Kwan-Jung Lee

In the present study, the aerodynamic characteristics of the Gurney flap were comprehensively investigated in terms of the performance requirements for a helicopter rotor by using two-dimensional Navier-Stokes equations. To this end, with the rotor operating flow conditions in mind, the static aerodynamic characteristics of the Gurney flap are thoroughly compared with those of the clean airfoil at various Mach numbers, incidences, and Gurney flap heights. Next, to understand the general dynamic

Autoencoder-based reduced-order modeling (ROM) has recently attracted significant attention, owing to its ability to capture underlying nonlinear features. However, two critical drawbacks severely undermine its scalability to various physical applications: entangled and therefore uninterpretable latent variables (LVs) and the blindfold determination of latent space dimension. In this regard, this study proposes the physics-aware ROM using only interpretable and information-intensive LVs extracte

This paper focuses on the uncertainty propagation in the flight performance of multirotor-type unmanned aerial vehicles from the systematic perspective in conceptual design phase. The multirotor performance is estimated by a conceptual design and analysis framework which is capable of predicting the performance for given mission profiles and multirotor specifications. In this study, not only are parametric uncertainties considered in multirotor components such as rotor, motor and battery, but al

Snow accumulation on the undercarriage of a train is an important issue that significantly degrades the safety and performance of the vehicle. This phenomenon is primarily attributed to snow saltation induced by train-generated wind gusts. This study numerically investigated the snow accumulation on a train by modelling the snow saltation for the initial movement of drifting snow from the ground. A semi-empirical snow saltation model was applied to the boundary condition for a snow-covered groun

In recent years, the technical advancement of electric propulsion systems has contributed to the growing applicability of multirotor-type unmanned aerial vehicles from personal hobbies to industrial fields. Industrial fields involve various mission profiles comprising several mission-legs, such as hover and forward flight. Thus, enhancing the applicability of multirotors requires them to be designed for specific mission profiles. This paper presents systematic design and analysis methods for rea

The wake vortices of an aircraft descend by self-induction that enables a pilot to identify approximate wake location based on the preceding aircraft path. A pilot taking off an aircraft can avoid a wake vortex encounter by performing early rotation and flying at or above the climb path of the preceding aircraft. Such operation results in a situation in which two wake vortices are present in the air simultaneously in close proximity. In this study, the transport and decay characteristic processe

Abstract The use of non‐intrusive reduced order modeling (NIROM) to approximate high‐fidelity computer models has been steadily increased over the past decade. Recently, local NIROM has been proposed to improve the model accuracy in highly nonlinear problems in which distinct characteristic regimes coexist. The core concept of local NIROM is the decomposition of the parameter domains into a subregime to create multiple models. However, the existing local NIROM not only partitions the individual