# The gradient of void fraction in UDF

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 July 11, 2006, 19:49 The gradient of void fraction in UDF #1 summer Guest   Posts: n/a Hello, everyone. Now I used the UDF to define the gradient of void fraction as follows: if(NULL!=THREAD_STORAGE(mix_thread,SV_VOF_G)) { v_s=C_VOF_G(c,thread_g)[1]; //Message()"it is OK!%f\n",v_s); } Next, I would like to multiply this gradient of void fraction into velocity(two vectors). In math, I know we could multiply them in x, y direction, respectively. How can I realize this since I do not know how to get the expression of this gradient in x and y direction? (Now I am using 2d) Thanks in advance.

 July 17, 2006, 12:03 Re: The gradient of void fraction in UDF #2 Asghari Guest   Posts: n/a Do you want scalar multiple product , for example A & B by udf?

 May 20, 2011, 04:34 #3 New Member   M. A. Join Date: Jul 2010 Posts: 27 Rep Power: 15 Hi friends, I'm simulating a tube with water flow. The tube encounters boiling near the wall. I intend to calculate 'void fraction versus enthalpy' along the channel. Can you help me how to calculate void fraction? I'm in an emergency condition. Waiting for your comments!!! Thanks Everybody