## 1 Introduction  
In tissue engineering (TE) and bone regeneration, a bone tissue scaffold [1] defines an artificially prepared temporary matrix with a three-dimensional structure. The scaffolds must consist of a three-dimensional porous structure with high inter-connectivity while supporting and maintaining the original tissue shape. These provide support and channels for cell seeding, proliferation and differentiation, vascularization, and transportation of nutrients, as well as metabolic waste [2, 3]. The mechanical properties of the scaffolds must match the implant site to ensure mechanical stability in the healing process, thus avoiding stress shielding. Similar to implants or prostheses, scaffolds must be biocompatible, biodegradable and osteoinductive [4, 5]. The mechanical stimulation of scaffolds in the body includes matrix deformation. The flow of interstitial fluid (ISF) is a relevant method for the mechanical stimulation of scaffolds [6, 7]. ISF flows under the action of a mechanical load, muscle contraction, blood pressure, etc. Furthermore, these forces generate fluid shear stress (FSS) and wall shear stress (WSS) [8, 9] on the scaffold surface. [PERSON] et al. [10] and [PERSON] et al. [11] have investigated the influence of pore size on the hydromechanical properties of porous scaffolds, as well as the correlation with cell response and bone regeneration. They describe a scaffold with pores the size of 650 \(\upmu\)m making use of titanium material. [PERSON] [12] have used the same pore size; however, they utilized a poly(t-lactic acid) electrospun microfibrous structure. [PERSON] et al. [13] have studied the distribution of FSS in scaffolds with different pore sizes: 300, 600, and 900 \(\upmu\)m. To generate the desired level of mechanical stimulation in FSS, [PERSON] et al. [14] have combined the CFD and the finite element (FE) methods to quantitatively evaluate the influence of scaffold geometry (structure, pore size, and porosity) on FSS. Despite the fact that there is only one type of ceramic material printed stereolithography (SLA) used, [PERSON] et al. [15] highlight the importance of the architecture of the scaffold and the relevance of the geometric parameters in its selection. However, none of these works show any use of CFD calculation methods or turbulence models. [PERSON] et al. [16] state that the k-\(\varepsilon\) model is the most often used model in fluid dynamics for the calculation of turbulent flows. Its standard version is only based on two transport equations for the estimation of turbulence: the eddy kinetic energy (k) and the eddy energy dissipation rate (\(\varepsilon\)), assuming a total turbulent flow. The k-\(\upomega\) standard or Wilcox model is based on the equations of k and the specific dissipation rate (\(\upomega\)). The k-\(\upomega\) SST (shear stress transport) model, developed by Ansys Fluent, improves the formulation in such a way as to take advantage of the robustness and efficiency of the k-\(\upomega\) model in the inner zones of the boundary layer. The precision of the k-\(\varepsilon\) model in the outer zones decreases the weakness of the Wilcox model given the presence of the higher Reynolds values. The model also improves the calculation of the FSS derived from turbulence, as well as the computation of the pressure gradients [17]. [PERSON] et al. [18] and [PERSON] 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. Thus, they are not suitable to calculate turbulence or anisotropic flows. In order to solve this limitation, the application of the Reynolds stress model (RSM) is necessary. Instead of assuming the eddy hypothesis, this model resolves the transport equations for each term of the Reynolds stress tensor. In many cases, the RANS models based on the Boussinesq hypothesis provide good results.