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Micro diffuser flow modeling for cold gas propulsion systems
Author(s) -
Groll Rodion
Publication year - 2014
Publication title -
pamm
Language(s) - English
Resource type - Journals
ISSN - 1617-7061
DOI - 10.1002/pamm.201410304
Subject(s) - knudsen number , mechanics , nozzle , slip (aerodynamics) , aerospace engineering , shear stress , slip ratio , hypersonic speed , thrust , physics , propulsion , materials science , engineering
The use of highly diluted and hypersonic gas flow is in the scope of application of cold gas thrusters for space applications. Satellites and small spacecrafts are navigated to their orbital trajectory with these nozzles. Inside these propulsion systems high density gradients are dominating the efficiency and the thrust steering behavior of the propulsion systems. Micro flows in the transient regime between free molecular flow and continuous flow are not able to be computed with trustworthy results by using a continuous model with no‐slip boundary conditions. Therefore boundary slip‐velocity models are used for modeling the reduced wall shear stress. Molecular shear stresses decrease the molecular mean velocity near the wall. With a Knudsen number depending slip‐velocity model the effective shear stress is computed by the mean gradient of the velocity profile near the wall. In the present study a trans‐sonic nozzle flow is computed by using a calibrated velocity slip model what depends on the Knudsen number. The Knudsen numbers are lower the Kn=1 at the nozzle neck of the propulsion system. The results are compared with simulation results of a uniform channel flow and computations of the corresponding no‐slip approach. The differences in the hypersonic region are following discussed. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)