This is a diagram for one derivation of Bernoulli's Equation. I created this image using MetaPost; in order to produce the raster form, I compiled the source with MetaPost, embedded the resulting file in a pdfLaTeX document, viewed the PDF file with GSview (I tried Acrobat Reader, but its antialiasing was rather poor), and took a screen capture.

The MetaPost source code for this image is provided below (it is licensed under the same licenses as the image) in order to allow easy modification of the image. It's not particularly well-written code (one of my goals in creating it was to learn MetaPost), but anyone who might find it useful can try to make some use of it.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % bernoulli.mp  % % A MetaPost diagram  % % Created on 12 July 2005  % % Copyright (c) 2005 by MannyMax  % % Some rights reserved; see accompanying information for details  % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% beginfig(1); u := 1cm; path t,b,m,pa[],pb[]; pair a[],b[]; picture alab[],blab[]; numeric lwidth,lheight,rwidth,rheight,tubelen,cpgap; color backcol,chunkcol,capcol; lwidth = 1u; rwidth = 2u; lheight= 2u; rheight= 3u; tubelen= 10u; cpgap = 1u; %set diagram colors backcol = 0.27734375*green + 0.73828125*blue; chunkcol= 0.62500000*green + 0.88281250*blue; capcol = 0.70703125*green + 0.90234375*blue; z0=( 0, lheight+(lwidth/2)); z4=((tubelen/2)-cpgap, lheight+(lwidth/2)); z5=((tubelen/2)+cpgap, rheight+(rwidth/2)); z1=( tubelen, rheight+(rwidth/2)); z2=( 0, lheight-(lwidth/2)); z6=((tubelen/2)-cpgap, lheight-(lwidth/2)); z7=((tubelen/2)+cpgap, rheight-(rwidth/2)); z3=( tubelen, rheight-(rwidth/2)); t=z0---z4..z5---z1; b=z2---z6..z7---z3; m=1/2[z0,z2]..1/2[z4,z6]..1/2[z5,z7]..1/2[z1,z3]; fill buildcycle(z0--z2,t,z1--z3,b) withcolor backcol; fill unitsquare xscaled tubelen yscaled 0.25u shifted (0,-0.25u) withcolor 0.75*white; linecap := butt; draw (0,0)--(tubelen,0); linecap := rounded; %DRAW CHUNK A a0=point(0.3) of t; a1=point(0.8) of t; a2=point(0.3) of b; a3=point(0.8) of b; pa1=buildcycle(a0--a2,t,a1--a3,b); pa2 = fullcircle rotated 180 xscaled (0.2*lwidth) yscaled lwidth shifted 1/2[a0,a2]; pa3 = halfcircle rotated -90 xscaled (0.2*lwidth) yscaled lwidth shifted 1/2[a1,a3]; pa4 = halfcircle rotated 90 xscaled (0.2*lwidth) yscaled lwidth shifted 1/2[a1,a3]; pa5 = buildcycle(pa2,t,pa3,b); fill pa2 withcolor capcol; fill pa5 withcolor chunkcol; draw pa2; draw pa3; draw pa4 dashed evenly; a9 = center(buildcycle(pa4,pa3)); pa6 = a9--(a9+(a9-center(pa2))/3); draw pa6 cutafter pa3 withpen pencircle scaled 1; drawarrow pa6 cutbefore pa3 withpen pencircle scaled 1; label.rt (btex $v_1$ etex, point(1) of pa6); pa7 = (a2-(0.2u,0.5u)){dir(90)}..2/5[a2,center(pa2)]; drawarrow pa7; label.bot(btex $A_1$ etex, point(0) of pa7); a4 = whatever[a0,a3]=whatever[a1,a2]; a5 = (xpart(a4),0); a6 = a5+(0,1u); drawdblarrow a5--a4; draw (a4-(0.1u,0))--(a4+(0.1u,0)); alab1 = thelabel(btex $h_1$ etex, (0,0)); unfill bbox alab1 shifted a6; draw alab1 shifted a6; a11 = center(pa2); a10 = a11+(a11-a9)/8; drawarrow a10--a11 withpen pencircle scaled 2; label.lft(btex $p_1$ etex, 1/4[a10,a11]); a7 = a0 + (0,0.35u); a8 = a1 + (0,0.35u); draw a0--(a7 + (0,0.175u)) withcolor 0.5*white; draw a1--(a8 + (0,0.175u)) withcolor 0.5*white; drawdblarrow a7--a8; alab2 =thelabel(btex $v_1\Delta t=s_1$ etex, (0,0)); unfill bbox alab2 shifted 1/2[a7,a8]; draw alab2 shifted 1/2[a7,a8]; %DRAW CHUNK B b0=point(2.2) of t; b1=point(2.6) of t; b2=point(2.2) of b; b3=point(2.6) of b; pb1=buildcycle(b0--b2,t,b1--b3,b); fill pb1 withcolor 0.6[blue,white]; pb2 = fullcircle rotated 180 xscaled (0.2*rwidth) yscaled rwidth shifted 1/2[b0,b2]; pb3 = halfcircle rotated -90 xscaled (0.2*rwidth) yscaled rwidth shifted 1/2[b1,b3]; pb4 = halfcircle rotated 90 xscaled (0.2*rwidth) yscaled rwidth shifted 1/2[b1,b3]; pb5 = buildcycle(pb2,t,pb3,b); fill pb2 withcolor capcol; fill pb5 withcolor chunkcol; draw pb2; draw pb3; draw pb4 dashed evenly; b9 = center(buildcycle(pb4,pb3)); pb6 = b9--(b9+(b9-center(pb2))/3); draw pb6 cutafter pb3 withpen pencircle scaled 1; drawarrow pb6 cutbefore pb3 withpen pencircle scaled 1; label.rt (btex $v_2$ etex, point(1) of pb6); pb7 = (b2-(0.2u,0.5u)){dir(90)}..2/5[b2,center(pb2)]; drawarrow pb7; label.bot(btex $A_2$ etex, point(0) of pb7); b4 = whatever[b0,b3]=whatever[b1,b2]; b5 = (xpart(b4),0); b6 = b5+(0,1u); drawdblarrow b5--b4; draw (b4-(0.1u,0))--(b4+(0.1u,0)); blab1 = thelabel(btex $h_2$ etex, (0,0)); unfill bbox blab1 shifted b6; draw blab1 shifted b6; b11 = center(pb2); b10 = b11+(b11-b9)/8; drawarrow b10--b11 withpen pencircle scaled 2; label.lft(btex $p_2$ etex, 1/4[b10,b11]); b7 = b0 + (0,0.35u); b8 = b1 + (0,0.35u); draw b0--(b7 + (0,0.175u)) withcolor 0.6*white; draw b1--(b8 + (0,0.175u)) withcolor 0.6*white; drawdblarrow b7--b8; blab2 =thelabel(btex $v_2\Delta t=s_2$ etex, (0,0)); unfill bbox blab2 shifted 1/2[b7,b8]; draw blab2 shifted 1/2[b7,b8]; %DRAW FLUID TUBE linecap := butt; draw t withpen pencircle scaled 1; draw b withpen pencircle scaled 1; path acap,bcap,bcapa,bcapb; acap = fullcircle rotated 180 xscaled (0.2*lwidth) yscaled lwidth shifted 1/2[z0,z2]; bcapa = halfcircle rotated -90 xscaled (0.2*rwidth) yscaled rwidth shifted 1/2[z1,z3]; bcapb = halfcircle rotated 90 xscaled (0.2*rwidth) yscaled rwidth shifted 1/2[z1,z3]; bcap = buildcycle(bcapa,bcapb); fill acap withcolor backcol; fill bcap withcolor backcol; linecap := rounded; draw acap withpen pencircle scaled 1; draw bcapa withpen pencircle scaled 1; draw bcapb withpen pencircle scaled 1 dashed evenly; %uncomment the following line to draw a density symbol in the center of the figure %label (btex $\rho$ etex, 1/2[point 1.5 of t, point 1.5 of b]); endfig;