Jaiyoung Ryu

Degenerative arthritis of the wrist follows very specific patterns from onset to terminal severe bone and joint destruction. About 95% of them occur as periscaphoid area problems: SLAC (scapholunate advanced collapse pattern) wrist (55%), triscaphe arthritis (26%), and a combination of the two (14%). In SLAC wrist, the repeating sequence of degenerative change is based on and caused by articular alignment problems between the scaphoid and the radius. Changes then progress between the capitate an

Abstract The interaction between vortical isotropic turbulence (IT) and a normal shock wave is studied using direct numerical simulation (DNS) and linear interaction analysis (LIA). In previous studies, agreement between the simulation results and the LIA predictions has been limited and, thus, the significance of LIA has been underestimated. In this paper, we present high-resolution simulations which accurately solve all flow scales (including the shock-wave structure) and extensively cover the

The Hyperloop system is a new concept that allows a train to travel through a near-vacuum tunnel at transonic speeds. Aerodynamic drag is one of the most important factors in analyzing such systems. The blockage ratio (BR), pod speed/length, tube pressure, and temperature affect the aerodynamic drag, but the specific relationships between the drag and these parameters have not yet been comprehensively examined. In this study, we investigated the flow phenomena of a Hyperloop system, focusing on

Hyperloop is a new, alternative, very high-speed mode of transport wherein Hyperloop pods (or capsules) transport cargo and passengers at very high speeds in a near-vacuum tube. Such high-speed operations, however, cause a large aerodynamic drag. This study investigates the effects of pod speed, blockage ratio (BR), tube pressure, and pod length on the drag and drag coefficient of a Hyperloop. To study the compressibility of air when the pod is operating in a tube, the effect of pressure waves i

The cerebral circulation is unique in its ability to maintain blood flow to the brain under widely varying physiologic conditions. Incorporating this autoregulatory response is necessary for cerebral blood flow (CBF) modeling, as well as investigations into pathological conditions. We discuss a one-dimensional (1D) nonlinear model of blood flow in the cerebral arteries coupled to autoregulatory lumped-parameter (LP) networks. The LP networks incorporate intracranial pressure (ICP), cerebrospinal

In this study, numerical simulations were conducted at various pod speeds (vpod= 100–350 m/s) using an unsteady, compressible solver with the Reynolds-averaged Navier–Stokes model to analyze the aerodynamic characteristics and pressure wave behavior in the Hyperloop system. Furthermore, the aerodynamic drag and pressure wave behavior were theoretically predicted based on quasi-one-dimensional assumptions. The flow around the pod is classified into three regimes according to the pod speed based o

A thermo-fluid-structural analysis procedure was proposed in this study to investigate the lifespan of a realistic cooling gas turbine blade. The temperature and pressure data extracted from computational fluid dynamics simulations were applied as the loading force to calculate the strain and stress using the finite element (FE) method. Subsequently, a fatigue analysis was conducted to estimate the blade life and predict the position of cracks. Here, the fatigue model used to calculate the blade

The present study conducts the numerical investigation of flow characteristics and thermal performance of spiral finned-tube heat exchangers. The effects of location of perforations (90°, 120°, and 150°) on heat transfer and pressure drop are analyzed for the air-side. The commercial computational fluid dynamics code ANSYS Fluent (V.17.0) is used for simulations with the RNG k-ε model based on the Reynolds-averaged Navier–Stokes equations. The velocity field, Colburn j-factor, and friction facto

In this article, large-scale experimental studies were conducted to figure out the fire characteristics, such as fire-spreading, toxic gases, and heat release rates, using large-scale calorimeter for one- and two-vehicle fires. The initial ignition position was the passenger seat, and thermocouples were attached to each compartment in the vehicles to determine the temperature distribution as a function of time. For the analysis, the time was divided into sections for the various fire-spreading p

The Hyperloop has been proposed as a high-speed vactrain system for freight and passenger transport. Given that the Hyperloop aims to operate at subsonic to supersonic speeds, the aerodynamic environment within the tube needs to be carefully considered. The shape of a pod is also very important with regard to reduction of aerodynamic drag and lift. Therefore, this study investigates the influence of the nose and tail shape of a Hyperloop pod on its aerodynamic drag, lift, and pitching moment by

This study provides a view of the primary aerodynamic design of Hyperloop pod considering the influence of tail shape and length on aerodynamic forces (drag and lift) and flow behaviors (pressure, Mach number, and temperature). Numerical simulations are performed considering two tail shapes (i.e., upward and downward tails) and five lengths of the downward tail (i.e., 1.725, 3.45, 6.9, 13.35, and 13.8 m). The dynamic overset mesh method utilizing polyhedral meshes is applied to simulate the move