To study fast Alfvén wave damping on fast ions, a Monte-Carlo code ORBIT-RF has been coupled with a 2D full wave code TORIC4. The ORBIT-RF/TORIC4 combination has been applied to DIII-D experimental conditions to investigate Fast Wave (FW) heating of injected beam ions over a range of ion cyclotron harmonics. ORBIT-RF using a single dominant toroidal and poloidal Fourier wave number qualitatively reproduces the strong FW-beam interaction at 60MHz (4 D and 5 D ) and the much weaker interaction at 116MHz (8 D ) in DIII-D L-mode plasmas, consistent with experimental observations. The result at 8 D differs from linear theory prediction using a Maxwellian to model the fast ion distribution function, suggesting the importance of finite orbit effect, Coulomb collisions for transport across flux surfaces and the details of the non-Maxwellian fast ion distribution.