Drag Definition and 751 Threads

I am working on simulating the movement of small spherical objects under the influence of drag and a number of other forces that, at least for now, don't depend on the object's velocity. Normally I would sum up all these forces, including drag, to ##F_\Sigma## and update the object's speed...

Since given F = -kdx/dt so I equated mx'' = -kx' which gave x(t) = A + B exp(-kt/m) hence v(t) = (-kB/m) exp(-kt/m) and using v(0) = u, v(t) = u exp(-kt/m) then I...

Hello, I would like to understand know how the lift coefficient ##C_L## versus AoA curve and the drag coefficient ##C_D## versus AoA curve are determined for the various tabulated NACA profiles. Are computer simulation run for the different profiles assuming a certain Reynolds' number? Or can...

Tell me now if this question is posted in the wrong place. This isn't a homework problem per se, it's just a question I need answered and I'm not sure how to answer it. If there is any information missing, chances are I know it and forgot to post it, so please ask if something is missing. I...

So I'm trying to figure out how to model a ball getting thrown vertically with the starting velocity v_0. So I've come up with a differential equation which I'm pretty sure is correct: Where D is a constant. So far so good. My problem is solving this. This is my attempt: And when i do this...

θ = 4 μs = 1 Fnet = Wpararell + fs m.a = 1/2.m.g.sinθ + μs.1/2.m.g.cosθ (divide by m) a = (g.sinθ+μs.g.cosθ)/2 a = ((9.8)sin4 + (1)(9.8)cos4)/2 a = 5.23 m/s^2 hello guys, I'm having trouble with this problem. Can anybody help me correct my attempt and explain it to me?? thanks

I first wrote down that 55% = Eout/Ein I also know that W = (Facos20)(4) and I substitute it into the first equation 55% = Eout/[(Facos20)(4)] But I'm missing two variables here. Did i forget something or is the question missing some information?

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Summary: Hello, I have a task to calculate the air drag coeficient experimentally. I have a cone which I had dropped from height of 1.5 m and measured the time. Then I derived the equation of of velocity and acceleration but they are very complicated. Is there any simpler method? a=g-k/m*V^2

Here is my attempt at setting up the equation: I set up the equation to find the acceleration of the box: F-Ffr= m*a after finding the acceleration, I can use the acceleration and plug it in the formula v^2=(v0)^2+2*a(x-x0), which will get me the value of (x-x0)The solution sheet says that F...

Stokes' Law gives us the value fo viscous force when a spherical body is under motion inside a fluid. ##F_{viscous} = 6\pi\eta av## (where ##a## is the radius of the spherical body and ##v## is the velocity with which it is moving) What is the reason for the Viscous drag to depend upon the...

(New thread following up to a conversation in another thread). I'm using SimFlow 3.1 with OpenFOAM 5 on Linux to try to evaluate the drag coefficient of a water rocket body, constructed from a 2-liter Coke bottle with a conical nose, traveling through air at 77 m/s. This should be a simple...

So using FBD, I came out with: since it reaches terminal velocity, I can assume F=0, thus mg = upthrust +drag So my density = mg - drag force/g * volume However the answer seems to be wrong from the answer key I was given. Any ideas why? Thanks

Hi there, I have modeled with MAXSURF a few variations of a prehistoric logboat in order to test a few theories. Now, I am trying to look at resistance-performance over a range of speed. To do so, I need to include a constant drag coefficient without knowing the drag force and velocity (both...

So as stated, I am calculating the pressure and drag forces on an obstacle, but have trouble with which velocities to take. This is my geometry: http://shrani.si/f/3l/13P/2Tihb3iM/projekt2.png . I am guessing that I have to take pressure just before the obstacle and just after the obstacle and...

hello i want to plot the drag coefficient vs x-coordinate using fluent 6.3.26 best regard

MODERATOR NOTE: NO TEMPLATE - MISPLACED HOMEWORK Hi All I was hoping someone could help with the following problem:- Concrete is being pumped along a pipe. All of the concrete that is more then 10cm from the wall of the pipe is moving at 0.2m/s, and the material in contact with the pipe wall...

