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.

View More On Wikipedia.org
Recent contents Top users
  1. I

    How Does an Ideal Fluid's Velocity Change When Hitting a Vertical Board?

    Hi, I`m seeking for help in the following problem. A flat vertical board is traveling in water which is to be considered as ideal. One of its ends is in water, the other one is outside the water. Its velocity is v with respect to its normal. What is the velocity of the water stream directed up...
  2. WeiShan Ng

    [Fluid Mechanics] Negative sign on the viscous work term

    Homework Statement I am revising on the derivation of the differential equation of energy (White's Fluid Mechanics 7th ed) and I'm having trouble understanding the sign convention used in the viscous work term. The textbook first define an elemental control volume and list out the inlet...
  3. boneh3ad

    Demystifying the Often Misunderstood Bernoulli's Equation - Comments

    Greg Bernhardt submitted a new blog post Demystifying the Often Misunderstood Bernoulli's Equation Continue reading the Original Blog Post.
  4. B

    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...
  5. Navin

    Capillary Tube Behavior in a Gravityless Environment

    Homework Statement A 20 cm long capillary tube is dipled in water.The water rises up to 8cm .if the entire arrangement is put in a freely falling elevator ,the length of the water column is A)10cm B)8cm C)20cm D)4cm Homework Equations Its a theoretical sum The Attempt at a Solution...
  6. S

    Fluid force at the end of a pipe

    Consider the very standard pipe problem used to calculate the force required to hold a pipe with a bend that has some fluid flowing through it, as shown in the image. We use Newton's second law of motion to calculate the external force required. However, why is there pressure acting into the...
  7. Domenico94

    Speed of fluid in a turbulent flow

    Suppose a fluid passes from having laminar flow, to having a turbulent flow (like when passing after an object). How do fluid speed and fluid density change after that?
  8. Frankenstein19

    Fluid Mechanics: resultant force of oil and water on a door

    Homework Statement Homework Equations The Attempt at a Solution [/B] My questions: 1. By resultant force, does that mean the force exerted on the side of the water + force exerted on side of the oil? Because I'd think that the force on the side of the water would be different than the...
  9. S

    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...
  10. T

    Fluid mechanics: Bernoulli's equation and conservation of mass

    Homework Statement A mechanical servo-mechanism comprising of a movable piston-cylinder within a vertical cylinder operates based on a venturi contraction in a horizontal 350mm diameter pipe that delivers a fluid of relative density 0.95. The upper end of the 100mm diameter vertical cylinder is...
  11. C

    Practical Fluid Mechanics: inversions & mixing

    I'm trying to think through a situation, and develop some confidence I've got it right. The situation is a apartment building, about 60'/20m high, with a courtyard in the middle about 60'/20m square. In the middle of the courtyard, is an low exhaust stack, about 8' high and around 8' square...
  12. K

    Why is the flow rate reversing in this fuel delivery system?

    Hi everyone, I have a real life fluids problem I am trying to solve theoretically. During a commissioning exercise we needed to discharge fuel into a 100L steel drum to test flow rates for a new re-fuelling skid. To minimise turbulent flow and static build up a drop pipe was used for the hose...
  13. Y

    I Force acting on a stationary object in a flowing pipe

    Greetings everyone, I've been recently trying to calculate the forces acting on a stationary object in pipe with flowing fluid. I've returned to my college textbooks to get some help and I've found examples that clearly demonstrated how to accomplish just that. Below is one example. This...
  14. Roy S Ramirez

    Adjusting the pressure drop in an injection plate

    Hello everybody, I'm designing a gas pressure feed system for a hydrogen peroxide - ethanol rocket engine, and after analyzing the devised injection plate, I noticed it is very sensitive to the propellants' pressure drops and discharge coefficients. Once the plate is manufactured, the only...
  15. A

    Scattering dynamics and viscosity

    I have been studying the statistical mechanics' viewpoint of fluid dynamics by considering the derivation of Navier-Stokes' equations from the Boltzmann equation involving the whole Chapman-Enskog expansion. It is clear that through this process, it is possible to account for the dependence of...
  16. K

    Control Volume, Fluid Mechanics

    Homework Statement Water flows over a dam as depicted below. Across section 1 and 2 we have a hydrostatic pressure distribution. Calculate the force on the dam. The Attempt at a Solution My question is regarding control volume. The solution manual has given us this: The two hydrostatic...
  17. F

    A1v1=a2v2? pressure and velocity are inversely proportional?

