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 - find distribution of a conserved variable

    I accidentally posted this to the "Calculus & Beyond" forum when I meant to post it to the physics forum. If someone can tell me how to move this post, I will get rid of it here! Homework Statement Consider a property, for example temperature θ, that is conserved during advection (i.e. Dθ/Dt =...
  2. F

    Calculating Minor Head Losses for Pumped Liquid System | Fluid Dynamics Question

    I have a question where I have to find minor head losses for a system using both the equivalent length method and number of velocity heads method . It will not let me attatch the drawing here but , a liquid is to be pumped from an underground vessel (which is vented) to a pressurissed...
  3. G

    Optics and fluid dynamics simulation software

    I am doing "Schlieren imaging" visualization of a gas flow from the nozzle. could anyone please recommend a software to simulate a gas flow from the nozzle. in addition please recommend a software to simulate optics, like the propagation of a light beam through the optics and image...
  4. F

    Fluid Dynamics Question - Pressure Difference in Horizontal Pipe

    Homework Statement The Trans-Alaska Pipeline System (TAPS) carries around 100,000m3 of oil per day from the Northern Alaskan oil fields to the nearest ice-free port of Valdez, around 1300km away. The pipe has an outer diameter of 1.22m and a wall thickness of 12mm. Eleven pumping stations...
  5. Z

    Need help for a CFD(computational fluid dynamics) software

    My friend is trying to reproduce a research paper calculated using the CFD(computational fluid dynamics) software package star-CD sold by CD-adapco, but so far he failed, what can he do? Here is the paper he is trying to reproduce: Endothelial Cell Layer Subjected to Impinging Flow Mimicking...
  6. crador

    Fluid Dynamics pipeline with a venturi injector

    Hey guys, I've been wracking my brain for a while, and thus I have landed here yet again. My problem is the following: Say you have a pipeline with a venturi injector, and intermittently a large tank of water with a portion of air on top -- I.e. a closed circuit communicating between the...
  7. mattyboson12

    Understanding Bernoulli's Equation for Fluid Dynamics with Electric Pumps

    Hi, am having a few problems applying bernoulli's equation when an electric pump is involved. I have attached a picture of the question. I understand how to apply bernoullis for venturi and pitot tubes but when it involves work being done on the system eg. a water pump, fan exhaust I don't know...
  8. K

    Analogy between fluid dynamics and electromagnetism

    I've recently heard of an analogy between fluid dynamics and electromagnetism in which the velocity flow field is identified with the magnetic vector potential, (and therefore the vorticity is identified with the magnetic field), and the vector \omega \times v is identified with the electric...
  9. B

    Fluid dynamics in horizontal pipe

    There's a figure that comes with the question but I'm having trouble attaching it so I will describe it the best I can. There is a large cylinder labeled the reservoir. A horizontal pipe is connected near the base of the reservoir and it is open at the other end so fluid flows out (point B)...
  10. N

    Solving Fluid Dynamics Pressure at Different Speeds

    Homework Statement If the pressure reading of your Pitot tube is 17.0 mm Hg at a speed of 150 km/h, what will it be at 700 km/h at the same altitude? Homework Equations The only eq I could think if is p = p2+ 1/2 density (v2^2 - v1^2) But I don't know the density The Attempt at...
  11. S

    Fluid dynamics, Pipe Flow, Hagen Poiseuille, Darcy's equation

    Homework Statement A water injection line is made from smooth capillary tubing with inside diameter D = 25.0 mm . If the length of the pipe is 0.75 m and assuming laminar flow is present up to Re = 2000, find (i) the maximum average velocity at which the flow is laminar (ii) the pressure...
  12. G

    Biological Fluid Dynamics - Approximate Navier Stokes Equations Solns

    Homework Statement Good evening. First post on this forum! The problem I wish to state would take too long to write by hand so I thought it best to do so via attachment. The question I am stuck on is part d and, in fact, part e also. Homework Equations All relevant equations are given...
  13. A

    Fluid dynamics and particulate diffusion question

    I have two cylindrical tubes connected at a 90 degree junction. One tube has a constant flow of a laminar fluid going through it and the fluid is saturated by a soluble particulate with a known concentration. The other tube has a much smaller radius, initially has no particles and is closed at...
  14. B

    Is it difficult for engineers to switch to mathematical fluid dynamics research?