It doesn't seem likely given that electrons in copper wire move even faster and i can't find anything on electric circuits creating frame drag. I don't expect anyone to tell me why there is no micro-frame drag . Likely the question itself contains some false assumptions. And thanks for your...

Hi! Does anyone know what drag coefficient has a person in a water slide? I've only found for full vertical/horizontal body, but not for a person in a water slide, considering it has a slope. Related to that, the cross area of a person can be calculated? Thanks.

Hi, My other post got deleted because it was flagged for spam, but it was just a link to a pdf. So I'm uploading the pdf instead. I am working on a model to predict drag on airfoils in 2D potential flow (e.g. vortex panel methods). Currently, XFOIL uses a semi-empirical wake-momentum-thickness...

1. A 20-lbf disc with diameter 18" and thickness of 3" is held static while completely submerged in water. Upon release of a lock, the disc experiences a torque from a torsional spring that causes rotation about its center of mass along the x/y axis (think coin toss, not wheel). If the spring is...

Hi all, I understand that both winglets and raked wingtips are for the same function (from what I have read) - to reduced the amount of induced drag. I understand the principles behind winglets, however I am uncertain how raked wingtips actually achieve this? Could anyone please explain the...

I am looking for a bit of guidance on how one could calculate the drag force of a sphere with holes in the sphere falling through a fluid, in my case water. So I know for a low Reynolds number the drag force on a sphere is given by stoke law, but what I would like to do is calculate the drag...

[Moderator: link removed] Can a jet engine the size of the tunnel mean that you can have an effectively have drag-free vehicle? Any lorry tethered to the jet engine would be basically be drag free? Is this correct? Thanks

When I was looking a project that included Mach vs Cd and Mach vs drag Force for a grid fin at different altitudes with different mach numbers, I saw that as Cd approached Mach 1, it increased but after passing Mach 1, it started to decrease but the drag force kept on increasing. I initially...

Homework Statement The final velocity of an object falling through air from various heights is given. From this, can you derive an equation for the drag force acting on the object with respect to velocity? Homework Equations Maybe relevant? Wno drag$$=mgh,$$ Wreal$$=\frac{1}{2}mv^2,$$...

When using Computational Fluid Dynamic (CFD) modeling you are able to see incredible complexity in water energy transfer. The Thermodynamic energy transfer occurs at much higher velocity so it does not apply in most of the cases I am looking at. What are the other parasitic energy transfers that...

Problem How to calculate the drag force of the model helicopter using the given data above? Research Question How does increasing the length of the wing planform of a model paper helicopter affect the time it takes the helicopter to fall to the ground and hence the air resistance? Variables...

What is the coefficient of drag on a flat surface? Note: The body is in free fall The object has 2 wings planform (it's a paper helicopter), which is flat The object's wing spin in a circular motion (anti-clockwise) during free fall

What is the most elegant way of predicting drag on an airfoil in inviscid and incompressible flow? Or is this still an open problem? It seems like the consensus for airfoils in incompressible and inviscid flow is that they cannot produce drag; or at least, we are not able to predict it...

https://aapt.scitation.org/doi/10.1119/1.5064562 The availability of inexpensive Doppler radar has made it practical to accurately measure drag coefficients in undergrad physics labs.ABSTRACT Undergraduate lab design balances several factors: 1) simple experiments connected with learning...

there's a stationary pebble on the flat shore of the beach. As the last of the wave heads back out to the ocean, it moves over the pebble and creates.. "lines" similar in shape to eg air stream around a jet, etc Wondering what these 'waves' are called?

Hello guys, I am trying to calculate the lift force and drag force in a wind tunnel at my school as a part of a project that i am doing. I am varying the length of the airfoils and trying to measure the lift force and drag force. I have 3-d printed 7 airfoils. However, I am not able to find any...

