Tephra3d {rTephra}

Tephra Lagrangian Transport Model

Description

This function models the transport of a single particle through a spatially variable, windy, turbulent atmosphere with gravity. It allows 4D-varying atmospheric wind and density. Currently, only Rayleigh drag (low Re) is permitted.

Usage

Tephra3d(vx0, vy0, vz0, x0 = 0, y0 = 0, z0 = 0, t0 = 0,
  rho_r = 2000, r = 1, dt = 0.01, Cd = 0.6, verbose = FALSE,
  rho_a = NULL, zt = NULL, wx = 0, wy = 0, wz = 0, mindist = 0,
  TOPO = NULL, Kh = 0, Kz = 0, eddy_timescale = 60, g = 9.80665)

Arguments

vx0

initial x component of velocity [m/s]

vy0

initial y component of velocity [m/s]

vz0

initial z component of velocity [m/s]

x0

initial easting [m]

y0

initial northing [m]

z0

initial elevation [m]

t0

initial time [s]

rho_r

density of tephra particle [kg/m^3]

r

rock radius [m]

dt

model time interval [s]

Cd

drag coefficient [unitless]

verbose

logical: print runtime info to screen?

rho_a

scalar or function(x,y,z,t) or function(z) giving atmospheric density [kg/m^3]. If NULL, use a variable-density isothermal atmosphere (T = 0 deg C)

zt

function(x,y) giving topographic height [m]

wx

scalar or function(x,y,z,t) or function(z) giving component of wind to the east [m/s]

wy

scalar or function(x,y,z,t) or function(z) giving component of wind to the north [m/s]

wz

scalar or function(x,y,z,t) or function(z) giving upward component of wind [m/s]

mindist

minimum distance a particle must travel before simulation can stop. This is to prevent early model ends due to spurious collision with crater.

TOPO

DEM: list containing vectors x and y and matrix z with dimensions (length(x), length(y))

Kh

horizontal eddy diffusivity [m^2/s]

Kz

vertical eddy diffusivity (often neglected) [m^2/s]

eddy_timescale

1/e decay time of turbulent eddies [s]

g

gravitational acceleration [m/s^2]

Examples

Tephra3d(vx0 = 40, vy0 = 0, vz0 = 40, z0 = 0)