Evaluation of the Multiple Reference Frame Approach for the Modelling of an Axial Cooling Fan

The modelling of rotating parts, such as axial fans, is one of the main challenges of current CFD simulations of industrial applications. Different methods are available, but the most commonly used is the multiple reference frame (MRF) method. This paper investigates how different flow properties, such as temperature, pressure and velocity, develop when passing through the MRF domain. The results are compared to the more physical rigid body motion (RBM) approach. It is found that the MRF method transports the upstream properties with the streamlines of the relative velocity from the upstream to the downstream interface. This leads to a non-physical rotation by an angle that is dependent on the length of the domain and the ratio between axial and tangential velocity in the MRF region. The temperature field is more affected than the flow field, since wake structures from upstream obstacles are destroyed due to the wake of the blades. Downstream structures affect the flow in the upstream region by an increase in static pressure, which causes the streamlines in the MRF zone to slow down. Depending on the size of the obstacle, this can cause substantial distortions in the upstream and downstream flow field

Um Jogo Sério para Suportar o Aprendizado do Modelo Atômico de Bohr

Um dos grandes problemas no ensino de física e química nas escolas é a carência dos laboratórios para que os alunos pratiquem e concretizem aquilo que visitaram de forma abstrata nas aulas teóricas. O uso de jogos na educação oferece oportunidades significativas de aprendizagem com a esperança de aumentar o interesse dos jovens nos conteúdos educacionais. O jogo, descrito neste artigo, permite que o aluno aprenda conceitos básicos do Modelo Atômico de Bohr. É um jogo do gênero ação, em que o aluno pilota uma nave que dispara projéteis. Entre cada uma das seis fases, ocorre um diálogo com o Dr. Niels Bohr, que explica o modelo e encerra com uma tarefa. Uma turma (n=28) do primeiro ano de ensino médio de uma escola pública experimentou o jogo. Os testes estatísticos apresentaram uma melhora significativa no desempenho após a experiência com o jogo. Apesar dos alunos terem achado alguma dificuldade em vencer no jogo, eles concordaram que se sentiram satisfeitos em divertir-se aprendendo com o jogo

Leveraging Case Study Research: A Mechanism to Measure Teaching Effectiveness

This article shares findings from a descriptive, multiple case study assessing graduate outcomes 2.5 years after the completion of a teacher education program. Case study was used as an alternative to value-added measures to holistically examine complex attributes of effective teaching. Mixed methods data collection included graduate and supervisor surveys, self and supervisor evaluation of skills and dispositions, interviews, and classroom observations. Results indicated participants effectively applied the knowledge, skills, and dispositions the program was designed to achieve in the areas of Learner and Learning, Content, Instructional Practice, and Professional Responsibility. Three major recommendations emerged: 1) the necessity to develop established proficiency levels for new teachers related to diverse learners, 2) the need for shared responsibility of outcomes and targeted induction support, and 3) support for supervisor evaluation as a viable mechanism for education program accountability of teaching effectiveness of graduates

Leveraging case study research: A mechanism for measuring teaching effectiveness.

This article shares findings from a descriptive, multiple case study assessing graduate outcomes 2.5 years after the completion of a teacher education program. Case study was used as an alternative to value-added measures to holistically examine complex attributes of effective teaching. Mixed methods data collection included graduate and supervisor surveys, self and supervisor evaluation of skills and dispositions, interviews, and classroom observations. Results indicated participants effectively applied the knowledge, skills, and dispositions the program was designed to achieve in the areas of Learner and Learning, Content, Instructional Practice, and Professional Responsibility. Three major recommendations emerged: 1) the necessity to develop established proficiency levels for new teachers related to diverse learners, 2) the need for shared responsibility of outcomes and targeted induction support, and 3) support for supervisor evaluation as a viable mechanism for education program accountability of teaching effectiveness of graduates

