Flow Definition and 1000 Threads

Homework Statement Write a program to find the equivalent resistance between two opposite corners within a grid of "infinite size" with resistors between each point. So basically we have an infinite cube made up of cubes with 1 ohm resistors between each node. Homework Equations Kirkoff's laws...

Hi PF! I am wondering why we define velocity for polar coordinates as $$\vec{V} = \nabla \times \frac{\psi(r,z)}{r} \vec{e_\theta}$$ and why we define velocity in spherical coordinates as $$\vec{V} = \nabla \times \frac{\psi(r,\phi)}{r \sin \phi} \vec{e_\theta}$$ The only thing I don't...

Homework Statement A reasonable approximation for the two-dimensional incompressible laminar boundary layer on the flat surface in Fig. P4.17 is u ≈ U(2*(y/δ) - 6*(y3/δ4) + y4/δ4) δ = Cx1/2 where C is a constant y ≤ δ Homework EquationsThe Attempt at a Solution Incompressible so...

As you know, resistance of a rectangular shape is given by R=ρ A/L But how do we theoretically calculate the resistance of the bottom case? ( now, the current flow is not parrallel, current flows from bottom through the right side) I would like to know if there is any references for this...

I am not a mechanical engineer; but I have physics background. I want to lift about 250 watts of heat from a metal block. At the same time I have to maintain its temperature at 30 deg Cel. For this I want to use water-air heat exchanger (HE). Heat exchanger will have inlet & outlet pipes. Hot...

1. Homework Statement Hi. This is a problem related to designing a RC hover craft. We are given a datasheet for a fan used as thrust. http://imgur.com/6liZSid Sorry image post no working, url: http://imgur.com/a/6XLwL We have to approximate the equation to a straight line through the curve...

Hey, I have an air tank that is at a set pressure, say 3000psi, and I have attached a regulator to the end that regulates the pressure down to 800psi. As the valve on the tank is opened the pressure and the mass in the container will decrease. If there was no regulator the mass flow rate would...

Hi, We have a canister at a set pressure (4500psi) full of compressed air. A single stage pressure regulator is fitted to the canister that reduces the outlet pressure to 850psi. The flow from the regulator is then used in a divergent nozzle to create a thrust force capable of lifting a small...

Hello, We have a system with a 70 bar pump and 9 nozzles connected to the pump lines. Total flow rate is 2 l/m. Is there a way to change only one nozzle flow rate manually, with a pressure regulator valf just behind that nozzle? Thank you.

Hey, So I have a system where there is an air tank (0.2Litres @ 3000psi, 293K) and I have a convergent-divergent nozzle attached directly to it. What I want to know is an expression for how the mass flow rate varies with time as the mass in the tank decreases causing the pressure to decrease...

Homework Statement You want to swim straight across a river that is 76 m wide. You find that you can do this if you swim at an angle of θ = 28° from the upstream direction at a constant rate of 1.5 m/s relative to the water. At what rate does the river flow? The angle θ is measured from the...

This is probably a simple question but I am really struggling as to where to start. We have a tank of compressed air, Volume of tank (V1) = 0.2litres Pressure of tank (P1) = 206.8 bar Regulator Pressure (P2) = 58.6 bar I would like to find the volume of air that can pass through the regulator...

I'd like to make a small shop press from an electric motor, say 18'' tall max, with 6" of travel. It should be able to press say 10,000 psi and hold for several second or even maybe indefinitely. My question is two fold. First, what type of mechanical action would be best to turn circular...

Homework Statement n = 3.8-mol of diatomic gas is allowed to expand isothermally from Vini = 1.9-m3 to Vfin = 10.5-m3. The initial pressure is Pini = 1.38-atm. After this the gas is raised at a constant volume by a temperature ΔT = 35-K. Calculate the total heat flow into the gas. Homework...

Hi, I am currently studying Thermodynamics and stumbled upon this equation and is slightly confused as to how this works. Hopefully someone can help me with the understanding. According to this text here, if I am not wrong e can be h + ke + pe or u + ke + pe depending on where i am looking...

