Rarefied Flow Field Analysis on a Re-entry Vehicle
Rarefied flow field analysis has been carried out on a re-entry vehicle (REV) for an altitude of 105 km. DSMC-based solver was used to calculate pressure, drag, temperature and heat-flux. A blunt nose re-entry vehicle (REV) was used for the analysis in a
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Abstract Rarefied flow field analysis has been carried out on a re-entry vehicle (REV) for an altitude of 105 km. DSMC-based solver was used to calculate pressure, drag, temperature and heat-flux. A blunt nose re-entry vehicle (REV) was used for the analysis in a rarefied flow field. The flow was considered to be in chemical and + + + + thermal non-equilibrium. 11 species (N2 , O2 , NO, N+ 2 , O2 , NO , N, N , O, O and − e ) model for gas composition was used with total of 47 chemical reactions. Observations were also made for the existence of shockwave, change in shock thickness and its properties. It was observed that there is a small variation in chemically non-reacting and reacting (chemically non-equilibrium) flow. The existence of shockwave can only be predicted by means of observations of properties such as temperature, pressure and density as the rarefaction is more. No clear distinct region of discontinuity was seen in the flow field and temperature and pressure field shows sudden variations in properties. Drag profile is fairly constant for both the conditions. Although the temperature is very large, the heat-flux to the body was found to be very less. Keywords Shockwave · DSMC · Rarefied region · Chemical reactions · Heat-flux · Chemical reaction (CR) · Non-chemical reaction (NCR)
M. Abhay Defence Institute of Advanced Technology (DIAT), Pune, India e-mail: [email protected] V. Kumar (B) · A. Chaphalkar (B) · J. Justus (B) CFDD/AERO, ISRO (VSSC), Thiruvananthapuram, India e-mail: [email protected] A. Chaphalkar e-mail: [email protected] J. Justus e-mail: [email protected] © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 N. Gascoin and E. Balasubramanian (eds.), Innovative Design, Analysis and Development Practices in Aerospace and Automotive Engineering, Lecture Notes in Mechanical Engineering, https://doi.org/10.1007/978-981-15-6619-6_57
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1 Introduction Macroscopic approach uses the set of continuity, momentum and energy equation for the calculation of properties such as pressure, temperature, velocity, etc. Same set of equations can also be used for microscopic analysis but requires incorporation of transport and heat-flux equations too. It is the use of these set of deterministic equations which accurately models rarefied flow. Use of these additional equations in an analysis breaks the assumption of macroscopic approach rather than the increase in mean free-path between two molecules. Basically, Knudsen number gives the degree of rarefaction and is defined as Kn =
λ l
(1)
where l is the characteristic length, λ is the mean free-path and ρ is the density of gas (air). For the flow to be considered as the rarefied flow, Kn should be more than 0.1 and molecular approach needs to be incorporated. Macroscopic approach starts to yields inaccurate results as rarefaction increases. At Kn equal to 0.2 it becomes important to use the molecular approach and macroscopic model no longer ca
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