A study of unsteady projectile aerodynamics using a moving coordinate method

Abstract

A computational fluid dynamics (CFD) method has been applied to simulate unsteady near-field aerodynamics of the projectile which is launched from a ballistic range. A moving coordinate scheme for a multi-domain technique was employed to investigate the unsteady flow with moving boundary. The coordinate system fixed to each moving domain was applied to the multi-domains, and the effect of virtual mass was added in the governing equations for each domain. The unsteady, axi-symmetric Euler equation systems were numerically solved using the third-order Chakravarthy-Osher total variation diminishing scheme, with Monotone Upstream-centered Scheme for Conservation Laws (MUSCL) approach. The present computations were validated with results of some other CFD works and experimental data available. The computed results reasonably capture the major flow features, such as shock waves, blast waves, shear layers, vortical flows, etc which are generated in launching a projectile up to a supersonic speed. The projectile mass, configuration, and the initial conditions behind the projectile have been varied to investigate its effect on the flow field and the unsteady projectile aerodynamics. The unsteady aerodynamics of the projectile is strongly affected by the projectile mass and configuration. The initial conditions behind the projectile have strong influence on the near flow field structures which govern the development of the blast wave along with the projectile motion.

Launch Dynamics of Supersonic Projectiles

“…The projecfile experiences drastic fluctuations in accelerafion due to multiple reflecfions owing to these wave excursions. However, it has previously been observed [23] that the fluctuafions in the projectile base pressure damp out very fast and the velocity doesn't seem to be affected greatly [5]. This is dependent on many factors, such as the diaphragm rupture pressure, area rafio of the pump tube to launch tube, projectile mass and diameter, and the type of the gas, etc.…”

“…Although the effect of the viscosity on the projectile aerodynamic characteristics is not significant, the viscosity greatly affects the unsteady flow structures around the projectile. T HE UNSTEADY flowfields induced by the projectile when it is launched from a barrel attracted the attention of many researchers because it involves various complicated fluid dynamic processes associated with its motion [1][2][3][4][5][6][7][8][9]. The primary flow disturbances that make the flowfield quite unsteady and complex are the flow interfaces in the primary blast wave [10][11][12][13] and their interactions [14].…”

“…The unsteady flow-fields induced by the projectile when it is launched from a barrel attracted attention of many researchers since it involve various complicated fluid dynamic processes associated with its motion [1][2][3][4][5][6][7][8][9] . The primary flow disturbances which make the flow field quite unsteady and complex are the flow interfaces in the primary blast wave [10][11][12][13] and its interactions 14 .…”

Investigation and comparison of performance of some air gun projectiles with nose shape modifications

“…where W * is the approximation to W n + 1 , t * denotes a pseudo-time variable and R * is the unsteady residual which is defined in Blazek. 13 The flow equations shown in equation (11) are solved using Jameson's four-stage scheme 17 and with the equations of the projectiles' motion and the turbulence equations k-k L -v in simultaneous and coupled form using a moving computational grid. In order to achieve the location and velocity of the projectiles, the aerodynamic loads at each time step are initially obtained by solving the Navier-Stokes equations and then placed into equation (9) to calculate the new values of acceleration, velocity and location of the projectiles using fourth-order Runge-Kutta method and, therefore, the solution preparations are provided for the next time step.…”

“…In projectile research, grid generation and flow field solution are of interest. Rajesh et al 11 simulated non-stationary aerodynamics of a projectile. A moving coordinate scheme for a multi-domain technique was employed to examine the non-stationary flow with a moving boundary.…”