A guide to online assessment in large engineering design classrooms

Abstract: Student protests in 2015 and 2016 along with the inherent colonial nature of African universities has sparked reflective conversation among university academics in the areas of curriculum development and teaching practice in South Africa. Consequently, the online classroom, though typically perceived as pedagogically unconventional at residential universities in South Africa, is increasingly seen as an innovative way to encourage educator and student engagement with discipline-specific content. In addition, online assessment at residential universities in South Africa is growing in popularity due to its time-saving and efficiency properties. However, there is very little guidance available to educators who wish to conduct online assessments in large classrooms. The purpose of this study is to provide a guide to educators on how to execute online assessment in large classrooms, with specific application to engineering design. The study begins by outlining why an educator may want to consider online assessment for a large classroom. Thereafter, the study explores face-to-face assessment theory vis-à-vis online assessment theory with respect to purpose and efficiency. Following this, the study characterizes the nature of the engineering design classroom used in this study. Subsequently, the study explains the merits and drawbacks of online assessment and provides practical recommendations on how to overcome potential and typical challenges faced in a large engineering design classroom. Findings may prove valuable to other teaching environments and disciplines interested in effective online assessment for large classrooms

Establishing a benchmark for effective intervention : first-year engineering students’ writing and their perceptions thereof

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An investigation into the applicability of the Lattice Boltzmann method to modelling of the flow in a hydrocyclone

The lattice Boltzmann method has gained popularity as a method for simulating fluid flow, particularly multiphase flow. Thus, it has potential in simulating fluid flow in hydrocyclones. While research on the method and its’ application to multiphase flow is mature, there is sparse research on its’ application to hydrocyclones. An overview of the literature on the use of the lattice Boltzmann method for simulating fluid flow in hydrocyclones is presented. A lattice Boltzmann model of single phase flow in a hydrocyclone is presented, which is compared to predictions from a Navier-Stokes based model. The lattice Boltzmann model predicts lower velocities than the Navier-Stokes model in certain areas of the hydrocyclone and higher velocities in other areas. In some areas both models are in close agreement. The lattice Boltzmann model predicts the low pressure region at the underflow and overflow. However, it does not display the low pressure region in the core of the hydrocyclone. It is proposed that these differences are related to the use of the single relaxation time implementation of the lattice Boltzmann method. The possible solution is to use the multiple relaxation time model which is more suitable to high-Reynolds number flows

Design life cycle of a 3-D printed hydrocyclone

Abstract: In mineral processing solid-fluid mixtures are separated in various ways. Of these, hydrocyclones are found to be a simple and low cost technique for particle separation. Additive Manufacturing (AM) technology has the potential to improve the design and testing process for hydrocyclones. The aim of this study is to evaluate the effectiveness of using AM and surface treatments to optimise hydrocyclone design. The hydrocyclone used in these experiments is based on a commercial model used in practice. The hydrocyclone was manufactured with a common plastic material (ABS+) and was fabricated by use a Rapid Prototyping Additive Manufacturing (RPAM) technique. This paper describes the 3-D design printing (3DDP) and manufacture of a hydrocyclone design based on a commercial design using RPAM and a surface protection process. Based on the results of this study, this process has the potential to reduce development time and cost to produce an optimal hydrocyclone design iteration

A computational fluid dynamics and experimental investigation of an airflow window

M.Ing.The characterisation of the flow field and thermal performance of supply air windows (airflow windows operating in supply mode) have been a topic of interest for at least two decades. Computational Fluid Dynamics (CFD) as well as other simulation methods have been used to model and characterise the flow field, temperature distributions and thermal performance of the supply air window in recent years. Where experimental validation of the velocity (only outlet velocity) and temperature predictions has been provided the error between experiment and CFD (and other forms of simulation) is in the order of 50 % and 3 ◦C (10-13 %), respectively. Furthermore, a large part of the literature does not have experimental validation of the simulation results. The significant error in many of the studies, that provide experimental val- idation of the velocity field, is attributed to inappropriate turbulence mod- els, unrealistic boundary conditions, neglecting significant three-dimensional effects, solar radiation effects not entirely accounted for, mesh sensitivity studies neglected and material properties of glass and air assumed constant. The aim of this research was to characterise a supply air window in terms of its velocity field, temperature distributions and thermal performance. This was done by mathematically modelling the fluid dynamics and heat trans- fer processes in a supply air window and solving the model in a commer- cial CFD code, namely ANSYS Fluent 12.1. Furthermore, an experimental rig was designed, constructed and used to measure the flow field and tem- peratures with the aim of validating the CFD models. The CFD models incorporated appropriate turbulence models, realistic boundary conditions, three-dimensional effects, solar radiation, temperature dependent material properties and a mesh sensitivity study. The CFD models and experiments were setup for forced and natural flow conditions. Laser Doppler Velocimetry has not been used for velocity field measure- ments in an airflow window to date. The experimental setup made use of Laser Doppler Velocimetry to measure the velocity field and turbulence in- tensities. The Laser Doppler Velocimeter (LDV) probe was positioned using a three axis computer controlled traversing mechanism. Furthermore, flow visualisation experiments were done to qualitatively capture the flow field. The results from the CFD are partially in good agreement with the exper- imental work. Qualitatively the flow field as predicted by CFD is in good agreement with the results from the flow visualisation experiments. Quan- titatively the results from the CFD are in good agreement with the tem- perature measurements, however, there is noticeable error between the LDV readings and the velocities as well as turbulence intensity values predicted by CFD. The error, with regards to velocity and turbulence intensity, may be attributed to the experimental error caused by problems with flow seeding as well as the isotropic turbulence assumption inherent in the turbulence model (SST k − ω) used

