Science method
AMG - Science method
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Questions related to AMG
Reversed flow on 28 faces of pressure-outlet 7.
Stabilizing mp-x-momentum to enhance linear solver robustness.
Stabilizing mp-x-momentum using GMRES to enhance linear solver robustness.
Stabilizing mp-y-momentum to enhance linear solver robustness.
Stabilizing mp-y-momentum using GMRES to enhance linear solver robustness.
Stabilizing k to enhance linear solver robustness.
Stabilizing k using GMRES to enhance linear solver robustness.
Divergence detected in AMG solver: k Stabilizing epsilon to enhance linear solver robustness.
Stabilizing epsilon using GMRES to enhance linear solver robustness.
Divergence detected in AMG solver: epsilon Stabilizing flue-gas-species-0 to enhance linear solver robustness.
Stabilizing flue-gas-species-1 to enhance linear solver robustness.
Stabilizing temperature to enhance linear solver robustness.
Stabilizing temperature using GMRES to enhance linear solver robustness.
Stabilizing vof-1 to enhance linear solver robustness.
absolute pressure limited to 5.000000e+10 in 2708 cells on zone 4
turbulent viscosity limited to viscosity ratio of 1.000000e+05 in 7089 cells
Divergence detected in AMG solver: k
Divergence detected in AMG solver: epsilon
Divergence detected in AMG solver: k
Divergence detected in AMG solver: epsilon
Divergence detected in AMG solver: k
Divergence detected in AMG solver: epsilon
Divergence detected in AMG solver: k
Divergence detected in AMG solver: epsilon
Divergence detected in AMG solver: k
Divergence detected in AMG solver: epsilon
Divergence detected in AMG solver: k
Divergence detected in AMG solver: epsilon
Divergence detected in AMG solver: k
Divergence detected in AMG solver: epsilon
Divergence detected in AMG solver: k
Divergence detected in AMG solver: epsilon
Divergence detected in AMG solver: k
Divergence detected in AMG solver: epsilon
Divergence detected in AMG solver: k
Divergence detected in AMG solver: epsilon
Divergence detected in AMG solver: k
Divergence detected in AMG solver: epsilon
Error at host: floating point exception
===============Message from the Cortex Process================================
Compute processes interrupted. Processing can be resumed.
==============================================================================
Error at Node 2: floating point exception
Error at Node 5: floating point exception
Error at Node 3: floating point exception
Error at Node 9: floating point exception
Error at Node 1: floating point exception
Error at Node 4: floating point exception
Error at Node 7: floating point exception
Error at Node 11: floating point exception
Error at Node 0: floating point exception
Error at Node 6: floating point exception
Error at Node 8: floating point exception
Error at Node 10: floating point exception
I am working on Battery Pack Thermal Analysis for an Electric Vehicle. Whenever I get to the point of pressing "Run Calculation", the solver displays 1 iteration only then displays some info and "Floating Point Exception". Here are the messages displayed in the console:
iter energy uds-0 uds-1 time/iter
1 1.6096e-07 7.8111e-07 7.7842e-07 0:00:40 10
Stabilizing temperature to enhance linear solver robustness.
Stabilizing temperature using GMRES to enhance linear solver robustness.
Divergence detected in AMG solver: temperature Stabilizing uds-0 to enhance linear solver robustness.
Stabilizing uds-0 using GMRES to enhance linear solver robustness.
Divergence detected in AMG solver: uds-0 Stabilizing uds-1 to enhance linear solver robustness.
Stabilizing uds-1 using GMRES to enhance linear solver robustness.
Divergence detected in AMG solver: uds-1
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: uds-0
Divergence detected in AMG solver: uds-1
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: uds-0
Divergence detected in AMG solver: uds-1
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: uds-0
Divergence detected in AMG solver: uds-1
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: uds-0
Divergence detected in AMG solver: uds-1
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: uds-0
Divergence detected in AMG solver: uds-1
Error at host: floating point exception
===============Message from the Cortex Process================================
Compute processes interrupted. Processing can be resumed.
