This study aims to develop an adaptive mesh refinement (AMR) algorithm combined with Cut-Cell IBM using two-stage pressure-velocity corrections for thin-object FSI problems. To achieve the objective of this study, the AMR-immersed boundary method (AMR-IBM) algorithm discretizes and solves the equations of motion for the flow that involves rigid thin structures boundary layer at the interface between the structure and the fluid. The body forces are computed in proportion to the fraction of the solid volume in the IBM fluid cells to incorporate fluid and solid motions into the boundary. The corrections of the velocity and pressure is determined by using a novel simplified marker and cell scheme. The new developed AMR-IBM algorithm is validated using a benchmark data of fluid past a cylinder and the results show that there is good agreement under laminar flow. Simulations are conducted for three test cases with the purpose of demonstration the accuracy of the AMR-IBM algorithm. The validation confirms the robustness of the new algorithms in simulating flow characteristics in the boundary layers of thin structures. The algorithm is performed on a staggered grid to simulate the fluid flow around thin object and determine the computational cost.

Purpose This study aims to simulate the influence of surface texturing produced via turning process toward pressure distribution and load capacity generation using computational fluid dynamics (CFD). Design/methodology/approach The dimple geometry was obtained via turning process, to be used for future application on piston skirt surfaces. Two cases were studied: a preliminary study using single periodic dimple assuming linear dimple distribution and an application study using multiple periodic dimples to address actual dimple orientation following the turning process. Findings For the first case, the dimple was proven to generate load capacity with regard to untextured surface, owing to the asymmetric pressure distribution. Increasing the Reynolds number, dimple width and dimple depth was found to increase load capacity. For the second case, although load capacity increases via surface texturing, the value was 97.4 per cent lower relative to the first case. This confirmed the importance of doing multiple dimple simulations for real applications to achieve more realistic and accurate results. Originality/value A new concept of dimple fabrication using a low-cost turning process has been developed, with a potential to increase the tribological performance under hydrodynamic lubrication. Previous CFD simulations to simulate these benefits have been done using a single periodic dimple, assuming equal distribution array between dimples. However, due to the different orientations present for dimples produced using turning process, a single periodic dimple simulation may not be accurate, and instead, multiple dimple simulation is required. Therefore, present research was conducted to compare the results between these two cases and to ensure the accuracy of CFD simulation for this type of dimple.

No abstract

This paper aims to simulate the interaction between a simplified tongue replica with expiratory air flow considering the flow in the pharyngeal airway to be turbulent. A three-dimensional model with a low-Re SST turbulence model is adopted. An Arbitrary Eulerian-Lagrangian description for the fluid governing equation is coupled with the Lagrangian structural solver via a partitioned approach, allowing deformation of the fluid domain to be captured. Both the three-dimensional flow features and collapsibility of the tongue are presented. In addition, examining initial constriction height ranging from 0.8 mm to 11.0 mm and tongue replica modulus from 1.25 MPa to 2.25 MPa, the influence of both of these parameters on the flow rate and collapsibility of the tongue is also investigated and discussed. Numerical simulations confirm expected predisposition of apneic patients with narrower airway opening to flow obstruction and suggest much severe tongue collapsibility if the pharyngeal flow regime is turbulent compared to laminar.

This study is intended to investigate the effect of various degree and position (pre-bifurcation and post-bifurcation) of stenosis on carotid artery hemodynamics trough realistic CFD numerical simulations with appropriate turbulence model. The blood rheological properties were assumed as incompressible and Newtonian fluid. A 3 dimensional model of a non-stenotic carotid artery model was used this investigation. Several turbulence model were tested. The non-stenotic artery geometry was altered as 30% and 70%pre-bifurcation stenosis model, 30% and 70% post-bifurcation stenosis model. Pulsatile simulations were conducted for the non-stenotic and each stenotic artery models. The SST k-ω with Low-Reynolds number was found to be more appropriate for the simulation. As the degree of pre-bifurcation stenosis increases from 30% to 70%, the ICA maximum velocity increases from 12% to 65%. Also, the ECA maximum velocity increases from 5% to 45%. Besides, the ICA velocity ratio decreases by 22% but the ECA velocity ratioincreases by 101%. As the degree of post-bifurcation stenosis increases, the ICA maximum velocity takes a longer time to decrease after the peak systole velocity and the ECA maximum velocity becomes higher than a non-stenotic artery throughout the cardiac cycle. A mild stenosis at post-bifurcation does not show much effect on the carotid artery hemodynamics. However, even a mild stenosis at pre-bifurcation resulted in fluctuating maximum velocity at both ICA and ECA, especially during the diastole of the cardiac cycle

