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Cfd simulation to study the effects of ribs in a converging nozzle flow at sonic mach number / Ambareen Khan

Cfd simulation to study the effects of ribs in a converging nozzle flow at sonic mach number_Ambareen Khan_A2_2020_MYMY
Kehadiran asas tumpul membawa kepada pemisahan aliran dalam badan aerodinamik, yang menyebabkan tekanan rendah di kawasan bangun. Pada nombor sonik Mach, tekanan rendah di kawasan bangun menyumbang sehingga enam puluh peratus daripada jumlah seret. Kajian ini dijalankan untuk mengkaji kesan rusuk segi empat tepat pada tekanan asas. Parameter yang dipertimbangkan adalah nisbah tekanan muncung, nisbah aspek tulang rusuk, Panjang kepada nisbah Diameter (L / D) salur apabila diletakkan beralih dari subsonik ke nombor Mach sonik. Simulasi dilakukan menggunakan CFD, dan model turbulensi k-ɛ digunakan. Pada mulanya, hasil simulasi yang diperolehi disahkan dengan kerja percubaan untuk nisbah L / D yang berbeza dari saluran pada pelbagai Numerik Tekanan Nozel (NPR), dan nisbah aspek tulang rusuk dari 3: 1 hingga 3: 3 untuk nisbah kawasan 6.25. Hasilnya dalam persetujuan yang baik dengan hasil eksperimen. Simulasi kemudian dilakukan untuk tulang rusuk tunggal, yang ditempatkan di pelbagai lokasi dan nisbah aspek untuk NPR dalam jarak antara 1.5 hingga 5 dari pangkalan. Variasi tekanan asas, halaju, dan perubahan medan untuk pembolehubah di atas dibincangkan. Keputusan simulasi menunjukkan bahawa tulang rusuk memecahkan vorteks utama di pangkalan dan membentuk pelbagai vorteks dan dengan itu mengawal tekanan asas di kawasan bangun. Keputusan menunjukkan bahawa rusuk segi empat tepat dengan nisbah aspek yang lebih rendah berkesan dalam mengurangkan tekanan asas, sedangkan rusuk dengan nisbah aspek yang lebih tinggi cenderung meningkatkan tekanan dasar. Simulasi juga dijalankan untuk saluran dengan garis pusat, D = 20 mm. Dalam hal ini, tulang rusuk segi empat tepat dengan rasio aspek 3: 1, 3: 2, dan 3: 3 ditempatkan pada lokasi 20 mm, 40 mm, 60 mm, dan 80 mm, untuk NPR yang sama. Keputusan menunjukkan bahawa ketinggian dan lokasi tulang rusuk memainkan peranan penting dalam mengawal tekanan asas. _______________________________________________________________________ The presence of a blunt base leads to flow separation in aerodynamic bodies, which causes a low-pressure in the wake region. At sonic Mach number, low pressure in the wake region contributes up to sixty percent of the total drag. This study is conducted to study the effect of the rectangular ribs on the base pressure. The parameters considered are the nozzle pressure ratio, rib’s aspect ratio, Length to Diameter (L/D) ratio of the duct when placed circumferentially operating from subsonic to sonic Mach number. The simulation is performed using CFD, and the k-ɛ turbulence model is employed. Initially, the simulation results obtained are validated with experimental work for different L/D ratio of the duct at various Nozzle Pressure Ratio’s (NPR), and the aspect ratio of the ribs from 3:1 to 3:3 for area ratio of 6.25. The results are in good agreement with the experimental results. Later simulations are done for a single rib, which is placed at different locations and aspect ratios for NPRs in the range from 1.5 to 5 from the base. Base pressure variations, velocity, and pressure field changes for the above variables are discussed. The simulation results indicate that the rib breaks the primary vortex at the base and form multiple vortices and hence controls the base pressure in the wake region. The results show that a rectangular rib with a lower aspect ratio is effective in reducing the base pressure, whereas the rib with a higher aspect ratio tends to increase the base pressure. The simulations are also conducted for a duct with a diameter, D = 20 mm. In this case, the rectangular rib with aspect ratios 3:1, 3:2, and 3:3 is placed at 20 mm, 40 mm, 60 mm, and 80 mm locations, for the same NPRs. Results show that the height and position of the rib plays a vital role in controlling the base pressure.
Contributor(s):
Ambareen Khan - Author
Primary Item Type:
Thesis
Identifiers:
Accession Number : 875008949
Language:
English
Subject Keywords:
Cfd simulation ; study the effects ; converging nozzle ; sonic mach number
Sponsor - Description:
Pusat Pengajian Kejuruteraan Aeroangkasa -
First presented to the public:
4/1/2020
Original Publication Date:
10/26/2020
Previously Published By:
Universiti Sains Malaysia
Place Of Publication:
School of Aerospace Engineering
Citation:
Extents:
Number of Pages - 86
License Grantor / Date Granted:
  / ( View License )
Date Deposited
2020-10-26 15:01:50.029
Submitter:
Mohamed Yunus Yusof

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Cfd simulation to study the effects of ribs in a converging nozzle flow at sonic mach number / Ambareen Khan1 2020-10-26 15:01:50.029