Where do you find propeller data

[drgondog]

While this is a crash-course for me: Having found some data on general aviation propellers, which may not work because of the fact that the older props generally had variations in chord and C/L as a function of radius from center to tip, and the formulas described don't factor in variable chord and CL as a function of radius as well as some searching on Google.

Zipper, There is a reason that books on Aero or Performance wave their arms in the air and state "assume prop efficiency is 0.80 (0.85)", and glib step into Thrust HP discussions. Most high performance props fit into that bandwidth. Ditto for Oswald efficiency. I'm too old and tired to devote a lot of cycles on helping you learn differential and integral calculus and the aerodynamics of propeller blades. BTW props have both Lift and Drag as a function of angle, blade section, chord, and radius from axis. Essentially if you wish to develop a Center of Pressure, integrated CL and CD, and spanwise pressure distribution - you must integrate the spanwise airfoil sections as a function of relative angle of attack, wing twist and chord. For 3-D wing, assuming a spanwise rotation from a lifting line to account for induced drag component

It appears that ß = blade angel; b = blade section in feet (I assume this is the chord); while I'm not sure what the difference between integrated and coefficient of lift, IIRC: Coefficient of lift was basically the amount of lift provided to calculated dynamic pressure or force (BTW: Does coefficient of lift and coefficient of thrust on a propeller mean the same thing?)

no.

 

[special ed]

Differential equations & Analytical Calculus are why I don't have a college degree.

 

[Zipper730]

Zipper, There is a reason that books on Aero or Performance wave their arms in the air and state "assume prop efficiency is 0.80 (0.85)", and glib step into Thrust HP discussions.

That bad eh?

 

[drgondog]

That bad eh?

How bad can it be to predict performance of multiple twisted airfoils rotating at high speed in a turbulent and rotational flow in which local velocities approach or exceed Mach1?

 

[drgondog]

Differential equations & Analytical Calculus are why I don't have a college degree.

I question the requirement for either math syllabus for Design engineers. The basic understanding of calculus is important when engaged in more theoretical analysis - as well as similarity with matrix operations - but for 99% of mechanical and structural engineering design activities I can't see the need. When I waded through MS program I took Control Theory, Calculus of Variations and Chaos Theory. Only calculus of variations was important in my experience in the abstraction of developing closed solutions for such esoteric stuff as 3-D envelopes (aircraft, wing, etc). That said, computational models developed by theoreticians are required for such esoteric models as CFD. The worst 'differential' equation to deal (for me) with was Navier Stokes - which also requires computational methods to solve because there are more variables than equations.

 

[special ed]

Those were required at USAFA in 1960.

 

[XBe02Drvr]

Differential equations & Analytical Calculus are why I don't have a college degree.

At university in 1965 the College of Science and Engineering required three semesters of calculus before a student could pursue ANY science major. I wanted to be a biologist, but found calculus hard going, so when I asked for help I was told if it wasn't intuitive to me, I didn't belong in any field of science. Engineers ruled the roost there, so I was transferred to the "College of Arts and Parties" to become a geographer.

 

[drgondog]

Those were required at USAFA in 1960.

I know - also every university with an engineering degree.

There are a lot of engineering graduates on this forum - so I would put the question? How necessary was Calculus in your engineering based career?

 

[drgondog]

At university in 1965 the College of Science and Engineering required three semesters of calculus before a student could pursue ANY science major. I wanted to be a biologist, but found calculus hard going, so when I asked for help I was told if it wasn't intuitive to me, I didn't belong in any field of science. Engineers ruled the roost there, so I was transferred to the "College of Arts and Parties" to become a geographer.

And yet one of the best textbook/reference book on drag, Hoener's Fluid Dynamic Drag has only one or two references of diffferentials - in which rate of change with respect to say CL as function of AoA. You had an amazingly negative experience with bigots that probably could not ever explain where calculus was useful in biology.

 

[special ed]

In my case, it was "oh well" if I had made it, the next year was Electrical Engineering and thermodynamics. Double E and thermo wiped out a lot of cadets.

 

[drgondog]

In my case, it was "oh well" if I had made it, the next year was Electrical Engineering and thermodynamics. Double E and thermo wiped out a lot of cadets.

Confess that EE was mostly B avg for me. Thermo/Fluid Mechanics seemed to be easy.

Unfortunately many of the academics teaching Engineering had PhD and an attitude of 'it sucks to be you' with respect to the theoretical vs practical. It is a mafia with respect to inbred textbooks.

My Engineering track at Ga.Tech and U.Texas contained a lot of raw math at the 'proof' level in which theorems ruled the early courses in differential calculus.

Amazing how such marvels as P-51, F-104, B-70 and SR-71 were managed with slide rules and Friden, then HP, calculators. I started my career in airframe industry in 67 when IBM360 and CDC6600 were the rage with 16K of memory and until applications like CAD and NASTRAN surfaced in 69-72 timeframe, computational apps were non-existent other than self developed Basic and Fortran programs.