==============================================================================
Error at Node 3: floating point exception
Error at Node 2: floating point exception
Error at Node 5: floating point exception
Error at Node 4: floating point exception
Error at Node 1: floating point exception
Error at Node 0: floating point exception
Error: floating point exception
Error Object: #f
I am new to Ansys Fluent, so I will be glad if anyone helps me throughout this problem. Thanks in advance!
Hello everyone.
I am doing a CFD simulation for waste heat boiler and simulation boiling in steam drum.
I used ANSYS Fluent to perform the simulation. However during the calculation section. I received this error
"reversed flow in 274 faces on pressure-outlet 18.
Stabilizing mp-x-momentum to enhance linear solver robustness.
Stabilizing k to enhance linear solver robustness.
Divergence detected in AMG solver: k temperature limited to 1.000000e+00 in 8519 cells on zone 2 in domain 3
turbulent viscosity limited to viscosity ratio of 1.000000e+05 in 18252 cells
Divergence detected in AMG solver: k
Error at host: floating point exception
Error at Node 0: floating point exception
Error at Node 1: floating point exception
Error: floating point exception
Error Object: #f"
May I know what are the possible cause of this error?
Any advice? Thank you
Hi there
Isohumic coefficient form SIMEOS AMG are not really correlated to our on field observation in no till farming fields in france.
The model is based on incubating plant cover residues at 25 tonnes of dry matter with 180 kg of nitrogen per hectare. However, the fertilization of plant cover is prohibited in France
So im looking for other references, all the datas i find are only from France.
Regards
Dear All,
In Ansys fluent 2021 R2, I compile and load a UDF file and even initialize successfully but when I click on calculate then at the beginning of 0% calculation I am getting the following error,
Divergence detected in AMG solver: uds-0
Divergence detected in AMG solver: uds-0
Error at host: floating point exception
===============Message from the Cortex Process================================
Compute processes interrupted. Processing can be resumed.
==============================================================================
Error: floating point exception
Error Object: #f
Please tell me the possible solution to solve this error, its been a week but I am stuck in solving this issue, I am really in need of someone who can give guidance. Please Help.
As I start the simulation of bubble column (air-water system), just after 15 iterations, it displays "floating point exception" and shows "divergence detected in AMG solver". What is the reason behind it?
Dear all,
I am simulating the combustion of diesel-biodiesel-gasoline mixtures, in which I developed the kinetic mechanism via Chemkin. My case is a 2-D constant volume bomb chamber, and the fuel is injected through the nozzle, while I ignite the mixture using the spark option. However, right when the timestep reaches the time where the spark is ignited, I get this error:
divergence detected in AMG solver: temperature
By this I mean there is no problem with the simulation if there was no spark activated. But when it is used, the running stops with a floating point.
I have searched a lot to find a solution, and I have tried, mesh refinement, BC, URF, smaller timesteps, energy equation, control limits and all you might possibly find on the internet. Could you please kindly guide me on what sort of action should I take to resolve this issue?
Appreciate it,
I am simulating a two-axisymmetric supersonic jet impinging on a flat plate.
When I am rotating my mesh in fluent and running simulation, i am getting the following error, "Divergence detected in AMG solver" (details in the attachments)
Please, need help.
Hello,
I have been trying to model evaporation at temperatures far well below 100C in Fluent. This is primarily driven by the vapor content of air at the water-air interface.
A saturation temperature UDF is attached below.
The setup this is used with has 2 phases, one a species mixture of air and water vapor and the other is water.
After some help from the forum, I have got it up and running and it seems to be performing fairly well in transient simulations. However, when I try to use this code to calculate the saturation temperature for any steady-state simulation, I get a floating-point error. This is sometimes instant and sometimes after a few iterations. An example error message is:
Error at Node 0: floating point exception
Error at Node 1: floating point exception
Error at Node 2: floating point exception
Error at Node 3: 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 temperature to enhance linear solver robustness.
