WOOYOUNG CHOI
Department of Mathematical Sciences
Center for Applied Mathematics and Statistics
New Jersey Institute of Technology
University Height
Newark, NJ 07102-1982
Office: Cullimore 513
Tel: (973) 642-7979
Fax: (973) 596-5591
Email: wychoi@njit.edu
RESEARCH INTERESTS
Theoretical and computational fluid mechanics.
Nonlinear wave mechanics, Applied mathematics, Geophysical flow processes,
Naval hydrodynamics
EDUCATION
PhD California Institute of
Technology, 1993
MS Seoul National University, 1986
BS Seoul National University, 1984
POSITIONS
Associate Professor, New Jersey Institute of Technology, 2005-
Assistant Professor, University of Michigan, 2001-2005
Technical Staff Member, Los Alamos National Laboratory, 1998-2001
Postdoctoral Research Associate, Los Alamos National Laboratory,
1994-1997
HONORS/FELLOWSHIPS
Quarterdeck Outstanding Faculty Member Award, Univ. of Mich., April
2005
Faculty Research Fellowship, Rackham School of Graduate Studies,
Univ. of Michigan, 2002
R. B. Chapman Memorial Award, California Institute of Technology,
1993
C. L. Powell Fellowships, California Institute of Technology, 1990
CURRENT RESEARCH TOPICS
Modeling of Evolving Nonlinear
Surface Waves
The objective of this research is to develop an
efficient numerical model to accurately forecast the evolution of highly
nonlinear, wide-banded, multi-directional surface wave fields in the ocean.
Nonlinear evolution equations derived via asymptotic expansion are solved
numerically using a pseudo-spectral method and numerical solutions are
validated with 2D and 3D laboratory experiments and field data. The effects of
variable bottom, surface currents, wind forcing, and wave breaking will be
included in the model. Supported by the US Office of Naval Research (MURI, May
2005 - Apr. 2010).
Investigators: Arnaud Goullet (NJIT, Postdoc),
Matt Malej (NJIT, Graduate Student), Yuan N. Young (NJIT); Marc Perlin, Kevin
Tian, Okey Nwogu (Univ. of Michigan)
Remote Sensing of Nonlinear
Internal Waves and Wave-Current Interaction
This research is to better understand surface
roughness due to the interaction of short surface waves with the slowly-varying
currents induced at the ocean surface by the long internal wave motions and,
therefore, to improve a capability for quantitative remote sensing of internal
wave characteristics. Using both the nonlinear surface wave model and the
modified wave action equation, we investigate wave-wave interactions,
specifically those involving the transfer of energy from wavelengths on the
order of 1 meter to centimeter scales relevant to higher-frequency imaging
radars. Supported by the US Office of Naval Research (NLIWI, Jan. 2005 - Dec.
2009).
Investigators: David Lyzenga (Univ. of
Michigan), Arnaud Goullet (NJIT, Postdoc)
Dynamics of Strongly Nonlinear Internal Waves in Stratified
Fluids
This research is to study the propagation of
large amplitude internal waves over bottom topography in stratified fluids by
adopting a combined analytical and numerical approach. The strongly nonlinear
models for two-layer system proposed by Choi and Camassa (1999) for both
shallow and deep configurations are further generalized to multilayer system,
and energy dissipation due to viscosity/turbulent mixing and bottom friction is
parameterized in the models. Our analytical/numerical solutions of the new models
will be validated with direct numerical simulations of the Navier-Stokes
equations and available laboratory/field experiments. Supported by the National
Science Foundation (DMS CMG, Sept. 2006 - Aug. 2009).
Investigators: Ricardo Barros (NJIT, Postdoc), Qiyi
Zhou (NJIT, Graduate Student), Yuan N. Young (NJIT); Roberto Camassa (Univ. of
North Carolina); Tae-Chang Jo (Inha Univ.); Steve Ramp (MBARI); Lyudmyla
Barannyk (Univ. of Idaho)
Pseudo-Spectral Method for Nonlinear Wave-Body
Interaction
This project is to develop a fast and accurate
numerical method to compute nonlinear hydrodynamic forces on submerged/floating
bodies moving in water of arbitrary depth. After solving the body problem in an
unbounded fluid domain using a conventional distribution of singularities on
the body surface, the free surface problem is reduced to a closed set of two
nonlinear evolution equations for the free surface elevation and velocity
potential using a systematic asymptotic expansion. The resulting evolution
equations for the free surface variables are then solved by using a
pseudo-spectral method based on the Fast Fourier Transform. Supported by the US Office of Naval Research (MURI, May 2005 –
Apr. 2010).
