MHIT36: Extension to wall-bounded turbulence and scalar transport equation

We present an extended version of MHIT36, a GPU-tailored solver for interface-resolved simulations of multiphase turbulence. The framework couples direct numerical simulation (DNS) of the Navier–Stokes equations, which describe the flow field, with a phase-field method to capture interfacial phenomena. In addition, the transport equation for a scalar can also be solved. The governing equations are discretized using a second-order finite difference scheme. The Navier–Stokes equations are time advanced with an explicit fractional-step method, and the resulting pressure Poisson equation is solved using a FFT-based method. The accurate conservative diffuse interface (ACDI) formulation is used to describe the transport of the phase-field variable. Simulations can be performed in two configurations: a triply-periodic cubic domain or a rectangular domain of arbitrary dimensions bounded by two walls. From a computational standpoint, MHIT36 employs a two-dimensional domain decomposition to distribute the workload across MPI tasks. The cuDecomp library is used to perform pencil transpositions and halo updates, while the cuFFT library and OpenACC directives are leveraged to offload the remaining computational kernels to the GPU. MHIT36 is developed using the managed memory feature and it provides a baseline code that is easy to further extend and modify. MHIT36 is released open source under the MIT license.