# Divergence detected in AMG solver. VOF.

 Register Blogs Members List Search Today's Posts Mark Forums Read

 May 7, 2021, 00:02 Divergence detected in AMG solver. VOF. #1 New Member   Join Date: May 2020 Posts: 5 Rep Power: 6 Hi guys. I'm simulating air-water flow through a T pipe with 26mm inner diameter. The pipe was created in a 2D domain, there are two inlets (one for air and the other for water) and one outlet. The two inlets have velocity inlet conditions and the outlet has pressure outlet conditions. The pipe is filled with water and then water and air start to flow from the inlets with their respective inlet velocities. I'm conducting a mesh independence test with four meshes. The time-step for each mesh was calculated based on the CFL condition and the total flow time for each one was 6 seconds. The first three simulations had no problems but the fourth one is presenting the following problems after the bubbles reach the outlet (which occurred approximately in 2,3 seconds): # Divergence detected in AMG for x-momentum: protective actions enabled! # Divergence detected in AMG for x-momentum, temporarily solve with BCGSTAB! Divergence detected in AMG solver: x-momentum# Divergence detected in AMG for y-momentum: protective actions enabled! # Divergence detected in AMG for y-momentum, temporarily solve with BCGSTAB! Divergence detected in AMG solver: y-momentum# Divergence detected in AMG for pressure correction: protective actions enabled! # Divergence detected in AMG for pressure correction, temporarily solve with BCGSTAB! Divergence detected in AMG solver: pressure correction# Divergence detected in AMG for pressure correction: protective actions enabled! # Divergence detected in AMG for pressure correction, temporarily solve with BCGSTAB! Divergence detected in AMG solver: pressure correction# Divergence detected in AMG for k: protective actions enabled! # Divergence detected in AMG for k, temporarily solve with BCGSTAB! Divergence detected in AMG solver: k# Divergence detected in AMG for omega: protective actions enabled! # Divergence detected in AMG for omega, temporarily solve with BCGSTAB! Divergence detected in AMG solver: omega Divergence detected in AMG solver: x-momentum Divergence detected in AMG solver: y-momentum Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: k Divergence detected in AMG solver: omega Divergence detected in AMG solver: x-momentum Divergence detected in AMG solver: y-momentum Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: k Divergence detected in AMG solver: omega reversed flow in 118 faces on pressure-outlet 9. Divergence detected in AMG solver: x-momentum Divergence detected in AMG solver: y-momentum Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: k Divergence detected in AMG solver: omega Error at host: floating point exception 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 Error: floating point exception Error Object: #f I checked the mesh quality and it looks good (min orthogonal quality = 0.68; max skewness = 0.60; max aspect ratio = 10.07). I tried to solve the problem by reducing the time step in half and decreasing the relaxation factors, but it didn't work. I don't know how to fix this problem, so I really need some help and I'm open to answering any questions. I'm going to list every piece of information I find relevant about the simulation. General: Parallel Solver type: Pressure-Based Time: Transient Planar 2D space Gravity on Models: Multiphase VOF with explicit formulation and Surface Tension Force Modeling (CSF) Default Courant number: 0,25 Implicit Body Force Turbulence Model: SST k-omega Cell Zone Conditions: Specified Operating Density: 1.225 kg/m³ (air density) Boundary conditions: air inlet velocity = 0.123 m/s water inlet velocity = 0.6 m/s outlet Gauge Pressure (pascal) = 0 pipe wall: stationary, no slip Solution Methods: PISO Scheme Least Squares Cell Based Gradient PRESTO! Pressure volume fraction: Geo-Reconstruct Momentum, Turbulent Kinetic Energy and Specific Dissipation Rate = Second order upwind Transient Formulation = First order implicit Solution Controls: Default Residuals = 10e-5 Standard initialization with default initial values

 May 17, 2021, 14:07 #2 New Member   Maharshtra Join Date: May 2021 Posts: 1 Rep Power: 0 You got the solution of this problem ?

 August 31, 2021, 19:42 #3 New Member   Join Date: May 2020 Posts: 5 Rep Power: 6 Hi Harshad Bhalerao, I still dont know the answer. It has been months since i posted this and nobody posted a reply.