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: pressure correction
Error at host: floating point exception
I can't understand why I am running into this issue. Is there anything I could try to remedy the problem? I have tested on many geometries, with a variety of problems. Is this UDF unsuitable for steady simulations? and if that's the case then what alternatives do I have? I really need this functionality.
I thought it may be because the system varies a lot so I set up a closed system with a little water in with the walls set to a temperature of 300k and initialized it at 300k. My logic was that the only thing left to solve was the vapor fraction. I got a simulation to run 10000 iterations. However, the vapor fraction was 1.0 everywhere in the gas phase leading to relative humidities many times larger than 100%. This makes me worry there is something wrong with the UDF itself. I know that this kind of study must be possible somehow as I have read papers of people doing similar things, yet these don't go into enough detail for me to successfully imitate.
Any help is appreciated.
Cheers
#include "udf.h"
#define MOLAR_MASS_WATER 18.01534 //g/mol
#define MOLAR_MASS_AIR 28.97 // g/mol
#define RHO_WV 0.5542 // kg/m3
#define RHO_AIR 1.225 // kg/m3
DEFINE_PROPERTY(saturation_temp, c, t)
{
// t: mixture thread
// c: cell variable
// Cell volume
real vol = C_VOLUME(c, t);
Thread *pt = THREAD_SUB_THREAD(t, 0); // Primary phase thread
Thread *st = THREAD_SUB_THREAD(t, 1); // Secondary phase thread
// Get the volume fraction of both phases
real vf_s = C_VOF(c, st);
real vf_p = 1 - vf_s;
// Get the pressure of the mixture
real p_mix = C_P(c, t);
// Get the operating pressure
real p_op = RP_Get_Real("operating-pressure");
// Primary phase density
real rho_p = C_R(c, pt);
// Get mass fractions in primary phase
real mf[2]; // Array to store mass fractions
Material *m = THREAD_MATERIAL(pt);
Material *sp = NULL;
int i; // Species index - 0 for water vapor and 1 for air
mixture_species_loop(m, sp, i)
{
mf[i] = C_YI(c, pt, i);
}
real p_w; // h20 pressure for cell
// If secondary phase only
if (vf_s == 1)
{
p_w = p_mix + p_op; //****** I'm not sure if this is right *******
}
// If primary phase or mixture of phases
else
{
// Find the partial pressure of water vapour
// partial pressure = cell pressure * water mole fraction
// mass of primary phase in cell
real m_prim = rho_p * vol * vf_p;
// mass of water vapour and air in cell
real m_wv = mf[0] * m_prim;
real m_air = m_prim - m_wv;
// No of moles in water vapour and air
real N_wv = m_wv / MOLAR_MASS_WATER;
real N_air = m_air / MOLAR_MASS_AIR;
real N_total = N_wv + N_air;
// water vapour partial pressure
p_w = (C_P(c, t)+ p_op)* (N_wv / N_total);
}
// Calculate saturation temperature
real t_sat;
t_sat = (1730.63 / (10.196 - log10(p_w))) + 39.724;
return t_sat;
}
Recently, I was simulating the tutorial file "SIEngine_PortInjected_AMG_Tutorial.ftsim". After the simulation completed I got some results. I have some basic questions that make me doubt the solver, maybe I am wrong.
The questions are as follows:
- 100% combustion efficiency. ( On which basis combustion efficiency is calculated? ) I calculated fuel mass multiplied by LHV which is greater than the chemical heat release rate. How is that possible? This seems like an ideal case.
- UHC is almost zero. How is this possible?
- Fuel Mass per Engine Cycle is showing 2.07651E-002 [g], whereas in the excel sheet iC8H18 concentration is 2.18E-002 gram before combustion. Why there is a deviation?
