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viscosity udf don't use correct temperature and strain rate 

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May 24, 2021, 08:08 
viscosity udf don't use correct temperature and strain rate

#1 
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yahya rezvani
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hello. im use udf for calculate strain rate and temperature dependent viscosity. but viscosity udf don't use correct temperature and strain rate. how to solve this problem? this is my udf
Code:
# include <udf.h> int counter=0; DEFINE_PROPERTY(U_Visc,c,t) { real Temp; real Visc; real str; real stress; real asinh_input; real asinh_output; real b; real Z; real A; real alfa; real blfa; real n ; real Q; real R;/* Specific gas constant */ real strlimit; real Visc_limit; real viscmin; A = 2.095E11 ;/* Material constant 304 ss*/ blfa = 3.233E5; alfa= 0.0000050867; n = 1.812; Q = 74640; R = 8.314; Visc_limit = 2.E5; Temp = C_T(c,t); /*0.7Tm*/ begin_c_loop(c, t) { str = C_STRAIN_RATE_MAG(c,t); b=exp(Q/(R*Temp)); Z = str*b; asinh_input = pow(Z/A,1./n); asinh_output = log(asinh_input + sqrt(asinh_input * asinh_input + 1)); stress = (1. /alfa)*asinh_output; Visc = stress/(3. *str); if ( (Visc > Visc_limit)  (str == 0) ) { Visc = Visc_limit; } if ( (Visc < 0) ) { Visc = 0; } C_UDMI(c,t,0)=stress; C_UDMI(c,t,1)=Visc; C_UDMI(c,t,2)=str; C_UDMI(c,t,3)=Temp; C_UDMI(c,t,4)=Z; C_UDMI(c,t,5)=asinh_input; C_UDMI(c,t,6)=asinh_output; C_UDMI(c,t,7)=b; if(counter<=20) { counter++;CX_Message("Strain= %E(1/s) Viscosity =%E PaS\n", str, Visc); /* CX_Message("Strain*1e6= %E\n", str*1e6); */ } return Visc; end_c_loop(c, t) } } thank you best regards Rezvani 

May 24, 2021, 11:31 

#2 
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Temp = C_T(c,t); /*0.7Tm*/
begin_c_loop(c, t) Switch these two lines.
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"The UDF library you are trying to load (libudf) is not compiled for parallel use on the current platform" is NOT the error after compiling. It is the error after loading. To see compiler errors, look at your screen after you click "build". 

May 24, 2021, 18:24 

#3 
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yahya rezvani
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thank you .still udm s are wrong. how to fix udm?


May 24, 2021, 23:06 

#4 
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Alexander
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try this code
Code:
# include <udf.h> int counter=0; DEFINE_PROPERTY(U_Visc,c,t) { real Temp; real Visc; real str; real stress; real asinh_input; real asinh_output; real b; real Z; real A; real alfa; real blfa; real n ; real Q; real R;/* Specific gas constant */ real strlimit; real Visc_limit; real viscmin; A = 2.095E11 ;/* Material constant 304 ss*/ blfa = 3.233E5; alfa= 0.0000050867; n = 1.812; Q = 74640; R = 8.314; Visc_limit = 2.E5; Temp = C_T(c,t); /*0.7Tm*/ str = C_STRAIN_RATE_MAG(c,t); b=exp(Q/(R*Temp)); Z = str*b; asinh_input = pow(Z/A,1./n); asinh_output = log(asinh_input + sqrt(asinh_input * asinh_input + 1)); stress = (1. /alfa)*asinh_output; Visc = stress/(3. *str); if ( (Visc > Visc_limit)  (str == 0) ) { Visc = Visc_limit; } if ( (Visc < 0) ) { Visc = 0; } C_UDMI(c,t,0)=stress; C_UDMI(c,t,1)=Visc; C_UDMI(c,t,2)=str; C_UDMI(c,t,3)=Temp; C_UDMI(c,t,4)=Z; C_UDMI(c,t,5)=asinh_input; C_UDMI(c,t,6)=asinh_output; C_UDMI(c,t,7)=b; if(counter<=20) { counter++; Message0("Strain= %E(1/s) Viscosity =%E PaS\n", str, Visc); /* Message0("Strain*1e6= %E\n", str*1e6); */ } return Visc; }
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May 25, 2021, 16:06 