 

[ThomasP]

I ran into a similar problem with the (theoretical) mathematics teachers, where they were teaching as if everyone had the same fascination/fixation with the math, and not how to apply it. It was very annoying to say the least, and made it significantly harder to learn what I wanted to learn. After the first class where I encountered the problem I just kept asking the teacher to show me how it could be applied. After a while (in some of the classes) all I had to do was raise my hand and the teacher would start on an example.

My sister gave me a HP programmable calculator (reverse polish notation) when I finished my Mechanical Engineering degree in '83. I remember thinking it was so cool, with its one line formula solving ability. Ah, back in the day . . . when men were men, and the newest hand held calculators had more calculating power than all of the Apollo space program.

 

[XBe02Drvr]

You had an amazingly negative experience with bigots that probably could not ever explain where calculus was useful in biology.

Unfortunately many of the academics teaching Engineering had PhD and an attitude of 'it sucks to be you' with respect to the theoretical vs practical. It is a mafia with respect to inbred textbooks.

Amazing how such marvels as P-51, F-104, B-70 and SR-71 were managed with slide rules and Friden, then HP, calculators.

Tell me about it! These guys were on a testosterone power trip. Freshman E & S students were encouraged to walk around with their slipsticks hanging from their belts in quick-draw holsters and challenge each other to "shoot-outs". Ever wonder why they didn't graduate many female engineering or science majors? The IBM 360 in the admin building that ran the entire campus actually belonged to E & S, whose students got first dibs on its academic availability.

 

[drgondog]

I ran into a similar problem with the (theoretical) mathematics teachers, where they were teaching as if everyone had the same fascination/fixation with the math, and not how to apply it. It was very annoying to say the least, and made it significantly harder to learn what I wanted to learn. After the first class where I encountered the problem I just kept asking the teacher to show me how it could be applied. After a while (in some of the classes) all I had to do was raise my hand and the teacher would start on an example.

My sister gave me a HP programmable calculator (reverse polish notation) when I finished my Mechanical Engineering degree in '83. I remember thinking it was so cool, with its one line formula solving ability. Ah, back in the day . . . when men were men, and the newest hand held calculators had more calculating power than all of the Apollo space program.

Hi Thomas - your narrative reminds me of my Academic advisor, Dr. Jack Fairchild, musing that theoretical mathematicians gleefully pursued esoteric math 'that nobody could use', and engineers gleefully applied them to real world problems/solutions.

 

[BobB]

I know - also every university with an engineering degree.

There are a lot of engineering graduates on this forum - so I would put the question? How necessary was Calculus in your engineering based career?

Even the early U-2 practice of graphing fuel flow vs time to get fuel consumed is a simplified calculus. In a thirty plus year engineering career, I very seldom consciously used calculus but probably got a lot of data given to me that had some calculus input. Gordon Israel said that he sometimes regretted his lack of formal education when he ran into a problem where he couldn't handle the math but he always knew somebody who could. On slide rules vs electronic computers, the computers tend to fool you into thinking that you have accuracy to ten decimal places when you've made so many assumptions and simplifications that you're lucky to be within an order of magnitude. Those guys with six inch slide rules in their pockets could get a quick answer that was "good enough".

 

[ThomasP]

re "How necessary was Calculus in your engineering based career?"

In all seriousness, I would have to say not very. In my life I have used calculus far more when trying to unravel the mathematics involved in my hobbies, ie 'Real' physics vs Quantum physics, astro-physics and Einstein space, old NACA reports , etc.

I will have to say, however, that having an understanding of the patterns of thought involved in the discipline of Calculus involving the construction of formulas was very helpful occasionally - both at work in engineering and in the pursuit of my hobbies.

 

[drgondog]

re "How necessary was Calculus in your engineering based career?"

In all seriousness, I would have to say not very. In my life I have used calculus far more when trying to unravel the mathematics involved in my hobbies, ie 'Real' physics vs Quantum physics, astro-physics and Einstein space, old NACA reports , etc.

I will have to say, however, that having an understanding of the patterns of thought involved in the discipline of Calculus involving, the construction of formulas was very helpful occasionally - both at work in engineering and in the pursuit of my hobbies.

I would say "occasionally" as in actually performing a Range estimate using Breguet range equation. Amusingly, the Post about Propeller calcs elsewhere was the weakest link as the prop efficiency is required. Not to mention accurate specific fuel consumption data. That said, 'few and far between' is the right answer for me.

I entirely agree that the fundamental understanding calculus and differentials in the grasp of change of one variable with respect to another is a key process to assist in thinking though many problems.

 

[ThomasP]

I have always liked the fact that Calculus was largely designed to present the data in a visual-graphic format. Although it is not always(often?) necessary in practice to do so, I found it sometimes helps in clearly grasping/understanding the interplay of forces.

 

[Aeroweanie]

I know - also every university with an engineering degree.

There are a lot of engineering graduates on this forum - so I would put the question? How necessary was Calculus in your engineering based career?

I still use calculus on a daily basis, 42 years into my career.

 

[ThomasP]

Hey Aeroweanie,

Do you mind if I ask what you do for a living? You may have said elsewhere but I did not catch it.