Numerical Simulation Of Semi-diurnal Tidal Waves In The Northern Indian Ocean

Based on the FVCOM(Finite Volume Coast and Ocean Model)model,this paper using unstructured triangular mesh and finite volume method to established a numerical model of the tidal waves of the M2 and S2 tidal constituent in the North Indian Ocean(area from 16°S?31°N,31°?102°E),and researched the North Indian Ocean distribution characteristics of Semi-diurnal tides and tidal currents.According to the Chezy-type friction relationship,a sensitivity numerical experiment was conducted on the bottom friction coefficient r.Using the cost function gradient descent method,we obtain the change curve of the root mean square error(RMSE)of the tidal constituent harmonic constant vector was obtained,which approximated and determined the optimal Bottom friction coefficient 1.1×10-3.Based on the generalized Manning-type friction relationship,multiple sensitivity numerical experiments were carried out on the bottom friction parameter combination(r1,r2),and the cost function gradient descent method was used to obtain the contour of the root mean square error of the tidal constituent harmonic constant vector was obtained,which approximate And determine the optimal bottom friction parameter combination(1.4×10-3,2.4×10-3).Through comparison,it is found that the simulation results based on the generalized Manning-type friction relationship are better.The simulation results of the optimal combination of bottom friction parameters are compared and verified with the data of harmonic constants at the intersection of TOPEX / Poseidon Satellite Altimeter,the data of tide stations in the International Hydrographic Organization(IHO)and some literatures,and the consistency is good.Among which the satellite data is compared The amplitude deviation is about 2?4cm,the delay angle deviation is about 7?8°,the amplitude deviation of the comparison tide station data is about 3?6 cm,and the delay angle deviation is about 8?9°.According to the simulation results,we plotted the M2 and S2 tidal constituent co-tidal charts,tidal ellipse distribution maps and the tidal energy flux distribution maps in the North Indian Ocean are drawn.The M2 tidal constituent has an amphidromic point in the southern Arabian Sea and two amphidromic points in the Persian Gulf,with a maximum amplitude of more than 80 cm;the tidal current mostly clockwise in the northwest Indian Ocean and the central Bengal Bay,and the remaining sea areas rotate counterclockwise.The tidal current velocity is larger in the northeast of the Arabian Sea,the Andaman Sea,the Persian Gulf and the northern part of the Bay of Bengal.The maximum velocity is 160 cm/s,and the other sea areas are smaller.The tidal energy is divided into two branches in the central Indian Ocean.The branch of westward propagation continues to act in the South Arabian Sea.The branch of eastward propagation decreases rapidly after encountering the terrain barrier.The maximum tidal energy flux is 5.5 MW/m.S2 tidal constituent's tide wave propagation characteristics,position of amphidromic point,spatial distribution characteristics of tidal ellipse and the propagation characteristics of tidal energy are similar to M2 tidal constituent,but tidal wave amplitude and tidal current velocity are relatively smaller than M2 tidal constituent.