VMT_CompMeanXS_PriSec

PURPOSE ^

Computes the mean cross section velocity components (Primary

SYNOPSIS ^

function [A,V,log_text] = VMT_CompMeanXS_PriSec(z,A,V)

DESCRIPTION ^

 Computes the mean cross section velocity components (Primary
 and secondary) from individual transects that have been previously mapped
 to a common grid and averaged. The Primary velocity is defined as the
 component of the flow in the direction of the discharge (i.e. rotated
 from the streamwise direction so the secrondary discharge is zero).

 This is referred to as the "zero net cross-stream discharge definition"
 (see Lane et al. 2000, Hydrological Processes 14, 2047-2071)

 (adapted from code by J. Czuba)

 P.R. Jackson, USGS, 12-9-08

CROSS-REFERENCE INFORMATION ^

This function calls: This function is called by:

SOURCE CODE ^

0001 function [A,V,log_text] = VMT_CompMeanXS_PriSec(z,A,V)
0002 % Computes the mean cross section velocity components (Primary
0003 % and secondary) from individual transects that have been previously mapped
0004 % to a common grid and averaged. The Primary velocity is defined as the
0005 % component of the flow in the direction of the discharge (i.e. rotated
0006 % from the streamwise direction so the secrondary discharge is zero).
0007 %
0008 % This is referred to as the "zero net cross-stream discharge definition"
0009 % (see Lane et al. 2000, Hydrological Processes 14, 2047-2071)
0010 %
0011 % (adapted from code by J. Czuba)
0012 %
0013 % P.R. Jackson, USGS, 12-9-08
0014 
0015 
0016 %% Rotate velocities into p and s components for the mean transect
0017 % calculate dy and dz for each meaurement point
0018 dy=mean(diff(V.mcsDist(1,:)));%m
0019 dz=mean(diff(V.mcsDepth(:,1)));%m
0020 
0021 % calculate the bit of discharge for each imaginary cell around the
0022 % velocity point
0023 qyi=V.v.*dy.*dz;%cm*m^2/s
0024 qxi=V.u.*dy.*dz;%cm*m^2/s
0025 
0026 % sum the streamwise and transverse Q and calculate the angle of the
0027 % cross section
0028 V.Qy=nansum(nansum(qyi));%cm*m^2/s
0029 V.Qx=nansum(nansum(qxi));%cm*m^2/s
0030 
0031 % Deviation from streamwise direction in geographic angle
0032 V.alphasp=atand(V.Qy./V.Qx);
0033 
0034 % Difference in degrees between the tangent vector of the ZSD plane and the
0035 % normal vector of the mean cross section
0036 V.phisp = V.phi-V.alphasp;
0037 
0038 % rotate the velocities so that Qy is effectively zero
0039 qpi=qxi.*cosd(V.alphasp)+qyi.*sind(V.alphasp);
0040 qsi=-qxi.*sind(V.alphasp)+qyi.*cosd(V.alphasp);
0041 
0042 V.Qp=nansum(nansum(qpi));%cm*m^2/s
0043 V.Qs=nansum(nansum(qsi));%cm*m^2/s
0044 %disp(['Secondary Discharge after Rotation (ZSD definition; m^3/s) = ' num2str(V.Qs/100)])
0045 log_text = ['      Qs after rotation (ZSD; m^3/s) = ' num2str(V.Qs/100)];
0046 
0047 V.vp=qpi./(dy.*dz);%cm/s
0048 V.vs=qsi./(dy.*dz);%cm/s
0049 
0050 %% Transform each individual transect
0051 
0052 for zi = 1 : z  
0053 
0054 % calculate the bit of discharge for each imaginary cell around the
0055 % velocity point
0056 A(zi).Comp.qyi=A(zi).Comp.v.*dy.*dz;%cm*m^2/s
0057 A(zi).Comp.qxi=A(zi).Comp.u.*dy.*dz;%cm*m^2/s
0058 
0059 % rotate the velocities so that Qy is effcetively zero
0060 A(zi).Comp.qpi=A(zi).Comp.qxi.*cosd(V.alphasp)+A(zi).Comp.qyi.*sind(V.alphasp);
0061 A(zi).Comp.qsi=-A(zi).Comp.qxi.*sind(V.alphasp)+A(zi).Comp.qyi.*cosd(V.alphasp);
0062 
0063 A(zi).Comp.Qp=nansum(nansum(A(zi).Comp.qpi));%cm*m^2/s
0064 A(zi).Comp.Qs=nansum(nansum(A(zi).Comp.qsi));%cm*m^2/s
0065 
0066 A(zi).Comp.vp=A(zi).Comp.qpi./(dy.*dz);%cm/s
0067 A(zi).Comp.vs=A(zi).Comp.qsi./(dy.*dz);%cm/s
0068 
0069 end
0070 
0071 
0072 %% Determine velocity deviations from the p direction
0073 
0074 V.mcsDirDevp = V.phisp-V.mcsDir;
0075 
0076 for zi = 1:z
0077     A(zi).Comp.mcsDirDevp = V.phisp - A(zi).Comp.mcsDir;
0078 end

Generated on Thu 21-Aug-2014 10:40:31 by m2html © 2005