Fluid dynamics Definition and 641 Threads

In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids—liquids and gases. It has several subdisciplines, including aerodynamics (the study of air and other gases in motion) and hydrodynamics (the study of liquids in motion). Fluid dynamics has a wide range of applications, including calculating forces and moments on aircraft, determining the mass flow rate of petroleum through pipelines, predicting weather patterns, understanding nebulae in interstellar space and modelling fission weapon detonation.
Fluid dynamics offers a systematic structure—which underlies these practical disciplines—that embraces empirical and semi-empirical laws derived from flow measurement and used to solve practical problems. The solution to a fluid dynamics problem typically involves the calculation of various properties of the fluid, such as flow velocity, pressure, density, and temperature, as functions of space and time.
Before the twentieth century, hydrodynamics was synonymous with fluid dynamics. This is still reflected in names of some fluid dynamics topics, like magnetohydrodynamics and hydrodynamic stability, both of which can also be applied to gases.

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  1. C

    Fluid Dynamics of two water reservoirs

    Homework Statement The two water reservoirs shown in the figure are open to the atmosphere, and the water has density 1000 kg/m3. The manometer contains incompressible mercury with a density of 13,600 kg/m3. What is the difference in elevation h if the manometer reading m is 25.0 cm...
  2. D

    How Can Nozzle Design Achieve Desired Thrust in Subsonic Flow?

    Homework Statement Open ended problem really, nothing is given except that I need a thrust of 30 lbf. Similar to Dyson fan which entrains and induces air, increasing airflow 15 times. Working around this concept, I'm trying to design a nozzle so I can calculate the ratio of inlet and exit...
  3. D

    Understanding Bernoulli Loss in Fluid Dynamics

    "Bernoulli Loss" Hi, I am reading a fluid dynamics paper about dissipation due to turbulence in the fluid causing "Bernoulli loss". What exactly is meant by this? The Bernoulli principle concerns energy conservation. So, does Bernoulli loss simply refer to a loss of energy within the fluid...
  4. B

    CFD (Computational Fluid Dynamics) Software Inquiry

    Hey All! Happy Monday (No one likes hearing that) I've been recently looking into the different CFD programs available, and have become somewhat overwhelmed. My purpose today is to get some opinions, reviews, or experienced guidance on which programs would be useful to look into further...
  5. QuarkCharmer

    Fluid Dynamics of saltwater in sealed tank

    Homework Statement A sealed tank containing seawater to a height of 12.8 m also contains air above the water at a gauge pressure of 2.90 atm. Water flows out from the bottom through a small hole. How fast is this water moving? Homework Equations I believe that Bernoulli's equation is...
  6. P

    Help understanding BASIC fluid dynamics behind faraday waves

    Dear Sir and Mam, So recently, I have been doing an experiment with Faraday waves. I feel like there are some critical things I don't understand about fluid dynamics (they don't offer it as a course where I go to school), so I was wondering if anyone on pf was good with fluid dynamics...
  7. E

    What are the Appropriate Orifice Sizes for Uniform Exit Temperatures?

    I need help, hope somebody can give me a hint Determine the appropiate orifice sizes for uniform exit temperatures of 140F from the four units in 70F ambient/ sea level pressure? Components (50W, 500W, 1000W and 300W) Thank you
  8. S

    Fluid Dynamics - Flow through a pipe

    I have a fluid dynamics homework question I could really use some help solving. "Consider a straight, circular pipe of inside radius R, through which flow an incompressible fluid. At the pipe entrance, the flow velocity Vo is uniform and parallel to the pipe centreline. The flow is affected...
  9. A

    Book on renormalization group in fluid dynamics?

    I found between my family's books (cousins mostly) 4 books for fluid mechanics, and since next semester i ll be taking it it d be cool if i could just chose between them. Oh btw its for mechanical engineering i currently have: Fluid Mechanics. Robert A. Granger...
  10. H

    Computational Fluid Dynamics - Couette flow & Reynolds Number

    Homework Statement This is a part of an assignment for a computational modelling paper requiring the modelling of couette flow between two (infinite) parallel plates in MATLAB. The lower plate is stationary while the upper plate moves at 0.1m/s, the plates are 0.01m apart and the no slip...
  11. J

    Preparation for Computational Fluid Dynamics (CFD)

