Plume impingement investigation using Monte-Carlo computations

Abstract

Numerical simulations have been performed to explore the effects of important design parameters on impingement disturbance properties of multiple hydrazine thruster plumes. The particle behaviour of the far-field plume flows near the impingement surfaces is modelled using the collisionless molecular direct simulation Monte-Carlo method with the inflow boundary condition derived from the velocity and temperature profiles at the nozzle exit. The entering molecular motions and the impact interactions between molecules and solid boundaries are treated on a probabilistic basis, whereas the main flow properties are preserved from the transformation of the microscopic fluid activities of simulated molecules. To validate the present computer code, the predicted transverse Pitot pressure profile was compared with the measured data in the far plume region of an MBB/ERNO 0.5-N conical nozzle. On the basis of the ROCSAT-1 design configuration, the calculated plume disturbance torques are examined in the yaw, roll, and pitch directions for different settings of the canted angle of the thruster mounting and the satellite centre-of-mass (CM) offset. Predictions show that the normalized yaw impingement disturbance torque reaches 6.3 per cent at the cant angle of 30°, indicating that the associated plume collision effect on the attitude control can be important at large cant angles. In addition, the location change of the satellite CM in the axial axis reveals insignificant influence on the impingement torque for the offset value varying from −5.0 to 5.0 cm.