S = vec2scal(V) returns scalar field(s) S given by the norm of the
vector field(s) V. The vector field(s) V can be obtained from loadvec
or loadset and the scalar field(s) S can be displayed by showscal.
S = vec2scal(V,MODE) specifies the conversion MODE:
norm norm (ux^2 + uy^2)^(1/2); by default.
ux, uy x or y component of the vector field
en, ken kinetic energy, norm^2 / 2
rad, deg velocity angle (tan(angle)=vy/vx), in rad or deg
curl (or rot) curl (vorticity field)
absrot absolute value of the curl
div 2D divergence (dux/dx + duy/dy)
ens enstrophy (=square of vorticity)
strain norm of the strain rate, sqrt(s1^2 + s2^2),
where s1 and s2 are the 2D strain eigenvalues.
q Q-criterion, Q = rot^2 - (strain^2)/2
eps squared strain rate, s1^2 + s2^2
duxdx, duxdy, duydx, duydy spatial derivatives (du_i / dx_j)
Adding '-' (minus sign) before MODE (e.g., '-rot') inverts the result.
The resulting scalar field S contains the following fields:
x,y: vectors containing the X and Y coordinates
w: matrix of scalar elements
namex, unitx, namey, unity: strings for the name and unit of coord
namew, unitw: strings for the name and unit of the matrix w
name: name of the VEC file from which originates V
setname: name of the current directory
history: Remind from which command S has been obtained
The scalar fields built from derivatives (e.g., rot, div, ens etc.)
are computed from 2nd-order centered differences.
Specify 'rot1', 'div1' etc. to use 1st-order finite differences (in
this case, the resulting field is decreased by 1 unit, and the x and y
coordinates are interpolated).
S = vec2scal(FILE) is a shortcut for S = vec2scal(loadvec(FILE)).
By default, vectors with a zero component are considered as erroneous,
and are not used for the computation of the derivative fields (rot,
div, eps, duxdx, ...). If however you want to keep them in the
computation, specify vec2scal(V,MODE,'keepzero').
Limitation: This option works only with 1st-order derivatives
(rot1, div1...) - it is not yet implemented for 2nd-order derivatives
(rot, div...).
vec2scal(...), without output argument, shows the result with showscal.
Examples
showscal(vec2scal(v,'div'));
showscal(vec2scal(filterf(loadset,2),'rot'));
stat_rot = statf(vec2scal(v,'rot'));
vec2scal *.vec
See Also
showvec, showscal, gradientf, operf.