Homework Statement - Question: Which cyclist (A, B or C) profits the most from cyclist slipstream (also called “aerodynamic drafting”)? - Given: the direction of the wind, the positions of each cyclist; an illustration representing this - NOTE that I am expected to solve this question...

Hello all... I have a question about an engine-driven propeller. While a propeller is being spun, the air resists it and the maximum power of the engine will turn at "max rpm" when the drag from the air interacting with the propeller becomes equal to the torque generated by that engine. Now...

I've done the math but because i can't find this answer anywhere in the book which I'm reading and on the web, I would like to be sure if my calculations are correct. I know that if two objects (starting at the same time) are free falling without a drag force being applied to them, the...

When I type "drag coefficient" in Google, and view some of the images, the standard list of geometrical shapes come into view, such as this one: https://upload.wikimedia.org/wikipedia/commons/thumb/3/37/14ilf1l.svg/220px-14ilf1l.svg.png If we take the cone for example, there is a drag...

Little confusion regarding one line on Resnick's book! This says light dragged by refractive medium ok but how 'by the ether'? In the rest of the topic he says ether is stationary with respect to the observer(i.e. not dragged along by the water and that is how the Fresnel's exp. was explained).

Consider a ball flying through the air. When there is turbulence, and the flow separates, say on a SMOOTH ball, then in the rear, there is circulation in the wide wake. There is pressure on the front, but no pressure on the rear due to the fact that the fluid is "busy" circulating around. So...

Homework Statement A beach ball is thrown upwards with initial speed v0. The drag force is given by Fd = −mαv for a drag coefficient α and speed v. (a) the height h reached (b) Show that the height may be expressed in terms of the final speed when the ball strikes the ground vf (c)Finally show...

Hi, When considering the drag coefficient of a rocket in transonic/supersonic flight, I always expected the drag coefficient to peak at exactly Mach 1 due to the abrupt increase in pressure that occurs when breaking the sound barrier. However, I have been looking at several websites and...

Homework Statement A professional thrower projects a football straight up in the air. 1. Assuming there is no air drag on the football, find the speed of the football as a function of height as the ball goes up. 2. Assuming the air drag on the football varies linearly with speed, find the speed...

Hi there, I am currently looking to build a rotating kiln to provide the necessary heat/res. time/gases to react a solid feedstock. The problem that I can envision, however, is that the solid (which is fed as small particles) may become entrained in the counter-current gas flow inside the...

I need help calculating travel time as a function of distance using drag equation: F_drag = crossection area * density * ballistic coefficient * 0.5 * v^2. Not posted in homework cause it's not, and I don't know how to solve integrals so I could not fill solution attempt box

Hello. I read an article about aerodynamics. http://www.cyclist.co.uk/in-depth/2873/fat-v-skinny-who-goes-downhill-faster I'm a little bit confused with this statement regarding mass, drag, and velocity: "When you increase the mass the speed increases by cubic function, whereas if you...

Homework Statement I'm writing a program to plot the trajectory of a baseball. the formula is given to me by the book, but I'm not sure what it means. Homework Equations The Attempt at a Solution I am given that v_d = 35 m/s and delta = 5 m/s what is v? as in what does it represent? is it...

Homework Statement Find the distance, x, that an object of mass m travels through a medium, given an initial veloicty v0. Homework Equations I searched the web and came across a site that showed how to deal with velocity dependent forces...

Hello, I'm trying to create a simulation of swimming "Animats" (artificial animal). However, I'm only an high school student, so I don't know how to deal with fluid drag and fluid dynamics. In this link you could find a short animation I made describing the swim motion my animat is going to...

So I have read many articles on tennis ball fuzz and golf ball dimples and I am more confused than before. Here is one that says that the dimples make the golf balls go faster: https://entertainment.howstuffworks.com/sports/golf/basics/question37.htm And just when it makes all sense, I read...

Hello everyone. I have a question about the fact that there is no drag in the thin airfoil theory. I have read that it comes from inviscid and incompressible flow (potential flow) but what i can not understand is why there would be no drag from pressure differences ? The skin drag is of course...