author = "Paolicchi, Lu{\'{\i}}s Thiago Lucci Corr{\^e}a and Santos, 
                         Wilson Fernando Nogueira dos",
          affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)}",
                title = "Compressibility effects on the aerodynamic surface quantities of 
                         hypersonic gap flows",
            booktitle = "Abstracts...",
                 year = "2013",
         organization = "European Conference For Aeronautics And Space Sciences (eucass 
                         2013), 5.",
                 note = "Setores de Atividade: Outras atividades profissionais, 
                         cient{\'{\i}}ficas e t{\'e}cnicas.",
             keywords = "DMSC, hypersonic flow, rarefied flow, gap.",
             abstract = "The thermal protection systems of vehicles like the space shuttle 
                         orbiter or crew rescue vehicle X-38 require gaps between the used 
                         protection elements to account for thermal expansion. For the 
                         optimized design of gaps and protection elements, it is necessary 
                         to predict the flow conditions and thermal loads as accurate as 
                         possible. The flow in the gap is complex because of staggered gap 
                         configuration, radiation cooling, transient flow, etc. In the case 
                         of reentry vehicles, the boundary layer transition prediction is a 
                         requirement to define the thermal protection system. This 
                         protection is usually designed as an assembly of tiles. The gaps 
                         between the tiles may modify the boundary layer state and 
                         eventually promote transition, inducing higher temperature levels 
                         than expected. For the particular case of gaps, some experimental 
                         studies have been conducted in order to understand the physical 
                         aspects of a hypersonic flow past to this type of surface 
                         discontinuities. In general, the major interest in these studies 
                         has gone into considering laminar or turbulent flow in the 
                         continuum flow regime. Nevertheless, there is little understanding 
                         of the physical aspects of a hypersonic flow over gaps related to 
                         the severe aerothermodynamic environment associated to a reentry 
                         vehicle. In this fashion, Paolicchi and Santos [1] have studied 
                         gaps situated in a rarefied hypersonic flow by employing the 
                         Direct Simulation Monte Carlo (DSMC) method. The work was 
                         motivated by the interest in investigating the length-to-depth 
                         (L/H) ratio effects on the flowfield structure. The primary 
                         emphasis was to examine the behavior of the primary properties, 
                         such as velocity, density, pressure and temperature, due to 
                         changes on the gap L/H ratio. The analysis showed that the gap 
                         flow behavior in the transition flow regime differs from that 
                         found in the continuum flow regime, for the conditions 
                         investigated. It was found only one vortex for the L/H ratio of 1, 
                         1/2, 1/3 and 1/4, as shown in the figure below. Conversely, in the 
                         continuum flow regime, the number of vortices inside the gap is 
                         approximately given by the amount H/L. Having established a 
                         physical picture of the flowfield structure in a gap, the current 
                         study expands on the results presented in the previous analysis 
                         [1] by investigating the effects of the compressibility as well as 
                         the L/H ratio on the aerodynamic surface quantities. In this 
                         manner, the purpose of the present account is to investigate 
                         numerically the sensitivity of the heat transfer, pressure and 
                         skin friction coefficients due to changes on the gap L/H ratio and 
                         on the freestream Mach number in the transition flow regime. In 
                         the present account, L/H ratio will change from 1 to 1/4, with L 
                         of 3 mm. The freestream Mach number will be 5, 15 and 25. The 
                         focus of the present study is the low-density region in the upper 
                         atmosphere. At high altitudes, and therefore, low density, the 
                         molecular collision rate is low and the energy exchange occurs 
                         under non-equilibrium conditions. In such a circumstance, the 
                         degree of molecular non-equilibrium is such that the Navier-Stokes 
                         equations are inappropriate. Therefore, the DSMC method will be 
                         employed to calculate the hypersonic two-dimensional flow on the 
  conference-location = "Munich",
      conference-year = "1-5 July, 2013",
                label = "lattes: 4859685163568596 2 PaolicchiSant:2013:CoEfAe",
             language = "en",
           targetfile = "a179-1.pdf",
        urlaccessdate = "21 jan. 2021"