# flow

1. ### How do peak flow meters measure flow rate?

I am in pharmacy school and my professor recently went over lung diseases with us. An important (and cheap) tool that many patients can use to detect whether their lung function is declining is a peak flow meter, which tells the patient how much air they are moving when they exhale with as much...
2. ### I Subsonic and Supersonic Airflow Through a Constriction

Hi everyone! For the past week I have spend a lot of time thinking about how de Laval nozzles work. But before I convince myself that I have understood it, I want to make sure that the (simpler) scenarios I describe below are correct. Setup: We have a long pipe with constant radius r = 1...
3. ### A Flow of Water into a Bowl with Holes

I'm facing a problem with that rhyming title up there. The design is thus: a downward-facing, vertical pipe with known constant flow and diameter has water flowing out of it, into a short (15cm-91cm) free fall. At the end of that fall is a bowl of indeterminate depth made of steel with holes...
4. ### Determining the flow rate for a cooling system

MODERATOR'S NOTE: HOMEWORK INCORRECTLY POSTED TO CLASSICAL FORUM, SO NO TEMPLATE I need help with the following question: Please have a look at the question and my attempt at the solution. Alternative cooling systems are considered for a large computing centre requiring 1 MW of cooling...
5. ### B Hp/Kw required to move 1.5L/m of diesel fuel at 17.2 Bar?

How much Hp/Kw required to move 1.5L/m of Diesel fuel at 17.2 Bar? Please note this is for a real life problem.
6. ### Circular duct problem

1. Homework Statement Shown in the figure attached. Circular duct with a diameter of 150 mm, strikes a cup and exits through a circumferential slot to the atmosphere. Mean velocity in the duct = 100 ms^-1 Air density = 1.1 kg/m^3 Dynamic viscosity of air = 19.05 x 10^-6 kgm^-1s^-1 (a)...
7. ### Injector pressure drop in a liquid rocket engine

Hello everybody, I hope you are doing fine. I'm currently designing an injector for a hydrogen peroxide - ethanol engine, and the following formula is confusing me: Q = Cd * A * sqrt( 2 * dP / rho); where Cd is the discharge coefficient, A the total area, dP the pressure drop, and rho the...
8. ### Relationship between volumetric flow rate and pressure

Hello everybody, This is my first post. I've been working on a liquid rocket engine for a while, but I have never gotten to work on its feed system (fluid mechanics), until recently. We are using a very simple pressure fed system, and its main goal is to deliver the propellants at a specific...
9. ### I How Does a Pressurized Tank Empty Over Time Through a Hole?

I having difficulty wrapping my head around a concept that I wish to solve. I have a 10L tank of compressed air at 100psi. When an outlet hole of cross-sectional area of 0.115 in^2 is opened, I wish to develop a curve of pressure vs. time from t=0 until pressure drops to atmospheric. Many things...
10. ### Pressure drop across a thick orifice

Greetings, I am trying to understand how to setup/solve for the pressure drop across an orifice L=3.5in The pipe diameter starts at 1in, then abruptly decreases to 0.5in for the length of the orifice, and abruptly transitions to 1in diameter. (See the attached file for an illustration.)...
11. ### I Pressure Drop Across a Change in Diameter

Greetings, I have very little experience with fluid dynamics and I was wondering how I can calculate a pressure drop across an abrupt change in diameter of the piping used for water. Any help is appreciated! Thanks!
12. Q

### I Shear Rate in a Rectangular Channel

Say you have a rectangular channel with a width, w (m), and a height, h (m) and an infinite length. The channel itself is fixed and none of the sides can move with respect to one another. If you know the volume flow rate, V (m3/s) of fluid through the channel, how do you calculate the shear rate...
13. ### I Doubt about irrotational flows

So, i just started an elementar study on hidrodynamics and i'm stuck with something. We have that the circulation in a closed path Γ is given by: $C_Γ=\oint_Γ \vec v⋅\vec {dl}$ And that, in a irrotational flow, $C_Γ = 0$ for any given Γ. But if we have an irrotational vortex wouldn't...
14. T

### Calculating pressure release time

Hey people, I have a pressure vessel pressurized to say 20MPa at 33C, of which i'm working with a gas (scCO2 to be exact) which will then be released into the atmosphere (standard pressure and temperature) through a release valve; i'm wondering how long it will take for the pressure to reach...
15. ### How to measure the air pressure of a pipe without having water resistance

Hello, I'm having a question regarding the sensors and the techniques in fluid mechanics. Since my skills are amazing in this field, here I'm asking you questions xD I want to measure the air pressure of this tube/pipe (P1,P2,P3). This pipe will be flushed with water and then with compressed...
16. ### I In which direction a spherical particle moves under torque?