- Fuel Lower Heating Value per g 44.00000 [kJ]. This LHV value remains the same if I change the combustion from gasoline to CNG also. I guess it may affect results also.
Please answer these questions.
Hello everyone!
I'm doing a simulation in fluent and at some point, usually after the first 15 steps, the error appears:
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Error at host: floating point exception
Error at Node 0: floating point exception
Error at Node 1: floating point exception
===============Message from the Cortex Process================================
Compute processes interrupted. Processing can be resumed.
==============================================================================
Error: floating point exception
Error Object: #f
I'm compiling a UDF file, Time transient, convergence criterion relative, number of time steps 1000, able Specified Operating Density like zero kg/m^3. The mesh is refined in the best possible way.
What is the reason behind it?
Best regards.
In 2D Model, Reaction in porous Zone, Error occurs on hooking UDF , DEFINE_VR_RATE in Fluent, .The error spikes just after running calculation after 1st iteration.
Divergence detected in AMG Solver:TEMPERATURE
Divergence detected in AMG solver species 0
and
Divergence detected in AMG solver species 1...2..3..4
Floating point exception error object #f
Any solution for this, Any one come across such a situation in using UDF in FLuent?
Dear All
Can you help me clarify the basic difference among the following command in STATA. xtmg, xtpmg, xtcce and xtdcce, xtdcce2. When and which method we should choose to estimate MG, AMG, PMG, CCE etc.
After building the udf on Ansys. Flow is getting converge but after starting the energy equation and UDS1, UDS2 UDS3 UDS4 and UDS5.The folowing type of error is getting detected:
# Divergence detected in AMG solver: uds-5 -> Increasing relaxation sweeps!
# You may try the enhanced divergence recovery with (rpsetvar 'amg/protective-enhanced? #t)
Error: Divergence detected in AMG solver: uds-5
Error: Divergence detected in AMG solver: uds-5
Error Object: #f
I split the model of the S-Duct into 4 separate parts and meshed them separately. (This is of utmost importance when I will add control methods to the geometry). I created a new Project and opened the .uns files one-by-one and clicked on Merge everytime. The only named selections were Wall, Inlet and Outlet. When I ran the simuation on Fluent, the solution never converged even after 1000 iterations, the residuals oscillated rather than converging.
Next, I tried to name the two interfaces and merge them, but now I'm left with an extra named selection "Interface" and could not specify an appropriate boundary condition to treat it as part of the interior.
I tried to name the interface as 'Interior' during meshing, but the Solver showed "Divergence detected in AMG Solver".
Kindly tell me how to merge the separate mesh files.
I've these errors and I tried so long to fix it but I couldn't .. I don't know what's the problem can anyone help me plzzz :-
# Divergence detected in AMG solver: temperature -> Increasing relaxation sweeps!
# You may try the enhanced divergence recovery with (rpsetvar 'amg/protective-enhanced? #t)
Error: Divergence detected in AMG solver: temperature
Error: Divergence detected in AMG solver: temperature
Error Object: #f
Hi,This is Prashant
I am trying to solve the multiphase flow simulation for countercurrent flow of Solid(ferrite Fe2O3) and reducing gas (CO)for reduction process in rotary kiln. To solve this I am using Euler-Euler TFM simulation scheme in which primary phase is the gas phase while secondary phase is solid phase and both phase patch. To account the reaction species I am using species transport reaction (Fe2O3 +2CO = 2Fe + 2CO2)(Fe and CO2 both consider as secondary species of phase3 and phase 4 respective phase mass fraction enter in the boundary condition) for radiation P1 model employed.In order to provide rotation moving wall motion given to adjacent cell with rotation speed of 5rpm.In calculation activities initially lower time step 0.01 time step 6000 for 100 iteration(I want to run this for 60 min as per experimentation).
