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Aerodynamic drag reduction in automobiles plays a vital role in reducing fuel consumption. Every vehicular structure contains multiple hotspots for drag increase. This paper analyses the effect of this increase in drag due to one of the many such hotspots -the vehicle's door handles. This takes place due to separation of flow at the handles. In this study, an attempt is made to understand the effect of various door handle designs on the drag coefficient of a car. Various designs such as the "lever type", the "push button type", the "lift back type" and the "pull type" variants are studied. In order to estimate the contribution of the door handles to the overall drag coefficient of the vehicle, a baseline analysis is performed on a reference bluff vehicle (an Ahmed body) implementing the Menter k-ω Shear Stress Transport (SST) model to analyse features of flow around it. The overall drag coefficient for the Ahmed body is then obtained. Further, the various door handle designs considered are modelled on the Ahmed body to calculate the change in the drag force coefficient. The purpose of this study is to deduce the most ideal configuration among the door handles -from the perspective of the obtaining the one with the least aerodynamic drag coefficient -currently used by various car manufacturers around the world. The necessity for a new design is highlighted in order to produce more streamlined flow around the side of the body while not compromising on the user's ease of entry into his/her vehicle. Nomenclature C D= overall drag coefficient F D = drag force ρ = air density (1.225 kg/m 3 ) A X = projected area of the Ahmed body in the x direction u = bulk upstream velocity (15 m/s) CFD = computational fluid dynamics

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As computational modelling becomes an increasingly reliable and key component in accelerating the design process for twin screw machines, the goals for engineers now include developing faster running and physically accurate component models to optimize machine performance and efficiency, minimize internal leakage, reduce unwanted noise and pulsations, and properly size bearing supports in the machine. Accurately capturing these aspects via physical models helps in analyzing operating points that were not tested as well as in understanding how the machine will perform in a surrounding system. Thereafter, engineers can find an optimal design in a timely manner for the fastest speed to market as well as reduce physical testing to keep development costs low. This paper presents the use of a multi-physics modelling platform - GT-SUITE - in conjunction with SCORG – a well-established tool for the design and analysis of twin screw machines – to explore meeting the aforementioned goals. Two case studies are presented for a 3/5 oil free air compressor and a 4/5 oil injected air compressor. Comparisons to the mass flow rates of the gas and oil, temperatures, indicated power and the instantaneous chamber pressure vs rotation angle were made against test data available from the Centre for Compressor Technology at City University. The sensitivity of oil injection timing on the discharge temperature and power is shown and an optimum timing was found. The validated chamber models may be integrated into a system as well as used for further optimization to improve the original compressor performance.