Pengaruh Variasi Radius Fillet Stern-Fin Terhadap Disortion Coefficient Inflow Propeller pada Kapal Selam Joubert BB2

Allam, Muhammad Yassar Taqi (2026) Pengaruh Variasi Radius Fillet Stern-Fin Terhadap Disortion Coefficient Inflow Propeller pada Kapal Selam Joubert BB2. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Kapal selam menuntut aliran masuk propeller yang seragam untuk menekan fluktuasi gaya dorong, getaran, dan kebisingan. Pada sambungan stern-fin, gradien tekanan lawan di pangkal sirip membentuk horseshoe vortex (HSV) yang merusak keseragaman wake di bidang propeller. Penelitian ini mengkaji pengaruh penambahan fillet concave quarter-circle dengan radius 5%, 10%, dan 15% dari panjang chord root pada sambungan stern-fin model kapal selam Joubert BB2 fully appended skala 1:35,1. Simulasi Reynolds-Averaged Navier-Stokes (RANS) tunak dijalankan pada tiga kecepatan (1, 2, dan 3 m/s) menggunakan dua model turbulensi, yaitu k-ε standar dan k-ω SST, kemudian keduanya dibandingkan. Kualitas aliran dinilai melalui distortion coefficient (DC), yakni simpangan baku wake fraction sirkumferensial (Seil dan Anderson) yang dihitung pada sembilan cincin radial dari 0,22R hingga 1,0R, serta melalui sebaran wake sirkumferensial pada bidang propeller dan bidang di belakang propeller. Setup numerik diverifikasi dengan Grid Convergence Index dan divalidasi terhadap data referensi, dengan selisih luas permukaan basah di bawah 0,5% dan error hambatan rata-rata 1,37%. Hasil menunjukkan bahwa fillet 5% dan 10% menurunkan DC, sedangkan fillet 15% menaikkannya, memperlihatkan hubungan non-monotonik dengan batas atas radius efektif. Konfigurasi optimum adalah fillet 10% dengan penurunan DC rata-rata inflow sebesar 1,31%, 0,94%, dan 2,16% berturut-turut pada V = 1, 2, dan 3 m/s, dan diperoleh tanpa penalti hambatan yang berarti karena perubahan koefisien hambatan total hanya 0,12 hingga 0,17%. Model k-ω SST menangkap struktur wake empat sirip lebih tajam, dengan kandungan harmonik orde tinggi yang lebih kuat, dibandingkan k-ε yang lebih difusif, meskipun urutan efektivitas fillet tetap konsisten pada kedua model dan kedua bidang. Analisis implikasi operasional menunjukkan bahwa perbaikan keseragaman oleh fillet terpusat di radius dalam hingga tengah dan hampir tidak mengubah advance coefficient efektif maupun eksitasi orde-daun propeller E1619 yang berdaun tujuh, sehingga manfaat fillet lebih pada kualitas keseragaman aliran daripada performa propulsi rata-rata.
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Submarines require a uniform propeller inflow to suppress thrust pulsation, vibration, and noise. At the stern-fin junction, the adverse pressure gradient at the fin root generates a horseshoe vortex (HSV) that degrades wake uniformity at the propeller plane. This study investigates the effect of adding concave quarter-circle fillets with radii of 5%, 10%, and 15% of the chord-root length at the stern-fin junction of a fully appended Joubert BB2 submarine model at a 1:35.1 scale. Steady Reynolds-Averaged Navier-Stokes (RANS) simulations were performed at three speeds (1, 2, and 3 m/s) using two turbulence models, namely the standard k-ε and k-ω SST models, which were subsequently compared. Inflow quality was assessed through the distortion coefficient (DC), defined as the standard deviation of the circumferential wake fraction (Seil and Anderson) computed over nine radial rings from 0.22R to 1.0R, as well as through circumferential wake distributions at the propeller plane and the plane behind the propeller. The numerical setup was verified using the Grid Convergence Index and validated against reference data, with a wetted-surface-area deviation below 0.5% and a mean resistance error of 1.37%. The results show that the 5% and 10% fillets reduce DC, whereas the 15% fillet increases it, indicating a non-monotonic relationship with an upper bound on the effective radius. The optimum configuration is the 10% fillet, which reduces the mean inflow DC by 1.31%, 0.94%, and 2.16% at V = 1, 2, and 3 m/s, respectively, without a meaningful resistance penalty, as the total resistance coefficient changes by only 0.12% to 0.17%. The k-ω SST model captures the four-fin wake structure more sharply, with stronger high-order harmonic content, than the more diffusive k-ε model, although the ranking of fillet effectiveness remains consistent across both models and both planes. An operational-implication analysis shows that the improvement in DC is concentrated at the inner-to-middle radii and barely changes the effective advance coefficient or the blade-order excitation of the seven-bladed E1619 propeller. Therefore, the primary benefit of the fillet lies in improving flow uniformity rather than mean propulsive performance.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	distortion coefficient, fillet, horseshoe vortex, inflow propeller, Joubert BB2, passive flow control.
Subjects:	V Naval Science > VM Naval architecture. Shipbuilding. Marine engineering V Naval Science > VM Naval architecture. Shipbuilding. Marine engineering > VM156 Naval architecture
Divisions:	Faculty of Marine Technology (MARTECH) > Naval Architecture and Shipbuilding Engineering > 36201-(S1) Undergraduate Thesis
Depositing User:	Muhammad Yassar Taqi Allam
Date Deposited:	07 Aug 2026 08:36
Last Modified:	07 Aug 2026 08:36
URI:	http://repository.its.ac.id/id/eprint/144213

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