Iungo, Giacomo V.

Permanent URI for this collectionhttps://hdl.handle.net/10735.1/4790

Giacomo Iungo is currently an Associate Professor of Mechanical Engineering and head of the WindFluX (Wind, Fluids, and eXperiments) Lab. His research interests include wind energy, flow instability, bluff body aerodynamics; atmospheric boundary layer, reduced order models; signal processing; wind tunnel design; experimental fluid mechanics; and wind LiDAR technology.

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Browsing Iungo, Giacomo V. by Author "Debnath, Mithu"

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    Assessing State-of-the-Art Capabilities for Probing the Atmospheric Boundary Layer: The XPIA Field Campaign
    (Amer Meteorological Soc) Lundquist, Julie K.; Wilczak, James M.; Ashton, Ryan; Bianco, Laura; Brewer, W. Alan; Choukulkar, Aditya; Clifton, Andrew; Debnath, Mithu; Hamidi, Armita; Iungo, Giacomo V.; Ashton, Ryan; Debnath, Mithu; Hamidi, Armita; Iungo, Giacomo V.
    To assess current capabilities for measuring flow within the atmospheric boundary layer, including within wind farms, the U.S. Department of Energy sponsored the eXperimental Planetary boundary layer Instrumentation Assessment (XPIA) campaign at the Boulder Atmospheric Observatory (BAO) in spring 2015. Herein, we summarize the XPIA field experiment, highlight novel measurement approaches, and quantify uncertainties associated with these measurement methods. Line-of-sight velocities measured by scanning lidars and radars exhibit close agreement with tower measurements, despite differences in measurement volumes. Virtual towers of wind measurements, from multiple lidars or radars, also agree well with tower and profiling lidar measurements. Estimates of winds over volumes from scanning lidars and radars are in close agreement, enabling the assessment of spatial variability. Strengths of the radar systems used here include high scan rates, large domain coverage, and availability during most precipitation events, but they struggle at times to provide data during periods with limited atmospheric scatterers. In contrast, for the deployment geometry tested here, the lidars have slower scan rates and less range but provide more data during nonprecipitating atmospheric conditions. Microwave radiometers provide temperature profiles with approximately the same uncertainty as radio acoustic sounding systems (RASS). Using a motion platform, we assess motion-compensation algorithms for lidars to be mounted on offshore platforms. Finally, we highlight cases for validation of mesoscale or large-eddy simulations, providing information on accessing the archived dataset. We conclude that modern remote sensing systems provide a generational improvement in observational capabilities, enabling the resolution of finescale processes critical to understanding inhomogeneous boundary layer flows.
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    Assessment of Virtual Towers Performed with Scanning Wind Lidars and Ka-Band Radars during the XPIA Experiment
    (Copernicus GmbH) Debnath, Mithu; Iungo, Giacomo V. .; Brewer, W. Alan; Choukulkar, A.; Delgado, R.; Gunter, S.; Lundquist, J. K.; Schroeder, J. L.; Wilczak, J. M.; Wolfe, D.; Debnath, Mithu; Iungo, Giacomo V. .
    During the eXperimental Planetary boundary layer Instrumentation Assessment (XPIA) campaign, which was carried out at the Boulder Atmospheric Observatory (BAO) in spring 2015, multiple-Doppler scanning strategies were carried out with scanning wind lidars and Ka-band radars. Specifically, step-stare measurements were collected simultaneously with three scanning Doppler lidars, while two scanning Ka-band radars carried out simultaneous range height indicator (RHI) scans. The XPIA experiment provided the unique opportunity to compare directly virtual-tower measurements performed simultaneously with Ka-band radars and Doppler wind lidars. Furthermore, multiple-Doppler measurements were assessed against sonic anemometer data acquired from the meteorological tower (met-tower) present at the BAO site and a lidar wind profiler. This survey shows that-despite the different technologies, measurement volumes and sampling periods used for the lidar and radar measurements - a very good accuracy is achieved for both remote-sensing techniques for probing horizontal wind speed and wind direction with the virtual-tower scanning technique.
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    Evaluation of Single and Multiple Doppler Lidar Techniques to Measure Complex Flow During the XPIA Field Campaign
    (Copernicus GmbH, 2018-08-20) Choukulkar, A.; Brewer, W. A.; Sandberg, S. P.; Weickmann, A.; Bonin, T. A.; Hardesty, R. M.; Lundquist, J. K.; Delgado, R.; Iungo, Giacomo V.; Ashton, Ryan; Debnath, Mithu; Bianco, L.; Wilczak, J. M.; Oncley, S.; Wolfe, D.; 0000-0002-0990-8133 (Iungo, GV); Iungo, Giacomo V.; Ashton, Ryan; Debnath, Mithu
