# pls. help : life-drag coefficient in dynamic mesh

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 November 30, 2007, 13:20 pls. help : life-drag coefficient in dynamic mesh #1 loogtaan Guest   Posts: n/a Hello, I solve flapping motion by using dynamic mesh but I don't know hoe to define force vector for cl,cd plot in force monitor.Have anyone can suggest me. thanks.

 December 1, 2007, 03:16 Re: pls. help : life-drag coefficient in dynamic m #2 zhang Guest   Posts: n/a firt,you can't define the foce vector, there are only three options you can choose:x_axis,y-axis and z-axis. but you can rotate the mesh to get different vector second, force monitor just plots the force coefficient.you must know how to change the reference value to get the real forces

 December 1, 2007, 09:32 Re: pls. help : life-drag coefficient in dynamic m #3 loogtaan Guest   Posts: n/a Thank you Zhang, But I don't know how to change the reference value because I use only DEFINE_CG_MOTION to predict airfoil motion. Please explain me. loogtaan

 December 1, 2007, 09:42 Re: pls. help : life-drag coefficient in dynamic m #4 loogtaan Guest   Posts: n/a This is my udf code #include #define PI 3.141592654 DEFINE_CG_MOTION(airfoil, dt, cg_vel, cg_omega, time, dtime) { real freq = 1.707; real amp = 1.4; cg_vel[0] = 2*PI*freq*amp*sin(2.0*PI*freq*time); /* x-velocity*/ cg_omega[2] = 2*PI*freq*0.78534*(sin((2.0*PI*freq*time)+1.5708)) ;/*angular-velocity*/ }

 December 8, 2007, 23:15 Re: pls. help : life-drag coefficient in dynamic m #5 zhang Guest   Posts: n/a Sorry loogtaan, I'm being busy on my job thess days. Beyond the report menu, you can see the reference values.Once you change denstity 1.225 to 2. The forces in the "Force Monitors" become the real forces

 December 20, 2007, 21:54 Re: pls. help : life-drag coefficient in dynamic m #6 loogtaan Guest   Posts: n/a Thank you Zhang, could you told me how about the velocity that I must use in the reference menu because I give same result for different Renolds Number.

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