Dataset of wall-resolved large eddy simulations for the investigation of turbulent pseudo-boiling and wall-functions in cryogenic hydrogen pipe flows

In this contribution a database of wall-resolved LES of cryogenic hydrogen at 5 MPa and different values of wall heat flux is presented. The aim is to provide a reference dataset for wall-functions development under trans- and supercritical conditions, such as those found in Liquid Rocket Engine applications. The employed numerical framework is a pressure-based segregated low-Mach number approach based on an equation-of-state independent formulation. The WALE sub-grid model is used for turbulence closure. Real-gas effects are taken from the NIST database and stored as a function of a non-dimensional temperature at the considered pressure. A validation and a grid-convergence analysis is first performed on an incompressible case without imposed heat flux. The effect of axial, radial and azimuthal refinements on first and second order velocity statistics is discussed and compared with DNS data from literature. A parametric analysis at different wall heat fluxes is then performed by keeping the inlet mass flux, temperature and Reynolds number constant. Particular attention is devoted to turbulent pseudo-boiling and its effect on the wall temperature. The latter shows a more pronounced increment as the heat flux increases attributed to the pseudo-change of phase in the core flow. Correspondingly, a flattening of the probability density function of temperature is observed, associated to the pseudo-boiling interface forming close to the wall and causing a more intense stratification. First and second order statistics for velocity and selected scalars are then presented and the effect of pseudo-boiling discussed. The effect of the wall heat flux on the viscous and thermal resolution of the computational grid is also assessed and considerations on the relation between turbulent pseudo-boiling and near wall gradients finally provided.