    Hi all, I have just completed my undergraduate studies in Mathematics from a UK university (specialising the Mathematical Physics and Fluid Dynamics) and will be continuing on a Masters programme in Applied Mathematics come fall. For my Masters, I would like to do something on CFD but the...
  12. K

    Fluid Dynamics: The nature of vortex's

    I've recently read a paper which suggested some properties of vortex's, which I could not confirm in my elementary physics textbooks or during a quick google search. I hope to find some evidence that: All vortex phenomena are actually composed of two vortex's: 1 - An outer vortex which...
  13. T

    Calculating Head Loss in a Mitre Bend Air Passage for Beginners

    I am trying to find the total head loss of an air passageway system but I have not taken a fluids class. I have been trying to teach myself the equations and principles but it tends to be very confusing without guidance. So here is my question: I have a wheel-end knuckle with an air passage...
  14. U

    Making a career in Computational Fluid Dynamics

    Hi, I've decided I want to pursue a career in CFD (Computational Fluid Dynamics) and I think the best career option for me would be be to take up 'teaching' in my area of interest (since I'm not sure how well I'd be able to do in hard-core research activities) . However, I'm completely unaware...
  15. H

    Fluid dynamics (2nd year undergrad) question on jet incident on a plate

    Homework Statement A circular jet of water of radius r1 is propelled vertically downwards and hits a circular plate of radius r2 (> r1 ) so that the centre of the jet is incident onto the centre of the plate. The velocity of the jet as it hits the plate is v and is normal to the plate...
  16. X

    Fluid dynamics (continuity equation), pressure on gate

    Homework Statement Consider the cross section of a sluice gate, which is a device for controlling the flow of water in channels. Determine the force on the gate per unit width of the gate. Hint: think of each line as a surface, with the length given above, and 1 foot of depth in the direction...
  17. X

    Pipe question (fluid dynamics), continuity equation, u and v momentum

    Homework Statement A pipe tapers from a diameter of 0.5 m at the inlet to a diameter of 0.25 m at the outlet, and turns by an angle of 45 degrees. The gauge pressure at the inlet and the outlet are 40000 N/m2 and 23000 N/m2, respectively. The pipe carries oil, with a density of 850 kg/m3, at a...
  18. R

    Is there a limit for the solution of Navier Stokes equation?

    Dear all I have 1 simple question. If the solution of Navier Stokes equation exists, its limits for infimum length, time and velocity would be the Kolmogorov Microscale equations, am I correct? Thanks, Robert
  19. D

    Fluid Dynamics - Small velocity field

    Suppose an inviscid, incompressible fluid is rotating uniformly with angular velocity \Omega. Take Cartesian axes fixed in a frame rotating with that angular velocity. Show that the evolution of a SMALL velocity field, u_1 = (u_1, v_1, w_1), relative to the rotating axes and starting from rest...
  20. R

    Help with a more difficult Fluid Dynamics Problem involving Bernoulli's equation

    Homework Statement Consider a water pipe that tapers down from a diameter d_A = 5.0 cm at end A to a diameter d_B = 2.5 cm at end B. At each end a vertical pipe that is open to the air at the top is attached to the pipe. Assume that water flows through the pipe at high enough pressure that the...
  21. D

    Fluid Dynamics - material derivative of vorticity/density

    Homework Statement Show that, for an inviscid fluid, we have \frac{D}{Dt}\bigg{(}\frac{\mathbf{\omega}}{\rho}\bigg{)} = \bigg{(}\frac{\mathbf{\omega}}{\rho}\cdot \nabla \bigg{)}\mathbf{u} - \frac{1}{\rho}\nabla\bigg{(}\frac{1}{\rho}\bigg{)} \times \nabla p Homework Equations Euler's...
  22. D

    Fluid dynamics - finding pressure for a rotating fluid

    Homework Statement An ideal fluid is rotating under gravity g with constant angular velocicy \Omega, so that relative to the fixed Cartesian axes \mathbf{u} = (-\Omega y, \Omega x, 0). We wish to find the surfaces of constant pressure, and hence the surface of a uniformly rotating bucket of...
  23. S

    Fluid Dynamics? Does it have to be dull?

