7.7. DIRECTIONAL (3-D) WAVE GENERATION
427
short-wave control signal plus the second-order higher harmonics control
signal, or
-^totai(0 = XOi(Z) 4(7.273)
Sand and Mansard (1986) conducted a variety of laboratory tests of
the second-order correction method, and they reported good agreement between theory and measurements for both regular and irregular wave trains.
Other sections of their paper discussed the higher harmonics and the distortion they bring to the wave profile, wave spectra of the higher harmonics,
and practical aspects of the second-order theory.
Sand and Mansard, in concluding their remarkable paper, stated that
the major advantages of generating natural wave trains with the secondorder control signal were:
• All higher harmonic free waves are eliminated.
• The generated wave shapes are realistic and the root-meansquare sea surface elevations do not fluctuate with distance
from the wave board (over a horizontal bottom).
7.7 Directional (3-D) Wave Generation
Directional wavemakers, often referred to as “snake” wavemakers, are long
wave machines comprised of numerous narrow wave board segments that
can be controlled independently using either electrical motors or hydraulic
servo-systems. Directional wavemakers are typically placed along one wall
of a wide basin and produce waves that propagate at an oblique angle to
the axis of the wavemaker as illustrated by Figure 7.11. At some point
these oblique waves encounter the basin side walls, so it is important that
wave reflection be minimized with efficient wave absorbers along the basin
boundaries.
Directional wavemakers are utilized in physical model studies where it
is necessary to test the impact of waves approaching from different directions. Typical examples include harbors, longshore sediment transport,
and stability of breakwater head sections. Rather than moving a portable
wave machine to different orientations in the basin to produce wave ap
proach from a particular direction, the directional wavemaker is simply
reprogrammed to accomplish the same effect.
Some directional wavemakers can simultaneously produce a multitude o
different wave trains moving in different directions, thus imitating a random
directional sea. This capability has been a valuable addition to the coastal
engineer’s toolbox.
427
short-wave control signal plus the second-order higher harmonics control
signal, or
-^totai(0 = XOi(Z) 4(7.273)
Sand and Mansard (1986) conducted a variety of laboratory tests of
the second-order correction method, and they reported good agreement between theory and measurements for both regular and irregular wave trains.
Other sections of their paper discussed the higher harmonics and the distortion they bring to the wave profile, wave spectra of the higher harmonics,
and practical aspects of the second-order theory.
Sand and Mansard, in concluding their remarkable paper, stated that
the major advantages of generating natural wave trains with the secondorder control signal were:
• All higher harmonic free waves are eliminated.
• The generated wave shapes are realistic and the root-meansquare sea surface elevations do not fluctuate with distance
from the wave board (over a horizontal bottom).
7.7 Directional (3-D) Wave Generation
Directional wavemakers, often referred to as “snake” wavemakers, are long
wave machines comprised of numerous narrow wave board segments that
can be controlled independently using either electrical motors or hydraulic
servo-systems. Directional wavemakers are typically placed along one wall
of a wide basin and produce waves that propagate at an oblique angle to
the axis of the wavemaker as illustrated by Figure 7.11. At some point
these oblique waves encounter the basin side walls, so it is important that
wave reflection be minimized with efficient wave absorbers along the basin
boundaries.
Directional wavemakers are utilized in physical model studies where it
is necessary to test the impact of waves approaching from different directions. Typical examples include harbors, longshore sediment transport,
and stability of breakwater head sections. Rather than moving a portable
wave machine to different orientations in the basin to produce wave ap
proach from a particular direction, the directional wavemaker is simply
reprogrammed to accomplish the same effect.
Some directional wavemakers can simultaneously produce a multitude o
different wave trains moving in different directions, thus imitating a random
directional sea. This capability has been a valuable addition to the coastal
engineer’s toolbox.