Drag and density relationship

Drag Force, Velocity, and Area Calculation

Tech Log - IAS, Drag, Density, TAS - Hello all.. I have a question regarding the relationship between IAS, Drag and Air Density (and also TAS I. Like friction, the drag force always opposes the motion of an object. Unlike simple When taking into account other factors, this relationship becomes. {F}_{\text{D}} =\frac{1 (Recall that density is mass per unit volume.) This equation can also. Drag increases with the density of the fluid (ρ). More density The hard part of this relationship lies in the detailed way speed affects drag. According to our.

Drag equation

Of course there may be greater efficiency at high speed, but would we really expect a ton of kerosene to produce twice the power simply because we're flying twice as fast? And if you look at a cutting-edge turbofan like the RB oh well, it's only 40 years oldthrust specific fuel consumption is indeed vastly higher at higher speeds. That doesn't mean that power specific fuel consumption is constant either, it's substantially lower at higher speeds.

But we're nowhere near the "ideal jet approximation" of constant TFSC. Isn't TSFC just a useful ratio to measure with no real presumption that it's independent of speed? Well perhaps, but when we start suggesting e.

Thus, increasing speed is the simple solution to maintaining the required lift. This line of reasoning brings us to an interesting question.

If drag keeps decreasing as density decreases and the aircraft can fly faster and faster, then why don't planes fly at even higher and higher altitudes until the density, and the drag, become zero? This issue leads us to the effect of density on propulsion. As you can read about in a previous question on jet enginesengines operate by compressing incoming air, mixing the compressed air with fuel, burning the mixture, and exhausting it to generate thrust.

IAS, Drag , Density, TAS - PPRuNe Forums

This process becomes more difficult as the air density decreases because the compression is less efficient. The air density eventually decreases so much that there is not sufficient compression to support combustion. When this occurs, the engine will "flame out" and the plane falls into a dive until density increases enough for the engine to be restarted. Piston engines suffer from similar effects at high altitude for two reasons. First, the piston engine is also an internal combustion engine like the jet.

More on this subject later in this section. A nice equation to work with — or is it? Well, yes and no. Yes, but it works only as long as the range of conditions examined is "small". That is, no large variations in speed, viscosity, or crazy angles of attack.

The way around this is to reduce the coefficient of drag to a variable rather than a constant. I can live with this. Say that C depends on some yet to be specified set of factors. It is totally acceptable to say that it varies with this that or the other quantity according to any set of rules determined by experiment. No, since speed is squared.

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Have you ever tried to solve a nonlinear differential equation? Well, welcome to hell. Wait, let me rephrase that — Welcome to Hell!

Just wait till you see what's in store for you when you try to solve the differential equations. The mathematics will consume you.