Radiofrequency ablation is a typical treatment for severe cases of cardiac arrhythmias. A catheter, inserted from the patient's groin, delivers current at frequencies 450-500kHz to the arrhythmogenic tissue, inflicting thermal damage. The electrical current delivered to the tissue is proportional to the direct contact with the tip electrode, which depends (among others) on the tip shape and the catheter orientation. A modified Penne's bioheat equation with an electric source and a blood cooling convection is the standard choice for RFA models. The Navier-Stokes equation simulates the interaction of the blood flow and the irrigated saline. The cardiac tissue is a nonlinear orthotropic hyperelastic material and the Hertz-Signorini-Moreau contact boundary conditions model the frictionless interaction of the electrode with the cardiac tissue. In this work, we consider a spherical electrode tip shape and different orientation angles (perpendicular, 30° and 45° from the vertical position). We perform a virtual ablation for a standard protocol of power 30W for a duration of 30s on a simulated porcine cardiac slab. We compare the contact surface of the electrode with the tissue for the different orientations and the characteristics of the generated lesions.