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vec2scal
Compute scalar fields from vector fields

Description ```S = vec2scal(V,MODE) returns scalar field(s) S computed from the vector field(s) V according to the specified MODE. The resulting scalar field(s) S can be displayed using showf. Available scalar modes are: norm2d 2D norm (ux^2+uy^2)^(1/2) norm3d 3D norm (ux^2+uy^2+uz^2)^(1/2) norm applies norm2d or norm3d, depending on the field ux, uy, uz x, y or z component of the vector field en, ken kinetic energy, norm^2 / 2 (where norm is 2D or 3D) curl (or rot) curl (z-component of vorticity field) absrot absolute value of the curl div 2D divergence (dux/dx + duy/dy) ens enstrophy (=square of z-vorticity / 2) rad, deg velocity angle (tan(angle)=vy/vx), in rad or deg strain norm of the strain rate, sqrt(s1^2 + s2^2), where s1 and s2 are the 2D strain eigenvalues. q Q-criterion, Q = (enstrophy - strain^2)/2 eps2D 2D squared strain rate (epsilon/nu) eps3D 3D squared strain rate (only 6 components) epsaxi axisymmetric (w.r.t. y-axis) squared strain rate duidxj spatial derivatives (du_i / dx_j), with i=x,y,z and j=x,y (for instance, duzdy) uiuj (or tij) Components of the Reynolds stress tensor u_i*u_j, with i,j=x,y,z (for instance, uxuy, uyuz, or txy, tyz, etc.) (Careful: the average is NOT subtracted) smin minimum eigenvalue real, imag extracts the real part or the imaginary part If input argument MODE is ommitted, 'norm' (for a 2D field) or 'uz' (for a 3D field) is taken by default. 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 containing the scalar field 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. 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'). vec2scal(...), without output argument, shows the result with showf. Examples showf(vec2scal(v,'div')); showf(vec2scal(filterf('*.vc7',2),'rot')); stat_rot = statf(vec2scal(v,'rot')); vec2scal *.vc7 ken See Also showf, gradientf, operf, convert3dto2df. Published output in the Help browser showdemo vec2scal ```
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