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A Study of Automotive Aerodynamics Using CFD
No full textThe objective of this thesis is to investigate the use of CFD methods to evaluate the aerodynamic drag of a vehicle. CFD methods, in some cases can be used as a substitute to physical testing if verified workflows are used. They can be used for rapid evaluation of design changes without the delays caused by wind tunnel testing.
In this study various models such as the Ahmed body, DrivAer model, AeroSUV model, GTU model, full-scale trailer truck model has been simulated at various conditions. The first study was with the simplified model of an automobile referred to as, the Ahmed body which is a crude representation of the variation of the C-pillar slant angles.
Next, more detailed models known as the DrivAer, AeroSUV and GTU which are detailed modular models of a sedan, an SUV, and a pick-up truck class of vehicles in various combinations of configurations, were simulated. All three models also include an open engine bay configuration which has a simplified engine, transmission, and exhaust system. The radiator is replaced with a simple cuboid porous area to simulate the velocity drop.
Finally, the aerodynamic performance of a full-scale trailer truck and a simple drag reducing device like a cabin air deflector and its effect on the drag coefficient were analyzed. Moreover, a homogenous platooning scenario, of trucks trailers where the trucks are moving at a distance of 5m between each other was investigated
Design and Construction of a Low-Cost Mechanical Scanning System and Control Interface for Scanning Acoustic and Photoacoustic Microscopy
No full textWe have designed and started construction of an instrument that will be able to serve as both a scanning acoustic microscope (SAM) and photoacoustic microscope (PAM). This instrument will be capable of imaging the volume of optically opaque specimens that are approximately 2 cm x 2 cm in lateral dimensions with both acoustic and optical contrast. When operating as a SAM, the specimen will be water-coupled to a high-frequency ultrasound transducer operating in pulse-echo mode. When operating as a PAM, short light pulses (\textasciitilde 100 ns, 5 to 10 μJ/pulse) from a 905 nm infrared laser diode located under the specimen will generate ultrasound pulses thermoelastically, which will then be received by a confocal high-frequency transducer. In both cases, the specimen will be raster-scanned under the transducer by a moving stage. The mechanical scanning system was designed and built using a spring-loaded microscope stage, micrometers, stepper motors, a shield board used for 3D printers, an Arduino Mega microcontroller, and a Raspberry Pi 4 microcomputer. A graphical user interface was written in Python using Tkinter to send the motion control commands to the stage. Future work will include incorporation of the laser and transducer control systems
First Deep Eutectic Solvent-Based (DES) Stationary Phase for Gas Chromatography and Future Perspectives for DES Application in Separation Techniques
No full textThe paper presents the first application of deep eutectic solvents (DES) as stationary phases for gas chromatography. DES obtained by mixing tetrabutylammonium chloride (TBAC) as a hydrogen bond acceptor (HBA) with heptadecanoic acid being a hydrogen bond donor (HBD) in a mole ratio of HBA:HBD equal to 1:2 was characterized by its ability to separate volatile organic compounds (VOCs). The Rohrschneider – McReynolds constants determined reveal that the synthesized DES is a stationary phase of medium polarity. A detailed retention characteristic was determined for a number of groups of chemical compounds, including aromatic hydrocarbons, alcohols, ketones, sulfides and thiophene derivatives. The synthesized DES was found to have a high selectivity towards alcohols. At the same time, the investigated stationary phase was found to have specific interactions with some analytes. For example, a stronger retention was observed for 1-hexanol and 1-heptanol compared to other alcohols. Retention times of these two alcohols are longer by 191% and 300%, respectively, relative to the expected value based on their boiling point. Such an increased retention is caused by a synergistic effect of various kinds of interactions – the possibility of formation of hydrogen bonds between the DES and the hydroxyl group of alcohols and hydrophobic interactions of alkyl chains of the DES with the alkyl chain of alcohols. The ability to modify properties of DESs by replacement of HBA or HBD with a different chemical compound or by dissolving in DES macromolecular substances makes the proposed stationary phase highly flexible. In addition to using the developed DES in chromatographic techniques, the retention data collected indicate the possibility of its application to other separation techniques, i.e. extractive distillation
