What is Fluid mechanics: Definition and 755 Discussions

Fluid mechanics is the branch of physics concerned with the mechanics of fluids (liquids, gases, and plasmas) and the forces on them.:3
It has applications in a wide range of disciplines, including mechanical, civil, chemical and biomedical engineering, geophysics, oceanography, meteorology, astrophysics, and biology.
It can be divided into fluid statics, the study of fluids at rest; and fluid dynamics, the study of the effect of forces on fluid motion.:3
It is a branch of continuum mechanics, a subject which models matter without using the information that it is made out of atoms; that is, it models matter from a macroscopic viewpoint rather than from microscopic. Fluid mechanics, especially fluid dynamics, is an active field of research, typically mathematically complex. Many problems are partly or wholly unsolved and are best addressed by numerical methods, typically using computers. A modern discipline, called computational fluid dynamics (CFD), is devoted to this approach. Particle image velocimetry, an experimental method for visualizing and analyzing fluid flow, also takes advantage of the highly visual nature of fluid flow.

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  1. V

    Fluid mechanics density problem

    Homework Statement If the density of iron is 7.8x103kg/m3, what is the highest possible height of a square based column of sides=40cm and mass of 1,000kg?Homework Equations \rho=m/v Fg=\rhovg (I think?)The Attempt at a Solution I took the length of the side of the square and used it to find a...
  2. E

    Fluid Mechanics - Linear Momentum

    I know the equation for conservation of linear momentum, and Bernoulli's equation: So I've tried using Bernoulli's equation to find V1, then use the continuity principle to find V2, but then I get stuck on the mass flow rate. I tried a different approach by trying to convert mass flow rate...
  3. I

    What do Rcm and Rcmob represent in this fluid mechanics problem?

    Q2. An incompressible fluid with density ρ is in a horizontal test tube of inner cross-sectional area A. The test tube spins in a horizontal circle in an ultracentrifuge at an angular speed ω. Gravitational forces are negligible. Consider a volume element of the fluid of area A and thickness dr'...
  4. T

    Fluid Mechanics Question: Calculation of kinematic velocity

    hey guys I am new to the forum... i am a first year civil engineering student trying to do a second year course over this summer holiday. for fluid mechanics i was given this h/w problem. could you please tell me if I am correct and if not make explain where i went wrong and how to correct it...
  5. N

    Fluid Mechanics Help - Please!

    Fluid Mechanics help...please! Hello...everyone... I've come along these lines from "Fluid Mechanics" - by Streeter,Wylie,Bedford These are the lines:
  6. A

    How to Determine the Angle of a Fluid in a Moving Vehicle Using Fluid Mechanics?

    Suppose you're driving along a straight, smooth, level stretch of highway with a constant velocity v. There is a cup of some fluid in your cup holder. How would you go about finding the angle \theta that the surface of the fluid makes with the bottom of the cup as a function of v? And what if...
  7. J

    Aerodynamics & Fluid Mechanics in Aerospace Engineering

    What would you say are the main focuses of research in aerospace engineering right now, specifically anything to do with aerodynamics or fluid mechanics in general. Is there a lot of research in new areas or is it mainly a lot of small tweaks in order to improve already existing systems? What do...
  8. R

    Can anyone help me out with fluid mechanics

    hello, i am having some troubles with this problem. please take a look and help me if you can. an open-ended can 1ft long is originally full of air @ 70 F. the can is now immersed in water. assuming that the air stays at 70 F and behaves like an ideal gas,how high will the water rise in the...
  9. L

    Fluid Mechanics (Shear Stress)

    1. Question A large plate moves with speed (v.o) over a stationary plate on a layer of oil of thickness (d) and viscosity (u). If the velocity profile is that of a parabola, with the oil at the plates having the same velocity as the plates, what is the shear stress on the moving plate from the...
  10. W

    Fluid Mechanics - Bouyancy Question

    Homework Statement A block of wood floats on water. The density of the wood is .634g/cm^3. Its mass is 243 g. Find the minimum mass (g) of lead we must attach to the block so that it will sink, along with the lead. The density of lead is 11.3 g/cm^3. Caution: you must take into account...
  11. S