The problem is solution not getting converged and showing following massage
1.Divergence detected in AMG solver
Reversed flow in 3 faces on pressure outlet
2.Divegence detected in AMG solver phase 1 species -3=increase relaxation sweep
3.You may try the enhanced divergence recovery with (rpsetvar ‘amg/protective-enhanced)
4.D.D. in AMG solver –mp x momentum –decreasing coarsening size
5. D.D. in AMG solver –mp x momentum-decresing relaxation sweep.
I am currently working on Gas Turbine Blade Cooling design where inside a turbine blade a cooling channel is incorporated. The cooling channel is made of a single
pipe system which is recirculated inside the turbine blade. Both inlet and outlet of the cooling channel is present at the base of the blade profile.
The blade is of dimension around 120mm span and 160mm tall.
Material- blade: N155
coolant: air
Simulation is being done in ansys fluent 18.2
General solver type set at pressure based, velocity formulation absolute and time steady.
For the initial run viscosity model taken as laminar and energy model ON.
Boundary condition imposed
inlet air of gas turbine section: Temp- 1100K Velocity- 265m/s Pressure-101325Pa(Gauge Pressure- 0)
coolant inlet: Temp-500K Velocity- 30m/s Pressure-101325Pa(Gauge Pressure- 0)
With the initiation of calculation only, divergence is occuring in the AMG solver.
Any suggestion or help would be highly appriciated.
22 country
22 year
two variables
1. Can i use Augmented Mean Group (AMG) Estimator even though there is no cross-sectional dependency?
2.Can i use the second generation unit root tests even though there is no cross-sectional dependency?
Thank you.
I am modeling Boiling in a vertical tube in Fluent 14.the model that i used is RPI model.after setting up, I faced this message:
'Divergence detected in AMG solver"
Temporarily relaxing and trying again...
I've decreased URFs, changed stablization method,changed cycle type from F-cycle to W-cycle and flexibe in advanced solution controls dialog box. But again I confronted divergency!
How can i control it? Is the mesh a factor of it? or is it affected by solution controls and methods?
Any help will be greatly appreciated.
How can i solve this error
Error: Divergence detected in AMG solver: pressure correction
Error Object: #f
?
Dear All,
Could you helps for this please,
I got identical problem as below after 3370 iterations in my 3D bluff body cantilevered using UDF
# Divergence detected in AMG solver: x-momentum -> Increasing relaxation sweeps!
# You may try the enhanced divergence recovery with (rpsetvar 'amg/protective-enhanced? #t)
reversed flow in 7250 faces on outflow 6.
Divergence detected in AMG solver: x-momentum
Divergence detected in AMG solver: y-momentum
Divergence detected in AMG solver: z-momentum
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: pressure correction
Error at Node 0: floating point exception
Error at Node 1: floating point exception
I just modify length bluff body from all case including UDF which original case it is running well. In addition, the case without UDF is run well.
I will send original UDF and my modified UDF if it possible.
I am totally a new comer in UDF
Thanks a lot in advance
regards
Barata
after iteration the solution is not converged, it shows error as temperature divergent in AMG and increase relaxation sweep. i am using energy equation with laminar condition.my objective is to find leakage between swash plate and slipper of an axial piston pump at different inlet pressure and rotational velocity of swash plate.
Not knowing all the details which support your question, I can only suggest the following:
1) You imply that the system is mathematically unstable,
by the fact that your solution is divergent;
2) In working the problem associated with helicopter dynamics, i experience a similar problem. It was corrected by modeling the system by its 2 equations.
3) The equations were defined as
- state propagation, and
- measurement.
