Grid Setups and Numerical Simulations of a Low Boom Concept at Off Design Flight Conditions

Abstract

The accurate prediction of the sonic boom along all parts of the mission trajectory is essential for the development and certification of a future low boom supersonic commercial aircraft. In this paper, the C25D low-boom concept geometry from the Second AIAA Sonic Boom Prediction Workshop is used to conduct numerical simulations at off-design flight conditions with the DLR TAU code. The flight altitude and flight Mach number are varied to simulate a mission trajectory while the lift is kept constant. The focus of this paper is the evaluation of a core grid setup with a non-circular cross section and the assessment of the applicability of the grid deformation and the Chimera technique for the variation of angle of attack while the farfield grid remains aligned to the Mach cone. It is shown that both techniques are viable and that differences in the pressure signatures between both techniques are negligible. Using the grid deformation technique resulted in lower grid node numbers and thus lower computational cost. In addition, the sensitivities of varying flight conditions on the pressure fields are evaluated. It is shown that the pressure signatures are strongly affected by varying flight conditions. While the shape of the front part of the pressure signatures stays constant for all flight conditions and only the magnitude changes, the impact on the aft part of the signature is large. The shocks and expansions are adversely interacting if only Mach number or the altitude are changed. Especially, the magnitudes of the main expansions are increasing. The lowest peak interactions for the on-track pressure signature can be found for accelerating while climbing