 September 21, 2022, 04:34 #4 New Member   CHEN TING Join Date: Sep 2022 Posts: 1 Rep Power: 0 can you solve it

September 25, 2023, 07:10
AMG solver divergence
#5
New Member

Outside North America
Join Date: Nov 2021
Posts: 14
Rep Power: 4
Quote:
 Originally Posted by Mr.Mister Hi guys. I'm simulating air-water flow through a T pipe with 26mm inner diameter. The pipe was created in a 2D domain, there are two inlets (one for air and the other for water) and one outlet. The two inlets have velocity inlet conditions and the outlet has pressure outlet conditions. The pipe is filled with water and then water and air start to flow from the inlets with their respective inlet velocities. I'm conducting a mesh independence test with four meshes. The time-step for each mesh was calculated based on the CFL condition and the total flow time for each one was 6 seconds. The first three simulations had no problems but the fourth one is presenting the following problems after the bubbles reach the outlet (which occurred approximately in 2,3 seconds): # Divergence detected in AMG for x-momentum: protective actions enabled! # Divergence detected in AMG for x-momentum, temporarily solve with BCGSTAB! Divergence detected in AMG solver: x-momentum# Divergence detected in AMG for y-momentum: protective actions enabled! # Divergence detected in AMG for y-momentum, temporarily solve with BCGSTAB! Divergence detected in AMG solver: y-momentum# Divergence detected in AMG for pressure correction: protective actions enabled! # Divergence detected in AMG for pressure correction, temporarily solve with BCGSTAB! Divergence detected in AMG solver: pressure correction# Divergence detected in AMG for pressure correction: protective actions enabled! # Divergence detected in AMG for pressure correction, temporarily solve with BCGSTAB! Divergence detected in AMG solver: pressure correction# Divergence detected in AMG for k: protective actions enabled! # Divergence detected in AMG for k, temporarily solve with BCGSTAB! Divergence detected in AMG solver: k# Divergence detected in AMG for omega: protective actions enabled! # Divergence detected in AMG for omega, temporarily solve with BCGSTAB! Divergence detected in AMG solver: omega Divergence detected in AMG solver: x-momentum Divergence detected in AMG solver: y-momentum Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: k Divergence detected in AMG solver: omega Divergence detected in AMG solver: x-momentum Divergence detected in AMG solver: y-momentum Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: k Divergence detected in AMG solver: omega reversed flow in 118 faces on pressure-outlet 9. Divergence detected in AMG solver: x-momentum Divergence detected in AMG solver: y-momentum Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: pressure correction Divergence detected in AMG solver: k Divergence detected in AMG solver: omega Error at host: floating point exception 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 Error: floating point exception Error Object: #f I checked the mesh quality and it looks good (min orthogonal quality = 0.68; max skewness = 0.60; max aspect ratio = 10.07). I tried to solve the problem by reducing the time step in half and decreasing the relaxation factors, but it didn't work. I don't know how to fix this problem, so I really need some help and I'm open to answering any questions. I'm going to list every piece of information I find relevant about the simulation. General: Parallel Solver type: Pressure-Based Time: Transient Planar 2D space Gravity on Models: Multiphase VOF with explicit formulation and Surface Tension Force Modeling (CSF) Default Courant number: 0,25 Implicit Body Force Turbulence Model: SST k-omega Cell Zone Conditions: Specified Operating Density: 1.225 kg/m³ (air density) Boundary conditions: air inlet velocity = 0.123 m/s water inlet velocity = 0.6 m/s outlet Gauge Pressure (pascal) = 0 pipe wall: stationary, no slip Solution Methods: PISO Scheme Least Squares Cell Based Gradient PRESTO! Pressure volume fraction: Geo-Reconstruct Momentum, Turbulent Kinetic Energy and Specific Dissipation Rate = Second order upwind Transient Formulation = First order implicit Solution Controls: Default Residuals = 10e-5 Standard initialization with default initial values

Hello, I recently encountered the same problem as you. Do you know the reason for this mistake? Thank you!

 Tags amd divergence; vof; 2d