CFD Simulation of Aero-acoustic Noise Generated in Air Vent

In Envac AB's automatic waste collection systems the air enters the pipe systems through air vents containing a nozzle. Unfortunately this air vent, and especially the nozzle, generates disturbing noise. This has as a consequence that silencers have been built which in turn leads to higher production costs and larger facilities for the air vents. The aim of the present work has been to evaluate a simulation method for studying these air vents and to use this method to analyze the generation of sound in the air inlet vents. The method studied in this thesis work is based on the simple idea that the experienced sound can be reduced by minimizing the sources of sound generation. The aeroacoustic sources represent the unsteady phenomena in the flow which creates the sound. The advantage of this method is that sound sources such as the Lilley and Linear Euler Equation sources can be calculated from a steady RANS solution. Compared to resolving the pressure fluctuations with an unsteady simulations this is a computationally less demanding method. In order to validate the proposed method CFD simulations has been performed. The first set of simulations is RANS calculations on round jets with different inlet velocities. The comparison between changes in calculated sound sources and theoretically derived changes in sound level [Ref 11] shows that a relationship exists between the predicted level of aeroacoustc sources and the theoretically generated sound. After this relation has been established simulations were performed on two test cases where the first one is a backward facing step and the second one is a similar geometry but with a bend before the step. These geometries are suitable for the present work because they include the same type of flow phenomena as the real air vent. Both unsteady LES and steady RANS calculations were performed in order to evaluate both turbulence models and aeroacoustic sources. The accuracy of the calculations on the backward-facing step has been validated through comparison with DNS data [Ref 9]. The simulations have given good results both in terms of recommending a turbulence model for geometries similar to the two test cases and in terms of evaluating the aeroacoustic method. It was shown that the k- SST model is the most suitable turbulence model for the two test cases and that the integral of Lilly's source term, the Linear Euler Equation source term and the Acoustic Power in the domain are good parameters to use when trying to minimize the generated sound

Experimental investigation of the air flow in a simplified underhood environment

In this paper, a simplified underhood environment is proposed to investigate the air flow distribution in a vehicle-like set-up and provide high quality measurement data that can be used for the validation of Computational Fluid Dynamic methods. The rig can be equipped with two types of front openings representative for electrified vehicles. Furthermore, it is possible to install differently shaped blockages downstream of the fan to imitate large underhood components. The distance between the blockages and the fan can be varied in longitudinal and lateral direction. The measurements are performed with Laser Doppler Anemometry at a fixed distance downstream of the fan. The results show that the lack of an upper grille opening in the configuration for a battery electric vehicle has a notable impact on the flow field in the reference case without any downstream blockage. However, the differences in the flow field between the two front designs become less when a downstream obstruction is present. The longitudinal and lateral position of the blockages have have a minor impact on the flow field compared to the shape of the obstacle itself

Experimental investigation of the air flow in a simplified underhood environment

In this paper, a simplified underhood environment is proposed to investigate the air flow distribution in a vehicle-like set-up and provide high quality measurement data that can be used for the validation of Computational Fluid Dynamic methods. The rig can be equipped with two types of front openings representative for electrified vehicles. Furthermore, it is possible to install differently shaped blockages downstream of the fan to imitate large underhood components. The distance between the blockages and the fan can be varied in longitudinal and lateral direction. The measurements are performed with Laser Doppler Anemometry at a fixed distance downstream of the fan. The results show that the lack of an upper grille opening in the configuration for a battery electric vehicle has a notable impact on the flow field in the reference case without any downstream blockage. However, the differences in the flow field between the two front designs become less when a downstream obstruction is present. The longitudinal and lateral position of the blockages have a minor impact on the flow field compared to the shape of the obstacle itself.</jats:p

Numerical Investigation of the Air Flow in a Simplified Underhood Environment

Thermal management plays a crucial role for the energy efficiency of electrified vehicles. Using numerical flow simulations, the air paths and temperature distributions in the underhood can be identified and optimised early in the development process. However, the numerical method needs to be verified in its accuracy for capturing the important flow features in the underhood. In this study, a numerical approach is developed that is robust with respect to spatial and temporal resolutions as well as to different turbulence models. The methodology is validated against experimental data from LDA measurements. The geometric configurations investigated are representative of electrified vehicles, with one or two front opening designs, two different fans, and with or without a blockage behind. The results showed that for one of the fan installations, although the major flow field structures were well captured, the locations of the peak velocities did not match the experiments. For the second fan, the CFD results agreed well with the measurements

Um Jogo Sério para Suportar o Aprendizado do Modelo Atômico de Bohr

Um dos grandes problemas no ensino de física e química nas escolas é a carência dos laboratórios para que os alunos pratiquem e concretizem aquilo que visitaram de forma abstrata nas aulas teóricas. O uso de jogos na educação oferece oportunidades significativas de aprendizagem com a esperança de aumentar o interesse dos jovens nos conteúdos educacionais. O jogo, descrito neste artigo, permite que o aluno aprenda conceitos básicos do Modelo Atômico de Bohr. É um jogo do gênero ação, em que o aluno pilota uma nave que dispara projéteis. Entre cada uma das seis fases, ocorre um diálogo com o Dr. Niels Bohr, que explica o modelo e encerra com uma tarefa. Uma turma (n=28) do primeiro ano de ensino médio de uma escola pública experimentou o jogo. Os testes estatísticos apresentaram uma melhora significativa no desempenho após a experiência com o jogo. Apesar dos alunos terem achado alguma dificuldade em vencer no jogo, eles concordaram que se sentiram satisfeitos em divertir-se aprendendo com o jogo.</jats:p