The high rpm of the turbocharger's impeller causes high stresses on the bearings. That and the chance of intermittent oil flow during maneuvers would drastically shorten the life of the supercharger. The same thing could be said of engines, but I'm erring on the side of caution and simplicity by avoiding turbo/supercharging and non-geared engines.Please explain.
I have a 16 core processor with 32GBs of RAM, a couple more iterations doesn't take that much longer :grin:As do I. It has a bug that I discovered and which was verified by SW: an external centerline-symmetrical flow analysis has significant errors along a significant strip of cells near the centerline. Cells away from the centerline are ok. (I've run a 767 half model at work with most excellent results for airflow along a sensor window away from the centerline.)
Even though a full model has more cells, it will solve faster (~2.5X to 4x fewer iterations!!!) than the half model. (Some of my half models had goals that never converged; I had to terminate the runs.)
When I told SW I'd update my seat if they fixed it, they said weren't going to. Notice the caveat in the instructions: don't use symmetry unless you know it won't cause errors.
This error will affect your analysis: you will probably get nose down pitching from your canopy and nose up pitching from the canopy downwash onto the aft fuselage. These numbers need to be correct to get a correct pitching moment. You can SWAG the canopy effect by hand calcing it as a little fat wing. Multhopp's method probably won't catch this.
If you doubt what I'm saying, run a test for yourself: run a hershey bar wing all by itself with centerline symmetry and full span. Notice the flow anomaly near the centerline. Compare the lift, drag, cp, and pitching moments, both to each other and to the hand calc numbers.
Thanks for the input.One big point.
Your design is really spread out. The back seater is fully aft of the front seater, which has tails. There is excess space between the front seaters feet and the engine. The back seater has big influence on CG, as does the aft baggage. This also adds length to the fuselage immediately, raising overall weight and reducing performance. The fix for all of this aft weight is a bigger tail and a more forward engine than you might otherwise have had, further adding wieght, which further reduces performance.
Fix? A couple things and then a bunch of iterating.
Move the back seater forward, putting the rudder pedals for the back seater next to the thighs of the front seater. That slides the backseater and aft baggage forward by about 30 inches, reducing the aftmost CG by a bunch, reducing the bending moments and weight, and improving the difficulty in making it work and have utility too.
Next, once you have the people closer together and the aft baggage less aft too, now start looking more seriosuly at the range of cg you have and start iterating the locations of the engine forward of the firewall, people and bags aft of the firewall, maybe play with splitting some of the bags forward and having a movable battery, balanced angainst how big the horizontal tail has to be to keep it all controllable and landable over the whole range of weights for fuel, peopel, and bags.
Once the people are closer together and you start looking at CG and tail size needed to flare while keeping enough static margin, you can come up with a shorter canopy with a more streamlined after section and perhaps take out some weight in both the fusealge and tail. You may still need to extend the engine mount a little to make it all work, but that is not the end of the world, it makes for more forward baggage, which lets you reduce your aft baggage, further streamline the bird aft of the wing, annd further reduce the tail area needed...
In all, you can take out weight while improving utility and performance.
Having ridden in the back of an RV-8 and -8A, which are set up with the "pedals" (such as they are) on either side of the front-seater, I can understand you. Some people are fine in that position, but both times I was quite anxious to get out after only half an hour. In that seating position you can't much do anything with your legs but push pedals. The lack of freedom of movement was killing me.For the rear pilot, I am adamant about there being two full sets of controls. I've flown in aircraft with the back rudder pedals spread out to the side and we're not doing that. So the placement stays. Adjustable seats are planned and the humans depicted are 6' tall; the seats move up/forward and the pedals back to accommodate shorter pilots.
Did not mean to offend, but to inform. Allow me to detail them.Thanks for the input.
That was looked at: there actually is no excess space between engine and the front pilot. What I didn't model were all the accessories behind the engine.With those, there is less than 12" between the engine and the firewall. The pilot's feet are 6 inches from the firewall, which is exactly how much space he/she needs for pedal movement.
For the rear pilot, I am adamant about there being two full sets of controls. I've flown in aircraft with the back rudder pedals spread out to the side and we're not doing that. So the placement stays. Adjustable seats are planned and the humans depicted are 6' tall; the seats move up/forward and the pedals back to accommodate shorter pilots.
Based on current component placement, the static margin (which is only a rough estimate of stability) ranges from 14% with only the forward pilot and no baggage, and 9% with rear pilot and 50lb luggage.
Yep, it's going to be a big bird. Just took the tape measure to the fuselage of my L-39 (a diminutive thing, for a jet), and it is over 10 feet between the forward bulkhead and the rear. That's 10+ feet of cockpit floor. That's a true dual cockpit, with essentially identical control stations front and rear, with no overlap....If you do slide a tandem rear seat all the way clear of the front seat, you will have a very long fuselage. Lots of extra to carry around...
Be careful with flow separation predictions using Flowsim with the out of the box settings.Looks like there's some flow separation ...
Sounds like I have an additional item to verify during the test flight via a tuff test...Be careful with flow separation predictions using Flowsim with the out of the box settings.
I purchased this program for home use after it gave exceptional correlation at work to wind tunnel tests and to flight tests for separated flow off a bluff body and for boundary layer flow.
After I encountered some discrepancies with separated flow off surfaces at much shallower angles to the flow, I was advised that the program has internal parameters that are set to more accurately predict bluff body separation at the expense of shallow angle separation. I was told the only way to tweak these is by a series of tests comparing CFD to real flow results. I had neither the time nor the money to do that.
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