The Atmospheric Flow at the Alcantara Space Center—In Situ Observations, Modeling, and Wind Tunnel Essays

The Alcantara Space Center (ALC) is the Brazil´s gate to acess the space. From this range, the brazilian rockets are launched to the atmosphere. The knowledge of the wind flow is very important for different phases of the flight, especially the wind at the surface (for determining the flight trajectory, criteria of rocket launching, air quality dispersion model, etc). The topography of the region is very particular one as ALC is located at the sea continent border and there is a steep cliff (40 m height) at this interface. The winds (trade winds) always blow from the oceanic (smooth surface) enconteres this barrier (steep cliff) and an internal boundary layer is created over the continent (rough surface) as well as enhanced turbulence. The strategy adopted by this project was to conduct field measurements (for data validation), wind tunnel essays and numerical modelling using an atmospheric meteorological models and computation fluid dynamics (CFD) techniques. For the field measurements, there were 3 field campaings already held at ALC in order to collect data that describes the spatial and temporal evolution of the flow. From this data-set (which includes radiosondes relesead at 6 hours, sonic anemometer data sampled at high frequency (20 Hz) and an array of 12 wind masts (slow response sensors and sample at 0.5 Hz of 10 m spaced located at ALC), some parameters of the turbulence were derived and used at the model simulations as input and boundary conditions. For the wind tunnel essays, a mock-up of the topography (including the assembly building) was constructed and the flow and turbulence were studied using hot wire anemometer and particle image velocimetry sensors. The vorticity field and profiles of turbulence (fluctuations) were computed at different positions at the launch pad. Also, a Large-Eddy Simulation model (PALM model from University of Hannover, Germany) and a comercial software (FLUENT ) of CFD are currently being used to study the spatial variation of the flow. The domain is 5 km X 5 km X 3 km and a Turbulent Kinetic Energy budged was performed. The horizontal and vertical transects of mean wind speed (10 min average), turbulence intensity, momentum fluxes obtained from CFD, LES and wind tunnel experiments compare reasonably well. The recirculating flows after building wakes and turbulent transport processes are well resolved by both CFD and LES and wind tunnel experiments. It is a project sponsored by CAPES (Pró-Estratégia n. 2240/2012) and CNPq (Edital Universal 2016 n. 403899/2016-8).