scholarly journals Distributed observations of wind direction using microstructures attached to actively heated fiber-optic cables

2020 ◽  
Vol 13 (3) ◽  
pp. 1563-1573 ◽  
Author(s):  
Karl Lapo ◽  
Anita Freundorfer ◽  
Lena Pfister ◽  
Johann Schneider ◽  
John Selker ◽  
...  
Keyword(s):  
Wind Speed ◽  
Wind Direction ◽  
Fiber Optic ◽  
Deterministic Model ◽  
Three Dimensional ◽  
Heat Fluxes ◽  
Fiber System ◽  
Wide Range ◽  
Spatially Distributed ◽  
Dynamics Simulations

Abstract. The weak-wind boundary layer is characterized by turbulent and submesoscale motions that break the assumptions necessary for using traditional eddy covariance observations such as horizontal homogeneity and stationarity, motivating the need for an observational system that allows spatially resolving measurements of atmospheric flows near the surface. Fiber-optic distributed sensing (FODS) potentially opens the door to observing a wide range of atmospheric processes on a spatially distributed basis and to date has been used to resolve the turbulent fields of air temperature and wind speed on scales of seconds and decimeters. Here we report on progress developing a FODS technique for observing spatially distributed wind direction. We affixed microstructures shaped as cones to actively heated fiber-optic cables with opposing orientations to impose directionally sensitive convective heat fluxes from the fiber-optic cable to the air, leading to a difference in sensed temperature that depends on the wind direction. We demonstrate the behavior of a range of microstructure parameters including aspect ratio, spacing, and size and develop a simple deterministic model to explain the temperature differences as a function of wind speed. The mechanism behind the directionally sensitive heat loss is explored using computational fluid dynamics simulations and infrared images of the cone-fiber system. While the results presented here are only relevant for observing wind direction along one dimension, it is an important step towards the ultimate goal of a full three-dimensional, distributed flow sensor.

scholarly journals Distributed observations of wind direction using microstructures attached to actively heated fiber-optic cables

2019 ◽  
Author(s):  
Karl Lapo ◽  
Anita Freundorfer ◽  
Lena Pfister ◽  
Johann Schneider ◽  
John Selker ◽  
...  
Keyword(s):  
Wind Speed ◽  
Wind Direction ◽  
Fiber Optic ◽  
Deterministic Model ◽  
Three Dimensional ◽  
Heat Fluxes ◽  
Fiber System ◽  
Wide Range ◽  
Spatially Distributed ◽  
Dynamics Simulations

Abstract. The weak-wind boundary layer is characterized by turbulent and submeso-scale motions that break the assumptions necessary for using traditional eddy covariance observations such as horizontal homogeneity and stationarity, motivating the need for an observational system that allows spatially resolving measurements of atmospheric flows near the surface. Fiber-Optic Distributed Sensing (FODS) potentially opens the door to observing a wide-range of atmospheric processes on a spatially distributed basis and to date has been used to resolve the turbulent fields of air temperature and wind speed on scales of second and decimeters. Here we report on progress developing a FODS technique for observing spatially distributed wind direction. We affixed microstructures shaped as cones to actively-heated fiber-optic cables with opposing orientations to impose directionally-sensitive convective heat fluxes from the fiber-optic cable to the air, leading to a difference in sensed temperature that depends on the wind direction. We demonstrate the behavior of a range of microstructure parameters including aspect ratio, spacing, and size and develop a simple deterministic model to explain the temperature differences as a function of wind speed. The mechanism behind the directionally-sensitive heat loss is explored using Computational Fluid Dynamics simulations and infrared images of the cone-fiber system. While the results presented here are only relevant for observing wind direction along one dimension it is an important step towards the ultimate goal of a full three-dimensional, distributed flow sensor.

scholarly journals Distributed sensing of wind direction using fiber-optic cables

2021 ◽  
Author(s):  
Anita Freundorfer ◽  
Karl Lapo ◽  
Johann Schneider ◽  
Christoph K. Thomas
Keyword(s):  
Wind Speed ◽  
Spatial Resolution ◽  
Wind Direction ◽  
Fiber Optic ◽  
Sonic Anemometer ◽  
Distributed Sensing ◽  
Spatial And Temporal Scales ◽  
Spatially Distributed ◽  
Temporal Structures ◽  
Direction Information