    Fluid mechanics Reynolds number equation query

    1.I have been asked to: Calculate the density of a fluid if a ctitical velocity of 2m/s at Re=2000 in a pipe of bore 90mm at a dynamic viscosity oc 0.09cP I have calcualted the variables to SI units and found \rho=? Um (V) =2m/s D=0.09m \mu=0.09X10^-3 I am rearranging this...
  12. R

    Pump Pressure for Fluid Mechanics: H, v, P0

    How large should be the pressure P, pumped by a pump to supply water with velocity v to a part of a building at the height H, where it is consumed. The liquid may be considered as incompressible and inviscid and the flow, as steady and irrotational. (Hint: take into account that the water inside...
  13. E

    Fluid Mechanics Development Length

    Hey all I wasn't 100% sure whether to ask this in the general forums or the homework forums, it's more of a theory question rather than straight-up calculation question. If this is the wrong forum, please notify me and I'll repost this in the homework forum. I've recently done a fluid...
  14. Saladsamurai

    Fluid Mechanics~ Wall shear stress

    Homework Statement My main problem here is that I do not understand what they are asking. What is the wall shear stress? Do they mean the stress at the "floor" (or whatever you want to call it)? If so, I am assuming I use Newton's Law of Viscosity \tau=\mu\frac{du}{dy} since this is...
  15. F

    Fluid Mechanics Pressure Intensity Diagrams

    I was wondering if anyone could please explain what an intensity diagram would look like if you had a layer of fresh water ontop of x amount of meters of salt water (or vice versa). What is the concept behind this? How could you draw it? The question keeps popping up in past exam questions but i...
  16. P

    Why Does the Velocity Profile in a Pipe Show a Dip at the Center?

    ive have recently conducted a lab for investigating the behaviour of fluids in a pipe system the fluid chosen was an oil with a density of 853 kg m-3 i used pitot-traversing gear to measure the pressure at different positions from the wall of the pipe (to the centre and then assumed a mirror...
  17. P

    Fluid Mechanics - similarity

    Homework Statement A body when tested in air of density 1.18 kg/m3 and dynamic viscosity 1.52x10^-5 Pas at a velocity of 35 m/s was found to produce a resistance of 250 N. A similarly shaped body 10 times longer than the original was tested in water of dynamic viscosity 1x10^-3 Pas. Determine...
  18. A

    Solving Fluid Mechanics Question: Radial Gate Forces and Direction

    Hey guys, I'm new here. I've been following PF on and off to get some hints in past but this is the first time I'm posting. I'm doing civil engineering second year and the following is an assignment question (there are total of four questions and I'm stuck on all four :( ). I'm not looking for...
  19. fluidistic

    A reversed funnel problem (static fluid mechanics)

    Hi, I've been thinking a while on the problem but I don't know how to proceed and if the method I'm thinking of is the most efficient. Homework Statement A reversed funnel (see the figure I posted) is on a table. We fill the funnel with water until the water reaches the height h. Because...
  20. J

    Fluid Mechanics: Upstream Pressure Distribution

    A few things I don't quite get... about why the surface pressure distribution UPSTREAM of the separation point of a body is different to the theoretical or ideal distribution...? I can see why there will be a difference between the theoretical static pressure distribution but not why the...
  21. S

    Fluid Mechanics - Find the required power

    Hi I don't know where to start with this problem. Any help would be greatly appreciated. A cone is rotating in a slot at constant angular speed w. The gap h separating the cone and the lsot's wall is much smaller than the cone's height b. A fluid with viscosity mu fills the gap. Obtain an...
  22. N

    Calculating Volumetric Flow Rate and Power in a Fluid Mechanics System

    If anyone could give any help with this problem it would be much appreciated. At A, a pipe has a bore(internal diameter) of 100mm and at B it is 150mm. The pressure head at A and B are 21m and 15m water coloumn respectively. There is no pump between A and B while the distance between A and B...
  23. S

