Abstract
Current commercial software tools implement turbulence models on computational fluid dynamics (CFD) techniques and combine them with fluid-structural interaction (FSI) techniques. There are currently a great variety of turbulence methods that are worth investigating through a comparative study in order to delineate their behavior on scaffolds used in tissue engineering and bone regeneration. Additive manufacturing (AM) offers the opportunity to obtain three-dimensional printed scaffolds (3D scaffolds) that are designed respecting morphologies and that are typically used for the fused deposition model (FDM). These are typically made using biocompatible and biodegradable materials, such as polyetherimide (PEI), ULTEM 1010 biocompatible and polylactic acid (PLA). Starting from our own geometric model, simulations were carried out applying a series of turbulence models which have been proposed due to a variety of properties, such as permeability, speed regime, pressures, depressions and stiffness, that in turn are subject to boundary conditions based on a blood torrent. The obtained results revealed that the detached eddy simulation (DES) model shows better performance for the use of 3D scaffolds in its normal operating regime. Finally, although the results do not present relevant differences between the two materials used in the comparison, the prototypes simulated in PEI ULTEM 1010 do not allow their manufacture in FDM for the required pore size. The printed 3D scaffolds of PLA reveal an elastic behavior and a rigidity that are similar to other prototypes of ceramic composition. Prototypes made of PLA reveal unpredictable variability in pore and layer size which are very similar to cell growth itself and difficult to keep constant.
Highlights
In tissue engineering (TE) and bone regeneration, a bone tissue scaffold [1] defines an artificially prepared temporary matrix with a three-dimensional structure
The 3D scaffold used in the simulation tests was made of PEI material [40,41], ULTEM 1010 filament biocompatible, which was supplied by Sabic (Riyadh, Saudi Arabia) and adapted for a Fortus 450 MC machine
There is a notable difference in the range of depressions in a pore size of 300 μm, which may be due to the difference of the drop pressure parameter
Summary
In tissue engineering (TE) and bone regeneration, a bone tissue scaffold [1] defines an artificially prepared temporary matrix with a three-dimensional structure. Despite the fact that there is only one type of ceramic material printed stereolithography (SLA) used, Mirkhalaf et al [15] highlight the importance of the architecture of the scaffold and the relevance of the geometric parameters in its selection None of these works show any use of CFD calculation methods or turbulence models. Tiftikçi et al [18] and Wei et al [19] conclude that the Reynolds average Navier–Stokes (RANS) models, using the Boussinesq eddy viscosity hypothesis, fail to take into account an isotropic eddy viscosity, as it does not fully reflect reality They are not suitable to calculate turbulence or anisotropic flows. The boundary layer is located in the buffer zone, that is, the transition region between the viscosity-dominated region and the turbulence-dominated part of the flow These values reveal a minimal relative influence of viscosity in the calculation of shear stresses [38]. Images were acquired at (x67–x71) magnification using a Dual Beam FEI Scios 2 microscope
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