DSpace Community: KAIST Dept. of Aerospace EngineeringKAIST Dept. of Aerospace Engineeringhttp://hdl.handle.net/10203/142024-03-02T00:57:07Z2024-03-02T00:57:07ZHybrid rich- and lean-premixed ammonia-hydrogen combustion for mitigation of NOx emissions and thermoacoustic instabilitiesJin, UkhwaKim, Kyu Taehttp://hdl.handle.net/10203/3180202024-02-13T07:00:24Z2024-04-01T00:00:00ZTitle: Hybrid rich- and lean-premixed ammonia-hydrogen combustion for mitigation of NOx emissions and thermoacoustic instabilities
Authors: Jin, Ukhwa; Kim, Kyu Tae2024-04-01T00:00:00ZParameter Optimization of Foldable Flapping-Wing Mechanism for Maximum LiftYang, Hyeon-HoLee, Sang-GilAddo-akoto, ReynodsHan, Jae-Hunghttp://hdl.handle.net/10203/3177952024-01-14T06:00:25Z2024-03-01T00:00:00ZTitle: Parameter Optimization of Foldable Flapping-Wing Mechanism for Maximum Lift
Authors: Yang, Hyeon-Ho; Lee, Sang-Gil; Addo-akoto, Reynods; Han, Jae-Hung
Abstract: A lot of flapping-wing mechanisms have been proposed to mimic the flight characteristics of biological flyers. However, it is difficult to find studies that consider the unsteady aerodynamics in the design of the flapping-wing mechanisms. This paper presents a systematic approach to optimize the design parameters of a foldable flapping-wing mechanism (FFWM) with a proper aerodynamics model. For the kinematic model, the eight design parameters are defined to determine the reference configuration of the FFWM. The geometrical constraints of each design parameter are derived, and the kinematic analysis is conducted using the plane vector analysis method. The aerodynamic simulation using an unsteady vortex lattice method is performed to compute the aerodynamic loads induced by the flapping motion. An optimization problem is formulated to search for the optimal design parameters that maximize the average lift force considering the required power corresponding to the aerodynamic torques. The parameter optimization problem is solved for three different length ratios of the outer wing to the inner wing using a genetic algorithm. The optimization results show that increasing the outer wing length can cause a significant loss in the required power. The optimal design parameters found by the proposed approach allow the FFWM to generate maximum lift force with appropriate consideration of the required power.2024-03-01T00:00:00ZEvaluation of stochastic particle Bhatnagar–Gross–Krook methods with a focus on velocity distribution functionPark, WoonghwiKim, SanghunPfeiffer, MarcelJun, Eunjihttp://hdl.handle.net/10203/3180142024-02-13T04:00:20Z2024-02-01T00:00:00ZTitle: Evaluation of stochastic particle Bhatnagar–Gross–Krook methods with a focus on velocity distribution function
Authors: Park, Woonghwi; Kim, Sanghun; Pfeiffer, Marcel; Jun, Eunji
Abstract: <jats:p>For precise application of Bhatnagar–Gross–Krook (BGK) methods, assessing its accuracy in non-equilibrium flows is necessary. Generally, this assessment relies on macroscopic parameters, which are moments of the velocity distribution function (VDF). However, in non-equilibrium flows, the significance of each moment diminishes as the VDF deviates from the Maxwellian VDF. This study investigates the VDF in non-equilibrium flows. Two Prandtl-corrected BGK methods, the ellipsoidal statistical BGK and Shakhov BGK (SBGK), are compared with the direct simulation Monte Carlo method. To observe the VDF while excluding the effects of convection, the homogeneous relaxation of the initial non-equilibrium state is analyzed. The VDF in Couette flow and normal shock waves, where collision and convection coexist, is then examined. When comparing the accuracy of the BGK methods using higher-order moments, inconsistencies are observed. However, when comparing the VDFs, the SBGK method reproduces the non-equilibrium VDF more accurately. The results demonstrate the importance of the VDF in the evaluation of non-equilibrium flows.</jats:p>2024-02-01T00:00:00ZImage Processing-Based Real-Time Safe Site Identification for Autonomous LandingChoi, JiminAhn, Jaemyunghttp://hdl.handle.net/10203/3178432024-01-16T02:00:18Z2024-01-12T00:00:00ZTitle: Image Processing-Based Real-Time Safe Site Identification for Autonomous Landing
Authors: Choi, Jimin; Ahn, Jaemyung
Abstract: Autonomous hazard detection and avoidance (HDA) is essential in both uncrewed aerial vehicle (UAV) and planetary landings, enabling successful landings despite potential hazards unrealized during mission planning. Various methods are proposed for safe landing site detection, but computational complexity limits their onboard real-time application. This paper introduces a real-time method to identify potential sites for safe autonomous landing based on image processing. The approach adopted in this paper regards the digital elevation model (DEM) as a two-dimensional array rather than geographic information. It employs image processing techniques using kernels to ensure real-time computation. Three safety maps were generated to evaluate the safety of the DEM for different purposes. The weighted sum optimization of generated safety maps is used to select the final landing site. The proposed method is evaluated by conducting two distinct case studies, encompassing UAV landing and Mars landing scenarios.2024-01-12T00:00:00Z