Modelling of the multiphase interactions in a hydrocyclone using Navier-Stokes and Lattice Boltzmann based computational approaches

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Modelling fluid and particulate flow through a ventriculoperitoneal shunt in a variable temperature environment

One of the most prevalent causes of failure for a ventriculoperitoneal shunt is blockage, the other being infection. This study looks at the blockage of the shunt valve, and whether the occlusion of a shunt valve is accelerated by the presence of an infection. This study assumes that an infection will raise the number of white blood cells contained in the cerebrospinal fluid to fight it and will thus accelerate shunt occlusion. The experiment simulates a shunt system by suspending a shunt valve in a water bath that has a temperature that varies between 37°C and 41°C. A computational fluid dynamics model of the shunt system is used to gain further insight into the flow behaviour under these conditions. The results of the CFD model were validated using the experimental results. There was an average error of 15% between the readings that were obtained in the experiment and the CFD model. The experimental results showed that there was a decrease in the volume flow rate at the outlet of the shunt system, which was not large enough to point towards any blockage. Both the model predictions and the experimental results show that increased temperature and particulate concentration alone do not result in shunt occlusion, particularly at the shunt valve. This result effectively excluded the shunt valve as a region of shunt occlusion due to infection, as an infection occurs due to the growth of bacteria along the surfaces of the shunt system and this bacterial growth is more likely to occur at the proximal and distal ends of the shunt system

The finite element method and its' link to the finite difference method for Poisson's equation

Abstract Poisson’s Equation on a rectangular domain describes conduction heat transfer on a plate. This equation can be solved using the Finite Difference Method (FDM) or the Finite Element Method (FEM). Previous literature has shown that the FEM discretisation equations for the nodal values are integrated averages of the FDM discretisation equations. This paper presents a corrected transformation from the FDM to the FEM, for Poisson’s Equation. For Poisson’s Equation on a rectangular domain the FEM discretisation is obtained by the area integral, in terms of Simpson’s and Midpoint Quadrature, of the FDM discretisation equations. Under the conditions investigated in this paper, the FEM provides the area integral of the partial differential equation (PDE) in terms of Simpson’s and Midpoint Quadrature. The transformation presented in this paper can be used to reduce computational cost and complexity in the FEM, specifically in the construction of the discretisation equations at the nodal point

The Modification of the Dynamic Behaviour of the Cyclonic Flow in a Hydrocyclone under Surging Conditions

The aim in this study was to determine how surging modifies the dynamic behaviour of the cyclonic flow in a hydrocyclone using computational fluid and granular dynamics models. The Volume-of-Fluid model was used to model the air-core formation. Fluid–particle, particle–particle, and particle–wall interactions were modelled using an unsteady two-way coupled Discrete Element Method. Turbulence was modelled using both the Reynold’s Stress Model and the Large Eddy Simulation. The model predictions indicate that the phenomenon of surging modifies the dynamics of the cyclonic flow in hydrocyclones and subsequently impacts separation. The results reveal that the primary cyclonic separation mechanisms break down during surging and result in air-core suppression. The flow and primary separation mechanism in the core of the hydrocyclone is driven by the pressure drop and the flow and primary separation mechanism near the wall is primarily driven by the gravitational and centrifugal force-induced momentum. However, surging causes a breakdown in this mechanism by swapping this primary flow and separation behaviour, where the pressure drop becomes the primary driver of the flow near the walls and gravitational and centrifugal force-induced momentum primarily drives the flow in the core of the hydrocyclone

The Modification of the Dynamic Behaviour of the Cyclonic Flow in a Hydrocyclone under Surging Conditions

The aim in this study was to determine how surging modifies the dynamic behaviour of the cyclonic flow in a hydrocyclone using computational fluid and granular dynamics models. The Volume-of-Fluid model was used to model the air-core formation. Fluid–particle, particle–particle, and particle–wall interactions were modelled using an unsteady two-way coupled Discrete Element Method. Turbulence was modelled using both the Reynold’s Stress Model and the Large Eddy Simulation. The model predictions indicate that the phenomenon of surging modifies the dynamics of the cyclonic flow in hydrocyclones and subsequently impacts separation. The results reveal that the primary cyclonic separation mechanisms break down during surging and result in air-core suppression. The flow and primary separation mechanism in the core of the hydrocyclone is driven by the pressure drop and the flow and primary separation mechanism near the wall is primarily driven by the gravitational and centrifugal force-induced momentum. However, surging causes a breakdown in this mechanism by swapping this primary flow and separation behaviour, where the pressure drop becomes the primary driver of the flow near the walls and gravitational and centrifugal force-induced momentum primarily drives the flow in the core of the hydrocyclone