up to now, the mutual interactions between rotor blades and turbulent wind flows have been treated by complex simulations or were observed at individual discrete points. In this paper, a measurement concept is presented where spatial information of the motion/deformation of a rotating wind turbine as well as the wind flow are recorded in wind tunnel experiments. Wind flow and motion behaviour are recorded simultaneously and contactless. Techniques from the field of photogrammetry and flow measurement techniques are combined, resulting in high demands on the measurement concept. Furthermore, solutions for the realisation of a common coordinate system as well as for the synchronisation of both measuring systems are presented. In addition, the validation of the entire measurement concept is carried out based on of some wind tunnel tests in which a single rotor blade is used for the moment. This showed that the measurement concept and the proposed solutions for the simultaneous recording of wind flows and rotor blade movements are suitable in principle and that movements can be recorded and reconstructed with high accuracy.

Lab experiments to quantify wind induced microstructural modifications of surface snow

2021 ◽  
Author(s):  
Benjamin Walter ◽  
Henning Löwe
Keyword(s):  
Wind Tunnel ◽  
Wind Velocity ◽  
Microstructural Evolution ◽  
Measurement Techniques ◽  
Initial Density ◽  
Rate Of Change ◽  
Snow Density ◽  
Vertical Heterogeneity ◽  
Surface Snow ◽  
Order Of Magnitude

&lt;p&gt;The microstructural evolution of surface snow under the influence of wind is hardly understood and poorly quantified, but crucial for polar and alpine snowpacks. Only few field studies addressed the process of wind affecting surface snow at the snow-atmosphere interface in detail. Available descriptions are based on empirical relations between snow density, wind velocity and air temperature. A microstructural picture discerning independent controls of snow crystal fragmentation, abrasion and sublimation is yet missing.&amp;#160;&lt;/p&gt;&lt;p&gt;The goal of this project is to analyze the relevant physical processes responsible for wind induced microstructural modifications, and develop parametrizations from controlled wind-tunnel experiments. A ring-shaped wind tunnel (RWT) with an infinite fetch was used in a cold lab to quantify the snow microstructural evolution through systematic variations of flow, snow, and temperature conditions. For the drift experiments, dendritic fresh snow was produced in a WSL/SLF snowmaker and slowly added to the wind tunnel during the experiments simulating precipitation. Measurement techniques like X-ray tomography, SnowMicroPen, density cutters and IceCube were applied to characterize the snow density (&amp;#961;), specific surface area (SSA), particle size and shape and vertical layering before and after the highly dendritic new snow was exposed to the wind.&amp;#160;&lt;/p&gt;&lt;p&gt;The vertical heterogeneity of the deposited snow was characterized by SnowMicroPen measurements, showing increasing densities towards the snow surface. Densification rates (normalized by the initial density &amp;#961;&lt;sub&gt;0&lt;/sub&gt;) of the surface layer measured with a density cutter show an increase with increasing wind velocity and are two to three orders of magnitude higher than those measured for isothermal metamorphism, underlining the importance of accurately understanding wind induced microstructural modifications. Densification rates simulated with stat-of-the-art snow physical models span an order of magnitude, significantly deviating from the measured values. The SSA, measured with the IceCube instrument, decreases with a rate of change of approximately -0.1 h&lt;sup&gt;-1&lt;/sup&gt;, which is an order of magnitude higher than the rates for isothermal metamorphism. We hypothesize that the smallest fragments disappear because of sublimation while being transported by the wind.&amp;#160;&lt;/p&gt;&lt;p&gt;The results of this project will lead to an improved, fundamental understanding of optically and mechanically relevant microstructural properties of surface snow and are thus applicable to many cryospheric processes like avalanche formation, exchange of chemical species with the atmosphere, alpine and polar mass balances, or radiative transfer.&lt;/p&gt;

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