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divergence in MAC Method
hello.
i have new problem with my program. i see than divergence equations fails. my divergence equation is: D[i][j] = (U[i][j] - U[i-1][j])/dx + (V[i][j] - V[i][j-1]; in paper by Harlow Welch (MAC method) he write than divergence cannot be larger than 3.5 * 10^(-4). Ok, but when divergence is too big for one of cells, then i cannot make it smaller (when i less dt, Divergence dont change). Any ideas? /// maq ps. just small question - width of output = 256 height of output = 256 number of cells x = 64 number of cells y = 64 thats means than dx,dy = 256/4 ??? |

errata :)
sorry: of corse:
D[i][j] = (U[i][j] - U[i-1][j])/dx + (V[i][j] - V[i][j-1]; and dx,dy = 256/64??? sorry. anyway anybody know? |

Re: errata :)
dear maq check ur D eqns, dy is missing there.if it is the typing mistake here alone, then the culprit is the way u evaluate the u and v.
u(i,j) is average of u(i,j) and u(i-1,j) and u(i-1,j) is average of u(i-2,j) and u(i-1,j) and so forth.check this out by senthil. |

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