Pompa jetli su altı araçları için optimizasyon temelli tasarım metodolojisi geliştirilmesi
Pompa jetli su altı araçları için optimizasyon temelli tasarım metodolojisi geliştirilmesi
Dosyalar
Tarih
2025-06-19
Yazarlar
Demir, Efecan Oğuz
Süreli Yayın başlığı
Süreli Yayın ISSN
Cilt Başlığı
Yayınevi
İTÜ Lisansüstü Eğitim Enstitüsü
Özet
Bu tez çalışmasında, su altı araçlarında kullanılması planlanan bir pompa jeti tahrik sistemi için yavaşlatıcı tipte nozul geometrisi tasarlanması üzerine optimizasyon temelli bir metodoloji geliştirmeyi amaçlamıştır. Su altında kullanılan pompa jetlerinde aracın kuyruk formu da sistemin bir parçası olarak davrandığı için nozul ve kuyruk geometrileri birlikte ele alınması gereklidir. Bu iki yapı birlikte bir akış alanı oluşturur ve bu alanın içerisine yerleştirilen rotor ve stator bileşenlerinin verimlerini doğrudan etkilerler. Bu sebeple bu çalışma kapsamında literatürdeki çalışmalardan farklı olarak su altı araçlarında kullanılması planlanan pompa jeti tahrik sistemine ait yavaşlatıcı nozul tasarım süreçlerine kuyruk formunun tasarımı da dahil edilmiştir. Çalışmanın ilk aşaması, geometrik parametrelerin belirlenmesidir. Pompa jeti nozulu bir hidrofol kesitinden türetilmiş olup, optimizasyon sürecinde NACA 4-haneli serisi kullanılmıştır. Bu seride, maksimum sehim noktası, maksimum sehim ve maksimum kalınlık temel parametreler olarak ele alınmıştır. Tüm bunlara ek olarak nozul açısı ile nozulun uzaydaki konumu (x ve y koordinatları) da eklenince toplamda 6 parametre ile nozul geometrisi tanımlanmıştır. Kuyruk geometrisini parametreleştirmek için ise yüksek mertebeden polinomlar kullanılmış ve kuyruk geometrisinin matematiksel olarak ifade edilmesinde 6. dereceden bir polinom tercih edilmiştir. Bu polinomun sınır koşulları ile birlikte çözümünden elde edilen 3 parametre ile kuyruk geometrisi kontrol edilebilir hale gelmiştir. Sonuç olarak 6 tanesi nozul geometrisinden ve 3 tanesi kuyruk geometrisinden gelmek üzere toplamda 9 parametre ile optimizasyon kontrol altına alınmıştır. Akışkan dinamiklerini doğru bir şekilde modellemek ve hesaplama maliyetlerini azaltmak için iki boyutlu eksenel simetrik bir analiz modeli oluşturulmuştur. Oluşturulan analiz modeli Siemens HEED programı içerisinde bulunan SHERPA algoritması entegrasyonu ile desteklenmiştir. SHERPA algoritması, 70 milyondan fazla olası varyasyon bulunmasına rağmen yaklaşık 1000 farklı yapılandırmayı değerlendirerek geniş tasarım alanında verimli bir şekilde gezinmiş ve optimum sonuca ulaşmıştır. Optimum geometri olarak tanımlanan ID-336, toplam direnç kuvvetini azaltma ve yüksek rotor giriş basıncını koruma arasında en iyi dengeyi göstermiştir. Bu sonuçlar, su altı araçlarının performansını artırmak için nozul ve kuyruk geometrilerinin birlikte optimize edilmesinin kritik önem taşıdığını göstermektedir. İki boyutlu optimizasyonun ardından, üç boyutlu analiz aşaması, optimize edilmiş nozul ve kuyruk geometrisinin yanı sıra rotor ve stator bileşenlerini de içerecek şekilde genişletilmiştir. İki boyutlu modelde basitleştirilmiş momentum kaynağı temsilinin yerini, gerçek rotor kanat geometrileri almıştır. Rotor-stator etkileşimlerinin entegrasyonu, nozul içindeki akış düzgünlüğünü iyileştirmiş, rotor girişindeki basınç dağılımını artırmış ve kavitasyon risklerini en aza indirmiştir. Bu iyileştirmeler, karşılaştırmalı basınç alanı görselleştirmeleri ile doğrulanmıştır. Optimum tasarımın doğrulaması, üç boyutlu hesaplamalı akışkanlar dinamiği (HAD) simülasyonları ile gerçekleştirilmiş ve iki boyutlu ile üç boyutlu sonuçlar arasındaki tutarlılık doğrulanmıştır. Üç boyutlu model, iki boyutlu sonuçlardan sadece %1,9 oranında basınç katsayısı ve %3,3 oranında toplam direnç kuvveti farkı göstermiştir. Bu bulgular, iki boyutlu optimizasyon metodolojisinin üç boyutlu uygulamalara güvenilir bir şekilde genişletilebileceğini göstermektedir. Çalışmada ayrıca rotor-stator etkileşimlerinin genel sistem performansı üzerindeki etkileri incelenmiştir. Optimize edilmiş stator konumlandırması sayesinde rotor girişindeki akış hizalanması iyileştirilmiş, bu da itki üretimini istikrarlı hale getirmiş ve akustik emisyonları azaltmıştır. Ayrıca, 15 metre derinlikte Schnerr-Sauer modeli kullanılarak yapılan kavitasyon analizi, optimize edilmiş tasarımın kavitasyon oluşumunu başarıyla sınırladığını, özellikle rotor arayüzünde daha yüksek basınç seviyelerini koruyarak sağladığını ortaya koymuştur. Sonuç olarak, optimize edilmiş nozul ve kuyruk yapılandırmasına rotor ve stator geometrilerinin entegrasyonu, pumpjet tahrik sistemlerinin genel performansını önemli ölçüde artırmaktadır. Bu çalışmada sunulan çoklu hedef optimizasyon yaklaşımı, yüksek hızlı su altı araçları için hem hidrodinamik verimlilik hem de kavitasyon kontrolü sağlayan verimli ve dayanıklı tahrik sistemleri tasarlamak için pratik bir çerçeve sunmaktadır.
