Calculate critical shear stress in Pascals
function [wset] = ST_taucr(d,varargin)
DESCRIPTION:
Calculate critical shear stress for threshold of motion in Pa
INPUT:
d: sediment grain size in m
[optional] 'temperature' = temperature of the seawater in C [default=10]
[optional] 'salinity' = salinity of seawater in PSU [default=35]
[optional] 'sdens' = sediment density in kg/m^3 [default=2650]
OUTPUT:
taucr: critical shear stress in N/m^2
EXAMPLE USAGE
TCR = ST_taucr(.0005,'temperature',10,'salinity',35,'sdens',2650)
Author(s):
Geoff Cowles (University of Massachusetts Dartmouth)
References
Soulsby Dynamics of Marine Sands (SC77)
Revision history
==============================================================================0001 function [taucr] = ST_taucr(d,varargin) 0002 % Calculate critical shear stress in Pascals 0003 % 0004 % function [wset] = ST_taucr(d,varargin) 0005 % 0006 % DESCRIPTION: 0007 % Calculate critical shear stress for threshold of motion in Pa 0008 % 0009 % INPUT: 0010 % d: sediment grain size in m 0011 % [optional] 'temperature' = temperature of the seawater in C [default=10] 0012 % [optional] 'salinity' = salinity of seawater in PSU [default=35] 0013 % [optional] 'sdens' = sediment density in kg/m^3 [default=2650] 0014 % 0015 % OUTPUT: 0016 % taucr: critical shear stress in N/m^2 0017 % 0018 % EXAMPLE USAGE 0019 % TCR = ST_taucr(.0005,'temperature',10,'salinity',35,'sdens',2650) 0020 % 0021 % Author(s): 0022 % Geoff Cowles (University of Massachusetts Dartmouth) 0023 % 0024 % References 0025 % Soulsby Dynamics of Marine Sands (SC77) 0026 % 0027 % Revision history 0028 % 0029 %============================================================================== 0030 0031 subname = 'ST_taucr'; 0032 %fprintf('\n') 0033 %fprintf(['begin : ' subname '\n']) 0034 0035 % constants 0036 grav = 9.8106; %g 0037 T = 10; %T (C) 0038 S = 35; %S (PSU) 0039 sdens = 2650; %sediment density in kg/m^3 0040 0041 % parse arguments 0042 for i=1:2:length(varargin)-1 0043 keyword = lower(varargin{i}); 0044 if( ~ischar(keyword) ) 0045 error('incorrect usage of ST_wset') 0046 end; 0047 0048 switch(keyword(1:3)) 0049 0050 case 'tem' 0051 T = varargin{i+1}; 0052 case 'sal' 0053 S = varargin{i+1}; 0054 case 'sde' 0055 sdens = varargin{i+1}; 0056 otherwise 0057 error(['Can''t understand value for:' keyword]); 0058 end; %switch keyword 0059 end; 0060 0061 0062 % calculate rho 0063 dens = SW_Density(T,S); 0064 0065 % calculate dstar 0066 dstar = ST_Dstar(d,'temp',T,'sal',S,'sdens',sdens); 0067 0068 % calculate theta_cr 0069 theta_cr = (0.30/(1+1.2*dstar)) + 0.055*[1 - exp(-.020*dstar)]; 0070 0071 % calculate taucr 0072 taucr = theta_cr*grav*(sdens-dens)*d; 0073 0074 0075 0076 %fprintf(['end : ' subname '\n'])