7.8. ADDITIONAL WAVE GENERATION TOPICS
443
Jamieson and Mansard (1987) described an extensive experimental program to develop an efficient wave absorber made of wire mesh screens of
progressively decreasing porosity. The screens were placed normal to the
direction of wave propagation on a flat bottom, and they were backed by a
solid vertical wall. Their goal was to minimize reflections over a wide range
of wave conditions and water depths without requiring excessive horizontal absorber length. Performance for various absorber configurations was
measured in terms of the wave reflection coefficients for both regular and
irregular nonbreaking waves. Jamieson and Mansard provided a long list
of findings with regard to mesh screen absorbers, some of which are listed
below.
• The frontal area of the supporting framework should be
minimal.
• High porosity mesh screens work best for absorbing energy
from high steepness waves.
• Low porosity screens work best for absorbing energy from
low steepness waves.
• Mesh screen porosity should decrease toward the rear of
the wave absorber.
• Screen locations should be selected to correspond approximately to node locations of the partial standing waves.
• Wider screen spacing is required for steeper waves and
longer wave periods, with sheet spacing progressively decreasing toward the rear of the wave absorber.
• Optimum wave absorber length varies between 0.35L and
1.0L where L is the maximum wavelength to be effectively
attenuated.
• The number of mesh screens in the absorber increases as
the range of wave heights and periods to be absorbed increases.
Jamieson, Mogridge, and Brabrook (1989) applied a similar configuration of mesh screens to absorb lateral wave energy at the side walls of a
large wave tank. This type of absorption is needed when incident waves
are reflected toward the side walls by model coastal structures in the wide
tank. Three rows of vertical mesh screens having decreasing porosity to
ward the side wall were installed and tested over a range of irregular wave
conditions. Jamieson, et al. concluded this configuration was particularly
well suited for directional wave basins because some of the incident wave
energy is directed at the side walls. However, it would be necessary in this
case to optimize the screen mesh for minimum reflections.
443
Jamieson and Mansard (1987) described an extensive experimental program to develop an efficient wave absorber made of wire mesh screens of
progressively decreasing porosity. The screens were placed normal to the
direction of wave propagation on a flat bottom, and they were backed by a
solid vertical wall. Their goal was to minimize reflections over a wide range
of wave conditions and water depths without requiring excessive horizontal absorber length. Performance for various absorber configurations was
measured in terms of the wave reflection coefficients for both regular and
irregular nonbreaking waves. Jamieson and Mansard provided a long list
of findings with regard to mesh screen absorbers, some of which are listed
below.
• The frontal area of the supporting framework should be
minimal.
• High porosity mesh screens work best for absorbing energy
from high steepness waves.
• Low porosity screens work best for absorbing energy from
low steepness waves.
• Mesh screen porosity should decrease toward the rear of
the wave absorber.
• Screen locations should be selected to correspond approximately to node locations of the partial standing waves.
• Wider screen spacing is required for steeper waves and
longer wave periods, with sheet spacing progressively decreasing toward the rear of the wave absorber.
• Optimum wave absorber length varies between 0.35L and
1.0L where L is the maximum wavelength to be effectively
attenuated.
• The number of mesh screens in the absorber increases as
the range of wave heights and periods to be absorbed increases.
Jamieson, Mogridge, and Brabrook (1989) applied a similar configuration of mesh screens to absorb lateral wave energy at the side walls of a
large wave tank. This type of absorption is needed when incident waves
are reflected toward the side walls by model coastal structures in the wide
tank. Three rows of vertical mesh screens having decreasing porosity to
ward the side wall were installed and tested over a range of irregular wave
conditions. Jamieson, et al. concluded this configuration was particularly
well suited for directional wave basins because some of the incident wave
energy is directed at the side walls. However, it would be necessary in this
case to optimize the screen mesh for minimum reflections.