3. Sédiment Transport
47
Wave
Propogation
Fig. 3.6 Principal radiation stresses.
Only if the wave conditions vary between planes 1 and 2 or 3 and 4, there
will be a résultant force. Thus, we can expect the radiation stress to influence physical processes only in areas where wave conditions change. Such
areas would, therefore, be at locations where wave refraction, diffraction,
shoaling, or breaking occurs.
The following example illustrâtes these changes in the principal radiation stresses caused, in this case, only by shoaling and breaking of the waves
as they approach the shore. The waves approach the shore with wave crests
parallel to the shoreline.
Note: The axes, used in radiation stress théories are different from the
ones used in Coastal engineering (see Fig. 3.3). One should be aware when
and which particular axes are being used. While, the évaluation of H, Sxx
and Syy are presented in Problem 3.1, the variations of the said parameters
along the water depth are projected in Fig. 3.7. Notice below the stresses
“grow” as the waves approach the coast outside the breaker zone, and how
breaking reverses this growth process.
If the waves approach the coast at an angle a, the principal radiation
stresses, Sxx, acts in the direction of wave propagation and Syy perpendicular to this direction. Since the Coastal processes to be studied in later
chapters of this syllabus can be split into components parallel and perpendicular to the coastline, it is convenient to work with radiation stress
components along these axes. Figure 3.8 shows a plan view of a Coastal area
with principal stresses acting on an element oriented parallel to the wave
crests and normal and shear stresses on an element parallel to the coastline.
Figure 3.9 shows the Mohr Circle for SXx and Syy as shown in Fig. 3.7.
Those familiar with the pôle method of using the Mohr Circle will recognize
that the pôle is at Sxx and the stresses on a plane located at an angle 0
47
Wave
Propogation
Fig. 3.6 Principal radiation stresses.
Only if the wave conditions vary between planes 1 and 2 or 3 and 4, there
will be a résultant force. Thus, we can expect the radiation stress to influence physical processes only in areas where wave conditions change. Such
areas would, therefore, be at locations where wave refraction, diffraction,
shoaling, or breaking occurs.
The following example illustrâtes these changes in the principal radiation stresses caused, in this case, only by shoaling and breaking of the waves
as they approach the shore. The waves approach the shore with wave crests
parallel to the shoreline.
Note: The axes, used in radiation stress théories are different from the
ones used in Coastal engineering (see Fig. 3.3). One should be aware when
and which particular axes are being used. While, the évaluation of H, Sxx
and Syy are presented in Problem 3.1, the variations of the said parameters
along the water depth are projected in Fig. 3.7. Notice below the stresses
“grow” as the waves approach the coast outside the breaker zone, and how
breaking reverses this growth process.
If the waves approach the coast at an angle a, the principal radiation
stresses, Sxx, acts in the direction of wave propagation and Syy perpendicular to this direction. Since the Coastal processes to be studied in later
chapters of this syllabus can be split into components parallel and perpendicular to the coastline, it is convenient to work with radiation stress
components along these axes. Figure 3.8 shows a plan view of a Coastal area
with principal stresses acting on an element oriented parallel to the wave
crests and normal and shear stresses on an element parallel to the coastline.
Figure 3.9 shows the Mohr Circle for SXx and Syy as shown in Fig. 3.7.
Those familiar with the pôle method of using the Mohr Circle will recognize
that the pôle is at Sxx and the stresses on a plane located at an angle 0