    Hi guys, I studied mechanical engineering and I am currently a graduate student (turbulence modeling). I am interested in the more formal/mathematical aspects of fluid dynamics, which are mainly worked in mathematical faculties and I would like to know if someone knows/have an idea about...
  15. M

    How much math for fluid dynamics?

    hey all im taking a graduate level fluid mechanics course. we are using a good amount of vector calculus (expected) and also tensor algebra, leading into the kronecker delta and Levi-Civita symbol (shockingly never saw these before, though implicitly used them). it seems linear algebra is...
  16. M

    Can someone please check my homework on fluid dynamics?

    Hi there, I just would like if someone could check over my work on my current homework assignment involving fluid dynamics. Homework Statement 1) Calculate the absolute pressure at an ocean depth of two kilometers. Assume the density of seawater is 1000 kg/m3, the density of air is 1.3...
  17. M

    Fluid Dynamics - Calculate the resultant moment

    Homework Statement A rigid vertical wall separates two liquid reservoirs. The first reservoir contains oil of density p=864 kgm-3 at a height of 6m above the ground, while the second reservoir contains water (1000kgm-3) at a height of 5m from the reservoir bottom. Calculate the resultant...
  18. N

    [Fluid dynamics] Normal shock wave problem

    Homework Statement Air, supplied by a reservoir at 450 kPa, flows through a converging-diverging nozzle whose throat area is 12 cm^2. A normal shock stands where A1 = 20 cm^2. (a) Compute the pressure, p2, just downstream of this shock. Still farther downstream, where A3 = 30 cm^2, estimate (b)...
  19. M

    Looking for Good Fluid Dynamics Book

    I know this question has been asked plenty of times, but nonetheless I wanted to get some recommendations that might better jive with my situation than other the other threads I've read about this topic. I'm a first year grad student in physics that hasn't had a course in fluid dynamics, but...
  20. M

    Incompressibility in boundary layer (Fluid Dynamics)

    I have started studying fluid mechanics recently and seems to be a very basic conceptual question that is bugging me and unfortunately I am unable to find a reasonable explanation for it. Your help would be more than appreciated. The mathematical definition for incompressiblility in fluid...
  21. R

    Programs Physics or Engineering undergraduate major: Interest Fluid Dynamics

    Currently I am intended to start next fall as a Physics major at the University of Delaware. My interest lies in Fluid Dynamics particularly in Geophysical Fluid Dynamics. I understand it's really early in my college career and I may change my interest, however I was surprised to find that as a...
  22. R

    MHB Fluid Dynamics in Action: (Mechanics)

    Viscous fluid flows between two rigid boundaries at y=0, y=h, the lower boundary moving in the x direction with constant speed U. The upper boundary is at rest. The boundaries are porous and the vertical velocity is V (constant) at each one...
  23. F

    Understanding Bernoulli's Principle in Fluid Dynamics: Quick Question Answered

    I understand everything up to B). I believe Bernoulli's is applicable here, however I am unsure as to whether or not the pressure before the tube (pgh) is the same or different as the pressure at the tube pgh +p0. I ask the same question for the opposite end of the tube. I know that pressure...
  24. J

    What is the Volume of Water Leaving a Tank Through a Rectangular Opening?

    Homework Statement 5. A rectangular opening on the side of a water tanks has a width of L. The upper part of the opening it's in a height of h1 underneath the water y and the bottom part it's in h2 . prove that the volume of water that leaves the tank is given by : 2/3(L)√(2g(h1³-h2³))...
  25. O

    Water Wavemaker calculation need. fluid dynamics help.?

    Hi guys, I haven't taken any physics classes or any of the sort to figure out the problem that I am faced with. basically what where creating is a wave maker like this (sorry this is the only video i found) basically the "float" that you see is shaped like a quarter of a circle...
  26. T

    Fluid Dynamics 2 Tynea: Unsolvable Pipe Network Problem?