    I am finding the recommended textbook for fluid dynamics really dull. It's slowly going from one formula to another with nothing interesting or any attempt at all to keep you awake... I'm strong with regard to maths, so are there any books that might make the subject more interesting? Even...
  24. S

    Help me, / Advanced Fluid dynamics Problems

    Help me, please / Advanced Fluid dynamics Problems Homework Statement Evaluate the radial component of the inertia term (u dot Del)u in cylindrical coordinates using the following identities: x=RcosΘ y=RsinΘ uEx+vEy = UrEr+UΘEΘ and any other vector identities from Appendix A as...
  25. J

    Fluid dynamics: Hydrostatic equilibrium and density stratification

    Firstly, the whole question is below, for now I need help on parts of the question- I've included it all for clarity and just in case I have further problems. An equilibrium ring of isothermal fluid orbits a star at radius R. In the plane of the ring, mechanical equilibrium results from a...
  26. C

    Fluid Dynamics Help (Force with a dynamic viscosity)

    Problem Statement A 50cm by 30cm by 20cm block weighing 150N is to be moved at a constant velocity of .8 m/s on an inclined surface with a friction coefficient of 0.27. (a) Determine the force f that needs to be applied in the horizontal direction. (b) if a .4mm thick oil film with a dynamic...
  27. F

    Fluid dynamics problem- bernoulli?

    Homework Statement A very large open water tank has a 50 cm diameter output pipe connected 10 m above the water main which is 6 cm in diameter. If the gauge pressure in the water main reads 9.8 E4 Pa what is the speed at which the water is supplied? Homework Equations I know you need...
  28. F

    What is the Speed of Water Supplied from a Tank to a Main?

    Homework Statement A very large open water tank has a 50 cm diameter output pipe connected 10 m above the water main which is 6 cm in diameter. If the gauge pressure in the water main reads 9.8 E4 Pa what is the speed at whic the water is supplied? Homework Equations Bernoulli's...
  29. J

    [Fluid Dynamics] Bernoulli's Eqn. Problem

    Homework Statement A bomb located 3 meters below the ground needs a certain pressure in order to pump the water through the pipe (connecting the ground to the bomb) and 12 meters above the ground. The radius of the pipe is 0.01 meters and the radius of the 'mouthpiece' of the tube in the...
  30. A

    Calculating Water Flow from a Limestone Tube in a Freshwater Pond

    Homework Statement A fresh water pond that is 15.0 m deep is contained on one side by a cliff. The water has eroded a nearly horizontal "tube" through a bed of limestone, which allows the water to emerge on the other side of the cliff. If the "tube" has a diameter of 4.26 cm, and is located...
  31. J

    Fluid Dynamics Problem: Effects of a Full Reservoir

    If this isn't the right forum, please move me to a better one. Assume that the output of a mountain spring is diverted to a reservoir about 200 feet below the spring through the following airtight system: A two inch pipe leads from the spring to a 40-gallon drum that lies on its side a few...
  32. M

    What is the stagnation point for a cylinder in a uniform stream?

    Fluid Dynamics - urgent Homework Statement A cylinder of radius a is placed in a uniform stream of speed U. Fluid is blown steadily outwards across the surface of the cylinder so that the normal component of velocity on the surface is V. a, find the velocity potential for the flow b, show...
  33. C

    Fluid dynamics in physics grad programs

    So basically I'm considering applying to physics or applied physics grad programs. But I'm also considering doing CFD as a career. I was hoping there was a way I could see them both in a grad program, but I haven't seen any physics grad programs with CFD as a research area by itself. Rather, I...
  34. D

    Fluid Dynamics - Multiple Pipe System Need

    Fluid Dynamics - Multiple Pipe System Need Help Please! There are 2 pumps at 2 locations with pipes (12") running from each of the pumps that are to both tied into 1 pipe (16"). In order to tie the 2 pipes into the one pipe there will be a 90 and a y fitting. The 16" pipe will then continue...
  35. A

    How Does Iceberg Buoyancy Relate to Sea Water Density?

    Homework Statement An iceberg is floating on sea water such that only 10% of its volume is above the water level. What is the density of sea water expressed in terms of the density of ice. Homework Equations \frac{Vf}{Vi} = \frac{\rho}{\rho} \rhof = density of sea water \rhoi =...
  36. A

    Courses Best math courses for fluid dynamics?

