Recent content by Dusan Stan

Lesson learned. After more experimenting: - different frequencies and measurement methods; - even filling most of the space of the clamp with leftover transformer I cores, the measured current stays the same. The idea was to find a way to prevent generation of external magnetic field without...

It seems I don't understand how magnetic shielding supposed to work. I tried shielding a wire, using some ferrites, but it doesn't work. I assumed the magnetic field will concentrate in the magnetic material, bypassing the meter magnetic loop, so less will be measured by the meter. I thought the...

Can I ask where is this from? I have a similar problem.

You could optimize the lift loading to be elliptical. And as CWatters suggested use an airfoil that provide more L/D for your specific Reynolds number.

Ha! It definitely seems that I'm confusing asymmetry and dissymmetry. I agree that the dissymmetry is the primary cause limiting the helicopter speed, but if the rotor was smaller, the retreating blade would be faster, and the stall delayed at a higher speed. All this at the expense of a lower...

Helicopters have indeed big rotors, and only because they need to have a lot of thrust for the static condition, when they are hovering, to increase figure of merit. Those big rotors are also an impediment for attaining high speeds, as drag increases, forward speed creating asymmetry of lift and...

The speed in the efficiency calculation is not the speed of air induced by the fan, but the speed of the aircraft trough the air. It is right there in the quoted paper:"For the same horsepower, the amount of static thrust that you can produce just keeps going up with diameter. This increased...

What you are saying is true for statically produced thrust, your link presents axial fans for ventilation, not really suited for aircraft. At higher speed, the propeller diameter starts to be less important, same input power theoretically generating same amount of thrust. Propeller efficiency...

As presented here: http://www.jefflewis.net/aviation_theory-theo_prop_eff.html, two propellers, one of 8ft and another 16ft are generating similar theoretical thrust above a certain forward speed (see the last graph), calculated for same input power, but without taking into consideration the...

@watters: A smaller propeller would need to rotate faster, but the tips speed would be the same; the bigger propeller having more surface spinning faster, so having more friction.

So far as i got the bigger the better, in theory, or at slow speeds, and I totally got this; and it makes sense, lower kinetic energy and low disk loading. But at higher speed, a bigger propeller will have actually have a higher drag than a smaller propeller, and excluding the transonic tip...

Thank you jedishrfu, I got some more info on this. The propeller blades act as airfoils, lift and drag acting as thrust and torque, respectively. One would want to drive the propeller at a optimum L/D ratio, generally alpha at about 5 deg as exemplified by Clark Y airfoil characteristics (...

The video shows some optimisations on the turbofan engine and reaches the conclusion it needs to be about 4m. The premise is that accelerating more air a little is more efficient than accelerating less air to a higher acceleration and speed, fact mentioned in all aerodynamics books, and that...

I found the most reasoning explanation for visualizing electrical phenomena is the hydraulic analogy: https://en.wikipedia.org/wiki/Hydraulic_analogy

Nice information guys! Returning to the original subject, If you consider the thrust created from the momentum theory perspective, a thin disk having pressure difference acting on the sides of it, Thrust = Disk_Area * Pressure_Difference; The pressure difference is not constant, it diminishes...