AbstractIn the atmospheric boundary layer, phenomena exist with challenging properties such as spatial heterogeneity, particularly during stable weak wind situations. Studying spatially heterogeneous features requires spatially distributed measurements on fine spatial and temporal scales. Fiber-Optic Distributed Sensing (FODS) can provide spatially distributed measurements, simultaneously offering a spatial resolution on the order of decimeters and a temporal resolution on the order of seconds. While FODS has already been deployed to study various variables, FODS wind direction sensing has only been demonstrated in idealized wind tunnel experiments. We present the first distributed observations of FODS wind directions from field data. The wind direction sensing is accomplished by using pairs of actively heated fiber optic cables with cone-shaped microstructures attached to them. Here we present three different methods of calculating wind directions from the FODS measurements, two based on using combined wind speed and direction information and one deriving wind direction independently from FODS wind speed. For each approach, the effective temporal and spatial resolution is quantified using spectral coherence. With each method of calculating wind directions, temporal resolutions on the order of tens of seconds can be achieved. The accuracy of FODS wind directions was evaluated against a sonic anemometer, showing deviations of less than 15° most of the time. The applicability of FODS for wind direction measurements in different environmental conditions is tested by analysing the dependence of FODS wind direction accuracy and observable scales on environmental factors. Finally, we demonstrate the potential of this technique by presenting a period that displays spatial and temporal structures in the wind direction.

scholarly journals Polymer cyclization for the emergence of hierarchical nanostructures

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Chaojian Chen ◽  
Manjesh Kumar Singh ◽  
Katrin Wunderlich ◽  
Sean Harvey ◽  
Colette J. Whitfield ◽  
...  
Keyword(s):  
Self Assembly ◽  
Three Dimensional ◽  
Hierarchical Structures ◽  
Structural Similarity ◽  
Vital Role ◽  
Nanomaterial Synthesis ◽  
Wide Range ◽  
Linear Poly ◽  
Polymer Folding ◽  
Dynamics Simulations

AbstractThe creation of synthetic polymer nanoobjects with well-defined hierarchical structures is important for a wide range of applications such as nanomaterial synthesis, catalysis, and therapeutics. Inspired by the programmability and precise three-dimensional architectures of biomolecules, here we demonstrate the strategy of fabricating controlled hierarchical structures through self-assembly of folded synthetic polymers. Linear poly(2-hydroxyethyl methacrylate) of different lengths are folded into cyclic polymers and their self-assembly into hierarchical structures is elucidated by various experimental techniques and molecular dynamics simulations. Based on their structural similarity, macrocyclic brush polymers with amphiphilic block side chains are synthesized, which can self-assemble into wormlike and higher-ordered structures. Our work points out the vital role of polymer folding in macromolecular self-assembly and establishes a versatile approach for constructing biomimetic hierarchical assemblies.

Experimental and Numerical Thermal Transient Behavior of Chips in a Liquid Channel During Loss of Pumping Power

2004 ◽  
Vol 126 (4) ◽  
pp. 546-553 ◽  
Author(s):  
C. P. Tso ◽  
K. W. Tou ◽  
H. Bhowmik
Keyword(s):  
Single Phase ◽  
Rectangular Channel ◽  
Three Dimensional ◽  
Transient Behavior ◽  
Heat Fluxes ◽  
Coolant Flow ◽  
Pumping Power ◽  
Channel Water ◽  
Wide Range ◽  
Transient And Steady State

Both transient and steady-state experiments are performed to study the single-phase heat transfer characteristics on an array of four in-line, flush-mounted simulated chips in a vertical rectangular channel. Water is the coolant media, and the flow covers the wide range of laminar regimes with the Reynolds number, based on heat source length, from 800 to 2625. The effect of heat fluxes, coolant flow rates, and geometric parameters (such as chip configuration number) are investigated. The operation is extended to study the transient natural convection during an accidental stoppage of coolant flow due to loss of pumping power. Results compare favorably with those obtained from three-dimensional numerical calculations. The transient correlation recommended is Nul=0.3Fo−0.2Ral*1/4.

scholarly journals The Large-eddy Observatory Voitsumra Experiment 2019 (LOVE19) with high-resolution, spatially-distributed observations of air temperature, wind speed, and wind direction from fiber-optic distributed sensing, towers, and ground-based remote sensing

2021 ◽  
Author(s):  
Karl Lapo ◽  
Anita Freundorfer ◽  
Antonia Fritz ◽  
Johann Schneider ◽  
Johannes Olesch ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Boundary Layer ◽  
Wind Speed ◽  
Air Temperature ◽  
Wind Direction ◽  
Fiber Optic ◽  
Layer Structure ◽  
Distributed Sensing ◽  
Near Surface ◽  
Large Eddy