    Hello Physics Forums, I am going into 2nd year physics and am thinking about taking some additional math courses. My interests lay with ships and the ocean. What math courses would be most useful for research in fluid dynamics and interactions with structures? Thanks, Adam
  37. Q

    Fluid dynamics (masters level)

    Q) " Estimate the average acceleration of water as it travels through the nozzle on your garden hose. List all the assumptions and show calculations. " Plz help...ny body before i come a dead body ! :mad:
  38. P

    Minimum diameter fluid dynamics

    Homework Statement A fire-hose must be able to shoot water to the top of a building 35.0 m tall when aimed straight up. Water enters this hose at a steady rate of 0.500 m³.s¯¹ and shoots out of a round nozzle. (a) What is the maximum diameter that this nozzle can have? (4 marks) (b)...
  39. E

    Help with Fluid Dynamics: Bernoulli's Equation & Diagram Provided

    I'm no good with fluid dynamics. I really am willing to improve can someone point me to what equation I should use for this question. I assume its bernoullis equation? I've drawn a diagram of how I see the pipe. To make things worse I haven't done fluids in quite a while. Homework...
  40. M

    What are the best books for self-studying computational fluid dynamics?

    i want to master computational fluid dynamics,i do not have that as a subject in my university.so if i do it on my own,please give an idea about the best books for it?
  41. G

    Fluid dynamics and pressure type question.

    Let's say I want to install a 55 gallon drum on the ground to collect rain water as it runs off the roof. What if for some strange reason I wanted to run a hose from a spigot in the bottom of the drum back up to water the plants on the roof deck (I'm looking into green roofs). Could we just...
  42. M

    Fluid Dynamics: Pressure, Velocity & Pipe Radius

    1.Water flows in a horizontal pipe with variable radius and which produces no drag. At one point in the pipe where the radius is 5.0cm, the flow is noted as .75 m/s at a pressure of 250 N/m^2. a) What is the velocity at a point in the pipe where the pressure is 200 N/m^2? b) What is the radius...
  43. B

    C/C++ HELP: Fluid Dynamics and Simulating with C++

    Sorry I'm not sure where to post this as there is no explicit fluid dynamics forum - i just did a search and noticed majority of posts fell into the "mechanical engineering" forum for some reason. Sorry about that. Today my professor has told the class that by next week we have to code in...
  44. J

    How Does Disk Placement Affect Air Flow Rate in Confined Spaces?

    Homework Statement Air flows from a hole of diamter .03 m in a flat plate as shown in the figure. A circular disk of diameter D = .15 m is placed a distance h from the lower plate. The pressure in the tank is maintained at 1 kPa. Determine the flowrate as a function of h, ignoring viscous...
  45. H

    Fluid Dynamics - Increasing Outlet Pressure

    Hi everyone, I am new to the forum, so please instruct me if I commit any posting faux pas in my first post. Here is my dilemma: I have an oxygen concentrator that outputs .5-5 liters per minute of 95% concentrated oxygen at 5 - 7 PSI. This is just fine for medical use, but I am trying to...
  46. M

    Archived Syringe Problem (Fluid Dynamics)

    Homework Statement A hypodermic syringe contains a medicine with the density of water. The barrel of the syringe has a cross-sectional area of 2.5*10^-5 m^2. In the absense of a force on the plunger, making the medicine squirt from the needle. If the syringe is horizontal and the pressure...
  47. V

    Fluid Dynamics interesting critical problem

    I am having a tank at the bottom of which a pump suction line is connected.. there is another parralel line to that bottom line which is coming from another tank and open to atmospheric pressure. Please note that this second pipe is connected to the bottom pipe; not to the first tank...
  48. J

    Fluid dynamics - mass flow rate -dimensionless number

    (a) Is it true that if the mass flow rate of a gas is low, say 2g/s (grams per second), the friction losses and other losses in the piping will be negligible? (b) If it is true that losses in the piping are negligible, is it the Euler's dimensionless number that we can use to prove this...
  49. B

    Finding h in the Fluid Dynamics Lab

    Homework Statement okay, so the lab that we did is called fluid dynamics. where we open a hole but before we are supposed to record h1 before the hole is open and also measure the height of the hole. h1 is higher than h. so every 30 seconds, we have to record h2, h3 ,h4 corresonding with...
  50. V

    Fluid Dynamics: Finding Speed in Venturi Tube

    Homework Statement The horizontal constricted pipe illustrated in lee (vl3765) – UTHW#34-Dluid Dynamics1 – hamaguchi – (32001) 3 the figure (a Venturi tube), can be used to measure flow velocities in an incompressible fluid. The ratio for the cross section areas of the tube is A2/A1 =...
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