    Fluid Mechanics: Acceleration Field

    Homework Statement A picture of the problem is attached Assume that the streamlines for the wingtip vortices of an airplane can be approximated by circles of radius r, and that the speed is V = K/r where K is a constant Determine the streamline acceleration as and the normal...
  24. C

    Fluid mechanics mercury problem

    Homework Statement Mercury is poured into a U-tube as in Figure P15.18a. [see the picture here: http://www.ux1.eiu.edu/~cfadd/1350/Hmwk/Ch15/Images/P15.18.gif] The left arm of the tube has a cross-sectional area of A1 = 10.0 cm2, and the right arm has a cross-sectional area of A2 = 5.00...
  25. A

    Where Can I Find Resources for Studying Fluid Mechanics?

    Hello, I am an undergraduate student interested in fluid mechanics and was wondering what courses would I need to take (or be useful)? Any recomendations for good introduction to fluid mechanics books? thanks for your time!
  26. A

    How to Calculate Foam Volume for Buoyancy Support of Cargo Block

    Homework Statement Determine the volume of foam needed to support one cargo block with the following conditions. The bottom of the block is 2 cm above the water line and when viewed from the top there is 1 cm of foam around all edges of the cargo block. The dimension of the block are 3.5...
  27. F

    Simple challenging fluid mechanics question(buoyancy)

    hello fluid knowers! here is a question i have asked from several students every time a different answer was given to me. now let's see what is your answer mechanicals! question: we have a steel block floating in mercury as shown below...
  28. U

    Fluid Mechanics - Distance to Centroid

    Homework Statement http://i284.photobucket.com/albums/ll12/uradnky/fluid.jpg I'm asked to solve for the force on the projected plane surface and show where it is acting. This problem seems pretty easy, but with the dimensions given I can't find Lc, so I can't find dc to begin it. Is...
  29. J

    Fluid mechanics involving stability

    Im working on a problem involving a 70 lb empty drum. The diameter and length are given. I am trying to find if it will float stably if placed upright in water. I did a similar problem to this involving a solid cylinder with no problem. But I am trying to figure what special...
  30. J

    How can I find the distance and centroid of a hatch in fluid mechanics?

    Im working on the problem below... http://img90.imageshack.us/img90/4939/dfadfgs5.jpg Im having trouble finding the distance I have labled in the problem...H_c...which is the distance from the fluid surface to the center of the hatch...It appears to be found just using geometry but I am...
  31. S

    Fluid mechanics: Separation surface of a source in a parallel flow (3D)

    Hello, I have the following problem with respect to fluid mechanics: A source of strength Q is in a 3D space and subjected to a parallel flow U along the x-axis. The position of the source is at (xq,yq,zq). This will lead to the following velocity potential in cartesian and cylindrical...
  32. L

    Calculating Instantaneous Flow in a Siphon - Help Needed!

    Fluid mechanics (urgent help) i got stuck in the middle... guess i could do with some help! A siphon has uniform cross sectional area of 10^(-3) sq.m consider that water has no viscisity. A tank has height upto 80m. half of it contains water. the end of the siphon inside the tank is 20m...
  33. L

    Hydrostatics and fluid mechanics

    Homework Statement A glass cube of length 2cm and specific gravity=3 is kept suspended via a spring balance and is kept exactly half immersed in water. surface tension of water is 75 dynes/cm. find the reading shown by the spring balance. (contact angle = 0 degree. g=1000cm/sec^2) i got...
  34. E

    Why Is the Dam Wall Area Constant in Fluid Pressure Calculations?

    Heya folks at Physics forums. I'm having a bit of a problem with the theory of maths behind a simple formula used in F.M. This is purely a problem dealing with with mathematics rather than fluid dynamics. You'll have to excuse me, I really am a bit slow when it comes to these things, and...
  35. J

    Fluid mechanics - ice melting into water

    Homework Statement A pure ice cube sits in water, floating. Prove that the water level will not change after the ice cube melts (meaning, the volume displaced by the cube will equal the volume of water added once the cube is melted). density of water = 1000 kg / m^3 density of ice = 920...
  36. M

    Finding Mass of an Object [Fluid Mechanics]