Abstract. The weak-wind Stable Boundary Layer (wwSBL) is poorly described by theory and breaks basic assumptions necessary for observations of turbulence. Understanding the wwSBL requires distributed observations capable of separating between submeso and turbulent scales. To this end, we present the Large Eddy Observatory, Voitsumra Experiment 2019 (LOVE19) which featured 1350 m of fiber optic distributed sensing (FODS) of air temperature and wind speed, as well as an experimental wind direction method, at scales as fine as 1 s and 0.127 m in addition to a suite of point observations of turbulence and ground-based remote sensing. Additionally, flights with a fiber optic cable attached to a tethered balloon provide an unprecedented detailed view of the boundary layer structure with a resolution of 0.254 m and 10 s between 1–200 m height. Two examples are provided demonstrating the unique capabilities of the LOVE19 data for examining boundary layer processes: 1) FODS observations between 1m and ~200 m height during a period of gravity waves propagating across the entire boundary layer and 2) tracking a near-surface, transient submeso structure that causes an intermittent burst of turbulence. All data can be accessed at Zenodo through the DOI https://doi.org/10.5281/zenodo.4312976 (Lapo et al., 2020a).

scholarly journals Measuring Three-Dimensional Temperature Distributions in Steel–Concrete Composite Slabs Subjected to Fire Using Distributed Fiber Optic Sensors

Sensors ◽  
2020 ◽  
Vol 20 (19) ◽  
pp. 5518
Author(s):  
Yi Bao ◽  
Matthew S. Hoehler ◽  
Christopher M. Smith ◽  
Matthew Bundy ◽  
Genda Chen
Keyword(s):  
Fiber Optic ◽  
Three Dimensional ◽  
Thermal Response ◽  
Point Clouds ◽  
Fiber Optic Sensors ◽  
Distributed Sensors ◽  
Temperature Distributions ◽  
Composite Slabs ◽  
Spatially Distributed ◽  
Dense Point

Detailed information about temperature distribution can be important to understand structural behavior in fire. This study develops a method to image three-dimensional temperature distributions in steel–concrete composite slabs using distributed fiber optic sensors. The feasibility of the method is explored using six 1.2 m × 0.9 m steel–concrete composite slabs instrumented with distributed sensors and thermocouples subjected to fire for over 3 h. Dense point clouds of temperature in the slabs were measured using the distributed sensors. The results show that the distributed sensors operated at material temperatures up to 960 °C with acceptable accuracy for many structural fire applications. The measured non-uniform temperature distributions indicate a spatially distributed thermal response in steel–concrete composite slabs, which can only be adequately captured using approaches that provide a high density of through-depth data points.

scholarly journals Wind turbine wake measurements with automatically adjusting scanning trajectories in a multi-Doppler lidar setup

2018 ◽  
Vol 11 (6) ◽  
pp. 3801-3814 ◽  
Author(s):  
Norman Wildmann ◽  
Nikola Vasiljevic ◽  
Thomas Gerz
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Wind Direction ◽  
Sonic Anemometer ◽  
Prevailing Wind Direction ◽  
Wide Range ◽  
Novel Method ◽  
Approach Velocity ◽  
German Aerospace ◽  
First Time

Abstract. In the context of the Perdigão 2017 experiment, the German Aerospace Center (DLR) deployed three long-range scanning Doppler lidars with the dedicated purpose of investigating the wake of a single wind turbine at the experimental site. A novel method was tested for the first time to investigate wake properties with ground-based lidars over a wide range of wind directions. For this method, the three lidars, which were space- and time-synchronized using the WindScanner software, were programmed to measure with crossing beams at individual points up to 10 rotor diameters downstream of the wind turbine. Every half hour, the measurement points were adapted to the current wind direction to obtain a high availability of wake measurements in changing wind conditions. The linearly independent radial velocities where the lidar beams intersect allow the calculation of the wind vector at those points. Two approaches to estimating the prevailing wind direction were tested throughout the campaign. In the first approach, velocity azimuth display (VAD) scans of one of the lidars were used to calculate a 5 min average of wind speed and wind direction every half hour, whereas later in the experiment 5 min averages of sonic anemometer measurements of a meteorological mast close to the wind turbine became available in real time and were used for the scanning adjustment. Results of wind speed deficit measurements are presented for two measurement days with varying northwesterly winds, and it is evaluated how well the lidar beam intersection points match the actual wake location. The new method allowed wake measurements to be obtained over the whole measurement period, whereas a static scanning setup would only have captured short periods of wake occurrences.

