NONLINEAR ASPECTS OBTAINING OF ORBITAL VELOCITIES FROM WAVES RECORDS

Waves are the main factors determining the dynamics of shelf and coastal zones. Therefore, recently, all over the world, much attention has been paid to global monitoring measurements of wave fields using remote sensing, lidar and satellite technologies. However, simpler methods of wave measurement using pressure sensors and submerged current meters are widely used to solve local problems. According to the linear theory of waves, the measured velocities and pressure can be recalculated into free surface elevations and in relation to each other using the dispersion relation of the linear wave theory. This makes it possible, for example, to measure free surface elevations and, based on these, to obtain velocities at different levels. Of more practical interest is the determination of free surface elevations (waves) from pressure data, because pressure gauges are easier to install for measurements. The accuracy with which records of orbital wave velocities are obtained from measured free surface elevations is very important since, sediment transport in coastal zones is determined by the asymmetry of near bottom wave velocities. The main purpose of our work is to study the relationship between free surface elevations and orbital velocity measurements at different distances from the bottom using the data from a laboratory experiments and numerical simulation to evaluate the contribution of free and bound waves.