We demostrate the importance of general relativistic apsidal precession in warped black hole accretion discs by comparing three-dimensional smoothed particle hydrodynamic simulations in which this effect is first neglected, and then included. If apsidal precession is neglected, we confirm the results of an earlier magnetohydrodynamic simulation by Krolik & Hawley (2015). We thus show that at least in this case the alpha-viscosity model produces very similar results to those of simulations where angular momentum transport is due to the MRI. This is shown below, with the twist (left) and tilt (right) shown in the same style as Krolik & Hawley (2015).

We re-examine the Bardeen-Petterson effect in accretion discs subject to Lense-Thirring precession in the bending wave regime (where the disc viscosity is smaller than the disc aspect ratio) using three dimensional smoothed particle hydrodynamics (SPH) simulations. Below are some of our simulations, each using 10 million particles.