This study focuses on the optimization-based numerical investigation of decelerating ducted pumpjets for high-speed underwater vehicles. Pumpjets are widely utilized in marine propulsion systems due to their higher efficiency at high speeds, improved cavitation performance, and lower acoustic noise compared to conventional propellers. The key components of a pumpjet system include the rotor, stator, and duct, each playing a critical role in propulsion efficiency and cavitation mitigation. In this context, optimizing these components collectively can significantly enhance overall system performance. In this study, a comprehensive numerical investigation of the aft-duct interaction in decelerating pumpjet propulsion systems for underwater vehicles is conducted. The primary objective is to optimize the effects of the pumpjet propulsion system on the total drag of the underwater vehicle and the pressure at the rotor inlet, while simultaneously considering the impact of aft geometry. Given that increased total drag directly escalates the power requirements of the underwater vehicle, and reduced pressure at the rotor inlet indirectly raises power demands by decreasing rotor efficiency due to cavitation, the optimization process is strategically designed within these two contexts. Numerical tools such as ANSYS Fluent, ANSYS CFX, and Siemens HEEDS were employed to achieve a systematic and efficient design process. Firstly, the geometric configuration of the pumpjet system is mathematically formulated to establish the optimization parameters. The duct geometry of the pumpjet is derived from a hydrofoil section, utilizing the NACA 4-digit series within the optimization framework. The 4-digit NACA series is characterized by three fundamental parameters: the location of the maximum camber, the camber line profile, and the distribution of thickness along this line. In addition to these, the duct's angle and the spatial coordinates (x and y positions) are included, resulting in a total of six parameters governing the duct geometry. To accurately parameterize the aft-body geometry, high-order polynomials are employed due to their efficacy in representing the complex curved surfaces typical of aft configurations. In this study, a sixth-order polynomial is specifically utilized to model the aft-body shape. This approach ensures a precise representation of the curvature and structural nuances inherent to underwater vehicle designs. Moreover, three additional parameters derived from the aft-body geometry are incorporated into the optimization process. Consequently, the comprehensive optimization methodology is initiated by systematically controlling a total of nine geometric parameters.In the first phase, the study focuses on the optimization of the duct and aft body configuration by using 2D axisymmetrical domain. Numerical simulations were performed using the k-ω turbulence model, with the rotor modeled as a momentum source. A wide range of geometric variations were considered to explore the optimal configuration that reduces drag and increase pressure inside the duct. To achieve a balanced optimization between these two conflicting performance criteria, the study adopts a multi-objective optimization approach, assigning equal weight (50%) to both total drag reduction and rotor inlet pressure increase. The SHERPA algorithm was employed to effectively reduce the computational cost by identifying the optimal point with fewer than 1000 analysis cases, despite the vast design space exceeding 70 million possible configurations. The use of two-dimensional axisymmetric models significantly reduced the computational burden without compromising accuracy. The optimization process revealed that the most favorable design point (ID-336) lies at the intersection of the two primary objectives—minimum drag and maximum rotor inlet pressure—indicating that both goals are inversely related. The Pareto diagram generated from the analysis shows that the optimal point balances these conflicting objectives efficiently. The study also identified two extreme configurations: ID-605, which achieves the highest rotor inlet pressure but at the cost of significantly increased drag, and ID-405, which minimizes drag but suffers from a low rotor inlet pressure. These findings underscore the inherent trade-off between minimizing drag and maximizing inlet pressure. Sensitivity analysis conducted to understand the influence of design parameters on performance metrics highlighted that the duct angle (α) and camber (M) of the duct cross-section have the most significant correlations with the total drag and pressure, as demonstrated by the Pearson correlation coefficients. For instance, the