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Due to the set of factors and conditions, the stream pressure through the orifice decreases, which can lead to the occurrence of the cavitation phenomenon. The most important factor in this regard is the geometry of orifice. In the first part of this study, the flow through two types of single-hole orifice and a multi-hole orifice were experimentally studied. The results showed that the single hole orifice with a two-sided sloped edge caused less pressure drop, which in order to control the cavitation phenomenon is more efficient compared to the single-hole and multi-hole orifices with one-sided sloped edges and the same equal diameter ratio. Additionally, all experiments were simulated in the second part of this research using finite volume methods. Considering the complexity of the problem, several numerical solutions were investigated to approach the experimental results. Finally, it was determined that the type of gridding, turbulence method, and cavitation model have a great influence on the accuracy of the obtained numerical results.

In this paper, the thermal behavior of nanofluids was numerically simulated during nanoparticle sedimentation. Using the finite volume method by combining appropriate solvers, a new solver was developed in the open-source framework, i.e., open Foam. Free convection flow was transiently modeled using this solver during the sedimentation of the second phase (nanoparticles). A relative velocity term from the Vesilind relation was added to the momentum equation to model the sedimentation. Bossiness and Maiga's relations were used to calculate the density changes with temperature and effective conductivity, respectively. Simulations were performed for square, triangular, and circular cross-sections with the same hydraulic diameter at three Rayleigh numbers. In addition, the changes in Nusselt number over time and the distribution of nanoparticles under different conditions were studied. The results showed that forming the sediment layers at the bottom of the enclosure reduced the streamlines and decreased natural convection and rotational flow. In addition, it contributed to conductive heat transfer, leading to a rapid decrease in the Nusselt number of cavities. Moreover, by increasing the Rayleigh number, the square and triangular cross sections had the highest and lowest heat transfer, respectively. [ABSTRACT FROM AUTHOR]

The dynamical response of a 3D hydrofoil in the cavitation flow is investigated. Fluid and Structure Interaction (FSI) simulation was performed using ANSYS Fluent Software. First, the validation of cavitation flow around NACA 0015 hydrofoil was carried out. To predict the essential features of cavitation flow, like the shedding of vortex and cloud cavities, the turbulent viscosity of SST (Shear-Stress Transport) k-ω model was modified by writing a UDF (User-Defined Function) code. To ensure the simulation of two-way Fluid-Structure Interaction (FSI), the results of NACA 66 hydrofoil in the uniform flow at non-cavitation conditions (wetted flow) are compared with experimental results, which indicates a good agreement. The results show that metallic alloys (aluminium and magnesium) have a slight effect on hydrofoil performance in comparison to each other. At the flexible foils, the hydrodynamic loads would cause bending and twisting deformations of the foil and the foil vibration. [ABSTRACT FROM AUTHOR]

In this proposed method, which is based on combination of the nonlinear Hybrid Extended Kalman Filter (HEKF) observer, Analytical and Semi-Empirical (ASE) formulas, and Computational Fluid Dynamics (CFD) simulations, all of the hydrodynamic coefficients of a REMUS AUV are estimated to simulate its motions in 6 Degrees of Freedom (6-DoF). First, Using ASE formulas along with necessary static simulations of the AUV using commercial CFD code of ANSYS CFX software, some hydrodynamic derivatives like drag, lift, and fin coefficients are obtained. Then, utilizing the dynamic simulation of the Straight-Line Test (SLT), the longitudinal added mass coefficient is derived. Finally, benefiting from the HEKF code based on the parameter identification, other unknown coefficients like added mass and damping are estimated in the MATLAB software environment. In HEKF, positions and velocities of the vehicle, which are the system output vector, are obtained from a 6-DoF dynamic maneuver in CFX. It is worth mentioning that, in the present study, the remeshing algorithm in the dynamic mesh approach is used to simulate the dynamic maneuvers of the vehicle. Results, obtained from the proposed combined method, indicate a good agreement for estimated coefficients in comparison with the available analytical and experimental values. [ABSTRACT FROM AUTHOR]