Good evening everyone, I have a pressure meter from where we determined a pressure drop of 5.5 psi (Initial pressure 45.5 psi, final pressure 40 psi). The working fluid is air. The diameter of one of the hoses that is connected to the pressure meter is 1/4". I wasn't able to take a picture of...

Homework Statement A sand-spraying locomotive sprays sand horizontally into a freight car. The locomotive and the freight car are not attached. The engineer in the locomotive maintains his speed so that the distance to the freight car is constant. The sand is transferred at a rate...

Homework Statement (This is more of a discussion question) [/B] My question is, if we have a pipe between two reservoir A and reservoir B (Height of A > height of B) , then if flow in the pipe is to happen from A to B, what sign would the pressure sign be at any point in the pipe? Homework...

Homework Statement ------------------ Homework Equations V=IR KCL/Node Voltage The Attempt at a Solution These are the solutions to some old homework assignments that my teacher posted, but I am very confused on the way he labeled his current flows in these problems. In the first picture...

Hello, I am working with the mass flow rate equation which is:$$\frac{d \dot{m}}{dt}=\dot{m}_{in}-\dot{m}_{out}$$ To determine the change of the height of water in a reservoir. Assuming m_in = 10 and m_out = sqrt(20h), then : $$\frac{d (\rho \cdot Q) }{dt}=\rho \cdot Q_{in} - \rho\cdot...

Hi, Homework Statement I have the following question in my course work. What I do not understand is why it provides the relative density of natural gas?! Calculate the equivalent choked flow of propane through a particular valve if the choked flow of natural gas through it is 10 litres s–1...

If I have a tank of volume V, pressure P, and temperature T, what is the most effective way to determine the volume flow rate if I were to suddenly allow the air to discharge through a hose? My first thought was that I could use Boyle's Law to determine the compressed volume of air in the tank...

If you was to pour the same about of water though a thin funnel say 1 inch and through a big funnel say 5 inch which of the funnels will the water reach a higher speed ??

Hi All, Quick question about the flow velocity in an air ringmain piping system. does the flow velocity in the ringmain pipe decrease every time it passes an outlet?

In the gas industry engineers often have to purge gas pipes. For example, if repair work must be done on a gas line the fuel gas in the system must be removed before work can be done safely. The Institute of Gas Engineers and Managers (IGEM) publication IGE/UP/1 stresses the need to achieve a...

Hey everyone. I thought about this problem the other day, but I don't know what theory I need to solve this problem. Given a 2D rectangle with a known, varying resistance, and a known voltage drop across the length, how would one calculate the current density at each point on the surface. By...

Homework Statement I would really appreciate if you could give me some hints regarding what exactly to iii) Homework Equations we know they are in parallel so Q=Q1+Q2+...+Qn delta hloss=delta hloss1+deltahloss2+... delta P=delta P1=delta P2=...The Attempt at a Solution We know flow is...

why does the pressure drop equation derived for the laminar flow has no parameter to indicate the surface roughness of the material of the pipe,unlike the turbulent flow !

Homework Statement I am having a bit of trouble interpreting flow charts given in my biology question sets. Given the following stimulus: The question is : In which of the following options does each substance play two different roles in the series of events from plaque ruprture to MI? ADP...

Hello! You apply a pressure to a pipe to maintain a specific flow. If the pipe diameter becomes half, how much pressure you need to apply to maintain the flow? Thanks!

Homework Statement Hello, I am struggling with this heat transfer and fluid flow problem.I would really appreciate if someone could have a look over what I have done on it. I am not sure if what I have done is correct ,I would really appreciate if you could tell me if it is correct or wrong.And...

Good afternoon all, I am doing some back of napkin calcs for work and am having trouble finding an answer (or one that I can understand--its been a while since undergrad). We have a valve that has particular flow rate requirements to prevent unseating the valve seal. This is a mass flow rate...

Picture a charging capactor, you know the E field, and the induced B field, the energy flow is just EXB. Please describe for me in rough terms the energy flow vector field near and far from the slowly charging capacitor? The flow of energy must ultimately come from the source of energy that...

Hello everybody, It is normally said that fluid flow in a larger diameter pipe is easier (less energy losses) than in a smaller diameter pipe. This indeed appears to be true in relatively high flowrate applications however, I'm struggling to understand why drinking from a normal straw (small...