4) Stability was evaluated by examination of the eigenvalues of the Dynamics matrix A of the state propagator -- see attachments
5) Rotational velocity may be expressed in terms of it's linear velocity by
noting that v = w x R where v = linear velocity ; w = angular velocity and R is the radius vector. Note: the linear velocity in this case is expressed in a moving coordinate frame-- see Einstein equations
i am now doing simulation in DPM model
viscous k - omega species transport of N2 and C02 and injections titanium with all specified diameter distribution(rossin rammler) and temperature and starting point of injection. pressure inlet is 45 atm and particle pressure inlet is 44 atm
temp of inlet gas - 1173 K and temp of particle inlet is 323 K
mesh are very fine - 5630375 nodes
Discrete Phase Method (DPM)
Rossin-Ramler distribution
Φmin = 10 μm, Φmax = 87 μm, Φmean = 34.8 μm
Spread Φ = 3.533, # of Φ = 20, T = 50 C
tried adjusting URF !! turn off energy equation for certain iterations !!
divergence detected in AMG solver - pressure!!
Modeling a sediment transport phenomena using Volume of Fluid (VOF) method for Multiphase problem and Eulerian-Larangian particle transport method for Discreet Phase Modeling (DPM). My mesh maximum skewness is around 0.5. For solver settings pressure-velocity coupling was introduced with Green-Gauss Cell Based gradient, PRESTO! pressure and Second Order Upwind momentum. I tightened all URF (Under-Relaxation Factors) to 0.1~0.2 and used 0.001 time step size.
After running the solution for some time everything looks fine in the animation but the solver fails showing "Error: Divergence detected in AMG solver: epsilon". Anyone has any idea on how it can be solved or the error can be removed?
hello every body, I was trying to simulate fluid flow and heat transfer in axisymmetric vertical channel but when I set all condition and solve the case I got this massage (Divergence detected in AMG solver: ads-0). and when I changed 2D space to planar case is solved. what is the problem? could anyone tell me what is the problem? I tried to refine the mesh but same problem. thanks in advance
I am working on a flame affected by external magnetic field using MHD module with fluent 14.5 . I am using compiled UDF to produce non-uniform profile for boundary condition. My settings are:
Model settings: 2D, k-w SST ,Non-premixed combustion (with 8 species), Magnetic Induction model with under relaxation of 0.6
Boundary conditions: axis,velocity inlet (for fuel), the non uniform magnetic field applied in x-direction for pressure inlet boundary
Solver: Pressure Coupled
But I got the following error:
# Divergence detected in AMG solver: pressure coupled -> Decreasing coarsening group size!
# Divergence detected in AMG solver: pressure coupled -> Increasing relaxation sweeps!
# Divergence detected in AMG solver: pressure coupled -> Changing to W-cycle!
After the detected error, I used Pseudo Trandient method, but nothing was changed.
I decreased “coarsen by” and increased the pre-sweep for scalar and coupled parameters in advanced solution controls, but the error persist. I also reduced the URF of the pressure,energy,density, fmean, and B_y to 0.1 step by step and I couldn’t fix the problem.
When I used BCGSTAB stabilization method for flow I encountered AMG Divergence for k Equation. As I changed the Stabilization method for k, AMG divergence detected in the next equation. Finally I changed all of the equation to BCGSTAB stabilization method, But immediately all the residual changed to 1.#QNBe+00 and the solution is converged!
I should mention that the combustion with MHD equation was solved without Lorenz Force and Joule Heating, but as I turned on Lorenz force the solution process stopped working (with b_0 Scale factor of 0.1).
When I applied magnetic field for cold flow (combustion model is off), the problem converged without any error. And when I turned off magnetic problem the combustion is converged. In other word, but I cannot combine both of them.
Thank you in advance for your help.
I am working on natural convection heat transfer in nano fluids flowing inside vertical annulus using Ansys FLUENT 14.0. When i use UDF for viscosity as function of temperature, output results are correct. But When i use UDF for thermal conductivity as function of viscosity and temperature, divergence detected in AMG solver. How this problem can be rectified?
