LEE- Isı Akışkan Lisansüstü Programı
Bu topluluk için Kalıcı Uri
Gözat
Konu "Aerodinamik" ile LEE- Isı Akışkan Lisansüstü Programı'a göz atma
Sayfa başına sonuç
Sıralama Seçenekleri
-
ÖgeAerodynamic shape optimization of the DLR-F6 wing by using openfoam as CFD solver integrated with rsm(Graduate School, 2023-06-15) Buluş, Halil ; Çadırcı, Sertaç ; 523201122 ; Heat FluidAerodynamic shape optimization plays a critical role in aerospace engineering as it allows designers to enhance aerodynamic performance by altering the shape of a body. The ability to optimize the shape of structures like aircraft wings, wind turbine blades, and rockets can lead to increased efficiency, reduced fuel consumption, and minimized emissions. Given the pressing need to address climate change and the exponentially escalating global crisis, it's essential to prioritize sustainable solutions in every aspect of design, including minimizing the impact of aircraft emissions. This requires a primary focus on decreasing the drag and increasing the lift on the airplane, which is one of the most significant factors affecting aerodynamic performance and range. As air traffic continues to grow, the importance of aerodynamic shape optimization in reducing emissions and increasing fuel efficiency becomes increasingly clear. This thesis on the aerodynamic shape optimization of the DLR-F6 wing demonstrates an effective and a comprehensive way of an optimization process that can contribute to the ongoing research in this field. The DLR-F6 wing is a common benchmark for aerodynamic research due to its complex geometry and challenging flow characteristics. By optimizing the shape of the wing, it is aimed to improve its performance and contribute to ongoing research in this field. To ensure that the structural strength of the wing is not compromised, the optimization process also involves some considerations on various design constraints like modal frequency and mass of the wing. In the optimization process, different chord slices at various locations along the span has been taken and twisted some angles by taking their aerodynamic centers as reference. The work focuses on to determine the best improved angle sets which let the better performance on L/D value without sacrificing its structural integrity. The optimization model tree was constructed using ModeFRONTIER software, which integrated different software tools and automated the optimization process. The construction involved four main stages. Firstly, Pointwise software was used to create a new wing database by twisting at the six sliced chords with angles determined by the software. The software automatically executed all the steps to twist, create a new database, make surface mesh, and create a pre-meshed geometry for Abaqus, with the help of a journal. In the second stage, volume meshes were prepared using ANSYS Fluent Meshing, which automatically executed all the meshing processes controlled by optimization software. Thirdly, CFD analysis was conducted using OpenFOAM as the CFD solver to simulate the flow around the wing. The volume mesh created by Fluent Meshing was used as the solution cells. With the help of a function, OpenFOAM can convert a fluent mesh to foam format. To make the optimization process faster and well talent based, the HPC (High Performance Computer) was used to run in OpenFOAM. ModeFRONTIER makes an automatic connection with HPC systems based on SSH protocol and with a Linux bash script, aerodynamic analysis had been conducted. After the simulation was done, a file storing all the forces at each iteration was transferred to the host computer, and lift, drag and L/D values were computed using an inner MATLAB stage. The L/D value and lift value were set as design objectives. The purpose was the maximize these values. Since the twisting rotation angles were set as the input values, the optimization tool organizes and selects the best input values to succeed the design objectives. Lastly, Abaqus software was used to perform structural analysis to ensure the strength of the wing, with the pre-meshed geometry file directly transferred after the first stage. With an Abaqus journal, for each different design mass and modal frequency are calculated and processed with another MATLAB stage. These were selected as another design objective, with the goal being to minimize the mass and maximize the frequency value. However, 'Lift' and 'L/D' objectives were prioritized to make the optimization processes easy to go on. The optimization process was streamlined through these main stages, with simultaneous file transfers and evaluation of results made in intermediate steps. About 220 DoE (Design of Experiments) were created and evaluated. Due to the expensive CFD simulations, direct optimizations were not feasible to proceed. Therefore, RSM (Response Surface Methodology) was used to reproduce more experiments in an inexpensive way. RSM, also known as Surrogate Models, are a collection of statistical