Hello, I was reading about the differences between Current Source Converters and Voltage source converters. One main difference was that Current source converters need to have a minimum DC power flow of 5-10% while VSC do not have a min flow requirement. It was also called a deadband. Why is...

Dear PF Forum, I've been wondering about this thing. The universe's radius is 46 gly. But a galaxy in 13.8 gly from us cannot be seen because it travels faster than the speed of light. So is there a galaxy in, say, 30 billions light years away from us? But before that, I'd like to know about...

1.There is an electric field between ionosphere and ground, also Earth's magnetic field is perpendicular to this E field, hence by poynting theorem integrating E x H across the entire surface of Earth gives a great deal of energy flowing west to east. 2. |S| = (E X B)/u0 = (150 V/m X...

Edit: Eh, sort of changed the question part way though, so if a mod could change the title to "Question regarding gas flow from high to low pressure". Moderator edit: Done I'm about 99% sure I already answered this question for myself but just wanted to make sure my logic was correct, so if...

Hello, PF! I'm currently brushing up my fluid mechanics and came across some questions while studying the compressible flow of an ideal gas using Bernoulli's equation. First, consider incompressible flow in the following system Neglecting any changes in elevation, the Bernoulli equation for...

Dear PF Forum, I've been wondering about how on Earth (and I do mean it, from earth :smile:) that we know there's a galaxy 20 billions light away. Considering that https://en.wikipedia.org/wiki/Age_of_the_universe is 13.8 billions years old. But before I'm asking about Supernova Ia and Hubble...

Hello, So say that I have a small four stroke engine that is designed to be kept static at ground level. I then take this engine and mount it to a small air plane, feeding the engine with either still air from inside the cabin (cargo) or the outside wind. The exhaust is fed out to the wind...

Hi, I am trying to model a counter flow diffusion flame using ansys fluent with fuel/oxidiser as methane/air. The problem is that the flame temperature(800 K) is much lower than what it should be(>1600 K). I am using Non premixed combustion module with steady diffusion flamelet and adiabatic...

Dear PF Forum, While learning why the net energy of the universe is zero. I've been reading about the expansion of the universe, and of course in it, Hubble Flow. https://en.wikipedia.org/wiki/Hubble's_law = 73km/s per Mega parsec https://en.wikipedia.org/wiki/Parsec = 3.26 light year. In the...

Hi i have calculated compressor , combustor , turbine inlet and outlet temperature , pressure so on and my output of gas turbine is 50MW , So for this i want to calculate the mass flow rate of air and fuel in compressor , combustor , turbine . Like m0=?,m1=?fan inlet,m2=? compressor inlet,m3=...

Hello, I have here a complex question. My background is Chemistry and Optoelectronics. I wasn't the best when we were studying Thermodynamics at uni so I have some knowledge-gaps. Anyways, here is my problem. Can somebody explain me the whole process of the convection in the coffee roaster. So...

Homework Statement I've a problem with defining x function for the lower horizontal bar on the left hand side. Is it shear flow for this part = Vx/Iy * 3 * s^2 * 0.5 (after integration) ? Or should I take whole x part on which is acting force Vx? Homework EquationsThe Attempt at a Solution

Homework Statement The tank in picture has section ##S_1## and it's linked with a tube of section ##S_2=\frac{1}{\sqrt{17}} S_1##. The tank is filled at an height ##h## and this level is kept constant by a sink ##R##, in such way that the exiting volumetric flow rate is ##Q=0.3 m^3/s## and...

i want to ask how flow resistance of connected tubes with different diameters is calculated. as you see in the uploaded image we imagine that there are 3 tubes. tube A is 2 meters long and cross section area is 2S. tube B is also 2 meters long but first 1 meter has 2S surface area and last 1...

I would like to ask you that why pressure drop is constant through pipe? How can we know that dP/dx=constant? Thank you.

I need to know the maximum compression speed that can be applied to a rectangular bladder which has a open air port that will avoid rupturing the bladder. The bladder is 40" wide, 100" long, and 10" tall. The compression equipment is a large metal panel that is larger than the surface area of...