# fluid flow

1. ### Maximum height for water from a fire hose

1. Homework Statement Fire hose has diameter of 4.0 cm and flow rate of 10 L/s. There is pressure of 2.2 bar inside the hose. How high the water can go at best? Water density is 1.00E3 kg/m^3 and air pressure outside the hose is 1.0 bar. 2. Homework Equations Flow rate $$Q = Av$$ Newtons...
2. ### Shear stress direction and the velocity gradient

1)In a flowing fluid in laminar fashion we know that it flows in planes which slides over each other, Lets take a fluid element (cylindrical) in a pipe(Radius=R) the resistive force is (stress)(cross section area of cylinder with radius 'r') acting in backward direction, now if I take Flow...
3. ### I Effective Resistance (Fluid Mechanics)

Imagine you have a vertical pressure head 2m tall with water flowing down to height 0m and emptying. Through this length we have 3 identical tubes of resistance R and length L. Assuming I know the volumetric flow rate(Q) as a function of height, how can I calculate the resistance of each tube...
4. ### Hydraulic head as a function of flow rate

Hello! 1. Homework Statement Symbols and variables: $\dot{V}$ : flow rate $H$ : Hydraulic head $g = 9.81 \frac{N}{kg}$ $P_{atmosphere} = 101325Pa$ $\rho = 1000\frac{kg}{m^3}$ I am given a piping system, with serie and parallel pipes, they start from one point and go back in to one...
5. ### I How does a fluid behave inside of a spherical cavity?

Suppose you have a spherical cavity, with a flow of a fluid ( in particular water), entering it from one side. What will happen to this flow? Will it create turbulences? Will speed increase? Will eventual waves entering the cavity be reflected, so creating waves with bigger amplitude? Suppose...
6. ### I Air resistance in projectile motion

In lower-division physics classes, air resistance is usually ignored to make the mathematics of projectile motion easier to understand. When air resistance is included, it's often stated that at lower velocities, air resistance is proportional to the velocity of the object, Fair ∝ kv At...
7. ### I Variation of Torriceli's theorem?

Hi there. Everyone knows about Torricelli's theorem that says about , in a too big container (opened) the speed of the liquid is given by: v=√(2gh) This result is just for containers that have a hole in the side and the fluid goes out perpendicular to the gravity. And also this result is just...
8. ### Difficuilt and/or interesting problems in fluid mechanics

1. Homework Statement Can anyone please give me hard and interesting problems regarding fluid mechanics problems such as hydrostatic and air prssure bouyance force and Bernoullis equation(Bernoullis equation problems only for liquids)? I tried looking for them but the ones I found were quite...
9. P

### Fluid Dynamics -- a spherical particle immersed in water

1. Homework Statement Consider a spherical particle immersed in water. It will experience random collisions with the surrounding water molecules. Suppose there are such water molecules around the particle. Half (n/2) of the water molecules will push the particle to the right and the other half...
10. ### Surface runoff

1. Homework Statement In my book , i was told that when the drainage of surface is high then the surface runoff will be low . However , i dont think it's correct . 2. Homework Equations 3. The Attempt at a Solution Definiton : Runoff can be described as the part of the water cycle that...
11. ### Modeling a multiple inlet piping system

Hello, PF! I’m trying to model a real piping system, which has multiple inlets and one outlet, so I can’t use Bernoulli’s equation. Instead, I’m planning to use the generalized macroscopic energy balances as shown in BSL, which allow for any number of inlets and outlets. However, first I want...
12. ### A Cellular Automaton, Random Walks, and Fluid Mechanics

Hi I'm trying to understand a paper that approximates the solution to Burger's equation (1D Navier Stokes) by a doing a one-dimensional cellular automaton simulation. I'm having a hard time understanding how all these topics connect. I have seen and walked through various demonstrations that...
13. ### B Fluid pressure and flow

So I was playing around with Fluid Pressure and Flow over on PHET animations and noticed something odd. When a fluid with high flow rate is going from a large pipe to a small pipe a lower density increases the pressure. And a higher density lowers the pressure in the narrow part of the pipe. My...
14. ### Falling film momentum balance

1. Homework Statement 2. Homework Equations 0=viscous+gravitational+pressure I saw in the solutions that pressure=0 in this case, but why? I also knew that : accumulation= flow in - flow out+generation, why not use this one? 3. The Attempt at a Solution (their solution) We are...
15. ### 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...
16. ### Fluid Flow Loss Analysis Using Real Gas Properties

