Air-Sea Interactions and Surface Wave Dynamics
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We are developing a fundamental understanding of surface wave and current interactions in the estuarine and coastal/marine environments.  We have developed methods to generate and detect three-dimensional breaking waves and wave-current interaction in the laboratory. Work is underway to study the kinematics and dynamics of breaking under wave-current interactions. Specifically, we are working on measurements of breaking waves on shear currents in a well-controlled wave-current interaction flume. For the field measurements, we are developing an in-situ ethernet-based (CBLAST-LIVE) and a real time self-contained video system (CBLAST-EYE) that can image air-sea surface characteristics at the Air-Sea Interaction Tower (ASIT) off the south shore of Martha’s Vineyard. In addition, observations of subsurface wave and current will be measured. This project is one component of the Coupled Boundary Layers, Air-Sea Interaction Experiment in Low to Moderate Winds (CBLAST-LOW). Our goal is to understand the role of shear currents on wave evolution and breaking and develop a temporal form of physics-based parameterizations of momentum, heat, and humidity fluxes across wave boundary layer processes for the coupled atmospher-ocean models. 

An image taken from the ASIT during the 2003 experiments is shown here. Using a digital photogrammetry processing technique, the whitecapping area can be estimated from the rectified orthoimage and correlated with the recorded wind speed. In addition, the following orthoimage shows a developing Langmuir streak under a wind speed of approximately 5 m/s. Currently, we are analyzing the time series of images and correlating 
with other concurrent measurements. 
           langmuir


To characterize complicated surface wave processes, we have been developing a novel Automated Trinocular Stereo Imaging System (ATSIS), a non-intrusive remote sensing technique, to measure temporal evolution of three-dimensional wave characteristics. The system consists of three progressive digital cameras to accurately estimate depth of a scene. In addition the advantage of using extra camera resolves the correspondence problems due to specular reflection on the water surface and provides additional constraints on image matching, dramatically reducing the chance of a mismatch. An oblique configuration for the trinocular system effectively increases spatial coverage, allowing observations of wave phenomena over a broad range of spatial scales. A new exterior calibration procedure is also developed to determine the orientation of cameras in the field. The height resolution is increased with the optical axes of the cameras pointed at an oblique angle with respect to vertical surface wave displacements. 

Efficient and accurate modeling of surface wave motions plays an important role in many coastal and ocean. For several decades, a great deal of efforts has been paid to develop unified models that can effectively predict water wave propagation with varying degree of dispersive and nonlinear effects. Our research group is focusing on develop an efficient and accurate non-hydrostatic modeling frame to predict large scale surface wave dynamics. Overall the goal is to develop full non-hydrostatic model using a small number of vertical layers (two ~ five layers) to simulate nearshore wave transformation including shoaling, dispersion, refraction, and diffraction phenomena. Furtermore we are also working on developing a non-hdyrostatic model that can examine deep-water wave-wave interactions including slowly modulated and rapidly evolving wave processess leading to the formation of freak waves.  

f_w       near         freak                  


Sponsor : Office of Naval Research 
                 NSF-Ocean Science
                 Hilldale Undergraduate/Faculty Research Fellowships
                Wisconsin Alumni Research Foundation
                Wisconsin Coastal Management Program - Freak waves in Apostle Islands
                 
Status :   Active
Student Investigators:  Adam Bechle (M.S.), Josh  Anderson (M.S.)
                                      Graduated: Jay Young (Ph.D.), Aifeng Yao (Ph.D.) and Justin Wanek (M.S.)
                                       Openings                  
Publications
  • Young, C.C. and Wu, C.H., Non-hydrostatic modeling of nonlinear deep-water wave groups, J. of Engineering Mechanics-ASCE, In Press, 2009.
  • Wu, C.H., Young, C.C., Chen, Q.J., and Lynett, P.J., Efficient non-hydrostatic modeling of nonlinear waves from shallow to deep waters, J. of Waterway, Port, Coastal, and Ocean Engineering, In Press, 2009.
  • Young C.C. and Wu, C.H., A σ - coordinate non-hydrostatic model with embedded Boussinesq-type like equations for modeling deep-water waves. International J. for Numerical Methods in Fluids, In Press, 2009.
  • Young, C.C., Wu, C.H., Liu, W.C., and Kuo, J.T.,A higher-order non-hydrostatic sigma model for simulating non-linear refraction-diffraction of water waves. Coastal Engineering, 56(9), 919-930, 2009.
  • Young, C.C. and Wu, C.H., An efficient and accurate non-hydrostatic model with embedded Boussinesq-type like equations for surface wave modeling, International J. for Numerical Methods in Fluids, 60(1), 27-53, 2009.
  • Wu, C.H. and Yuan, H.L., Efficient non-hydrostatic modelling of surface waves interacting with structures, Applied Mathematical Modelling, 31(4), 687-699, 2007.
  • Young, C.C., Wu, C.H., Kuo, J.T., and Liu, W.C., A higher-order sigma-coordinate non-hydrostatic model for nonlinear surface waves, Ocean Engineering, 34(10), 1357-1370, 2007.
  • Yao, A. and Wu, C.H., Spatial and temporal characteristics of transient extreme waves on depth-varying currents, J. of Engineering Mechanics-ASCE, 132 (9), 1015-1025, 2006.
  • Yuan, H.L. and Wu, C.H., Fully non-hydrostatic modeling of surface waves,  J. of Engineering Mechanics-ASCE, 132 (4), 447-456, 2006.
  • Wanek, J. and Wu, C.H., Automated trinocular stereo imaging system for three-dimensional surface wave measurements, Ocean Engineering, 33(5-6), 723-747, 2006.  (see breaking wave evolution here)
  • Yao, A. and Wu, C.H., Incipient breaking of unsteady waves on sheared currents, Physics of Fluids, 17, 082104, 2005.
  • Yao, A. and Wu, C.H., An automated image-based technique for tracking surface wave profiles, Ocean Engineering, 32(2) 157-173, 2005.
  • Wu, C.H. and Yao, A., Laboratory measurements of limiting freak waves on currents, J. Geophysical Research-Oceans, 109, C12, C12002, 1-18, 10.1029/2004JC002612, 2004.
  • Yao, A. and Wu, C.H., Energy dissipation of unsteady wave breaking on currents, J. Physical Oceanography, 34, N10, 2288-2304, 2004.
  • Wu, C.H., Yao, A., and Chang, K.A., DPIV measurements of unsteady deep-water wave breaking on following currents, "PIV and Modeling Water Wave Phenomena, World Scientific Publication Co., Advances in Coastal and Ocean Engineering - Vol. 9, 2004.
  • Wu, C.H., Nepf, H.M., Cowen, E.A., Surface current and vorticity generated by three-dimensional breaking waves, accepted under revision J. Fluid Mech., 2004.
  • Wu, C.H. and Nepf, H. M, Breaking wave criteria and energy losses for three-dimensional breaking waves, C10, 3177, 10.1029 2001JC001077, 41-1-18, J. Geophysical Research-Oceans, 2002.
  • Nepf, H.M., Wu, C.H., Chan, E.S., A comparison of two- and three-dimensional wave breaking, J. Physical Oceanography, 28, N7, 1496-1510, 1998.
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 		 Laboratory three-dimensional breaking waves

Laboratory breaking under wave-current interaction

Breaking waves at the ASIT

Orthophoto of the red area on the previous image 

 
 

Stereo-imaging of a 3D breaking wave

3D view of the processed image