Long period harbor oscillations due to short random waves
Sponsored Links
This presentation is the property of its rightful owner.
1 / 31

Long-period Harbor Oscillations due to Short Random Waves PowerPoint PPT Presentation


  • 86 Views
  • Uploaded on
  • Presentation posted in: General

Long-period Harbor Oscillations due to Short Random Waves. Meng-Yi Chen & Chiang C. Mei Massachusetts Institute of Technology. Typhon Tim 1994 : Hualien Harbor,Taiwan. H. outside. # 00. outside. # 05. (# 00). inside. # 22. inside. # 8. inside. # 10. 0. T (sec). 200.

Download Presentation

Long-period Harbor Oscillations due to Short Random Waves

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Long-period Harbor Oscillations due to Short Random Waves

Meng-Yi Chen & Chiang C. Mei

Massachusetts Institute of Technology

Shallow Water Hydrodynamics, Trondheim, Norway


Typhon Tim 1994: Hualien Harbor,Taiwan

H

outside

# 00

outside

# 05

(# 00)

inside

# 22

inside

# 8

inside

# 10

0

T (sec)

200

Shallow Water Hydrodynamics, Trondheim, Norway


Port of Hualien

Shallow Water Hydrodynamics, Trondheim, Norway


2

10

22

8

2

Shallow Water Hydrodynamics, Trondheim, Norway


Typhoon Longwang, Oct. 2nd 2005

Shallow Water Hydrodynamics, Trondheim, Norway


Past Works

  • Harbor Oscillations

    - Linear theory

    Miles & Munk (1961), Miles( 1971), Lee(1971),

    Unluata & Mei (1973), (1978) , Carrier,Shaw & Miyata(1971)

    • Nonlinear approximation -- narrow-banded

      Bowers(1977), Agnon & Mei (1989), Wu & Liu (1990)

Shallow Water Hydrodynamics, Trondheim, Norway


Standing waves near a cliff-Random sea

  • Sclavounos (1992)

    -Stochastic theory

    -Simple progressive and standing wave in deep water

    -Incident waves: stationary, Gaussian

    -Higher order spectrum depends on

    first, second, and third-order

Shallow Water Hydrodynamics, Trondheim, Norway


Shallow Water Hydrodynamics, Trondheim, Norway


Shallow Water Hydrodynamics, Trondheim, Norway


Shallow Water Hydrodynamics, Trondheim, Norway


Shallow Water Hydrodynamics, Trondheim, Norway


Shallow Water Hydrodynamics, Trondheim, Norway


Pairs of frequencies

Shallow Water Hydrodynamics, Trondheim, Norway


Shallow Water Hydrodynamics, Trondheim, Norway


Frequency responses By Mild slope Approximation

First-order

Chamberlain & Porter (1995)

Far field : analytical solution +radiation condition

Near field: FEM

Shallow Water Hydrodynamics, Trondheim, Norway


Shallow Water Hydrodynamics, Trondheim, Norway


Hybrid finite element method (Chen & Mei,1974)(HFEM)

Far Field

Analytical

Near Field

Finite element

Shallow Water Hydrodynamics, Trondheim, Norway


Shallow Water Hydrodynamics, Trondheim, Norway


Shallow Water Hydrodynamics, Trondheim, Norway


Shallow Water Hydrodynamics, Trondheim, Norway


Shallow Water Hydrodynamics, Trondheim, Norway


Square harbor, Normal incidence 300m by 300 m, depth h=20m

Effect of entrance(1) 60 m opening withoutprotection

(2) 30 m opening withoutprotection

(3) 30 m openingwithprotection

Shallow Water Hydrodynamics, Trondheim, Norway


Random sea: TMA Spectrum

Shallow Water Hydrodynamics, Trondheim, Norway


First-order average response

60m, no protection

30m, no protection

30m with protection

Shallow Water Hydrodynamics, Trondheim, Norway


Mean Linear spectrum

60m, no protection

30m, no protection

30m with protection

Shallow Water Hydrodynamics, Trondheim, Norway


Second-order Mean: setup/down

60m

30m, no protection

30m, with protection

Shallow Water Hydrodynamics, Trondheim, Norway


Nonlinear correction: long wave

60m, no protection

30m, no protection

30m with protection

Shallow Water Hydrodynamics, Trondheim, Norway


Mean Harbor Spectrum

60m

30m,no

30m, protected

Shallow Water Hydrodynamics, Trondheim, Norway


Qualitative comparison with field data

30m, protected

out

in

out

in

Shallow Water Hydrodynamics, Trondheim, Norway


Numerical Aspects

  • For 2-nd order problem must be solved for a many pairs of frequencies by FEM

  • Large sparse matrix for each pair

    -- for variable depth: modes are coupled

    --10620 pairs, each pair need around 15 minutes, at least 100 days for ONE single computer,

    --20-25 parallel computer (4G ram, 2.8G Hz), weeks

Shallow Water Hydrodynamics, Trondheim, Norway


Summary

- Stochastic theory for long-period harbor resonance by a broad-banded sea

-Long-wave part of response spectrum is dominated by second-order correction, not first or third-order

-Mild-slope equation for second order in wave steepness is sufficient

-High-frequency part of response spectrum is dominated by first-order wave

-Extendable to Slow drift of floating structures

Shallow Water Hydrodynamics, Trondheim, Norway


  • Login