Showing 4 results for Drop
P. Shojaei Shahmirzadi, H. Saeidi Googarchin,
Volume 6, Issue 4 (12-2016)
Abstract
Off-road cars’ windshields are vulnerable to different types of stones, road debris and pebbles due to common off paved and gravel surfaces in which they drive. Any attempt to design windshield that minimizes injury and death of occupants during a vehicle accident requires a thorough understanding of the mechanical behavior of automotive windshield subjected to foreign object impact loads.
In this study, some drop ball tests in different impact energy levels are conducted in order to monitor fracture behavior of an off-road automotive windshield. Also dynamic crack patterns of laminated glasses are examined based on the impact energy levels and impact conditions. In addition, the acceleration which is imposed to impactor during the accident is recorded. The experimental results are compared to an analytical approach regarding the resultant impact force as well. There is a good agreement between the impact forces of experimental test results and analytical approaches ones. All in all, in low velocity impacts, impact energy releases through powdering region in impact area, radial cracks and strain energy in PVB. It is concluded that in lower impact energy levels, the higher impact speed, the more number of radial cracks. In addition, at higher energy levels, number of radial cracks decease due to higher strain energy levels in PVB interlayer. Therefore, in low velocity impacts, number of radial cracks has reverse relationship with penetration depth in PVB interlayer.
Mr Mohammad Fakhari, Mr Ghanbar Ali Sheikhzadeh,
Volume 10, Issue 1 (3-2020)
Abstract
In this experimental study, heat transfer and pressure drop, ΔP, of a coolant nanofluid, obtained by adding alumina nanoparticles to Ethylene Glycol-water mixture (60:40 by mass), in a automotive radiator have been investigated. For this purpose, an experimental setup has been designed and constructed. The experiments have been performed for base fluid and nanofluid with different volume fractions of 0.003, 0.006, 0.009 and 0.012 and under laminar regime with various coolant flow rates of 9, 11 and 13 lit/min and two air velocities of 3.75 and 2.85 m/s. The thermophysical properties have been calculated using the recently presented temperature dependent models. According to the results, the heat transfer and ΔP increase with increasing the coolant flow and nanoparticles volume fraction. Increasing the air velocity causes enhancement of heat transfer. Although Nusselt number decreases when nanofluid is utilized, it enhances as the nanoparticles volume fraction increases. The performance evaluation using nanofluid in the car radiator shows remarkable enhancement in radiator thermal efficiency. However, the ratio of heat transfer rate to the needed pumping power (Merit parameter) decreases.
Seyed Reza Hosseini, Mahdi Moghimi, Norouz Mohammad Nouri,
Volume 14, Issue 3 (9-2024)
Abstract
The impact of a supercooled droplet on a surface is a primary challenge of many industrial and aeronautical processes. However, in some cases, such as frost formation on vehicle windshields or wind turbine blades, the supercooled droplet collision does not occur in stagnant air. In this study, for the first time, the effects of the air transverse flow (ATF) on the thermal-fluid behavior of a supercooled droplet were investigated numerically. Also, different patterns of a superhydrophobic pillared surface were used in 24 three-dimensional simulations in ANSYS Fluent software. The volume of fluid method is chosen for the simulation of the multiphase flow. The freezing model is improved by the supercooling temperature consideration method. The results show that the ATF velocity reduces the separation time exponentially and helps the droplet bounce from the surface before freezing inception. However, the excessive increase in ATF velocity has the opposite effect and may prevent the droplet from detaching the surface due to notable drag. The best value of the ATF velocity is obtained to be 8 m/s , which reduces the separation time exponentially from 16.3 ms to 12.5 ms for a cold surface with a simple pillar pattern. The separation time is entirely affected by the simulation conditions and varies from 11.85 ms to 29.2 ms . The maximum spreading factor, despite the separation time, is seriously influenced by the void fraction percentage of different pillared surfaces and varies from 1.53 to 1.69.
Mohsen Karmozdi,
Volume 15, Issue 2 (6-2025)
Abstract
The liquid metal droplets in the mercury magnetic reciprocating micropump are actuated by Lorentz force and reciprocated inside some sub-channels. The droplets in sub-channel act as pistons to pump the working fluid. The initial step in establishing the performance of the mercury magnetic reciprocating micropumps is to study the motion of droplet inside the channel. The extraction of the analytic equation governing the droplet motion inside the channel is complicated due presence of electromagnetic fields and three dimensional effects of the flow. Further, the existence of a pumped fluid in contact with the droplet and the adhesion force due to small dimensions are considered as the other reasons. In this study, the forces operating on the droplet were figured out by the Lagrangian approach and lumped mass assumption for the droplet. Accordingly, forces less than 5% of the actuation force were eliminated from the motion equation of droplet employing dimensional analysis. The simplified equation was presented as an ordinary differential equation and solved numerically. In addition to the analytic solution, the issue was experimentally investigated for a case study. The analytic and empirical results accord well with one another. The method pointed out in this study can be applied to predict the droplet motion in various microsystems.
