Air flow quality analysis of an open-circuit boundary layer wind tunnel and comparison with a closed-circuit wind tunnel

Abstract

The wide use of wind tunnels, as a tool to measure the flow properties and the flow effects on different structures/ecosystems, makes it necessary to guarantee the correct functioning of the facility and to carry out a continuous monitoring. The aim of this work is (i) to check the homogeneity and quality of the air flow in an open-circuit boundary layer wind tunnel, (ii) to provide data and ideas that could help other researchers to improve similar tunnels, and (iii) to compare some of the results with the behavior of a classic closed-circuit wind tunnel. Experiments are carried out working with a constant reference velocity, using a hot cross wire anemometry system to obtain high resolution measurements, in the entrance and test sections for different longitudinal and cross planes. The results concern the characteristics of the mean and turbulent flow. In this manuscript, we report the analysis of the turbulence production, the Reynolds stresses, the vertical velocity skewness, the vorticity, and the spectral properties, and a quadrant decomposition is also performed. Finally, comparing the results with respect to a closed-circuit wind tunnel, it is shown that the turbulence intensity is generally higher and the mean flow is more homogeneous in the present open-circuit wind tunnel. Moreover, the Reynolds number is similar in both tunnels, which indicates that both tunnels are mechanically similar.

Velocity and density measurements in forced fountains with negative buoyancy

“…for vertical velocities. The indicator s w gives also information on the structure of the flow field, 30 since the triple correlation w 03 represents the transport of w 0 w 0 by the turbulence itself. Moreover, skewness plays the same role in the equation for the evolution of turbulent kinetic energy (TKE).…”

A New Methodology for Assessing the Interaction between the Mediterranean Olive Agro-Forest and the Atmospheric Surface Boundary Layer

“…Neutral atmospheric stability was used, due to the limitations of mechanical wind tunnel testing [30]. However, according to the results of Moon et al [13], there is a small contribution from changes in atmospheric stability, so the main change is generated by the wind speed.…”

“…As a preliminary step, the incoming flow homogeneity in the wind tunnel with an empty test section was performed for different velocities and elements for turbulence control [30]. Vertical profiles of the wind velocity (U), turbulence (IT and TKE), aerodynamic roughness length (z o ), friction velocity (u * ) and Reynolds number (Re) were obtained (Table 4) and taken as reference values for the ABL.…”

“…For this purpose, the spatial evolution of the wind dynamics was calculated from temporal wind speed measurements, recorded in regularly spatially distributed points located behind the agro-forest system (in the x, y and z directions), based on the physical principles previously provided. Physical experiments were carried out in the BLWT of the University of Granada [30], based on a dimensional analysis of the variables of interest and the particularities of the Andalusian olive grove.…”

Design of Low Subsonic Wind Tunnel with Open Return System for Testing Wind Turbines at Low Airspeeds

“…Open return wind tunnel dan close return wind tunnel memiliki kebihan dan kekurangan masingmasing sesuai dengan kebutuhan. Kelebihan open return wind tunnel adalah Intensitas turbulensi umumnya lebih tinggi dan aliran rata-rata lebih homogen, biaya konstruksi rendah, desain unggul untuk propulsi dan visualisasi asap, dan tidak ada akumulasi produk buangan di terowongan terbuka [14,15].…”