Simulations of the Atmospheric Boundary Layer in a Wind Tunnel with Short Test Section

Abstract

This article presents a study of three different passive devices (spires, screens, and a carpet) separately and in various combinations, to simulate the atmospheric boundary layer (ABL) in a wind tunnel with a short test chamber (465×465x1200mm). The influence of distances between these devices on the formation of the ABL is established, and optimization of variation of thicknesses of the screens (thin, medium, and coarse) on pressure loss is explored. The results obtained in this work gave support for the analysis of the atmospheric flow and turbulence at Alcantara Launching Center (ALC) in order to launch Brazilian space vehicles under safe conditions. The results show that the "spires" and the thin screen are the devices that require the least area to form an ABL in a test chamber. The physical proximity of two devices (the spires and the medium screen) also influences the size of the ABL formed, which varies from 180 to 200 mm. The power law exponent ranged from 0.12 up to 0.14 after the insertion of a carpet.

CFD Modeling of the Atmospheric Boundary Layer in Short Test Section Wind Tunnel

“…An unstructured Triangle grid was constructed based on refinements with a factor of 2 (397258 elements). The distance between the centre point of the wall-adjacent cells and the wall (carpet) is 0.002 m. The inlet mean wind speed profile and the turbulence intensity profile are taken according to the experimental work [4]. Fig.1(b) shows the grid of the computational domain related to the physical domain [4] as shown in Fig.1(a).…”

“…The distance between the centre point of the wall-adjacent cells and the wall (carpet) is 0.002 m. The inlet mean wind speed profile and the turbulence intensity profile are taken according to the experimental work [4]. Fig.1(b) shows the grid of the computational domain related to the physical domain [4] as shown in Fig.1(a). Grid sensitivity study using velocity profile at x = 1.42 m, non-uniform flow at inlet, KP = 0.75, and distance 0.3 m from experimental work [4] with different grid sizes as shown in Fig.…”

“…According to [4], the domain represents a rectangular wind tunnel test section with dimensions 0.41 × 0.41 m 2 with a length of 1.8 m, as shown in Fig. 1a.…”

“…Thus, improved techniques for reproduction of the main characteristics of natural winds, as well as the formation of the atmospheric boundary layer (ABL), are needed. These techniques will permit shorter test chambers, so that existing aeronautical tunnels could be used for atmospheric simulations of meteorological interest, with the advantage of flow control and improved data collection [4]. The several studies using the wind tunnel for simulating the characteristics and behavior of the atmosphere can be found in Refs.…”

A Study of the Internal Boundary Layer Generated at the Alcantara Space Center

“…For this study, a channel apparatus with a width of 410 mm and length of 1200 mm, consisting of an uncovered wooden frame, with free edges and side walls parallel to each other and perpendicular to the floor of the wind tunnel, was used to extend the test section for the formation of the atmospheric Boundary Layer (ABL) based on the roughness correspondent to the rural terrain. Details about this simulation can be found at Pires et al [38]. The atmospheric flow was simulated by electric fans with 30 hp (22 kW) power, which generated a maximum wind velocity of 33 m s-1.…”