Many turbulent flows are driven by sustained temperature differences. Applications span a wide spectrum from heat exchangers in power plants and energy efficient indoor ventilation to convection in the Earth's atmosphere and oceans all the way to the Sun and other stars. Turbulent Rayleigh-Benard convection (RBC) is the paradigm for all these convection phenomena. In RBC, a fluid cell is kept at a constant temperature difference between top and bottom. The Rayleigh number measures the strength of convection. One of the key questions in RBC is that of the turbulent transport mechanisms of heat and momentum. Since the fluid is confined between rigid and/or impermeable walls, tiny boundary layers of the temperature and velocity fields will form in the vicinity of the walls. As the Rayleigh number increases, first the bulk becomes fully turbulent, while the boundary layers remain closer to laminar, although they become increasingly unsteady. There is a well- known theoretical scaling of Nusselt number, a measure of the heat transport, with a Rayleigh number that has been verified both experimentally and numerically. What is not well-understood is if the boundary layers become fully turbulent and the system then enters the ultimate regime of RBC for which the law of turbulent heat transport changes. This project advances the team’s Direct Numerical Simulations (DNS) to Rayleigh numbers that have never been accessed before numerically. Their efforts are based on the nekRS spectral element software package which was developed for solving the flow equations on massively parallel GPU supercomputers. DNS will provide new insights into the global structure of the convection flow and the details of the boundary layer dynamics. The new data record will help to resolve the contradictory experimental results for the onset of the transition to the ultimate regime of convective turbulence in which the boundary layers become fully turbulent thus causing a significantly enhanced turbulent heat transfer. This study will provide new insights into the heat and momentum transport as a function of Rayleigh number and the transition to the ultimate regime. As such, research will be transformational in the domain of fluid dynamics with a variety of important applications in nature and technology.