Thank you for your answer. OK. I realize that I have tested an old version. I only have access to my old laptop with windows XP (32 bit) for the moment. I will have access to my new 64 bit machine in a week or two. Perhaps I will perform a new test with that

I don't have any earlier experience with CFD on my own. I am an electrical engineer (MScEE) with skills in mechanical engineering and embedded software design. I design (mostly) electronics as a hierd engineer. My clients have asked for simulations of air flow and heat exchange and I thought it was good to test this for myself. I am using a lot of simulations in my designs (electrical simulations with SPICE and mech simulations (forces only) with COSMOSExpress built into SolidWorks). I would like to be able to recommend my clients a good CFD for heat transfer. I will test other CFD/FEM simulators and attend seminars in the close future. I like your idea "CFD for all". That is the reason for my tests and I see the feedback to you as my way to give something back and hopefully get a better application in the future. I hope you don't find my email too long or uninteresting

I continued with Caedium using STEP-files instead of IGES after your recommendation. That worked better, but I couldn't get Caedium to handle volumes assembled from multiple objects. I also didn't manage to simulate flow in voids (volumes trapped by solid (thick) walls), I had to convert the voids to volumes and remove the wall thickness. This will be quite hard with a model of a circuit board

I also couldn't get Caedium to solve the equations when I have a slanted wall for input or output. I am not really sure that this is the reason, but I performed several tests that show this. I got results that say that the flow of air makes a narrow right angle turn when it comes into a large open volume. I attach the simulation file so you can see what I mean. The geometries are just test geometries so I have no real data to compare with, but the result is just ridiculous. I don’t see why the flow shouldn't be close to symmetrical in a completely symmetrical volume. I could have done something wrong though. Please let me know if you want more information like the STEP-file or native model file or if you find whats wrong

I think a lot of my frustration with the controls is that I have a feeling that I need to answer "yes" to the same question many times for everything that happens. Like everything needs to be confirmed twice in two different ways. I think that selecting things should be one mouse click only (left!). No confirmation. Then a clearly visible highlight of that object (not just thicker black that can’t be seen when out zoomed). If my select is wrong then I just click ones more. If I want to apply a command I don't want to confirm that or press apply a second time. If it goes wrong then I "undo" that command and simply change the feature of the command. (Ctrl-z should preferably be implemented as undo.) An applied command needs to change something visually. I.e. no "silent" commands. For instance if I add air in a volume this could me marked with (x) after substance or something

Besides that I don't think that the media (air) got so much to do with the speed of the air. This should be set separately. It feels ambiguous that you can set the air speed in "air" and then there is a "velocity" command that does (?) nothing. I couldn't get it to work. A vector is nice, but setting a scalar value for velocity that is perpendicular to the input face is probably much more common. I didn't find anywhere where I could specify a (back) pressure as a boundary condition in the outlet. This could be due to inexperience from my side, but its not easy to find. It could also be useful to have an option of setting the output flow to be laminar. In the example I send you I have a reverse flow velocity in the outlet (input flow that in the outlet) in one point of a magnitude more than my inlet flow!&newline;I suggest you use colors in your wire frame/solids models. Like green for things selected, red for input surface, blue for output, lighter gray for faces that are not walls. A simple button to switch between solid walls and wire frame would be nice. A simple button to switch on and of the mesh. Why do I need to select all faces as walls? This could be default. The fluid inside the volume could also default to air or whatever selected last time. Particle tracks and vector fields can be done much easier like a pop up dialogue when right click a face. You could use left button to select and right button to show preferences. WITHOUT asking for confirmation! Ctrl+left button selects more (or removes selective). Pushing several times in the same location toggles selection between the possible things to select. Edges are selected on edges and faces only between edges. Volumes should probably never need to be selected in the view. They can be changed in an operations tree that should contain all starting conditions clearly viewable/changeable. Colors of highlight and also mechanical parts like wireframes should be selectable or visual or not with a simple button. (All "simple" button suggestions refer to buttons in a toolbar.)&newline;I read through the "Play, Interrupt, and Freeze Controls". This doesn't make sense to me at all. I either like to change the simulation conditions like boundary conditions, change my model, speed and start all over with the simulation. Or I like to save the result. I can't see that there is anything between that I like to "roll back" to. These buttons seem to destroy both my boundary conditions and the unusable result and in the same time not resetting the software enough so my next result will be impaired by the previous result

I think that a good idea is to make the simulation able to run in two separate stages. Like one button for meshing and another button for differential equation solving. It seems like the mesh is viewable when the faces are solid (non transparent). The mesh could also be viewable in wire frame mode (transparent) with a separate toggle on/off button. As it is now the meshing takes place by itself when accuracy is changed. Say that I have a simulation to do over night, then I like to wait with the mesh until everything else is ready to begin

Don't put any more effort in the mechanical design parts of the program. You will never be able to come close to a mech design software. Its better to put effort in import/export of model data

I didn't understand this part of your answer: "If you want a model tree, then select the background and the Select dialog has the entire model in a tree." How do I "select the background"? Left click in view window does nothing, right click gives a dialogue for model entities, but it contains no information on the fluid media selected (attached to volumes), no information on boundary conditions, no marking on input surface or output surface, nowhere where I can change accuracy or see what is selected. The mechanical entities are only a very small part of the starting conditions. Please refer to the design tree of SolidWorks (similar to many other modern mech design SW). I think this would be a better thing to have on the screen instead of all the commands. Or why not list the selected faces under "inlet"? Then I can review and change the selection. Usage of +/- like an expandable tree helps

As I wrote before, no I haven't used any other CFD but I don't see a reason to why this should be complicated. I know that the FEM-analysis is not trivial, but the user interface could be. It feels like a poor excuse that there are others that are worse.