# [GAMBIT] Exponential en Bi-exponential grading

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 March 11, 2016, 14:42 Exponential en Bi-exponential grading #1 New Member   Rob Vervoort Join Date: Nov 2015 Posts: 20 Rep Power: 3 Hello everyone, I am experiencing some problems with grading in gambit. I could not find a gambit manual since all the links to user manuals are offline. I found another source that mentions the following (that obtained the formula from the gambit manual). For exponential grading, gambit uses the following formula: R = exp( (L/n) * (x-0.5)) or: x = ( ln(R) / (L/n)) + 0.5 in which: R = the ratio's of the cells. L = the length of the edge n = the number of intervals and x is the ratio to specify in gambit For example when having a edge with a length (L) of 15 with a cell ratio (R) of 2 and 4 intervals (n), thus a line with intervals with a length of 1-2-4-8, this results in a ratio of 0.6868 in gambit. However when specifying this ratio in gambit and when looking at the intervals, the stretching ratio's of the cells are not equal to 2 (closer to 1.5). A ratio around 0.776 in gambit is required to obtain the stretching ratio (R) = 2. Could someone tell me how the exponential and bi-exponential grading works? In grid I want to apply stretching ratio's of 1.1 over the entire domain. Thank you in advance, Rob

 March 14, 2016, 02:27 #2 Super Moderator     Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 3,232 Rep Power: 34 __________________ In memory of my friend Hervé: CFD engineer & freerider

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