Simulation validation of static and forced motion flow physics of a canard configured TransCruiser

Abstract

The basic objective of this work is to validate CFD simulations performed on a transonic cruiser configuration called the TCR. The low speed aerodynamic characteristics of the TCR have previously been investigated at the Russian TsAGI T-103 wind tunnel as part of the European Framework 6 SimSAC project. The experimental results showed that static and dynamic pitch moment curves are very nonlinear. These experimental data are used in this work to validate CFD predictions using the Cobalt flow solver with an overset grid approach. Two types of wind tunnel tests were conducted: static tests for angle-of-attack sweeps at zero degrees sideslip and angle-of-sideslip sweeps at different angles of attack. The dynamic tests include forced sinusoidal oscillations in one of three modes of pitch, yaw, and roll. Both static and dynamic tests were conducted with/without a vertical tail and at different canard deflections. Dynamic tests are small- and large-amplitude motions with frequencies of 0.5, 1.0, and 1.5 Hz. CFD results were obtained with different turbulence models and using a single mesh or an overset grid approach, and then compared with the experimental data. The effects of the canard downwash flow on the wing aerodynamic performance are also investigated. The comparison between the experimental and CFD simulations show that the results match well. The overset mesh that includes a gap between the canard and fuselage leads to the same predictions as the single mesh that has no gaps. The CFD solutions show that vortices are formed over the canard, fuselage, leading-edge extension (LEX), wing, and the vertical tail (at sideslip angles). Each vortex appears to have a primary vortex accompanied by a smaller counter-rotating secondary vortex. These vortices are influenced by the canard presence and deflection. At high angles of attack, the canard vortex has two favorable effects in terms of increasing the maximum lift and delaying the wing vortex breakdown. In the range of angles of attack between 18° and 24°, the canard vortex core moves upward off the canard surface and the LEX and wing vortices interact and then merge; both effects lead to a sudden change in the slopes of the force and moment curves. Finally, the CFD data show that increasing the canard deflection produces a stronger vortex over the canard, but leads to smaller fuselage and LEX vortices.