Investigators: Svetlana
Tlupova (NJIT, Postdoc), Matan Shavit (NJIT, Undergraduate Student);
Christopher Kent (CSC)
Numerical Study of Unsteady Vortex Shedding
Using a Vortex Blob Method
This is a numerical study to simulate unsteady
vortex shedding by a thin flexible body in motion or in an oscillatory flow
using the regularized vortex blob method of Krasny. The unsteady Kutta
condition is imposed to find the strength of the free vortex sheet and the
interaction between the free vortex sheet and the body is carefully examined.
Investigators: Justin Bertschi (BP); Robert Krasny (Univ. of Michigan)
SELECTED PUBLICATIONS
Choi, W. (2008) Nonlinear
surface waves interacting with a linear shear current. Mathematics and
Computers in Simulations. Accepted.
Goullet, A. and Choi, W. (2008) Large amplitude internal solitary waves in a
two-layer system of piecewise linear stratification. Physics of Fluids, 20, 096601.
Tian, Z., Perlin, M. & Choi,
W. (2008) Evaluation
of a deep water wave breaking criterion. Physics of Fluids, 20, 066604.
Jo, T.-C. & Choi, W. (2008) On stabilizing the strongly nonlinear internal
wave model. Studies
in Applied Math., 120, 65-85.
Kent, C. P. & Choi, W.
(2007) An explicit
formulation for the evolution of nonlinear surface wave interacting with a
submerged body. Int. J.
Num. Methods in Fluids, 55, 1019-1038.
Nachbin, A. & Choi, W.
(2007) Nonlinear
waves over highly variable topography. Eur. Phys. J. ST, 147, 113-132.
Choi, W. & Lyzenga, D. R.
(2006) Nonlinear
surface wave dynamics in slowly varying ocean environments. Proceedings of the 26th Symposium
on Naval Hydrodynamics.
Choi, W. (2006) The effect of a background shear current on large
amplitude internal solitary waves. Phys.
of Fluids, 18, 036601.
Camassa, R., Choi, W., Michallet,
H., Rusas, P.-O., & Sveen, J. K. (2006) On the realm of validity of strongly nonlinear
asymptotic approximations for internal waves. J. Fluid Mech. 549, 1-23.
Choi, W., Kent, C. P., &
Schillinger, C.J. (2005) Numerical
modeling of nonlinear surface waves and its validation. Advances in Engineering Mechanics –
Reflections and outlooks in honor of Theodore Y.-T. Wu., edited by A.T. Chwang,
M.H. Teng & D.T. Valentine, 94-110.
Choi, W. & Kent, C. P.
(2004) A
pseudo-spectral method for nonlinear free surface hydrodynamics. Proceedings of the 25th
Symposium on Naval Hydrodynamics.
Li, Y. A., Hyman, J. M., &
Choi, W. (2004) A numerical
study of the exact evolution equations for surface waves in water of finite
depth. Studies
in Applied Math. 113, 303-324.
Choi, W., Prasad, D., Camassa,
R., & Ecke, R. E. (2004) Traveling waves in the Rayleigh-Bernard
convection with rotation, Phys.
Rev. E 69 05631.
Choi, W. (2003) Strongly nonlinear long gravity waves in uniform
shear flows. Phys.
Rev. E 68, 026305.
Jo, T. & Choi, W. (2002) Dynamics of strongly nonlinear internal solitary
waves in shallow water. Studies in Applied Math.
109, 205-228.
Choi, W. (2000) Modeling of strongly nonlinear internal waves in
a multilayer system. Proceedings
of the Fourth International Conf. on Hydrodynamics (Goda, Y.,
Ikehata, M. and Suzuki, K., Eds), pp453—458, 2000.
Choi, W. & Camassa, R.
(1999) Fully
nonlinear internal waves in a two-fluid system. J. Fluid Mech. 396, 1-36.
Choi, W. & Camassa, R.
(1999) Exact evolution
equations for surface waves. J. Eng.
Mech. 125, 756-760.
Choi, W. (1997) On the fission of algebraic solitons. Proc. Roy. Soc. Lond. A 453, 1753-1762.
Choi, W. & Camassa, R.
(1996) Weakly
nonlinear internal waves in a two-fluid system. J. Fluid Mech. 313, 83-103.
Choi, W. & Camassa, R.
(1996) Long
internal waves of finite amplitude. Phys. Rev. Lett. 77, 1759-1762.
Choi, W. & Wu, T. Y. (1996) Vortex solitons in a rotating fluid within a
non-uniform tube. Wave
Motion 24, 243-262.
Choi, W. (1995) Nonlinear evolution equations for two-dimensional
surface waves in a fluid of finite depth. J. Fluid Mech. 295, 381-394.
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