This paper presents analyses of the effect of blowing flow control and variations on front geometry towards the reduction of aerodynamic drag on vehicle models. Blowing flow control is an alternative measure in modifying the onset of flow separation in the boundary layer on the surface of the vehicle. The modification is expected to reduce the dominating influence of the separation area on the total drag. Conducted in computational and experimental approaches, the research investigated the effect of frontal slant angle variations (θ) of 25°, 30° and 35° towards the reduction of aerodynamic drag on vehicle models on the application of blowing flow control with upstream and blowing speed of 16.7 m/s and 0.5 m/s, respectively. Load cells were used in the experimental method to validate the reduction of aerodynamic drag obtained from computational method. It is indicated that the effects of blowing flow control and variations on front geometry are significant in the increasing on pressure coefficients and the reduction of aerodynamic drag on vehicle models. The largest increase on pressure coefficients of 38.93% is indicated on the vehicle model with θ=35°, while the largest reduction of aerodynamic drag occurred on the same model with the values of 14.81 and 12.54 for computational and experimental methods, respectively.
Drag aerodinamika pada kendaraan disebabkan adanya tekanan rendah dan separasi aliran di bagian belakang, yang berdampak pada menurunnya kecepatan, meningkatnya penggunaan bahan bakar, dan turunnya efisiensi kendaraan. Blowing merupakan salah satu pilihan rekayasa kendali aktif aliran yang dapat diterapkan pada desain kendaraan yang dapat mengendalikan pembentukan separasi aliran dan berefek positif berupa pengurangan hambatan aerodinamis. Penelitian ini bertujuan menganalisis pengaruh penerapan blowing terhadap pola aliran, distribusi tekanan, dan hambatan aerodinamika yang bekerja pada bagian belakang model. Dengan bantuan CFD Fluent 6.3, model uji yang digunakan adalah model kendaraan dengan sudut kemiringan geometri depan (α) 35o dan rasio terhadap model Ahmed bodi original adalah 0.17 (1:6), yang dilengkapi dengan blowing dengan kecepatan 1.0 m/s. Hasil komputasi mengindikasikan bahwa penerapan blowing dapat mengurangi pembentukan wake dan menunda separasi aliran dan dapat meningkatkan koefisien tekanan minimum pada bagian belakang model kendaraan sebesar 24.690%. Pengurangan hambatan aerodinamika diperoleh sebesar 9.583%.
Ground source cooling system (GSCS) is promising technology to serve cooling demands of buildings. This study presents a development of an open-loop GSCS for space air conditioning at Hasanuddin University Gowa campus. Experimental study was carried-out by pumping water from well of 57 m depth and flowing the water over a heat exchanger to cool refrigerant of air conditioning (AC) unit. The performance of AC unit was investigated under actual operation with various water flowrates. The temperatures of inlet and outlet water in the heat exchanger were also measured. The system operated from 11:00 until 18:00 o'clock local time with 3 (three) flowrates such as 3.6; 6.5 and 14.3 L/min respectively. In the low flowrate, the temperature of outlet water is approximately 37 o C. However, the compressor power is also increase significantly. The coefficient of performances (COPs) of the system in average are 2.9 in the low flowrate and 3.4 in the high flowrate. Also. the result shows that the utilization of GSCS is appropriated for cooling buildings in the hot climate like Indonesia.
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