and mathematical techniques used to create, model, and analyze the relationships between input variables and output responses. By using RSM, the number of experiments needed can be reduced to obtain optimal results, saving time and resources in the optimization process. The direct optimization results were used to train the data set to build a good quality RSM. After using good RSM strategies, 1000 more experiments were created. After selecting the best design, a real analysis was conducted and showed that the RSM predicted the design output very well. The results of the optimization process were evaluated using a set of performance metrics, including the L/D ratio, maximum lift, minimum drag. Since the mass and modal frequency objectives were required to assure the structural integrity of the new design, they were not included as optimization performance metrics. The modified DLR-F6 aircraft was then compared with the original DLR-F6 aircraft using these performance metrics. The results show that the modified aircraft had a 13.15% improvement in L/D ratio and 2.24% improvement in lift compared to the original aircraft. A 3DOF flight simulation was done using MATLAB Simulink tool, with two aerodynamic databases created by sweeping 2 Mach numbers and 13 angle of attacks. One was for the airplane with the original wing, and the other was for the airplane with the optimized wing. Overall, the thesis demonstrates the effectiveness of using a multi-disciplinary optimization approach to improve the performance of complex aerodynamic shapes such as the DLR-F6 wing. The optimized wing not only shows a significant improvement in its aerodynamic performance but also maintains its structural strength. Although the flow chart may seem complex, it helps make the optimization process comprehensive and efficient. The optimization process and methodology used in this research can be applied to other complex aerodynamic shapes to improve their performance as well.
-
ÖgeComputational fluid dynamics modeling the store separation from a jet trainer aircraft(Graduate School, 2024-11-08) Coşar, Ziya ; Güneş, Hasan ; 503201142 ; Heat and FluidThe issue of ensuring the safe and predictable separation of munitions from aircraft has become an area of growing interest in recent years. This highlights the necessity of eliminating potential risks associated with the interaction between munitions and the aircraft, while ensuring the safe and effective execution of operational missions. Solutions to this problem include flight tests, wind tunnel experiments, and Computational Fluid Dynamics (CFD) analyses. The Captive Trajectory System (CTS) and grid methods are wind tunnel techniques designed to solve the store separation problem. In this thesis, both CTS and grid methods were modeled using CFD. Furthermore, a new method called the 'Captive Carry with Flow-Field' was developed as an alternative to the conventional grid method. The primary objective of this research is to validate the munition trajectory calculated through the developed CFD methodology with experimental results, and to compute the trajectory of the munition separating from a jet trainer aircraft using the CTS, grid, and Captive Carry with Flow-Field methods. Furthermore, a comprehensive investigation was conducted to assess the impact of mach number and angle of attack on store separation analyses. The results of simulations performed at various mach numbers and angles of attack clearly illustrated the effect of these parameters on the munition's trajectory behavior. The CFD studies related to store separation were conducted using the commercial software Simcenter Star-CCM+. In the first phase of this thesis, a Computational Fluid Dynamics (CFD) methodology was developed for the Captive Trajectory System (CTS) using the Eglin geometry, a widely employed configuration in store separation studies, along with its corresponding wind tunnel test data. The methodology development included selecting an appropriate turbulence model, conducting a mesh independence study, and determining a suitable time step to ensure the accuracy of unsteady simulations for store separation analyses. Unsteady analyses were carried out using the Spalart Allmaras, Realizable K-ε, and K-ω SST turbulence models, with the munition's trajectory computed for each model. The simulation results were then validated against wind tunnel data. After identifying the optimal turbulence model, a detailed mesh independence study was performed to confirm that the numerical results remained unaffected by variations in mesh density. This study tested five different mesh with varying densities, during which aerodynamic forces along the X, Y, and Z axes acting on the munition were calculated. The evaluation of these results led to the selection of the most accurate and efficient mesh for store separation analyses. Subsequently, the determination of an appropriate time step, a key factor in unsteady simulations, was