Consider a small rigid spherical particle of radius a, fully immersed in a viscous incompressible Newtonian fluid of shear viscosity η above a hard-wall with stick (no-slip) boundary conditions, located at the plane z = 0. A constant positive (external) torque Tx is applied on the particle. My...
17. ### Circuit that reverses the flow of current to a motor

Hello, I am building a small car that upon hitting a wall will go backwards, in other words reverse the current flow. I have all the components requiered (resistors 3k and 1k, wires, 6V battery, and an H-bridge, locking button) only thing I do not know is how to connect them all together. If...
18. ### Hagen-Poiseuille Law

Hello, I am doing a project which includes attempting to map a theoretical pressure distribution across a capillary tube. I am trying to do a finite element analysis using Hagen-Poiseuille's Law to map the theoretical pressure distribution before I move onto using a SolidWorks Flow Simulation...
19. ### I Terminal velocity of fluid in pipe

Hello, How do you calculate the terminal velocity of a fluid through a pipe. My problem includes turbulent flow, very high reynold number, and water (incompresible).
20. ### A Fluid Dynamics Bernoulli

Can someone smarter than I, please express p1 and p2 in terms of f, or v and r? The pump pushes out water at f rate which creates velocity v in the bigger pipe. When the water comes to the restriction velocity increases while flow rate is conserved. Bernouli tells us that the change in...
21. ### Acoustics and Fluid Flow - COMSOL 4.2

Hello everyone, First of all I am new here~ Second, I would like to "prove" on COMSOL that soundwaves (sound vibration) can alter/reshape the fluid flow Can someone tell me the physics i should use as well as all the other parameters to make it work? if someone is more experience can they...
22. ### Flowmetry Analysis (relating height to flow rate)

Hello! 1. Homework Statement I need to find the instantaneous height of a liquid during the simultaneous filling and emptying (through a hole) of a cylinder. I have varying Qin at incremental time of 1 sec. with cylinder area=5 cm and orifice area=0.5 cm. 2. Homework Equations Torricelli's...
23. ### Making a shop press using a electric motor

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...
24. ### I Flow Resistance of Connected Tubes

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...
25. ### Multi-Suction Point Pipe Flow

If I a pump with a main suction header and 4 smaller branch connections of difference sizes. Lets say for this example we have (2) 3", (1) 1", and (1) 2". Also lets say our pump is requiring 20 gal/min. The flow rate of each branch would be proportional to the area of the pipe correct? flow =...
26. ### Theoretical Pipe Flow

Hey guys, I am doing an internship and I have had some thoughts about fluid flow that have come up and I am having trouble fully grasping some concepts due to no one being able to thoroughly explain any answer that they might come up with. So I have a crude understanding of some fluid dynamics...
27. ### Python Doublet + Uniform Flow // Streamfunction Polar Plot Help

Hello, Python,CFD and PF newbie here. I am using Spyder (Python 3.5) and I managed to plot my streamfunction in cartesian coordinates. I tried transforming and plotting in polar coordinates but I am not sure that what i have done is correct. I am not even sure what the plot should look like :/...
28. ### 1 pipe branching into 3 pipes, pressure of each branch?

Hello all, I am a mechanical engineer, graduated just last year. Although I am not working with fluid mechanics right now, I was browsing through my fluids book from school and saw the section on pipe networks. As I was reading, I developed this question which I could not find an answer to in...
29. ### Measuring flow rate (Doppler device)

Hello, I am new in this field, so maybe my questions will be stupid :) sorry for that :) In the company where I work, they measure flow rates of wastewater using Flow meter (Doppler device). The problem is, that the flow rate is very low, so this device is not submerged completely in the...
30. ### Blasius Solution for Boundary Layer

Is the Blasius solution valid for internal flow in an underdeveloped pipe? Can the function for the boundary layer thickness be used to calculate when the boundary layers will meet in the center of the pipe? I don't see how it could be valid since the assumption in its derivation is that...