A direct forcing immersed boundary method for cavitating flows

Abstract

In the current study, an immersed boundary method for simulating cavitating flows with complex or moving boundaries is presented, which follows the discrete direct forcing approach. Although the immersed boundary methods are widely used in various applications of single phase, multiphase, and particulate flows, either incompressible or compressible, and numerous alternative formulations exist, to the best of the authors' knowledge, a handful of computational works employ such methodologies on cavitating flows. The herein proposed method, following previous works of the author's group, tries to fill this gap and to solidify the development of a computational tool of a simple formulation capable to tackle complex numerical problems of cavitation modeling. The method aims to be used in a wide range of applications of industrial interest and treat flows of engineering scales. Therefore, a validation of the method is performed by numerous benchmark test-cases, of progressively increasing complexity, from incompressible low Reynolds number to compressible and highly turbulent cavitating flows. K E Y W O R D Scavitation, diesel injector, direct forcing, immersed boundary method, turbulence modeling INTRODUCTIONWithin the framework of computational fluid dynamics, applications of industrial interest often refer to flows in complex geometries or around moving bodies; their simulation may be numerically challenging and computationally expensive. Many cases of cavitating flows fall into that category. For example, cavitation formation in diesel injector nozzles with moving needle, gear pumps, or propellers mounted under ship hauls, refer to problems with moving geometrical parts and include different geometrical features with wide range of length scales and topological features that impose severe constraints in mesh generation. The conventional strategy of generation of boundary-conforming grids for such problems, may become demanding and time consuming. When the numerical simulation involves moving parts with large displacements, common conformal grid strategies result in remeshing of the entire domain in every time-step, 1 or deforming the grid and adding or removing cell-layers when a desired cell size is reached. 2 In the case of marine propellers, to accommodate their rotational motion, either the entire computational domain would be rotated accordingly, 3 or a multi-region mesh would be used, which lets the part of the grid that conforms with the propeller blades to slide with regards to the global domain. 4 Another approach of over-set grids 5 (also known as Chimera grids), employs multiple overlapping 3092

Prediction of shock heating during ultrasound-induced bubble collapse using real-fluid equations of state

“…Popinet et al [43] explored the viscosity's impact on bubble collapse near solid surfaces where reduction of the jet impact velocity at higher viscosity was observed. There are also some relevant studies for cavitation modelling using mass transfer rates [44] , [45] , [46] , [47] , [48] , cavitation modelling using air-vapor–liquid and barotropic EoS [49] , [50] , [51] , [52] , [53] , and heating effects and real-fluid thermodynamic closure in cavitating flows [54] , [55] , [56] .…”