Lower Pressure Distribution Research Articles

3D CFD simulation of the interaction between front wheels&brake ducts and optimised five-element F1 race car front wings under regulations

This investigation analyses the 3D performance of two optimal front wing designs according to the Federation Internationale de l’Automobile 2021 regulations. These regulations imply a 3D five-element front wing, with ground effect and more than 30 design parameters and geometry constrains in practice, which has not been studied before in the literature. The two optimal front wing designs were obtained by parametric optimisation with sampled Kriging interpolation surrogates and a posteriori adjoint-based design refinement. The optimal front wings have been tested on 3D Computational Fluid Dynamic simulations to analyse the generated downforce and flow interaction with the front wheels and brake ducts, as well as the reproduction of influential vortices. Although the parametric design achieved a slightly better downforce-to-drag ratio, the adjoint-based design exhibited a greater ground suction effect, lower pressure distribution on the tire treads, and some deviation of the Y250 vortices to the wheel, which affected the flow over the wheel&brake ducts. This work demonstrated that quick improvements can be achieved starting from 2D analysis and running 3D simulations of relevant parts of the car, which is unaffordable to date for direct 3D simulation in a design space reduced to 17 dimensions and constrained by regulations.

Grease thermal elastohydrodynamic lubrication properties of tripod sliding universal couplings

PurposeThis paper aims to improve the grease thermal elastohydrodynamic lubrication (TEHL) properties of the tripod sliding universal coupling (TSUC) under automotive practical conditions. For this purpose, the effect of effective radius was theoretically investigated.Design/methodology/approachBased on the simplified geometric model, the effect of effective radius on the pressure distribution, film thickness and temperature distribution of the TSUC was theoretically investigated using the multigrid and stepping methods. The TEHL properties were compared with the results obtained using the isothermal calculation method.FindingsThe results show that the thermal effect has a great impact on the film thickness and the pressure distribution of grease lubrication properties. Moreover, larger effective radius results in a wider but lower pressure distribution, a wider and thicker lubricating film and a lower temperature distribution.Originality/valueThe TSUC can be widely used in the front drive automotive transmission because it can transmit larger torque than before. The effect of effective radius on the thermal grease lubrication properties under automotive practical conditions provides a new direction for designing it.

Discrete phase method particle simulation of ultra-fine package assembly with SAC305-TiO2 nano-reinforced lead free solder at different weighted percentages

This paper presents a 3D numerical simulation of nano-reinforced lead (Pb)-free solder at the ultra-fine joint component for 01005 capacitor with dimension of 0.2×0.2×0.4mm3. The nano-reinforced particles introduced in the Sn-3.0Ag-0.5Cu (SAC305) solder is titanium oxide (TiO2) nanoparticles with approximate diameter of ≈20nm at different weight percentages of 0.01, 0.05 and 0.15wt% respectively. The 3D model developed is based on the reflow thermal profile of nano-reinforced Pb-free solder in the wetting zone temperature of 217°C–239°C. A two way interactions utilizing both volume of fluid method (VOF) and discrete phase method (DPM) are introduced in the current study. The study effectively shows the distribution of the nanoparticles as it is being doped in the molten solder after undergoing soldering process. Based on the findings, it was shown that good agreement can be seen between experimental data obtained using High Resolution Transmission Electron Microscope (HRTEM) system as compared to multiphase DPM based simulation. At weight percentage of SAC305+0.05% TiO2 nanoparticles, the nanoparticles are well distributed. The fillet height of nano-reinforced solder also meets the minimum requirement for 01005 capacitor. Additionally, as the weight percentage of the doped nanoparticles increases, the time required for the formation of wetted solder also increases. In terms of the velocity and pressure distribution of the nano-reinforced lead (Pb)-free solder, higher weight percentage of doped nanoparticles have higher velocity distribution and lower pressure distributions.

An in vitro comparison of tracheostomy tube cuffs.

IntroductionThe Shiley™ Flexible adult tracheostomy tube with TaperGuard™ cuff has been designed through its geometry, materials, diameter, and wall thickness to minimize micro-aspiration of fluids past the cuff and to provide an effective air seal in the trachea while also minimizing the risk of excessive contact pressure on the tracheal mucosa. The cuff also has a deflated profile that may allow for easier insertion through the stoma site. This unique design is known as the TaperGuard™ cuff. The purpose of the observational, in vitro study reported here was to compare the TaperGuard™ taper-shaped cuff to a conventional high-volume low-pressure cylindrical-shaped cuff (Shiley™ Disposable Inner Cannula Tracheostomy Tube [DCT]) with respect to applied tracheal wall pressure, air and fluid sealing efficacy, and insertion force.MethodsThree sizes of tracheostomy tubes with the two cuff types were placed in appropriately sized tracheal models and lateral wall pressure was measured via pressure-sensing elements on the inner surface. Fluid sealing performance was assessed by inflating the cuffs within the tracheal models (25 cmH2O), instilling water above the cuff, and measuring fluid leakage past the cuff. To measure air leak, tubes were attached to a test lung and ventilator, and leak was calculated by subtracting the average exhaled tidal volume from the average delivered tidal volume. A tensile test machine was used to measure insertion force for each tube with the cuff deflated to simulate clinical insertion through a stoma site.ResultsThe average pressure exerted on the lateral wall of the model trachea was lower for the taper-shaped cuff than for the cylindrical cuff under all test conditions (P<0.05). The taper-shaped cuff also demonstrated a more even, lower pressure distribution along the lateral wall of the model trachea. The average air and fluid seal performance with the taper-shaped cuff was significantly improved, when compared to the cylindrical-shaped cuff, for each tube size tested (P<0.05). The insertion force for the taper-shaped cuff was ~40% less than that for the cylindrical-shaped cuff.ConclusionIn a model trachea, the Shiley™ Flexible Adult tracheostomy tube with TaperGuard™ cuff, when compared to the Shiley™ Disposable Inner Cannula Tracheostomy tube with cylindrical cuff, exerted a lower average lateral wall pressure and a more evenly distributed pressure. In addition, it provided more effective fluid and air seals and required less force to insert.