When i reduced the pressure and momentum relaxation factors to 0.2 and 0.5 respectively and run my simulation i get another ; Error: Divergence detected in AMG solver: vof-1 Error Object: #f
I am simulating condensation of water vapor in a vertical, square minichannel with VOF - modified HRIC, steady state, SIMPLE method and 3rd order MUSCL for energy, momentum and turbulence equations. I am having "turbulent viscosity ratio limited to.." and "temperature limited to ...". I am also encountering convergence issues with temperature AMG and sometimes VOF-1 AMG. Can anyone help or advice? Thank you
Why there are two types of transient studies for laminar two phase flow level set (tpf) module in Comsol (Time dependent and transient with phase initialization) and how to tune the parameters "phi" and "epsilon" for phase initialization? Also, what are the physical meanings of these parameters?
Same problem for the "phase field" method exists.
If anyone can help and share his experience I will be very greatful.
I am doing a CFD simulation for Plate Heat Exchangers.
I used ANSYS Fluent to perform the simulation. However during the calculation section. I received this error "Divergence detected in AMG Solver:TEMPERATURE". The error appears even when the iteration has just started
May I know what are the possible cause of this error? I activated the energy equation and also reduced the UDF (Pressure, Momentum and Turbulent Kinetic). Also, I reduced the limit of the static temperature but it seems that these 2 modifications does not help me get rid of this error.
Any advice? Thank you
I am doing the simulation of binary particles in Ansys Fluent 15.0 for 2D multiphase case. Divergence detected after 583 time steps ,and I want to know how to solve it.
I am doing the simulation of binary particles in Ansys Fluent 15.0, and also I use UDF to modified the solid viscosity, solid ressure, granular conductivity,bulk viscosity.The problem takes place when I use the partial differential equation (granular temperature model), and it doesn't appear when choose the phase property.But the partial differential equation is that I want, for I also have to add a source term.
I have tried to refine the mesh and changed the URF,but these didn't work. So, I want to know how to solve the error "Divergence detected in AMG solver: vof-2" when the partial diffenrential equation is choosed?
The erro is as followed:
# You may try the enhanced divergence recovery with (rpsetvar 'amg/protective-enhanced? #t)
Error: Divergence detected in AMG solver: vof-2
Error: Divergence detected in AMG solver: vof-2
Error Object: #f
The scaled residuals is as attached.
Thanks!
I built an electrowetting model. But when I compute it, it had some error like this:
Repeated error test failures. May have reached a singularity.
Last time step is not converged.
Does anyone have a solution for this?
Hello Dear all,Greetings
I am conducting a CFD analysis of Double pipe heat exchanger .In doing so,I am trying to compare SIMPLE vs COUPLED solution methods.SIMPLE looks fine ,but takes too much time for convergence.However,when I try to use COUPLED approach,the iteration stops after 5 or 6 iterations displaying" #Divergence detected".How can I take care of this problem?
Warm regards,
Tarikayehu
During ASPEN Adsorption simulation for single PSA bed. This message shows in simulation message: Group 9: Nonlinear solver failed. A sub-group in the decomposition failed to solve. Initialization failed at time 0.
Thank you in advanced.
I am doing transient simulation for what is called friction stir welding processes of Aluminium 6061, so far the model is facing a problem. The problem takes place when I use the UDF for defining Aluminium viscosity which is a temperature dependent property. Although, the UDF seemed successfully Interpreted, the next error appeared when running the model.
# Divergence detected in AMG solver: x-momentum -> Increasing relaxation sweeps!
# You may try the enhanced divergence recovery with (rpsetvar 'amg/protective-enhanced? #t)
Error: Divergence detected in AMG solver: x-momentum
Error: Divergence detected in AMG solver: x-momentum
Error Object: #f
Registering SurfaceMonitors, ("surf-mon-1.out")
Registering Udf, ("C:\Users\u1473797\Desktop\Deforming_files\dp0\FFF\Fluent\mu.c.C")
I was running a fluent natural convection simulation with a time step of 0.5 seconds and everything was going fine until i decided to increase to 0.7s then there was a divergence in the solution until it crashed. I've been on this simulation for the past 2 days and I can't afford to restart the simulation. I have just the case (.cas) file for the last time step saved and the CFD post compatible data file (.cdat) extension. Is it possible to restart the simulation from the last saved timestep using these files?
