Source code for opendrift.models.sedimentdrift

# This file is part of OpenDrift.
# OpenDrift is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, version 2
# OpenDrift is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# GNU General Public License for more details.
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# along with OpenDrift.  If not, see <>.
# Copyright 2020, Knut-Frode Dagestad, MET Norway

SedimentDrift is an OpenDrift module for drift and settling of sediments.
Based on work by Simon Weppe, MetOcean Solutions Ltd.

import numpy as np
import logging; logger = logging.getLogger(__name__)
from opendrift.models.oceandrift import OceanDrift
from opendrift.models.oceandrift import Lagrangian3DArray

[docs] class SedimentElement(Lagrangian3DArray): variables = Lagrangian3DArray.add_variables([ ('settled', {'dtype': np.uint8, # 0 is active, 1 is settled 'units': '1', 'default': 0}), ('terminal_velocity', {'dtype': np.float32, 'units': 'm/s', 'default': -0.001}) # 1 mm/s negative buoyancy ])
[docs] class SedimentDrift(OceanDrift): """Model for sediment drift, under development """ ElementType = SedimentElement required_variables = { 'x_sea_water_velocity': {'fallback': 0}, 'y_sea_water_velocity': {'fallback': 0}, 'upward_sea_water_velocity': {'fallback': 0}, 'x_wind': {'fallback': 0}, 'y_wind': {'fallback': 0}, 'sea_surface_wave_stokes_drift_x_velocity': {'fallback': 0}, 'sea_surface_wave_stokes_drift_y_velocity': {'fallback': 0}, 'sea_surface_wave_period_at_variance_spectral_density_maximum': {'fallback': 0}, 'sea_surface_wave_mean_period_from_variance_spectral_density_second_frequency_moment': {'fallback': 0}, 'land_binary_mask': {'fallback': None}, 'ocean_vertical_diffusivity': {'fallback': 0.02}, 'ocean_mixed_layer_thickness': {'fallback': 50}, 'sea_floor_depth_below_sea_level': {'fallback': 10000}, } def __init__(self, *args, **kwargs): """ Constructor of SedimentDrift module """ super(SedimentDrift, self).__init__(*args, **kwargs) self._add_config({ 'vertical_mixing:resuspension_threshold': { 'type': 'float', 'default': 0.2, 'min': 0, 'max': 3, 'units': 'm/s', 'description': 'Sedimented particles will be resuspended if bottom current shear exceeds this value.', 'level': CONFIG_LEVEL_ESSENTIAL }}) # By default, sediments do not strand towards coastline # TODO: A more sophisticated stranding algorithm is needed self._set_config_default('general:coastline_action', 'previous') # Vertical mixing is enabled as default self._set_config_default('drift:vertical_mixing', True)
[docs] def update(self): """Update positions and properties of sediment particles. """ # Advecting here all elements, but want to soon add # possibility of not moving settled elements, until # they are resuspended. May then need to send a boolean # array to advection methods below self.advect_ocean_current() self.vertical_advection() self.advect_wind() # Wind shear in upper 10cm of ocean self.stokes_drift() self.vertical_mixing() # Including buoyancy and settling self.resuspension()
[docs] def bottom_interaction(self, seafloor_depth): """Sub method of vertical_mixing, determines settling""" # Elements at or below seafloor are settled, by setting # self.elements.moving to 0. # These elements will not move until eventual later resuspension. settling = np.logical_and(self.elements.z <= seafloor_depth, self.elements.moving==1) if np.sum(settling) > 0: logger.debug('Settling %s elements at seafloor' % np.sum(settling)) self.elements.moving[settling] = 0
[docs] def resuspension(self): """Resuspending elements if current speed > .5 m/s""" threshold = self.get_config('vertical_mixing:resuspension_threshold') resuspending = np.logical_and(self.current_speed() > threshold, self.elements.moving==0) if np.sum(resuspending) > 0: # Allow moving again self.elements.moving[resuspending] = 1 # Suspend 1 cm above seafloor self.elements.z[resuspending] = self.elements.z[resuspending] + .01