The Impact of Assimilating SSM/I and QuikSCAT Satellite Winds on Hurricane Isidore Simulations

2007 ◽  
Vol 135 (2) ◽  
pp. 549-566 ◽  
Author(s):  
Shu-Hua Chen
Keyword(s):  
Wind Speed ◽  
Wind Direction ◽  
Mesoscale Model ◽  
Three Dimensional ◽  
Storm Track ◽  
Initial Position ◽  
Wind Speeds ◽  
The Impact ◽  
Quikscat Winds

Abstract Three observational datasets of Hurricane Isidore (in 2002) were analyzed and compared: the Special Sensor Microwave Imager (SSM/I), the Quick Scatterometer (QuikSCAT) winds, and dropsonde winds. SSM/I and QuikSCAT winds were on average about 1.9 and 0.3 m s−1 stronger, respectively, than dropsonde winds. With more than 20 000 points of data, SSM/I wind speed was about 2.2 m s−1 stronger than QuikSCAT. Comparison of the wind direction observed by QuikSCAT with those from the dropsondes showed that the quality of QuikSCAT data is good. The effect of assimilating SSM/I wind speeds and/or QuikSCAT wind vectors for the analysis of Hurricane Isidore was assessed using the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5) and its three-dimensional variational data assimilation system. For the Hurricane Isidore case study, it was found that the assimilation of either satellite winds strengthened the cyclonic circulation in the analysis. However, the increment of the QuikSCAT wind analysis is more complicated than that from the SSM/I analysis due to the correction of the storm location, a positive result from the assimilation of wind vectors. The increase in low-level wind speeds enhanced the air–sea interaction processes and improved the simulated intensity for Isidore. In addition, the storm structure was better simulated. Assimilation of QuikSCAT wind vectors clearly improved simulation of the storm track, in particular during the later period of the simulation, but lack of information about the wind direction from SSM/I data prevented it from having much of an effect. Assessing the assimilation of QuikSCAT wind speed versus wind vector data confirmed this hypothesis. The track improvement partially resulted from the relocation of the storm’s initial position after assimilation of the wind vectors. For this case study, it was found that the assimilation of SSM/I or QuikSCAT data had the greatest impact on the Hurricane Isidore simulation during the first 2 days.

scholarly journals Wind Turbine Wake Measurements with Automatically Adjusting Scanning Trajectories in a Multi-Doppler Lidar Setup

2018 ◽  
Author(s):  
Norman Wildmann ◽  
Nikola Vasiljevic ◽  
Thomas Gerz
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Wind Direction ◽  
Sonic Anemometer ◽  
Prevailing Wind Direction ◽  
Wide Range ◽  
Engineering Models ◽  
Novel Method ◽  
German Aerospace ◽  
Turbine Wake

Abstract. In the context of the Perdigão 2017 experiment, the German Aerospace Center (DLR) deployed three long-range scanning Doppler lidars with the dedicated purpose of investigating the wake of a single wind turbine at the experimental site. A novel method was established to investigate wake properties with ground-based lidars over a wide range of wind directions. For this method, the three lidars, which were space- and time-synchronized using the WindScanner software, were programmed to measure with crossing beams at individual points up to ten rotor diameters downstream the wind turbine. Every half hour, the measurement points were adapted to the current wind direction to obtain a high availability of wake measurements in changing wind conditions. The linearly independent radial velocities where the lidar beams intersect allow the calculation of the wind vector at those points. Two approaches to estimate the prevailing wind direction were tested throughout the campaign. In the first approach, VAD scans of one of the lidars were used to calculate a five-minute average of wind speed and wind direction every half hour, whereas later in the experiment, five-minute averages of sonic anemometer measurements of a meteorological mast close to the wind turbine became available in real-time and were used for the scanning adjustment. Results of wind speed deficit measurements are presented for two measurement days with varying westerly winds and it is evaluated how well the lidar beam intersection points match the actual wake location. The new method allowed to obtain wake measurements over the whole measurement period, whereas a static scanning setup would only have captured short periods of wake occurrences. The analysed cases reveal that state-of-the-art engineering models for wakes underestimate the actual wind speed deficit.

scholarly journals Site-dependent decrease of odour-related peak-to-mean factors with distance

2014 ◽  
Vol 11 (1) ◽  
pp. 69-73 ◽  
Author(s):  
M. Piringer ◽  
W. Knauder ◽  
E. Petz ◽  
G. Schauberger
Keyword(s):  
Wind Speed ◽  
Wind Direction ◽  
Three Dimensional ◽  
Stability Parameter ◽  
Dispersion Models ◽  
Site Specific ◽  
Input Parameters ◽  
Meteorological Input

Abstract. The peak-to-mean concept developed earlier by the authors to calculate odour-related separation distances is applied here to meteorological input for dispersion models provided by ultrasonic anemometers. In addition to conventional meteorological input parameters like wind direction, wind speed and stability classes, three-dimensional sonics provide also turbulence information via the Obukhov stability parameter and the variance of the wind speed, which can be used directly to determine peak-to-mean ratios depending on the distance from the source. The influence and importance of these site-specific peak-to-mean ratios on the resulting direction-dependent separation distances is investigated and discussed.

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