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klinedancer

铜虫 (小有名气)

[求助] fluent 自定义曳力系数

欧拉双流体模型自定义曳力系数,现在曳力系数模型是CD=CD0 *(-31.4565+32.4451void_g);
(其中,CD为曳力系数,CD0为单颗粒曳力系数,void_g是空隙率,请问用udf怎么编写)
DEFINE_EXCHANGE_PROPERTY(custom_drag_syam, cell, mix_thread, s_col, f_col) 宏返回值到底是什么东西??是曳力,还是曳力系数,,还是什么别的东西??求解

如果我的用DEFINE_EXCHANGE_PROPERTY(custom_drag_syam, cell, mix_thread, s_col, f_col)编写,是直接return CD=CD0 *(-31.4565+32.4451*void_g)吗??







我翻阅别人的如下
/* This is a routine for customizing default Syamlal drag law in Fluent 6.
   The default drag law uses 0.8 (for void<=0.85) and 2.65 (void>0.85) for
   bfac. This is for a min fluid vel of 25 cm/s. The current drag law has been
   tuned for a min fluid vel of 8 cm/s and uses 0.28 and 9.07 for these
   parameters. */

#include "udf.h"
#include "sg_mphase.h"

# define pi 4.*atan(1.)
#define diam2 3.e-4

DEFINE_EXCHANGE_PROPERTY(custom_drag_syam, cell, mix_thread, s_col, f_col)
{
Thread *thread_g, *thread_s;
real x_vel_g, x_vel_s, y_vel_g, y_vel_s, abs_v, slip_x, slip_y,
      rho_g, rho_s, mu_g, reyp, afac,
      bfac, void_g, vfac, fdrgs, taup, k_g_s;

/* find the threads for the gas (primary) and solids (secondary phases).
These phases appear in columns 2 and 1 in the Interphase panel respectively*/

thread_g = THREAD_SUB_THREAD(mix_thread, s_col);/*gas phase*/
thread_s = THREAD_SUB_THREAD(mix_thread, f_col);/* solid phase*/

/* find phase velocities and properties*/

x_vel_g = C_U(cell, thread_g);
y_vel_g = C_V(cell, thread_g);

x_vel_s = C_U(cell, thread_s);
y_vel_s = C_V(cell, thread_s);

slip_x = x_vel_g - x_vel_s;
slip_y = y_vel_g - y_vel_s;

rho_g = C_R(cell, thread_g);
rho_s = C_R(cell, thread_s);

mu_g = C_MU_L(cell, thread_g);

/*compute slip*/
abs_v = sqrt(slip_x*slip_x + slip_y*slip_y);

/*compute reynolds number*/

reyp = rho_g*abs_v*diam2/mu_g;

/* compute particle relaxation time */

taup = rho_s*diam2*diam2/18./mu_g;

void_g = C_VOF(cell, thread_g);/* gas vol frac*/

/*compute drag and return drag coeff, k_g_s*/

afac = pow(void_g,4.14);

if(void_g<=0.85)
  bfac = 0.281632*pow(void_g, 1.28);
else
  bfac = pow(void_g, 9.076960);

vfac = 0.5*(afac-0.06*reyp+sqrt(0.0036*reyp*reyp+0.12*reyp*(2.*bfac-
              afac)+afac*afac));
fdrgs = void_g*(pow((0.63*sqrt(reyp)/vfac+4.8*sqrt(vfac)/vfac),2))/24.0;

k_g_s = (1.-void_g)*rho_s*fdrgs/taup;

return k_g_s;

}



我的函数返回值return应该是什么呢?
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apo1016

新虫 (初入文坛)

【答案】应助回帖

你贴上来的例子,直接返回的是k_g_s的值,所以你在编写曳力系数的时候,返回的应该也是曳力系数的值
2楼2015-01-06 10:09:57
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zhengquan23

新虫 (初入文坛)

【答案】应助回帖

你把这个帮助文件案例修改下就行,返回值可以也是kgs(两相交换系数)
3楼2015-05-12 16:10:13
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与一碰

铜虫 (初入文坛)

【答案】应助回帖

s-o模型中的气固交换系数Kgs.
万般带不走,唯有业随身!
4楼2015-12-10 16:01:03
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-183413

木虫 (小有名气)

引用回帖:
3楼: Originally posted by zhengquan23 at 2015-05-12 16:10:13
你把这个帮助文件案例修改下就行,返回值可以也是kgs(两相交换系数)

同学你好,CD=CD0 *(-31.4565+32.4451void_g),空隙率这一项是手算的吗,我怎么搞不出来
5楼2020-08-14 16:41:10
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