What is the cause of the floating point error message during Fluent simulation and how can it be addressed?
January 25, 2023 at 7:16 amFAQParticipant
The issue of ‘Floating Point’ error can be related to either the hardware on which the simulation is being run or the model settings of the case in Fluent. Hardware Related Hardware based reasons for this error are as follows: 1) The CPU or OS is 32-bit only. The maximum address space of a 32-bit machine is 4GB (2^32-1), out of which space has to be reserved for the Operating System (OS) related processes, leaving a usable memory of close to 3 GB or less. The floating point error may be due to this memory limitation if your computation requires more than the available memory. The solution would be to go for parallel computing using a multi-processor machine orm upgrading to a 64-bit system. 2) The memory required for a simulation depends on the mesh size, solver settings, physical models, etc. Generally 1GB RAM is sufficient for 1 million cell case with a basic pressure-based solver in single precision mode with no additional models turned on. But with double-precision mode (which is recommended for computational accuracy) and addition of other models (turbulence, species/reactions, multiphase etc.), the memory requirements increase due to the additional variables that need to be stored at any iteration. So, depending on the available RAM it is possible that the limit of available memory is being surpassed for the computation. This can be addressed by increasing the available memory (upgrading to a higher memory machine) or using a multi-processor system. Software Related On the software side, floating point error usually indicates a mathematical operation where a variable is divided by zero leading to an undefined value. This might happen due to several reasons mentioned below: 1) Mostly floating point error issue is related to the wrong solver settings, boundary conditions, and initialization set-up. Please ensure that the different numerical and physical parameters are set correctly before starting the simulation. 2) If there are any UDFs used for boundary conditions please make sure that the values of all variables fall within a physical range and that the UDF is hooked at the correct boundary. 3) Before starting the simulation please check the Reference values set in Report > Reference Values panel to ensure they are cvorrectly set for the problem. 4) Please check the mesh quality to ensure that there are no invalid, highly skewed (orthogonal quality < 0.02)cells.
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