maximum camber location (P) showed a strong positive correlation with drag force but an insignificant correlation with rotor inlet pressure. Similarly, the angle of attack (α) exhibited a robust negative correlation with both drag and inlet pressure, indicating that its optimization is critical for achieving balanced performance. Following the 2D axis-symetrical duct optimization, the second phase involves the optimum configuration's performance in 3D domain together with 3D modeled rotor and stator. The validation of the optimized design was conducted through three-dimensional computational fluid dynamics (CFD) simulations, which confirmed the consistency between two-dimensional and three-dimensional results. The three-dimensional model demonstrated a minimal difference from the two-dimensional outcomes, with pressure coefficients varying by only 1.9% and total drag by 3.3%. These findings indicate that the two-dimensional optimization methodology can be reliably extended to three-dimensional applications without significant loss of accuracy. The study also explored the effects of rotor-stator interactions on the overall system performance. The alignment of flow at the rotor inlet was improved through optimized stator positioning, which contributed to stabilizing thrust production and minimizing acoustic emissions. Furthermore, cavitation analysis performed using the Schnerr-Sauer model at a depth of 15 meters revealed that the optimized design successfully mitigated cavitation formation, primarily by maintaining higher pressure levels at the rotor interface. In conclusion, the integration of rotor and stator geometries into the optimized duct and tail configuration significantly enhances the overall performance of pumpjet propulsion systems. The multi-objective optimization approach presented in this study offers a practical framework for designing efficient and robust propulsion systems for high-speed underwater vehicles, ensuring both hydrodynamic efficiency and cavitation control. By integrating advanced CFD techniques with experimental validation, the study not only advances current methodologies but also lays the groundwork for future optimization efforts. The use of multi-objective algorithms like SHERPA enables balancing competing performance criteria, making it a valuable tool in propulsion system design.
This study focuses on the optimization-based numerical investigation of decelerating ducted pumpjets for high-speed underwater vehicles. Pumpjets are widely utilized in marine propulsion systems due to their higher efficiency at high speeds, improved cavitation performance, and lower acoustic noise compared to conventional propellers. The key components of a pumpjet system include the rotor, stator, and duct, each playing a critical role in propulsion efficiency and cavitation mitigation. In this context, optimizing these components collectively can significantly enhance overall system performance. In this study, a comprehensive numerical investigation of the aft-duct interaction in decelerating pumpjet propulsion systems for underwater vehicles is conducted. The primary objective is to optimize the effects of the pumpjet propulsion system on the total drag of the underwater vehicle and the pressure at the rotor inlet, while simultaneously considering the impact of aft geometry. Given that increased total drag directly escalates the power requirements of the underwater vehicle, and reduced pressure at the rotor inlet indirectly raises power demands by decreasing rotor efficiency due to cavitation, the optimization process is strategically designed within these two contexts. Numerical tools such as ANSYS Fluent, ANSYS CFX, and Siemens HEEDS were employed to achieve a systematic and efficient design process. Firstly, the geometric configuration of the pumpjet system is mathematically formulated to establish the optimization parameters. The duct geometry of the pumpjet is derived from a hydrofoil section, utilizing the NACA 4-digit series within the optimization framework. The 4-digit NACA series is characterized by three fundamental parameters: the location of the maximum camber, the camber line profile, and the distribution of thickness along this line. In addition to these, the duct's angle and the spatial coordinates (x and y positions) are included, resulting in a total of six parameters governing the duct geometry. To accurately parameterize the aft-body geometry, high-order polynomials are employed due to their efficacy in representing the complex curved surfaces typical of aft configurations. In this study, a sixth-order polynomial is specifically utilized to model the aft-body shape. This approach ensures a precise representation of the curvature and structural nuances inherent to underwater