I am trying to model fluid flow and losses through a component (e.g., pipe) using REAL GAS properties since 1) I have access to RefProp from NIST, and 2) I am dealing with refrigerants, which are far from ideal. I have seen nowhere an analysis of fluid flow losses (e.g., drag, friction...
17. ### Bernoulli's Equation and pressure differences

1. Homework Statement Problem in attached image 2. Homework Equations $$P_1+\frac{\rho v_1^2}{2}=P_2+\frac{\rho v_2^2}{2}$$ 3. The Attempt at a Solution I understand everything in the solution except why $$P_A-P_B=h(\rho_{Hg}-\rho)g$$ Why do we have to subtract the density of water from...
18. ### I Pitot Tubes and Static Pressure

Hey so I am learning physics on Khan academy and they had a video on Pitot tubes: https://www.khanacademy.org/science/physics/fluids/fluid-dynamics/v/venturi-effect-and-pitot-tubes I had a question. I understand that the lower part of the pitot tube in the video is measuring the pressure...
19. ### Compressible air flow from a tank through a regulator

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...
20. ### Boundary Layer Separation in Laminar and Turbulent Flows

When compared to laminar flows, the fluid "sticks" with the solid surface longer in case of turbulent flows. For example, the angle of separation for flow over a circular cylinder is 80 degrees for laminar flows, and 140 degrees for turbulent flows. What is the reason?
21. ### Bernoulli equation exercise from Fanning and Moody

1. Homework Statement I would really appreciate it if you could give me a hand with this exercise, not sure on what I've done. Data: Moody: L=55*10-3m D=10-1m k=0.0002m 2. Homework Equations $Re=\frac{D*u*ρ} {μ}$ $Re=\frac{4*m} {pi*D*μ}$ Relative roughness $ξ=\frac k D$ where...
22. ### Fluid flow/heat transfer Area dilemma

1. Homework Statement I have a confusion regarding areas. Usually in fluid flow I am using the A=(pi*D^2)/4 However in heat transfer we usually use A=pi*D*L Could you please explain this?I mean in first case(fluid flow) it is cross sectional area and in the 2nd case(heat transfer) is like the...
23. ### Parallel flow exercise

1. Homework Statement I would really appreciate if you could give me some hints regarding what exactly to iii) 2. Homework Equations we know they are in parallel so Q=Q1+Q2+.....+Qn delta hloss=delta hloss1+deltahloss2+...... delta P=delta P1=delta P2=...... 3. The Attempt at a Solution...
24. ### Diameter of hole vs time to submerge

Hey everyone, I'm new to physics forums and I would really like some help with my physics report. For my high school physics topic I have chosen an experiment where holes with differing diameters are drilled into the centre of the bottom of PVC pipe caps and the time taken for the each cap to...
25. ### Bernoulli equation with losses dilemma

1. Homework Statement Hello,Could you please lend me a hand with this problem?I would really appreciate it. Question: Their Answer: KL=2*0.75(2 elbows) D=5*10^-2 m ;f=0.001(fanning friction factor) Assumptions I made: Point 1 which is at the top of the liquid in the tank: h1=23 m...
26. ### Heat transfer and Fluid Flow Struggling Problems

1. 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...
27. ### Fluid Flow/Heat Transfer question struggle

1. Homework Statement I would really appreciate if someone could help me out with this exercise in fluid flow/heat transfer ,because I really struggling with it.Below I am attaching photo of problem+table with values. Thank you in advance ! 2. Homework Equations Question link...
28. ### I What will be the flow direction?

I guess there would be no flow in case 2; case 3 seems easy to me applying fluid mechanics principle; flow will be 1 to 2. But I doubt case 1; it is not in thermal equilibrium ??? Pls help
29. ### I Difference between Partial pressure and vapor pressure

Partial pressure must be less than or equal to the vapor pressure if there is no liquid present. However, when both vapor and liquid are present and the system is in the phase equilibrium, the partial pressure of the vapor must be equal to the vapor pressure and system is said to be saturated...
30. ### Solve question using Excel or Matlab

water moves over a stationary horizontal flat plate of one-meter length. if velocity of water is 1 m/s, draw boundary layer and friction coefficient versus x for this plate. hint: start your curves from x=1cm. Professor asked us to do it in Matlab or Excel and I'm not sure I understand how...