ST_Dstar

 Calculate non-dimensional grain size D*

 function [dstar] = ST_Dstar(d,varargin)

 DESCRIPTION:
    Convert grain size from d (m) to dimensionless D 

 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:
    Dstar:  nondimensional grain size

 EXAMPLE USAGE
    dstar = ST_Dstar(.0005,'temperature',10,'salinity',35,'sdens',2650) 

 Author(s):  
    Geoff Cowles (University of Massachusetts Dartmouth)

 Revision history
   
==============================================================================

0001 function [dstar] = ST_Dstar(d,varargin)
0002 % Calculate non-dimensional grain size D*
0003 %
0004 % function [dstar] = ST_Dstar(d,varargin)
0005 %
0006 % DESCRIPTION:
0007 %    Convert grain size from d (m) to dimensionless D
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 %    Dstar:  nondimensional grain size
0017 %
0018 % EXAMPLE USAGE
0019 %    dstar = ST_Dstar(.0005,'temperature',10,'salinity',35,'sdens',2650)
0020 %
0021 % Author(s):
0022 %    Geoff Cowles (University of Massachusetts Dartmouth)
0023 %
0024 % Revision history
0025 %
0026 %==============================================================================
0027 
0028 subname = 'ST_Dstar';  
0029 %fprintf('\n')
0030 %fprintf(['begin : ' subname '\n'])
0031 
0032 % constants
0033 grav  = 9.8106;   %g
0034 T     = 10;       %T (C)
0035 S     = 35;       %S (PSU)
0036 sdens = 2650;     %sediment density in kg/m^3
0037 
0038 % parse arguments
0039 for i=1:2:length(varargin)-1
0040         keyword  = lower(varargin{i});
0041         if( ~ischar(keyword) )
0042                 error('incorrect usage of ST_Dstar')
0043         end;
0044 
0045         switch(keyword(1:3))
0046 
0047         case 'tem'
0048              T = varargin{i+1};
0049         case 'sal'
0050              S = varargin{i+1};
0051         case 'sde'
0052              sdens = varargin{i+1}; 
0053         otherwise
0054                 error(['Can''t understand value for:' keyword]);
0055         end; %switch keyword
0056 end;
0057 
0058 
0059 % calculate nu
0060 nu = SW_Kviscosity(T,S);
0061 
0062 % calculate rho
0063 dens = SW_Density(T,S);
0064 
0065 % calculate dstar
0066 s = sdens/dens;
0067 dstar = ([grav*(s-1)/(nu^2)])^(1/3)*d;
0068 
0069 %fprintf(['end   : ' subname '\n'])