    Homework Statement A professor gave a pipe network problem to be solved by the Hardy-Cross method. However when I attempted to create a scale drawing of the figure to get a better idea of the problem I realized it is physically impossible to create his design. Now i am wondering if because...
  27. D

    Question about fluid dynamics (calculating concentration)

    Hi all, I have a question about calculating the concentration of continuous air and carbon monoxide flowing through a pipe. If the gas cylinder originally has 20% CO and 80% air and it will be diluted by another gas cylinder of air, how do you account for temperature, pressure, and...
  28. Astronuc

    Computational Fluid Dynamics by John D. Anderson

    Author: John D. Anderson Title: Computational Fluid Dynamics: The Basics with Applications Amazon Link: https://www.amazon.com/dp/0070016852/?tag=pfamazon01-20 Prerequisities: Calculus, Introductory Physics and/or Aerospace Engineering, Fluid Mechanics, Heat Transfer Level...
  29. B

    Basic Fluid Dynamics: Calculating Exit Velocity & Mass Flow Rate

    Hi guys and girls, I hope you can help an electronics engineer out of his place in the mechanical world:rolleyes: My very basic question is for a vessel holding a liquid at a given pressure and a given opening in the vessel how can i calculate exit velocity and mass flow rate? Like if i...
  30. S

    Fluid Dynamics - increasing pressure

    I am working on hobby project with almost no budget. I bought some "nice" (cheap & simple) electronic solenoid valves for water flow. I've since discovered that they need 3PSI to open. Which is ok for the supply lines. But the drain line requires that as well. Now I either need a column of water...
  31. L

    How Fast Can Water Flow from a Kitchen Faucet on the Third Floor?

    Homework Statement water in main pipe at the street level is at a gauge pressure of 170 KPa and is moving with neglibible speed. A pipe connected to the main pipe is used to deliver the water to kitchen located on the third floor of a building, at a 15-m height from the street level. what is...
  32. P

    Fluid Dynamics - Spanwise Vorticity of Turbulent Boundary Layer

    Hi all, Am reading a few papers for a Uni case study about structures in Turbulent Boundary Layers over a Flat Plate (water), particularly low-speed streaks. I'm confused over what mechanism causes the span wise variations in velocity that seems to cause low speed streaks. Would...
  33. S

    Fluid Dynamics - Extracting Information from Instantaneous Snapshot

    I have questions about how fluid dynamics may be used in general, particularly flow visualisation and extraction of flow parameters. I currently use a DNS code to propagate a wake near the fluid surface (fixed), from which I extract snapshots of the surface velocity field at particular...
  34. D

    Fluid dynamics of entry region in a pipe

    Homework Statement Steady, laminar flow of an incompressible Newtonian fluid with constant physical properties. The area of interest in the problem is in the entrance region between two wise, horizontal parallel plates separated by distance 2B. z is in the direction of flow and x is the...
  35. M

    Ability to customise in fluid dynamics experiments

    Is it usual to customise experiments in fluid dynamics and to what extent? I understand that lasers and imaging tools will be fairly untouchable by a fluid dynamicist, although does an experimental role require any 'tampering/customising of general system equipment i.e. rewiring/handy work...
  36. A

    Why do we take convective derivative in fluid dynamics

    I am studying plasma physics. While treating the plasma as a fluid, we replace the generla time derivative of velocity of any particle by the convective derivative. I would like to know the reason and also what is the frame of reference when we work with fluid dynamics.
  37. M

    Is fluid dynamics a true physics subject?

    Are fundamental discoveries made in fluid dynamics currently, or is it just particular solutions based upon known fundamentals? From reviewing journal literature, it appears that either application based problems have been studied (engineering), or fluids under certain conditions that form a...
  38. A

    Fluid dynamics: Knowledge continuity equation

    Homework Statement Please click on the link for the question. http://i1154.photobucket.com/albums/p526/cathy446/physicsquestion_zps49e16ab1.jpg Assume that air spreads out after coming out from the tube at 2. The speed over tube 1 is almost zero. Homework Equations Knowledge problem on...
  39. Nono713

    Fluid dynamics, friction and pressure

    Hello, this is not homework, I am trying to derive some physics results using intuition, I am currently looking at some fluid dynamics problems. Consider a water droplet on a frictionless horizontal plane, subject to gravity. The cross-section of the droplet would look something like this...
  40. N

    [fluid dynamics] are they trying to use the ideal gas law for LIQUIDS?