COMPARATIVE STUDY OF SUPERSONIC NOZZLES

In this experiment, comparative flow analysis of two different nozzles has been performed. The analysis has been performed according to the shape of the nozzles by keeping the same input parameters. The experiment has been carried out in two preliminary steps. First one includes modeling and CFD analysis and the later part is about comparing their different properties. For this analysis, two dimensional axisymmetric nozzle geometries were drawn in Solid Works and CFD analysis is done using Fluent. The basic difference between these two nozzle geometries is their outlet divergence angle, whereas the inlet crosssectional area, throat cross-sectional area and nozzle length are exactly same. These two nozzle geometries were drawn having outlet divergence angle 10° and 20° respectively. Velocity, pressure and temperature distribution on both nozzles have been studied to take the final decision. From analysis, it is clearly observed that the nozzle having outlet divergence angle 20° gives higher exit velocity with Mach number of 5.62 whereas the nozzle with outlet divergence angle 10° gives an exit velocity with Mach number of 4.31. Besides, lower temperature distribution and lower pressure distribution were observed in the nozzle with outlet divergence angle 20° throughout the expansion zone and nozzle with outlet divergence angle 10° exhibits higher temperature and pressure throughout the expansion zone. As the nozzle with divergence angle 20° gives higher exit velocity, it is the better one between these two nozzles.

FSI Simulation of Wire Sweep PBGA Encapsulation Process Considering Rheology Effect

This paper presents a 3-D fluid-structure interaction (FSI) technique using mesh-based parallel code coupling interface (MpCCI) for the visualization of wire sweep during encapsulation of the plastic ball grid array packaging, considering the polymer rheology effect. In the molding process, the encapsulant flow behavior is modeled by the Castro-Macosko viscosity model including the curing effect and volume of fluid technique for melt-front tracking. The viscosity model is written in C language and compiled using user-defined functions into the FLUENT analysis. Wire sweep behavior is analyzed by ABAQUS and integrated with FLUENT software by MpCCI as an interface of fluid and solid interaction. Three types of epoxy molding compound (EMC), namely, Cases 1-3, were utilized for the study of fluid flow inside the mold cavity. The melt-front profiles and viscosity versus shear rate for all cases are analyzed and presented. The degree of conversion of the molding compound during the encapsulation process at the top view of the package for different EMCs is also studied. Pressure distribution around the wire region and wire sweep profiles within the mold are presented. The numerical results of the melt-front behavior and wire sweep are compared with the previous experimental results and found in good conformity. In the present case, Case 2 with a lower viscosity shows lower air trap, lower pressure distributions, and lower wire deformation. Therefore, the strength of MpCCI in handling FSI problems is proven to be excellent. The work presented in this paper is expected to be a reference and guide for the microelectronics industry.

Reduction of sitting pressures with custom contoured cushions

Previous research indicated that matching a cushion to the shape of the buttocks results in less tissue distortion and lower interface pressures. A system was developed to measure body contours and fabricate a cushion to match the measured contour. This project fabricated contoured foam cushions for 11 persons with spinal cord lesions (C5-L3). Mean pressures were compared on two flat and two contoured foams with different degrees of stiffness. Deflection characteristics on flat foam were compared to deflection on contoured foam in order to analyze loading differences. Material studies were determined by examining the load-deflection curves for flat foams of 1-, 2-, and 3-inch thicknesses. It was found that sitting on contoured foam resulted in a lower pressure distribution than sitting on flat foam (p less than 0.05), and sitting on a soft foam (ILD = 45) resulted in a lower pressure distribution than sitting on a stiffer foam (ILD = 55) (p less than 0.05). Results of the deflection measurements and compression tests were used to explain the loading differences at the seat interface of flat and contoured cushions. Loaded contoured foam demonstrated increased enveloping of the buttocks, decreased foam compression, and a more uniform pressure distribution. These attributes are typical of a safer sitting surface and may indicate less tissue distortion.