Hi I've been working on Fluent 6.0 to simulate a fuel cell with multi-channels to evaluate its performance by way of current density... i have written udf for calculation of source terms... during compilation of the code... I got this error message several times, it says - Error: Access Violation. I dont know the exact reason for this error, if someone can help shed some light on it, it wud be useful... i think i have found two sources of this error, although i m sure there a re many more... 1. this happens when any of the calculated parameters reaches the value infinity, may be because the denominator is zero. This happens a lot when you are trying to extract parameters on a face, by a udf - macro.. a lot of the times that value is zero and when u divide something by it, it will lead to the above error. 2. this happens when you are trying to calculate some parameter using a wrong type of macro, say, current density by way of a DEFINE_PROFILE or DEIFNE_ADJUST macro... then there is often a mismatch between the return type that is expected and the return type that you are calculating... make sure that u define the correct macros along with correct return types... hope this helps some of u...

hi,sid. i hv work on fuel cell too. As my experiences, the error appear when you want to access some variables which the marco could not get. such as C_YI_G in the mass source udf. you have to text: solve-set-expert, and type yes to keep memory from freed.Then iteraing a few steps without the mass source, and again set on the mass source udf. the error would disappear. If possible, you can post your udf and we could find out the problem. BTW, i am using DEIFNE_ADJUST to caculate current density, i do not know why you say it is using a wrong type of macro?

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wicwawa