In this study, aerodynamic forces acting on the windshield wiper system at critical wiper angles are simulated using different wiper blade geometries, i.e., wiper and spoiler modifications, to solve the wiping problem occurring at high speeds due to lifting forces. Undesired aerodynamic lift forces reach a peak at critical blade angles, thus turbulent air flow around the wiper blades at critical angles on a car model is investigated numerically in detail to solve this problem. Previous experimental studies have shown that the front windshield wiper blades can be lifted up by aerodynamic forces between wiper blade angles of 30-40°, if no geometric modifications are done to prevent this. The possible modifications which can have a positive effect on wiper's performance include wiper's profile (also spoiler's curvature), wiper's height and connection type of the rubber part to the metal part. Aerodynamic lift and drag forces acting on the wiper blade and wiper arm are calculated for both driver's and passenger's sides. It is revealed that for both wiper blades on the driver's and passenger's sides, an increased wiper height with a blunt connection type can supply most satisfactory results in terms of decreased lift forces, in other words negative lift forces. Utilizing the output of the numerical analysis, the new wiper-blade-spoiler profile is selected and then manufactured to test its wiping performance in a thermal wind tunnel by soiling tests. Numerical studies are validated by experimental tests, since the new wiper profile has been proven as a more efficient prototype in terms of wiping performance compared to the original one.
In this study we present models for the parametric optimization of a centrifugal fan impeller using kriging-simulated annealing (SA) meta-algorithm. First, a kriging model is constructed using a limited number of CFD simulations for the centrifugal fan impeller to be optimized. The inlet and outlet blade angles are chosen to optimize the impeller. A dataset consisting of 22 different blade angles are determined by Latin Hypercube Sampling (LHS). After validation of the kriging model, it is used in conjunction with the simulated annealing and thus a meta-algorithm is developed for the solution of global optimization problem for the impeller optimization. Within the desired range of parameters, it is shown that this meta-algorithm provides a robust, reliable and fast optimization method. The procedures can be used to many problems in engineering. In this study a centrifugal fan impeller is successfully optimized using this procedure.
Windshield wipers were developed to improve visibility during inclement weather and belong to standard safety equipment. A conventional wiping system of a vehicle consists of three components; namely, motor and mechanism, wiper arm and wiper blade. The wiper arm transfers the movement to the wiper blade and cleaning is achieved by wiping water and dirt from the windscreen by a blade rubber. In order to wipe water and dirt from the windscreen, the wiper blade should be forced onto the windscreen with a specified force. The necessary force is obtained by the spring mechanism within the arm. In this study the effect of free-stream velocity, turbulence models on the drag and lifting forces acting on the windshield wiper and spoiler geometry are investigated numerically. The spoiler geometry is modified to reduce the lifting force.
In this study, it is aimed to simulate aerodynamic forces acting on the windshield wiper system on a simplified geometry at different blade angles. Numerical simulations reveal that at critical blade angles, undesired lift forces can reach their peak values. The blade-spoiler geometry is modified in a manner to alter aerodynamic lift and drag coefficients. On a simplified front windshield it is shown that at a blade angle of 40 , lift forces can be converted to pressing forces by implementing suggested modifications. Furthermore 2 vortex identification is used to understand the formation of vortex structures at different blade angles. On the other hand, soiling tests are performed both on original and modified wiper geometries and their performances are compared.
In this paper, a computational fluid dynamics (CFD) study is carried out in an effort to design and optimize the cabin geometry and its various parts for drag reduction that include the side deflectors, the mirrors and the sun visor. For the validation of computational results, an experimental investigation using a 1/5 scale truck model has been carried out in a wind tunnel. The aerodynamic force as well as the surface-pressure point measurements carried out at selected wind speeds. The flow visualizations using smoke and oil were also performed. With the experimental results, the basic characteristics of flow over the cabin geometry (including the flow separation locations) are compared with the CFD results. The both steady and unsteady CFD simulations are performed. The comparison of steady/unsteady results reveals that the time-averaged unsteady flow characteristics are practically the same as the steady calculations for design purposes. In addition to CFD simulations involving the actual (real) truck cabin geometry, for the optimization of the specific cabin accessories, (e.g., side deflectors and mirrors), a generic truck model is also used for CFD analyses. The optimized side deflector geometry (e.g., the ratio of the air inlet and outlet area), and the optimum form of the mirrors for drag reduction have been realized by numerical investigations.
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