undertaken. Using four different time steps, unsteady simulations were conducted, and the munition's trajectory was compared to wind tunnel results to identify the optimal time step. These unsteady CFD analyses were performed at a mach number of 0.95 and an altitude of 26,000 feet. For the trajectory calculation, the overset mesh algorithm was employed in unsteady analyses. The trajectory was calculated by solving the RANS equations under the assumption of compressible and viscous flow. The developed CFD methodology was validated by comparing the computed trajectory with wind tunnel results. In the second phase of the study, different methods were modeled using CFD to calculate the trajectory of the munition separating from the jet trainer aircraft. Initially, the CTS methodology developed in the first phase was employed to model the separation process. The K-ω SST turbulence model and a time step of 0.001 seconds, identified during the validation phase, were used in the CFD simulations of the munition separation. A thorough mesh independence study was conducted to enhance the reliability and accuracy of the CFD analyses by assessing the influence of mesh density on numerical results. As part of this study, five different mesh configurations were tested, and the aerodynamic forces acting on the munition along the X, Y, and Z axes were evaluated. The results demonstrated that the numerical outcomes remained consistent regardless of changes in mesh density. Following the identification of the optimal mesh density, the trajectory of the munition separating from the jet trainer aircraft was computed for various flight conditions. Another approach used for trajectory calculation was the grid method. Two aerodynamic databases were generated for this method. The first was the freestream aerodynamic database for the munition, which contained force and moment coefficients derived from CFD analyses under various flight conditions. The second was the aerodynamic database for the aircraft-munition configuration, developed by placing the munition in different positions and attitudes under the aircraft and performing CFD analyses. After developing both the aircraft-munition configuration and freestream databases, a 6-DOF model was created in MATLAB Simulink. The aerodynamic data from the CFD analyses were used as inputs in this model to calculate the munition's displacements and Euler angles under different flight conditions. An alternative approach to the grid method, the 'Captive Carry with Flow-Field' method, was developed to calculate the munition's trajectory. This method enables a rapid assessment of separation analyses for newly designed munitions across various aircraft configurations. The Captive Carry with Flow-Field approach models the non-uniform flow field experienced by the munition due to aerodynamic disturbances caused by the aircraft during separation. For this method, a freestream database was created through CFD analyses of the munition under different flight conditions, and a flow-field database for the jet trainer aircraft (without the munition attached) was also generated using CFD. These databases were utilized in a 6-DOF model in MATLAB Simulink to calculate the munition's displacements and Euler angles under different flight conditions. In the third and final phase of this thesis, the trajectory of the munition separating from the jet trainer aircraft was computed under various flight conditions using the CTS, grid, and Captive Carry with Flow-Field methods, and the results were compared. The Captive Carry with Flow-Field method demonstrated a significant advantage in its ability to rapidly compute the munition's trajectory. The developed method has been proven to serve as an efficient and rapid solution for the design and evaluation processes of new munitions. Furthermore, a detailed investigation was conducted into the effects of mach number on store separation analyses. In this context, the trajectory of the munition separating from the jet trainer aircraft was evaluated under various flight conditions using different Computational Fluid Dynamics (CFD) methods, and the results were systematically compared. Additionally, the influence of the angle of attack on store separation analysis was thoroughly examined. To this end, the munition's trajectory was simulated under a range of flight conditions employing various CFD approaches, and the effects of this parameter on the munition's behavior were meticulously analyzed.In the third and final phase of this thesis, the trajectory of the munition separating from the jet trainer aircraft was computed under various flight conditions using the CTS, grid, and Captive Carry with Flow-Field methods, and the results were compared. The Captive Carry with Flow-Field method demonstrated a significant advantage in its ability to rapidly compute the munition's trajectory. Additionally, the effects of mach number and AoA on store separation analyses were examined in detail.