조연우 교수

Jet-like surface waves generated by an electric-spark-generated underwater bubble are experimentally studied. Three different motions of jet-like surface waves are observed depending on the inception position of the bubble ( $d$ : 0.28–7 mm) below the free surface and the maximum radius of the bubble ( $R_{m}$ : 1.5–3.6 mm). When $d/R_{m}>1.3$ , the surface wave shows a simple smooth hump (case 1). When $0.82<d/R_{m}<1.3$ , a single droplet or multiple droplets are pinched off sequentia

This experimental study examines ventilated supercavity formation in a free-surface bounded environment where a body is in motion and the fluid is at rest. For a given torpedo-shaped body and water depth ( $H$ ), depending on the cavitator diameter ( $d_{c}$ ) and the submergence depth ( $h_{s}$ ), four different cases are investigated according to the blockage ratio ( $B=d_{c}/d_{h}$ , where $d_{h}$ is the hydraulic diameter) and the dimensionless submergence depth ( $h^{\ast }=h_{s}/H$ ). Case

A theoretical model is presented for the generation of waves by a localized pressure distribution moving on the surface of deep water with speed near the minimum gravity–capillary phase speed, c min . The model employs a simple forced–damped nonlinear dispersive equation. Even though it is not formally derived from the full governing equations, the proposed model equation combines the main effects controlling the response and captures the salient features of the experimental results reported in

Gravity–capillary solitary waves are generated by a moving ‘air-suction’ forcing instead of a moving ‘air-blowing’ forcing. The air-suction forcing moves horizontally over the surface of deep water with speeds close to the minimum linear phase speed $c_{min}=23~\text{cm}~\text{s}^{-1}$ . Three different states are observed according to forcing speeds below $c_{min}$ . At relatively low speeds below $c_{min}$ , small-amplitude linear circular depressions are observed, and they move steadily ahead

<div class="htmlview paragraph">A model was developed to study engine oil vaporization and oil vapor transport in the piston ring pack of internal combustion engines. With the assumption that the multi-grade oil can be modeled as a compound of a number of distinct paraffin hydrocarbons, a set of equations governing the oil vapor density variations were derived by applying mass conservation law to the amount of oil vaporized from the piston and the amount of oil vapor transported within the

When a dispersive wave system is subject to forcing by a moving external disturbance, a maximum or minimum of the phase speed is associated with a critical forcing speed at which the linear response is resonant. Nonlinear effects can play an important part near such resonances, and the salient characteristics of the nonlinear response depend on whether the maximum or minimum of the phase speed is realized in the long‐wave limit (zero wavenumber) or at a finite wavenumber. The focus here is on th

Longitudinal and transverse instabilities of gravity-capillary solitary waves on shallow water are investigated based on the numerical analysis of the fifth-order Kadomtsev-Petviashvili (KP) equation, which describes the wave phenomena on shallow water where the relevant Bond number is less than and close to 1/3. Two-dimensional (2D) depression gravity-capillary solitary waves are stable to longitudinal perturbations. 2D elevation gravity-capillary solitary waves are unstable to longitudinal per

For supercritical cases (forcing speed > the minimum phase speed, 0.23 m/s), the problem of two-dimensional linear, inviscid gravity–capillary waves generated by a moving delta-function type pressure source is well known. Using harmonic functions or Fourier transform, Lamb [Hydrodynamics, 6th ed. (Cambridge University Press, 1993)] and Rayleigh [Proc. London Math. Soc. s1-15(1), 69–78 (1883)] detailed the steady-state full-space wave-profile solution using an artificial viscosity. Whitham

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.

Long-time simulations are conducted on a forced three-dimensional (3D) nonlinear viscous gravity-capillary wave equation that describes the surface wave pattern when the forcing moves on the surface of deep water with speeds less than the linear phase speed ${c}_{\mathrm{min}}=23\phantom{\rule{0.16em}{0ex}}\mathrm{cm}/\mathrm{s}$. Three different states are identified according to forcing speeds $U$ below ${c}_{\mathrm{min}}$. At relatively low speeds below a certain speed (${c}_{1}$), a steady