Widiastuti, Asna (2021) Studi Numerik Pengaruh Reynolds Number Dan Geometry Scaling Terhadap Performansi Aerodinamika Desain Kereta Cepat Jakarta-Surabaya. Undergraduate thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Untuk meningkatkan kualitas sarana transportasi, PT. INKA membuat rencana pembangunan insfrastruktur kereta cepat Jakarta-Surabaya dengan kecepatan 300 km/jam. Salah satu topik penting yang perlu diteliti adalah seberapa besar gaya hambat aerodinamika yang dialami kereta ketika dioperasikan pada kecepatan tinggi semakin besar energi yang dibutuhkan untuk mengoperasikan kereta tersebut. Untuk itu perlu adanya penelitian studi numerik terhadap desain kereta cepat untuk mengetahui performansi aerodinamika. Proses simulasi membutuhkan pembuatan mesh yang cukup rapat agar detail aliran dapat tertangkap dengan baik dengan kata lain jumlah mesh akan meningkat. Dengan besarnya domain geomeri kereta, tentu akan menambah numerical resources yang diperlukan. Salah satu cara mengurangi beban numerical resources adalah dengan melakukan scaling terhadap geometri kereta. Menggunakan model scaling dalam simulasi telah banyak dilakukan, akan tetapi masih belum banyak yang meneliti lebih lanjut terkait efek scaling geometri terhadap performansi aerodinamika kereta. Scaling geometri diharapkan dapat memberikan detail aliran yang cukup baik dibandingkan simulasi CFD menggunakan model full-scaling.
Metode yang digunakan dalam penelitian ini adalah studi numerik tiga dimensi dengan model kereta cepat Jakarta-Surabaya menggunakan pola aliran steady dan incompressible flow. Analisa numerik dilakukan menggunakan software ANSYS Fluent. Geometri yang diuji terdiri dari dua model konfigurasi desain kereta cepat Jakarta-Surabaya yaitu model konfigurasi 3 cars setengah geometri dengan skala geometri 1:1 dan 1:10. Simulasi dilakukan dengan menggunakan kecepatan aliran 83.33 m/s untuk model kereta dengan skala 1:1 dan menggunakan kecepatan 15 m/s, 50 m/s, dan 83.33 m/s untuk simulasi model kereta cepat yang diskala 1:10. Model turbulensi yang digunakan adalah turbulensi steady k-ω SST. Boundary condition yang digunakan berupa velocity inlet, pressure outlet, no-slip moving wall pada tanah, dan symmetry. Pengolahan data dilakukan setelah simulasi dilakukan, dimana data yang disajikan meliputi grafik dan kontur koefisien tekanan, kontur kecepatan, analisis boundary layer, head pressure pulse, koefisien drag kereta cepat, dan grid independency test terhadap nilai CD.
Hasil penelitian menunjukkan bahwa variasi Reynolds number berpengaruh terhadap boundary layer thickness dan koefisien drag. Penurunan ketebalan boundary layer akibat kenaikan Reynolds number dari 2,05x107 ke 2,5x105 sebesar 33.33% pada head car, 19.35% pada middle car, dan 6.06% pada tail car. Penurunan koefisien drag (CD) akibat kenaikan Reynolds number dari 2,05x107 ke 2,5x105 sebesar 23.57% pada head car, 26% pada middle car, dan 18.78% pada tail car. Variasi Reynolds number berpengaruh terhadap negative peak Cp upper side, sisi samping kereta dan sisi bawah kereta. Nilai Reynolds number yang semakin tinggi menyebabkan negative peak semakin rendah pada ketiga sisi kereta sebesar 1.92% pada upper surface, 0.62% pada lower surface, dan 1.7% pada permukaan samping kereta. Hasil independency test terhadap nilai CD pada setiap Reynolds number yang digunakan dalam simulasi adalah nilai koefisien drag (CD) telah independen terhadap nilai Reynolds number pada rentang 7,4x106 hingga 2,05x107 dimana pada rentang tersebut error relative yang dihasilkan telah kurang dari 5%.
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To improve the quality of transportation facilities, PT. INKA has planned to construct the Jakarta-Surabaya high-speed train infrastructure with a speed of 300 km/hour. One important topic that needs to be researched is how much aerodynamic drag is experienced by the train when it is operated at high speed, the greater the energy required to operate the train. For this reason, a numerical study of the fast train design is needed to determine aerodynamic performance. The simulation process requires making a mesh that is tight enough so that the details of the flow can be captured properly, in other words, the number of meshes will increase. With the large geometry domain of the train, it will certainly add to the necessary numerical resources. One way to reduce the numerical resources is by scaling the train geometry. Using scaling models in simulations has been done a lot, but there are still not many studies related to the effect of geometric scaling on tight aerodynamic performance. Scaling geometry is expected to provide sufficient flow details compared to CFD simulations using the full-scaling model.
The method used in this research is a three-dimensional numerical study with the Jakarta-Surabaya high-speed train model using steady flow patterns and incompressible flow. Numerical analysis was performed using ANSYS Fluent software. The geometry tested consisted of two models of the Jakarta-Surabaya fast train design configuration, namely the 3 car half-geometry configuration model with a geometric scale of 1: 1 and 1:10. The simulation is carried out using a flow rate of 83.33 m / s for a model train with a scale of 1: 1 and using a speed of 15 m / s, 50 m / s, and 83.33 m / s for simulating a 1:10 scale fast train model. The turbulence model used is steady k-ω SST turbulence. The boundary conditions used are velocity inlet, pressure outlet, no-slip moving wall on the ground, and symmetry. Data processing is carried out after the simulation is carried out, where the data presented includes graphs and contours of pressure coefficients, velocity contours, boundary layer contours, and fast train drag coefficients.
The results showed that the Reynolds number variation has an effect on the boundary layer thickness and drag coefficient. The decrease in boundary layer thickness due to the increase in Reynolds number from 2.05x107 to 2,5x105 was 33.33% for the head car, 19.35% for the middle car, and 6.06% for the tail car. The decrease in drag coefficient (CD) due to the increase in Reynolds number from 2.05x107 to 2.05x106 is 23.57% for the head car, 26% for the middle car, and 18.78% for the tail car. The Reynolds number variation has an effect on the negative peak Cp on the upper side, the side of the train and the bottom of the train. The higher the Reynolds number, the lower the negative peak on the three sides of the train by 1.92% on the upper surface, 0.62% on the lower surface, and 1.7% on the side surface of the train. The result of the independence test on the CD value for each Reynolds number used in the simulation is that the drag coefficient (CD) is independent of the Reynolds number value in the range 7.4x106 to 2.05x107 where in that range the resulting relative error is less than 5%.
| Item Type: | Thesis (Undergraduate) |
|---|---|
| Uncontrolled Keywords: | Aerodinamika, Geometry Full-scaling, Geometry Scaling, Kereta Cepat, Koefisien Drag, Koefisien Tekanan, Reynolds Number |
| Subjects: | T Technology > TF Railroad engineering and operation > TF1327.O58 High speed ground transportation (train) T Technology > TJ Mechanical engineering and machinery > TJ820 Wind power T Technology > TL Motor vehicles. Aeronautics. Astronautics > TL521 Aerodynamics, Hypersonic. |
| Divisions: | Faculty of Industrial Technology and Systems Engineering (INDSYS) > Mechanical Engineering > 21201-(S1) Undergraduate Thesis |
| Depositing User: | Asna Widiastuti |
| Date Deposited: | 06 Aug 2021 05:19 |
| Last Modified: | 06 Aug 2021 05:19 |
| URI: | http://repository.its.ac.id/id/eprint/84917 |
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