This manuscript contains the development stages of a multi-purpose wind tunnel built at the Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia. The fully automated wind tunnel is named Pangkor after an island in Perak, Malaysia. The development of the wind tunnel consists of three stages namely the design, fabrication and testing & commissioning. The computational fluids dynamic (CFD) approach was employed to ascertain the main geometries to optimize space utilization. Calculations are made based on typical wind tunnel design guidelines. Pitot tubes-pressure transducer, hotwire anemometry, temperature, room humidity and barometric sensors were used to verify actual flow of our construction. A traverse installed at the wind tunnel is capable of a two dimensional movements. The 15 kW axial fan used is especially selected because of space limitation. A variable frequency drive (VFD) connected to fan’s motor allows velocity control from a computer. All devices are connected a computer with one single controlling software; Scilab – ensuring ease of operation. The project shows that, with a limited budget, a wind tunnel with full functionalities could be constructed

Increasing environmental and energy concerns constitutes an encouraging development of future automobiles and autonomous vehicles that utilize cleaner and renewable energy. Although primarily an aerodynamic device, car rear spoilers experience various vibrations and limited attention has been given to exploiting these vibrations for generating alternative energy. This paper aims to investigate the potential of using the flow-induced vibration of rear spoilers on automobiles for energy harvesting. To that end, a fluid-structure interaction analysis of an inverted NACA 2408 spoiler behind an Ahmed body was undertaken. An Arbitrary Lagrangian-Eulerian flow solver was coupled to a non-linear structural dynamic solver using a commercial software application. The vibrations of the rear spoiler placed at 0, 50 and 100 mm below the top face of the Ahmed body under Reynolds number Re = 2.7 × 10 6 were simulated. It was found that the vibration of the rear spoiler at the highest elevation showed the largest amplitudes and strain, but the vibration of the rear spoiler at the lowest elevation offers an extended period of vibration before reaching a steady state. With the rear spoiler positioned at the highest elevation, a vibration frequency of 70 Hz and a steady-state principal strain of 350  may be achieved. These vibration levels compared well with previous investigation to sufficiently charge storage capacitors for wireless transmitters. The rear spoiler vibration may offer potential means for energy harvesting, and warrants further experiments under actual driving conditions.

In this study, the effect of oxygen addition on the microstructures of Ti-18%Mo-10%Cr alloy was investigated. The alloy was fabricated by a powder metallurgy method. The samples were subjected to sintering at 1300°C for 4 hours and furnace cooling. A Bo-Md method was initially applied for predicting stable phase. Calculation using the Bo-Md method showed that Ti-18%Mo-10%Cr alloy have bcc (β) phase at ambient temperature. All samples with various oxygen contents exhibited needle-like structures within equiaxed grains. The increase of oxygen content promoted formation of porosity in the α phase. Calculation of phase stability using JMatProTM showed that the decrease of β phase’s stability was not due to formation of the α phase on sintering, but due to promotion of nucleation and grain growth of diffusional α phase upon furnace cooling. It was also shown that vol.% of porosity of the alloy slightly increased with increasing oxygen content. Therefore, the increase of oxygen concentration could accelerate the formation of α phase and reduce the alloy’s density. The hardness increased as the oxygen concentration increased. The increase of the hardness might be due to combination of the solid solution hardening of oxygen and the precipitation hardening of α phase.