#5 
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yahya rezvani
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hello. if dont use begin_c_loop(c, t) fluent show this error
Code:
4 1.0000e+00 4.1831e02 1.6884e02 1.7000e02 3.5638e04 0:22:44 46 Stabilizing temperature to enhance linear solver robustness. temperature limited to 1.000000e+00 in 4967024 cells on zone 4 in domain 1 temperature limited to 5.000000e+03 in 19391 cells on zone 4 in domain 1 Artificial walls on 82 faces (0.7% area) of pressureoutlet 9 to prevent fluid from flowing into the boundary. 5 1.0000e+00 3.9380e02 2.1037e02 2.0857e02 1.6664e03 0:27:24 45 Error at Node 1: floating point exceptiEon rror at Node 0: floating point exception Stabilizing pressure correction to enhance linear solver robustness. Stabilizing pressure correction using GMRES to enhance linear solver robustness. Divergence detected in AMG solver: pressure correction Stabilizing pressure correction to enhance linear solver robustness. Stabilizing pressure correction using GMRES to enhance linear solver robustness. Divergence detected in AMG solver: pressure correction Stabilizing pressure correction to enhance linear solver robustness. Stabilizing pressure correction using GMRES to enhance linear solver robustness. Divergence detected in AMG solver: pressure correction Stabilizing pressure correction to enhance linear solver robustness. Stabilizing pressure correction using GMRES to enhance linear solver robustness. Divergence detected in AMG solver: pressure correction Stabilizing pressure correction to enhance linear solver robustness. Stabilizing pressure correction using GMRES to enhance linear solver robustness. Divergence detected in AMG solver: pressure correction Stabilizing pressure correction to enhance linear solver robustness. Stabilizing pressure correction using GMRES to enhance linear solver robustness. Divergence detected in AMG solver: pressure correction Stabilizing pressure correction to enhance linear solver robustness. Stabilizing pressure correction using GMRES to enhance linear solver robustness. Divergence detected in AMG solver: pressure correction Stabilizing pressure correction to enhance linear solver robustness. Stabilizing pressure correction using GMRES to enhance linear solver robustness. Divergence detected in AMG solver: pressure correction Stabilizing pressure correction to enhance linear solver robustness. Stabilizing pressure correction using GMRES to enhance linear solver robustness. Divergence detected in AMG solver: pressure correction Stabilizing pressure correction to enhance linear solver robustness. Stabilizing pressure correction using GMRES to enhance linear solver robustness. Divergence detected in AMG solver: pressure correction Stabilizing pressure correction to enhance linear solver robustness. Stabilizing pressure correction using GMRES to enhance linear solver robustness. Divergence detected in AMG solver: pressure correction Stabilizing pressure correction to enhance linear solver robustness. Stabilizing pressure correction using GMRES to enhance linear solver robustness. Divergence detected in AMG solver: pressure correction Stabilizing pressure correction to enhance linear solver robustness. Stabilizing pressure correction using GMRES to enhance linear solver robustness. Divergence detected in AMG solver: pressure correction Stabilizing temperature to enhance linear solver robustness. Stabilizing temperature using GMRES to enhance linear solver robustness. Divergence detected in AMG solver: temperature Artificial walls on 5428 faces (46.2% area) of pressureoutlet 9 to prevent fluid from flowing into the boundary. Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: temperature Error at host: floating point exception ===============Message from the Cortex Process================================ Compute processes interrupted. Processing can be resumed. ============================================================================== thank you 

May 25, 2021, 16:31 

#6 
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Check those UDMs that you used. Plot them, see which one is not what you expect.
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"The UDF library you are trying to load (libudf) is not compiled for parallel use on the current platform" is NOT the error after compiling. It is the error after loading. To see compiler errors, look at your screen after you click "build". 

May 26, 2021, 05:14 

#7  
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yahya rezvani
Join Date: Aug 2019
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Quote:
but udm s(temperature, stress,... ) are wrong. if i use begin_c_loop(c, t) udm s are wrong. if i dont use begin_c_loop(c, t) then give error!! thank you. best regards. 

May 26, 2021, 09:11 

#8 
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If temperature and stress are wrong, focus on that.
You don't give me much to work with, so I can't help more.
__________________
"The UDF library you are trying to load (libudf) is not compiled for parallel use on the current platform" is NOT the error after compiling. It is the error after loading. To see compiler errors, look at your screen after you click "build". 

May 27, 2021, 06:40 

#9  
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Alexander
Join Date: Apr 2013
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begin_c_loop(c, t) is already included in DEFINE_PROPERTY macro
you don't need to make additional loop over cell from your log I can see the error comes out on 4th iteration. look at domain on 3th iteration, check udms distribution, analyse all variable you have applied to model: temperature, stresses so on Quote:
in that case simulation doesn't work cause of viscosity values you've applied
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