Thanks.
i have convex problem that start solved for first 50 iteration the after that its go to inaccurate solved .How to resolve the problem?
Hello,
I'm running 2 phase flow implicit Eularian-Eularian flow model.
created model.
defined material to each phase.
defined boundary conditions-for inlet, it's mass flow rate with initial gauge pressure defined
defined outlet pressure boundary condition- as outlet pressure values.
Then velocity slip ratio defined based on variable mass flow rate of phase 1 but constant mass flow rate of phase 2.
All above boundary conditions are defined as profile UDFs as function of flow time.
then phase coupled simple solver is used.
rest is just a calculations activities, with surface monitors.
the case successfully setup and started calculations till 300 time steps with 1 second as time step size.
after that UDF, as function of time, provides new values to the solver. and that's where everything goes wrong and suddenly I receive divergence in AMG solver. Which I shouldn't be getting since the case ran successfully for first 300 time steps
so I need help to know what exactly went wrong.
thank you,
regards,
I am solving a conjugate heat transfer case for flow through microchannels and inlet from a small opening to distribution manifold. Its a 3d case. Kindly suggest something to remove this error.
Dear Sir/ Madam,
I need your assistance, please.
I see the following error message after run calculation of ANSYS-Fluent.
“Divergence detected in AMG solver: temperature”
How can I overcome this problem, please?
Regards,
Ahmed Alkaisi
Hi all,
Commercial solvers like COMSOL and Fluent uses Algebraic multigrid methods to solve the PDEs. AMG method uses V, F, W cycles.
I was just going through a link,but i could not understand the method at all.
Can anyone please tell me a easy to read materials for beginners or explain it ?
Thanks
Vivek
Hello everyone
I am doing a fluid mechanics project on a vortex tube
I am utilizing a 3D full vortex tube with 4 tangential nozzles with a conic valve hot outlet using Ansys fluent.
But I don't know what model to use and what dimensions to apply on my 3D geometry.
When I tried, I used the standard k-epsilon model ( steady flow) with 5 bars inlet pressure with an extremely fine mesh ( around 5 millions elements ) but each time I got a problem like
divergence detected in amg solver Temperature.
I need this to be done fast and I am working hard on it.
I hope I can find someone to help me and show me how to do it properly. Best regards
Hi,
I just started to work with Fluent. I am trying to model a 2D axisymmetric problem.
The simulation is transient conduction (material has constant conductivity and heat capacity), and a heat generation that is a function of temperature.
Boundary conditions:
Bottom edge is adiabatic, sides have free convection, and top edge has constant heat flux.
For the heat generation, I interpret the following UDF:
#include "udf.h"
DEFINE_SOURCE(ecomb,c,t,dS,eqn)
{
real source;
real temp = C_T(c,t);
int A = 29.8e18;
int B = -12779.78;
source = A*exp(B/temp);
dS[eqn] = -A*B*exp(B/temp)/(temp*temp);
return source;
}
I have tried the following without success: refine the mesh, lower the timestep or the relaxation, hybrid initialization (with very low courant), and initialize with temperature higher than ambient.
Any ideas what could be the cause?
Hello,
The case is with regards to a 2-D Axis-symmetric pipe - turbulent flow - water - density varying with temperature - polynomial ( 6th order )
I have reduced the under relaxation factors for all of them to very low but am still getting the same error.
Thanks a lot.. !!!
Am solving species transport, melting and evaporation problem and I keep getting this error which reads "Error: Divergence detected in AMG solver: species-0". How do I deal with this?
I am investigating the wave propagation in a tube with a Helmholtz resonator attached to one end by using CFD. I am using a temperature profile and an UDF unsteady solver. each time I run it, fluent is giving this error 'divergence detected in AMG solver: x-momentum', floating point exception. whatever I tried, it did not go away.
Is there any solution to this problem?
