Sahl Rowther

A Warped Disc

• The disc is first evolved without a warp until the disc is gravitationally stable and in a steady state. We then include an idealised warp to understand the impact of a warp on the disc's evolution.
• As the disc evolves, the warp propagates radially both inwards and outwards.
• Since the warp was introduced numerically, it is not sustained. Thus as the disc continues to evolve, the warp smooths out and the disc becomes coplanar.
• The influence of the warp quickly suppresses the spiral structures yielding an axisymmetric gravitationally stable disc.

The PdV work plays an important role in altering the disc's evolution. The divergence of the velocity is directly linked to the PdV work, so we use it as a proxy for the PdV work.

Impact of the warp

• In the warped region of the disc, adjacent annuli of gas are misaligned with varying vertical height \(z\). This results in an (oscillating radial pressure gradient) as the gas traverses an orbit.
• This oscillating radial pressure gradient can trigger a strong response in the radial velocity of the disc (Lodato & Pringle 2007), which heats up the disc. This is especially apparent in the early stages as seen by the large magnitudes of the velocity divergence.
• As the warp dissipates, there is little variance in the pressure gradient. Thus, the magnitude of velocity divergence has greatly decreased as expected leading to less heating from PdV work.