    A cube of wood having an edge dimension of 20.0 cm and a density of 650kg/m^3 floats on water. a) what is the distance from the horizontal top surface of the cube to the water level? b)what mass of lead should be placed ont eh cube so that the top of the cube will be just level with the water...
  37. A

    Fluid Mechanics PDE's and existence of solutions in inviscid, axisymmteric case

    I'm writing a major paper on fluid flow in vortices (think tornado) and the solutions don't generally exist at all. Truly original research is not required, but I want to give a rigorous proof of the Navier-Stokes eq, starting from the basic continuity equation, explain their assumptions...
  38. M

    Complete Analytical Exact Solutions of Navier-Stokes Eqs: Fluid Mechanics Book

    Is there a book, series of notes, lectures, PDF, PPT or anything that contains all known complete analytical exact solutions of the Navier-Stokes equations?
  39. U

    Fluid Mechanics- Two liquids in a U-Bend

    Homework Statement The problem- http://img87.imageshack.us/my.php?image=physics4cw0.jpg Homework Equations Part of the problem is, I don't know which equations to use. (See below) The Attempt at a Solution Ok, I'm not quite sure how to approach this problem. It would help if I knew...
  40. X

    Fluid Mechanics: Inviscid flow v.s. Laminar flow

    Hey guys, I am kind of confused here but can you guys define for me inviscid flow and laminar flow? In my understanding, inviscid flow is when viscous effect is very weak and laminar flow is when reynolds number is in general, less than 2300. In that effect, does that mean that viscosity for...
  41. V

    Text book for fluid mechanics

    could anybody suggest me a book on fluid mechanics which provide strong basics as well as detailed knowledge thanks
  42. P

    Good Textbooks for Mass, Heat Transfer, Material & Energy Balances, Fluid Mechanics and Thermodynamics

    Hi, What are good first texts in mass and heat transfer, material and energy balances, fluid mechanics and thermodynamics? I was recommended Felder and Rosseau, and Incropera and Dewitt. However, no books have been recommended for fluids and thermo and the consensus on amazon seems to...
  43. W

    Fluid Mechanics Texts: White, Segel, Tritton, L&L, Aris

    What would you recommend as good texts. Here's what I've found searching the site: White Segel Tritton L&L Aris
  44. S

    Conceptual questions in Fluid Mechanics

    Homework Statement Define:Static pressure Dynamic Pressure Continuum hypothesis Kinetic Viscosity Kinematic Viscosity 2. The attempt at a solution The real question is : are these answers sufficient? Static Pressure - The pressure exerted by a fluid on an object placed within the...
  45. T

    Boundary Divergence and Potential Formulation in Fluid Mechanics

    Does anyone have any ideas about this?
  46. S

    Mechanical Engineering Student with Fluid Mechanics Problem

    Hey everyone! I'm having difficulty and wondering if someone would be kind enough to help me figure out how to approach this problem. I'm a mechanical engineering student and reasonably new to fluid mechanics, and quite confused. :blushing: Thanks for any help anyone can give me :smile...
  47. 5

    Fluid Mechanics - Split Pipe Flow Question (momentum and Bernoulli eqns)

    Hi, I am stuck on this question as I haven't encountered anything similar to it. Normally I have only dealt with pipe with one inlet/outlet. Homework Statement I am given a diagram of the pipe shown on the attachment (Sorry for the crude diagram). Hosted it while the attachment is "reviewed"...
  48. D

    What are some real-world examples of compressible fluid mechanics in action?

    Hi Guys, I know that the compressible Euler Equations are: \partial_t (\rho \mathbf u) + (\mathbf u \cdot \nabla)(\rho \mathbf u) + \nabla p = 0 \partial_t \rho + \nabla \cdot (\rho \mathbf u) = 0 Subject to suitable initial conditions and solving for \mathbf u, \; \rho unknown...
  49. O

    Where Can I Find Beginner-Friendly Simulation Software for Fluid Mechanics?

    Hi everyone, Does anyone know what simulation software to learn fundamentals of fluid mechanics for beginner student of mechanical engineering like I can create it by my own? Thanks in advance Huygen
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