    Accurate three-dimensional information of wind flow fields can be an important tool in not only visualizing complex flow but also understanding the underlying physical processes and improving flow modeling. However, a thorough analysis of the measurement uncertainties is required to properly interpret results. The XPIA (eXperimental Planetary boundary layer Instrumentation Assessment) field campaign conducted at the Boulder Atmospheric Observatory (BAO) in Erie, CO, from 2 March to 31 May 2015 brought together a large suite of in situ and remote sensing measurement platforms to evaluate complex flow measurement strategies. In this paper, measurement uncertainties for different single and multi-Doppler strategies using simple scan geometries (conical, vertical plane and staring) are investigated. The tradeoffs (such as time-space resolution vs. spatial coverage) among the different measurement techniques are evaluated using co-located measurements made near the BAO tower. Sensitivity of the single-/multi-Doppler measurement uncertainties to averaging period are investigated using the sonic anemometers installed on the BAO tower as the standard reference. Finally, the radiometer measurements are used to partition the measurement periods as a function of atmospheric stability to determine their effect on measurement uncertainty. It was found that with an increase in spatial coverage and measurement complexity, the uncertainty in the wind measurement also increased. For multi-Doppler techniques, the increase in uncertainty for temporally uncoordinated measurements is possibly due to requiring additional assumptions of stationarity along with horizontal homogeneity and less representative line-of-sight velocity statistics. It was also found that wind speed measurement uncertainty was lower during stable conditions compared to unstable conditions.
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    Identification of Tower-Wake Distortions Using Sonic Anemometer and Lidar Measurements
    (Copernicus GmbH, 2018-08-31) McCaffrey, K.; Quelet, P. T.; Choukulkar, A.; Wilczak, J. M.; Wolfe, D. E.; Oncley, S. P.; Alan Brewer, W.; Debnath, Mithu; Ashton, Ryan; Iungo, Giacomo V.; Lundquist, J. K.; 0000-0002-0990-8133 (Iungo, GV); Debnath, Mithu; Ashton, Ryan; Iungo, Giacomo V.
    The eXperimental Planetary boundary layer Instrumentation Assessment (XPIA) field campaign took place in March through May 2015 at the Boulder Atmospheric Observatory, utilizing its 300 m meteorological tower, instrumented with two sonic anemometers mounted on opposite sides of the tower at six heights. This allowed for at least one sonic anemometer at each level to be upstream of the tower at all times and for identification of the times when a sonic anemometer is in the wake of the tower frame. Other instrumentation, including profiling and scanning lidars aided in the identification of the tower wake. Here we compare pairs of sonic anemometers at the same heights to identify the range of directions that are affected by the tower for each of the opposing booms. The mean velocity and turbulent kinetic energy are used to quantify the wake impact on these first-and second-order wind measurements, showing up to a 50 % reduction in wind speed and an order of magnitude increase in turbulent kinetic energy. Comparisons of wind speeds from profiling and scanning lidars confirmed the extent of the tower wake, with the same reduction in wind speed observed in the tower wake, and a speed-up effect around the wake boundaries. Wind direction differences between pairs of sonic anemometers and between sonic anemometers and lidars can also be significant, as the flow is deflected by the tower structure. Comparisons of lengths of averaging intervals showed a decrease in wind speed deficit with longer averages, but the flow deflection remains constant over longer averages. Furthermore, asymmetry exists in the tower effects due to the geometry and placement of the booms on the triangular tower. An analysis of the percentage of observations in the wake that must be removed from 2 min mean wind speed and 20 min turbulent values showed that removing even small portions of the time interval due to wakes impacts these two quantities. However, a vast majority of intervals have no observations in the tower wake, so removing the full 2 or 20 min intervals does not diminish the XPIA dataset. © 2017 Author(s).
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    Vertical Profiles of the 3-D Wind Velocity Retrieved from Multiple Wind Lidars Performing Triple Range-Height-Indicator Scans
    (Copernicus GmbH, 2018-08-20) Debnath, Mithu; Iungo, Giacomo V.; Ashton, Ryan; Alan Brewer, W.; Choukulkar, A.; Delgado, R.; Lundquist, J. K.; Shaw, W. J.; Wilczak, J. M.; Wolfe, D.; 0000-0002-0990-8133 (Iungo, GV); Debnath, Mithu; Iungo, Giacomo V.; Ashton, Ryan
    Vertical profiles of 3-D wind velocity are retrieved from triple range-height-indicator (RHI) scans performed with multiple simultaneous scanning Doppler wind lidars. This test is part of the eXperimental Planetary boundary layer Instrumentation Assessment (XPIA) campaign carried out at the Boulder Atmospheric Observatory. The three wind velocity components are retrieved and then compared with the data acquired through various profiling wind lidars and high-frequency wind data obtained from sonic anemometers installed on a 300 m meteorological tower. The results show that the magnitude of the horizontal wind velocity and the wind direction obtained from the triple RHI scans are generally retrieved with good accuracy. However, poor accuracy is obtained for the evaluation of the vertical velocity, which is mainly due to its typically smaller magnitude and to the error propagation connected with the data retrieval procedure and accuracy in the experimental setup.

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