    In my course they're using the equality U = \frac{p}{\alpha \rho} with alpha some constant (U = internal energy per mass, p = pressure, rho = density). They explicitly derive it for an ideal gas yet later apply it to a liquid (in the context of deriving the Navier-Stokes energy equation). Seems...
  41. N

    [fluid dynamics] why are there no shear forces in a fluid at rest?

    It is said that the stress tensor \mathbf T for a fluid at rest is diagonal. Why is this? The fact that the fluid is at rest means there is no net force, i.e. the body and surface forces cancel each other: 0 = \mathbf F + \nabla \cdot \mathbf T, but from this condition is does not follow...
  42. N

    Applying Reynold's Theorem to Infinitesimal Element: Fluid Dynamics

    So Reynold's transport theorem states that \frac{\mathrm d}{\mathrm d t} \int_{V(t)} f \; \mathrm d V = \int_{V(t)} \partial_t f \; \mathrm d V + \int_{V(t)} \nabla \cdot \left( f \mathbf v \right) \; \mathrm d V. Now I would expect (on basis of conceptual reasoning) that if I were to apply...
  43. J

    How Can SolidWorks Help Calculate Air Flow in a Hamster Cage?

    Hi I'm creating a hamster cage for better ventilation(circulation) without too much flow.(draft) How would I work out mathematically the air flow going into a plastic box. The flow rate etc.. The plastic box will be inside a normal home. Things I want to know and improve The overall...
  44. Q

    Fluid dynamics - Where to post questions?

    Fluid dynamics -- Where to post questions? Is this the place to post to discuss fluid dynamics?
  45. A

    Help Needed with Fluid Dynamics Problems

    Fluid Dynamics help?? Homework Statement A boiler is supplied with water at a rate of 0.5 kg/s through a pipe of diameter 80mm a) Calculate the velocity of the water in the pipe b) The velocity of the water just before it enters the boiler through a pipe and is raised by a means of a...
  46. M

    Normal Forces and Fluid Dynamics

    1. A 5 kg board is arranged between 2 sawhorses (at right). If the board is in static equilibrium, what is the normal force on the board from sawhorse 2. Link for the picture the question is referring to. h.ttp://i.imgur.com/nBC6A.jpg a. F2,normal = 0 N b. F2,normal = 49.0 N c...
  47. S

    How Does Plaque Constriction Affect Blood Velocity in Arteries?

    Homework Statement An artery with a 3 mm radius is partially blocked with plaque. In the constricted region the effective radius is 2 mm and the average blood velocity is 0.5 m/s. What is the average velocity in the unobstructed region? Assume no changes to η, L, and ΔP. Ans; 0.22 m/s...
  48. N

    How High Can Water Climb in a Tank with a High-Velocity Inlet?

    In a tank there is a hole at the bottom of radius 5cm.If water entering the vessel with pipe of radius 5cm with velocity 30m/s. Find maximum height to which tank can be filled.
  49. J

    How Do You Calculate Display Readings from Pressure in a Cream-Filled Silo?

    Homework Statement A 150 m^3 silo(cylinder) (12 m high) is used to store cream (density 850 kg m-3). An electronic pressure sensor (measures gauge pressure) is mounted 0.6 m up from the base of the tank, and a 0 to 100% display is used to indicate the level. It is not possible to sense the...
  50. R

    Is There an Error in My Bernoulli's Equation Application for Fluid Dynamics?

    attached is the problem. I use bernoulli's equation along a "streamline" from the inlet at point 1 to outlet at point 2. I do this to obtain the velocity V2. After working through it (simple algebra) I end up with 10.20 m/s ...seems right to me... however upon doing a conservation of mass...
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