vehicle designs. Moreover, three additional parameters derived from the aft-body geometry are incorporated into the optimization process. Consequently, the comprehensive optimization methodology is initiated by systematically controlling a total of nine geometric parameters.In the first phase, the study focuses on the optimization of the duct and aft body configuration by using 2D axisymmetrical domain. Numerical simulations were performed using the k-ω turbulence model, with the rotor modeled as a momentum source. A wide range of geometric variations were considered to explore the optimal configuration that reduces drag and increase pressure inside the duct. To achieve a balanced optimization between these two conflicting performance criteria, the study adopts a multi-objective optimization approach, assigning equal weight (50%) to both total drag reduction and rotor inlet pressure increase. The SHERPA algorithm was employed to effectively reduce the computational cost by identifying the optimal point with fewer than 1000 analysis cases, despite the vast design space exceeding 70 million possible configurations. The use of two-dimensional axisymmetric models significantly reduced the computational burden without compromising accuracy. The optimization process revealed that the most favorable design point (ID-336) lies at the intersection of the two primary objectives—minimum drag and maximum rotor inlet pressure—indicating that both goals are inversely related. The Pareto diagram generated from the analysis shows that the optimal point balances these conflicting objectives efficiently. The study also identified two extreme configurations: ID-605, which achieves the highest rotor inlet pressure but at the cost of significantly increased drag, and ID-405, which minimizes drag but suffers from a low rotor inlet pressure. These findings underscore the inherent trade-off between minimizing drag and maximizing inlet pressure. Sensitivity analysis conducted to understand the influence of design parameters on performance metrics highlighted that the duct angle (α) and camber (M) of the duct cross-section have the most significant correlations with the total drag and pressure, as demonstrated by the Pearson correlation coefficients. For instance, the maximum camber location (P) showed a strong positive correlation with drag force but an insignificant correlation with rotor inlet pressure. Similarly, the angle of attack (α) exhibited a robust negative correlation with both drag and inlet pressure, indicating that its optimization is critical for achieving balanced performance. Following the 2D axis-symetrical duct optimization, the second phase involves the optimum configuration's performance in 3D domain together with 3D modeled rotor and stator. The validation of the optimized design was conducted through three-dimensional computational fluid dynamics (CFD) simulations, which confirmed the consistency between two-dimensional and three-dimensional results. The three-dimensional model demonstrated a minimal difference from the two-dimensional outcomes, with pressure coefficients varying by only 1.9% and total drag by 3.3%. These findings indicate that the two-dimensional optimization methodology can be reliably extended to three-dimensional applications without significant loss of accuracy. The study also explored the effects of rotor-stator interactions on the overall system performance. The alignment of flow at the rotor inlet was improved through optimized stator positioning, which contributed to stabilizing thrust production and minimizing acoustic emissions. Furthermore, cavitation analysis performed using the Schnerr-Sauer model at a depth of 15 meters revealed that the optimized design successfully mitigated cavitation formation, primarily by maintaining higher pressure levels at the rotor interface. In conclusion, the integration of rotor and stator geometries into the optimized duct and tail configuration significantly enhances the overall performance of pumpjet propulsion systems. The multi-objective optimization approach presented in this study offers a practical framework for designing efficient and robust propulsion systems for high-speed underwater vehicles, ensuring both hydrodynamic efficiency and cavitation control. By integrating advanced CFD techniques with experimental validation, the study not only advances current methodologies but also lays the groundwork for future optimization efforts. The use of multi-objective algorithms like SHERPA enables balancing competing performance criteria, making it a valuable tool in propulsion system design.
Açıklama
Tez (Yüksek Lisans)-- İstanbul Teknik Üniversitesi, Lisansüstü Eğitim Enstitüsü, 2025
Anahtar kelimeler
gemi mühendisliği,
marine engineering