Generation of spatio-temporally high resolved datasets for the validation of LES-models simulating flow and dispersion phenomena within the lower atmospheric boundary layer

Abstract

In order to develop and improve new concepts for grid-adaptive eddy resolving numerical simulations of natural flow phenomena, the German Research Foundation (DFG) established the priority program ‘MetStröm’. The program is intended to bundle the specific expertise currently available in the fields of Meteorology, Fluid Dynamics, and Applied Mathematics, fostering the development of the LES approach. Although the main focus of the program is on the theory and methodology of multi-scale modeling approaches, the program incorporates also a number of experimental contributions which are intended to provide relevant test data. As part of ‘MetStröm’, the Environmental Wind Tunnel Laboratory (EWTL) at Hamburg University is tasked to generate spatially and temporally high resolved data for the validation of Large Eddy Simulation (LES) models. Based on the conceptual work provided by Bastigkeit et al*), an extensive set of experiments has been designed and partially already realized. Flow as well as concentration measurements generating data of sufficiently high quality and quantity were carried out in two boundary layer wind tunnel facilities (WOTAN and BLASIUS) using LDA, PIV and other measurement techniques. In the style of the already existing validation data base for RANS-type models (CEDVAL), systematic data sets were generated at different levels of complexity. As explicitly requested by developers of LES models, different types of atmospheric boundary layer flows have been modeled at different scales and were completely documented. Following the style of CEDVAL, a further data base especially for the validation of LES-models CEDVAL-LES was established. The paper will elucidate the high experimental effort which needs to be spent in order to provide reference data qualified for the validation of LES codes. Special attention is given to data quality assurance procedures and an automated post-processing of the experimental results in order to minimize the need for manual interference which can be time consuming and even error-prone. Quality assurance as well as the automated data post processing is provided by a set of software tools, especially developed for processing data from wind tunnel measurements. On the other hand, the contribution will illustrate the capabilities of carefully designed and performed wind tunnel experiments.