File:DiffusionMicroMacro.gif
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DiffusionMicroMacro.gif (360 × 300 pixels, file size: 402 KB, MIME type: image/gif, looped, 60 frames, 6.5 s)
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Summary[edit]
DescriptionDiffusionMicroMacro.gif |
English: Diffusion from a microscopic and macroscopic point of view. Initially, there are solute molecules on the left side of a barrier (magenta line) and none on the right. The barrier is removed, and the solute diffuses to fill the whole container. Top: A single molecule moves around randomly. Middle: With more molecules, there is a clear trend where the solute fills the container more and more evenly. Bottom: With an enormous number of solute molecules, the randomness is gone: The solute appears to move smoothly and systematically from high-concentration areas to low-concentration areas, following Fick's laws.
Image is made in Mathematica, source code below. |
Date | |
Source | Own work |
Author | Sbyrnes321 |
Licensing[edit]
Public domainPublic domainfalsefalse |
I, the copyright holder of this work, release this work into the public domain. This applies worldwide. In some countries this may not be legally possible; if so: I grant anyone the right to use this work for any purpose, without any conditions, unless such conditions are required by law. |
<< Mathematica source code >>
(* Source code written in Mathematica 6.0, by Steve Byrnes, 2010. I release this code into the public domain. Sorry it's messy...email me any questions. *) (*Particle simulation*) SeedRandom[1]; NumParticles = 70; xMax = 0.7; yMax = 0.2; xStartMax = 0.5; StepDist = 0.04; InitParticleCoordinates = Table[{RandomReal[{0, xStartMax}], RandomReal[{0, yMax}]}, {i, 1, NumParticles}]; StayInBoxX[x_] := If[x < 0, -x, If[x > xMax, 2 xMax - x, x]]; StayInBoxY[y_] := If[y < 0, -y, If[y > yMax, 2 yMax - y, y]]; StayInBoxXY[xy_] := {StayInBoxX[xy[[1]]], StayInBoxY[xy[[2]]]}; StayInBarX[x_] := If[x < 0, -x, If[x > xStartMax, 2 xStartMax - x, x]]; StayInBarY[y_] := If[y < 0, -y, If[y > yMax, 2 yMax - y, y]]; StayInBarXY[xy_] := {StayInBarX[xy[[1]]], StayInBarY[xy[[2]]]}; MoveAStep[xy_] := StayInBoxXY[xy + {RandomReal[{-StepDist, StepDist}], RandomReal[{-StepDist, StepDist}]}]; MoveAStepBar[xy_] := StayInBarXY[xy + {RandomReal[{-StepDist, StepDist}], RandomReal[{-StepDist, StepDist}]}]; NextParticleCoordinates[ParticleCoords_] := MoveAStep /@ ParticleCoords; NextParticleCoordinatesBar[ParticleCoords_] := MoveAStepBar /@ ParticleCoords; NumFramesBarrier = 10; NumFramesNoBarrier = 50; NumFrames = NumFramesBarrier + NumFramesNoBarrier; ParticleCoordinatesTable = Table[0, {i, 1, NumFrames}]; ParticleCoordinatesTable[[1]] = InitParticleCoordinates; For[i = 2, i <= NumFrames, i++, If[i <= NumFramesBarrier, ParticleCoordinatesTable[[i]] = NextParticleCoordinatesBar[ParticleCoordinatesTable[[i - 1]]], ParticleCoordinatesTable[[i]] = NextParticleCoordinates[ParticleCoordinatesTable[[i - 1]]]];]; (*Plot full particle simulation*) makeplotbar[ParticleCoord_] := ListPlot[{ParticleCoord, {{xStartMax, 0}, {xStartMax, yMax}}}, Frame -> True, Axes -> False, PlotRange -> {{0, xMax}, {0, yMax}}, Joined -> {False, True}, PlotStyle -> {PointSize[.03], Thick}, AspectRatio -> yMax/xMax, FrameTicks -> None]; makeplot[ParticleCoord_] := ListPlot[ParticleCoord, Frame -> True, Axes -> False, PlotRange -> {{0, xMax}, {0, yMax}}, Joined -> False, PlotStyle -> PointSize[.03], AspectRatio -> yMax/xMax, FrameTicks -> None] ParticlesPlots = Join[Table[makeplotbar[ParticleCoordinatesTable[[i]]], {i, 1, NumFramesBarrier}], Table[makeplot[ParticleCoordinatesTable[[i]]], {i, NumFramesBarrier + 1, NumFrames}]]; (*Plot just the first particle in the list...Actually the fifth particle looks better. *) FirstParticleTable = {#[[5]]} & /@ ParticleCoordinatesTable; FirstParticlePlots = Join[Table[makeplotbar[FirstParticleTable[[i]]], {i, 1, NumFramesBarrier}], Table[makeplot[FirstParticleTable[[i]]], {i, NumFramesBarrier + 1, NumFrames}]]; (* Continuum solution *) (* I can use the simple diffusion-on-an-infinite-line formula, as long as I correctly periodically replicate the initial condition. Actually just computed nearest five replicas in each direction, that was a fine approximation. *) (* k = diffusion coefficient, visually matched to simulation. *) k = .0007; u[x_, t_] := If[t == 0, If[x <= xStartMax, 1, 0], 1/2 Sum[ Erf[(x - (-xStartMax + 2 n xMax))/Sqrt[4 k t]] - Erf[(x - (xStartMax + 2 n xMax))/Sqrt[4 k t]], {n, -5, 5}]]; ContinuumPlots = Join[ Table[Show[ DensityPlot[1 - u[x, 0], {x, 0, xMax}, {y, 0, yMax}, ColorFunctionScaling -> False, AspectRatio -> yMax/xMax, FrameTicks -> None], ListPlot[{{xStartMax, 0}, {xStartMax, yMax}}, Joined -> True, PlotStyle -> {Thick, Purple}]], {i, 1, NumFramesBarrier}], Table[ DensityPlot[1 - u[x, tt], {x, 0, xMax}, {y, 0, yMax}, ColorFunctionScaling -> False, AspectRatio -> yMax/xMax, FrameTicks -> None], {tt, 1, NumFramesNoBarrier}]]; (*Combine and export *) TogetherPlots = Table[GraphicsGrid[{{FirstParticlePlots[[i]]}, {ParticlesPlots[[i]]}, {ContinuumPlots[[i]]}}, Spacings -> Scaled[0.2]], {i, 1, NumFrames}]; Export["test.gif", Join[TogetherPlots, Table[Graphics[], {i, 1, 5}]], "DisplayDurations" -> {10}, "AnimationRepititions" -> Infinity ]
File history
Click on a date/time to view the file as it appeared at that time.
Date/Time | Thumbnail | Dimensions | User | Comment | |
---|---|---|---|---|---|
current | 13:41, 7 March 2012 | 360 × 300 (402 KB) | Dratini0 (talk | contribs) | Just removed the white last fram for aesthetic purposes, and prologed the display time of the last frame to mark the reatart of the animation. | |
19:37, 25 March 2010 | 360 × 300 (402 KB) | Aiyizo (talk | contribs) | Optimized animation, converted to 256 color mode | ||
09:57, 16 January 2010 | 360 × 300 (529 KB) | Sbyrnes321 (talk | contribs) | sped up bottom panel to match better with middle panel | ||
09:46, 16 January 2010 | 360 × 300 (508 KB) | Sbyrnes321 (talk | contribs) | {{Information |Description={{en|1=Diffusion from a microscopic and macroscopic point of view. Initially, there are solute molecules on the left side of a barrier (purple line) and none on the right. The barrier is removed, and the solute diffuses to fill |
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