As computer specifications increase out in the market it is natural for anyone to want to apply all available resources to increase their job productivity. We will discuss how RAM is utilized in SOLIDWORKS Simulation. The common misconception with a computer that gets an increase of RAM is that it will increase your performance speed of your simulations. This is in fact incorrect, although increasing the amount of RAM may slightly increase speed as a side effect, it is primarily meant to increase the number of degrees of freedom (DOF) that can be calculated on any given Simulation study. If this fact is not known or clear, users may become puzzled as to why when solving their Simulation studies they notice in the Windows Task Manager that only a small portion of the RAM on the machine is being used. In most cases the answer to this is that the study may not need all of your RAM to run the calculation.
There are many factors that contribute to the amount of RAM Simulation will use that involve the setup of your study. Anything from the combination of options you check-boxed in the study properties, to the constraints you have created in your study may affect your DOF. We will review three major contributing factors that directly affect the DOF. To begin with, since Simulation only uses the amount of RAM it needs, the mesh size and order of your mesh in your study is an important factor in determining the amount of RAM the system will utilize. Having a coarse mesh with the Draft Quality Mesh option turned on (1st order elements) will typically amount to the least RAM usage while having a fine mesh with a high quality mesh (2nd order elements) combination will cause the most RAM being used. Next, since not all studies use the same kind of elements to mesh your model, element types can play a role in RAM usage. Solid tetrahedral elements will typically take up the most RAM due to the amount of calculation nodes it utilizes, where as beam elements will use the least amount of RAM. Shell elements fit somewhere in between the two element types in RAM usage in a typical Simulation. Most importantly, it boils down to the total number of DOF the element types yield: 3 DOF per node for solid elements and 6 DOF for Shell and Beam elements.
Since the majority of the RAM used in Simulation involves the DOF calculated in the study, there is one more factor that we need to consider. This is the type of solver the Simulation utilizes. There are two major solver types utilized in SOLIDWORKS Simulation, Direct Sparse and FFEPlus. Direct sparse requires much more RAM than the FFEPlus Iterative solver. It has been documented that the Direct Sparse solver for a linear static study will use about 1 Mb for every 200 DOF while the FFEPlus solver is significantly less demanding at around 1Mb for every 2000 DOF (SOLIDWORKS Knowledge base, S-037675).
After reviewing how RAM is used in Simulation as a best practice it is always better to have more RAM than not enough. Not enough RAM may result in an “Out-Of-Core Solution” warning message that indicates the amount of RAM currently available is not sufficient to store all the data needed to perform the calculation. At that point the study will begin to use the Virtual Memory (paging file) on your hard drive to continue the calculation. This will severely reduce your calculation speed to the data transfer rate of your hard drive. Having More RAM available on your computer will eliminate the risk of this potential performance bottleneck.
If you do run out of RAM during calculation, in 2014 and future versions of Simulation, there is another solver type available called “Large Problem Direct Sparse” which uses enhanced memory-allocation algorithms for data caching to help calculate simulation problems that exceed the RAM limitations of your computer. This solver type is only available for Static and Nonlinear studies at the moment but is a good start to have a solution for the calculation of large scale studies that normally would not solve in previous versions of SOLIDWORKS.