4.3. LONG-WAVE HYDRODYNAMIC MODELS
161
4.3.6
Long-Wave Model Scale Selection
There are a number of factors that go into scale selection for a long-wave
hydrodynamic physical model, and these factors vary widely from one modeling application to the next. In the broadest sense, the engineer must
consider:
• Size of the model facility and wave generation capability
• Flow Reynolds numbers for the proposed scale
• Past experience with physical models of similar problems
• Range of parameters to be considered in the model
• Funding limitations
Economic considerations for long-wave models are the same as discussed
for short-wave models. However, in long-wave models the ocean area that
needs to be included increases with wavelength, and this results in a much
larger area requirement than short-wave models. In addition, long-wave
basin models must provide a greater area for wave absorbers. These requirements often weigh heavily in the economic decision to employ a geometrically distorted long-wave model.
Typical Long-Wave Model Scales
Length scales used in physical hydrodynamic long-wave models vary widely.
Typical scale ranges for just a few examples are listed below.
• Undistorted Harbors - 1:50 to 1:150
• Distorted Harbors or Ports - 1:50 to 1:100 (vertical);
1:80 to 1:400 (horizontal)
• Distorted Estuarine Systems - 1:100 to 1:150 (vertical); 1:300 to 1:800 (horizontal)
• Undistorted Inlets - 1:75 to 1:150
• Ship Motion Studies - 1:80 to 1:120
Generally, geometric distortion in long-wave models (which is defined
as Nx/Nz) is between 3 and 5. For example, the distorted model pictured
in Figure 4.5 has a horizontal length scale of 400 and a vertical length scale
of 100, giving it a distortion factor of 4.
161
4.3.6
Long-Wave Model Scale Selection
There are a number of factors that go into scale selection for a long-wave
hydrodynamic physical model, and these factors vary widely from one modeling application to the next. In the broadest sense, the engineer must
consider:
• Size of the model facility and wave generation capability
• Flow Reynolds numbers for the proposed scale
• Past experience with physical models of similar problems
• Range of parameters to be considered in the model
• Funding limitations
Economic considerations for long-wave models are the same as discussed
for short-wave models. However, in long-wave models the ocean area that
needs to be included increases with wavelength, and this results in a much
larger area requirement than short-wave models. In addition, long-wave
basin models must provide a greater area for wave absorbers. These requirements often weigh heavily in the economic decision to employ a geometrically distorted long-wave model.
Typical Long-Wave Model Scales
Length scales used in physical hydrodynamic long-wave models vary widely.
Typical scale ranges for just a few examples are listed below.
• Undistorted Harbors - 1:50 to 1:150
• Distorted Harbors or Ports - 1:50 to 1:100 (vertical);
1:80 to 1:400 (horizontal)
• Distorted Estuarine Systems - 1:100 to 1:150 (vertical); 1:300 to 1:800 (horizontal)
• Undistorted Inlets - 1:75 to 1:150
• Ship Motion Studies - 1:80 to 1:120
Generally, geometric distortion in long-wave models (which is defined
as Nx/Nz) is between 3 and 5. For example, the distorted model pictured
in Figure 4.5 has a horizontal length scale of 400 and a vertical length scale
of 100, giving it a distortion factor of 4.