Question

Waves breaking on a quartz-sand beach have a significant wave heights producing a flow of energy ( ECn) of 18,900 newtons per second. If the mean breaker angle of 5°, evaluate the longshore immersed-weight and volume transport rates for these wave conditions. Later the angle increases to 10° while maintaining the same height. What is the transport under these new conditions?

Answer 1

SINCE

immersed weight=KP

K=non dimensional calibration coeffiecnt=0.77

P=longshore wave power/unit lentgh

given by

P=E*Cgbr*Sinbr*Cosbr

br=breaker angle,Cgbr=nbr*Cbr, nbr=1 at breaker line

E is the wave energy density

wave energy (in Joules) can be computed as

E=0.125*p*g*H^2

So, H=sqrt(18900/(0.125*997*9.81))=15.4 m wave height

so, shallow depth Cbr wave phase speed at breaker

Cbr = 3.1 x square root (15.4)=12.16 m/s

so

P=E*Cgbr*Sinbr*Cosbr=18900*12.16*0.087*0.996=19914..71 watt/m

immersed weight=0.77*19914.71=15334.33 newton