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In WF4 Mechanica, I keep getting a fatal error after the analysis has begun with the alert: "Highlighted solid element has singular mapping". When I validate the mesh beforehand, it doesn't give me an error then. And the highlighted element never looks unusual. What the heck is singular...

I've recently noticed that Mechanica will mesh using any datum points in the model. As I am analyzing a fan blade with 4500 datum points (for profile curves) and I really don't want the mesh to be that fine, how do I tell Mechanica to not mesh using datum points? The work-around I currently...

I am wondering if drag coefficients apply only to moving fluids (dynamic pressure) or if they can also be used for calculating force on an object due to static pressure. The static pressure in this case is due to static pressure rise across a normal shock in a supersonic wind tunnel. The...

Sheiko, Thanks for the suggestion but 1) I'm a mechanical engineer. I'm trying to derive the thrust for a simple model rocket engine (.1 inch throat) which is part of a larger model to be tested in our 1'x1' Mach 6 wind tunnel. I only need to do this once and then I have to move on to other...

Thanks Latexman. I've been told that the volume % of a gas = the mole % and I've read it too but I didn't understand it until I worked the numbers. Where would you divide by MW in my mole fraction equation? I'm looking for the easiest way to calculate the molar fraction. My method seems to...

Wow, that all makes this clear as mud. It reminds me why I cared so little for chemistry in high school and college. Could never get a definitive, uncomplicated answer then either :) I'm working with 79% Helium, 21% Oxygen. k He = 1.667, k O2 = 1.4. The first way I calculated the specific...

Is the specific heat ratio (isentropic expansion factor) of a gas mixture simply a molar weighted average of the individual heat ratios? If not, how is it calculated? I apologize if this is not the correct forum for this question. The other forums that might be more appropriate seem to be...

To rb1957: The ID is machined after the epoxy cures. This has been done before several times. I didn't mention it since I didn't think it mattered how the epoxy thickness was arrived at. :) It's the holes that are new. I just work for a contractor. NASA comes up with the far-out ideas...

I definitely like the idea of edm-ing the holes before the epoxy is applied. Of course, plugging the holes and then de-plugging them would not be much fun... Are you suggesting an automated process for plugging the holes? How does the wire plug stay in the hole? Interference fit? The...

Thanks for your help so far. Corypad: I was told that the $8,000 electron-beam thingamajig would be ruined and only received a no-quote. The electron beam works in a vacuum and the epoxy particles (molecules?) would collect on the optics. I guess the off-gas problem would affect the optics...

Actually, the holes go through both the aluminum and epoxy so laser is out. This is what I meant when I wrote that the epoxy will off-gas and ruin the laser. I do like TheTick's suggestion to drill the epoxy to make way for EDM. However, we are still talking lots of machine time and $$$...

I am trying to find a machining process for making 63,000 very small (.020” dia) holes through .200” thick 6061 aluminum with .050” layer of epoxy (Scotch-Weld, Shore D hardness = 55) bonded to it. Hole spacing is .056” resulting in 318 holes per square inch. The holes do not have to be...

I think everyone has contributed helpful information except it still doesn't answer the problem. RGasEng: I agree that this would be simple for sub-critical flow. However, with an inlet pressure of 2215 psia, and an outlet at 55 psia, this is definitely critical flow for at least one...

In my system, which is supplied by a 2200 psig, 50 Liter Nitrogen bottle, I am required by NASA safety requirements to use two pressure regulators in series in case one fails. I need to size a relief valve which will be able to handle the flow at the downstream pressure (55 psia). Although I...