Title: An LES-based airborne Doppler lidar simulator and its application to wind profiling in inhomogeneous flow conditions

Abstract

Wind profiling by Doppler lidar is common practice and highly useful in a wide range of applications. Airborne Doppler lidar can provide additional insights relative to ground-based systems by allowing for spatially distributed and targeted measurements. Providing a link between theory and measurement, a first large eddy simulation (LES)-based airborne Doppler lidar simulator (ADLS) has been developed. Simulated measurements are conducted based on LES wind fields, considering the coordinate and geometric transformations applicable to real-world measurements. The ADLS provides added value as the input truth used to create the measurements is known exactly, which is nearly impossible in real-world situations. Thus, valuable insight can be gained into measurement system characteristics as well as retrieval strategies. As an example application, airborne Doppler lidar wind profiling is investigated using the ADLS. For commonly used airborne velocity azimuth display (AVAD) techniques, flow homogeneity is assumed throughout the retrieval volume, a condition which is violated in turbulent boundary layer flow. Assuming an ideal measurement system, the ADLS allows to isolate and evaluate the error in wind profiling which occurs due to the violation of the flow homogeneity assumption. Overall, the ADLS demonstrates that wind profiling is possible in turbulent wind field conditions with reasonablemore » errors (root mean squared error of 0.36 m s^–1 for wind speed when using a commonly used system setup and retrieval strategy for the conditions investigated). Nevertheless, flow inhomogeneity, e.g., due to boundary layer turbulence, can cause an important contribution to wind profiling error and is non-negligible. Results suggest that airborne Doppler lidar wind profiling at low wind speeds (<5 m s^–1) can be biased, if conducted in regions of inhomogeneous flow conditions.« less

Authors:

Gasch, Philipp ^[1]; Wieser, Andreas ^[1]; Lundquist, Julie K.  ^[2];

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Kalthoff, Norbert ^[1]

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+ Show Author Affiliations

1. Karlsruhe Inst. of Technology (KIT) (Germany)
2. Univ. of Colorado, Boulder, CO (United States); National Renewable Energy Lab. (NREL), Golden, CO (United States)

Publication Date:

2020-04-02

Research Org.:

National Renewable Energy Lab. (NREL), Golden, CO (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE); Helmholtz Association

OSTI Identifier:

1659814

Report Number(s):

NREL/JA-5000-74195
Journal ID: ISSN 1867-8548; MainId:6108;UUID:3157457c-b08e-e911-9c24-ac162d87dfe5;MainAdminID:13413

Grant/Contract Number:  

AC36-08GO28308

Resource Type:

Accepted Manuscript

Journal Name:

Atmospheric Measurement Techniques (Online)

Additional Journal Information:

Journal Name: Atmospheric Measurement Techniques (Online); Journal Volume: 13; Journal Issue: 3; Journal ID: ISSN 1867-8548

Publisher:

Copernicus Publications, EGU

Country of Publication:

United States

Language:

English

Subject:

17 WIND ENERGY; Doppler lidar simulator; inhomogenous flow conditions; wind; wind profiling