    If Bernoulli's equation P + 1/2ρv2 + ρgh = constant, implying that pressure decreases as velocity increases, and the Venturi effect states that a1v1 = a2v, what resolves this apparent contradiction? The velocity slows as the cross sectional area increases, but a narrower pipe would have greater...
  18. K

    Control volume, Fluid mechanics

    Homework Statement I have a situation as illustrated by the image above, where the red box illustrates the CV. The pressure on the left side of CV is P1, while the pressure on the right side of CV is P2. Here I´ve directed the pressure forces acting inwards on CV. The problem arises with Fk. I...
  19. S

    Sanity check on falling steel ball in water

    Homework Statement What is the speed of a 5 mm steel ball falling through water at 10 C[/B] Viscosity of water: 1.3059 * 10-3 Pa*s (Various online sources) Homework Equations Laminar flow: Vt = gd2 (ρp - ρm)/18μ Vt = terminal velocity g = gravity (10m/s2) d = diameter of ball ρp =...
  20. Irl495

    Minimum gas pressure to measure its volume with an eudiometer

    Hello, As you can see in the attached hand drawing+calculation, my question concerns the typical method of evolved gas volume measurement by water displacement in an inverted graduated cylinder or "eudiometer". Once a bubble (cavity to be precise) of gas leaves the end of the tube through...
  21. J

    Method of images for a line source

    Homework Statement Consider the curve C (image attached). C coincides with the real-z axis for $$|z| > a$$ and, in $$|z| < a$$ C coincides with the semi-circle $$|z| = a, =z > 0$$ In terms of simple singular flows, what is the image in C of a line source of strength 2πm lying at z = z_0, above...
  22. H

    Force exerted on the horizontal bottom of the container

    Homework Statement In an empty container, having the shape of a Rectangular Parallelepiped, with width l=0.5m and MN=H=0.4m, and NP=L=0.75M. we poureda mass of mercury =2448kg. T0,T1,T2 have the same section which is 0.2 m^2. we give g=10N/kg, and density of mercury u=13.6 g/(cm^3)...
  23. Z

    Upward force on each anchorage

    Homework Statement A steel pipeline carrying gas has an internal diameter of 120 cm and an external diameter of 125 cm. It is laid across the bed of a river, completely immersed in water and is anchored at intervals of 3 m along its length. Calculate the buoyancy force per meter run. Upward...
  24. K

    Finding power as a function of time in transferring water

    Homework Statement A completely filled cylindrical tank of height H contains water of mass M. At a height h above the top of the tank there is another wide container. The entire water from the tank is to be transferred into the container in time T such that level of water in tank decreases at a...
  25. Z

    Fluid Dynamics -- Use the Milne-Thomson circle theorem to show the complex potential for a fluid....

    Homework Statement Two equal line sources of strength k are located at x = 3a and x = −3a, near a circular cylinder of radius a with axis normal to the x, y plane and passing through the origin. The fluid is incompressible and the flow is irrotational (and inviscid). Use the Milne-Thomson...
  26. MCTachyon

    Resultant force and its point of action

    Homework Statement A storage tank has the cross-sectional shape shown attached and is of 1m breadth. Calculate the resultant force acting on the inclined surface AB and its point of action. The density of the liquid is 900kgm–3 and take g = 9.81ms–2. Homework Equations P = ρgh F = ρA Point...
  27. N

    Fluid Mechanics: Choosing a fuel line diameter for a required pressure drop

    Homework Statement [/B] Homework Equations - The pressure drop equation. [/B]The Attempt at a Solution
  28. MiMiCiCi22

    Determine Force on 6ft Door Due to Water & Air Pressure

    Homework Statement Determine the total force and its direction (left or right) due to water and air pressure in the surface shown in Fig. P3.62 (lb f). The door is hinged at the top and is 6 feet wide. See attached image.Homework Equations Fp (force of pressure) = specific weight of fluid *...
  29. F

    Understanding Viscosity: Solving a Fluid Mechanics Problem

    Homework Statement the picture has all the information Homework Equations I am assuming we will be needing the viscosity equation, tao= mue(dv/dy) where v is velocity The Attempt at a Solution I do not know how to approach this exercise.
  30. mkematt96

    Force required to dislodge a sphere from pipe (Valve design)

    I'm designing a valve that uses a ball to seal the valve. When the valve is empty there is no force acting on top of the ball. When water flows in, it will push up on the ball to dislodge it, water will flow into the valve and push the ball up until it seats into the top hole/chamfer which then...
  31. I

    Surface Tension, find number of stitches to be made

    Homework Statement The tension in the skin of the left ventricle of heart is 4.90 N/m. A cut is made on the left ventricle during surgery. How many stitches must be used to repair the cut? Each stitch will safely support a tension of 0.4 N. Homework Equations Surface tension = force/length...
  32. I

    Hydrostatics, Length of a mercury column

    Homework Statement What will be the length of mercury column in a barometer tube, when the atmospheric pressure is 75 cm of mercury and the tube is inclined at an angle of 60° with the horizontal direction? Homework Equations Pascal's Law The Attempt at a Solution l ⋅ sinϑ = h l = h / sinϑ l...
  33. I

    Hydrostatics, find length of kerosene column in U tube

    Homework Statement A glass tube is bent into a U shape. Water is poured into the tube until it sands 12 cm high on each side. Kerosene (density = 870 kg/m3) is added slowly to one side until water on the other side raises 5 cm. What is the length of kerosene column? Homework Equations (ρhg)1 =...
  34. E

    Calculating Surface Shear Stress in a Boundary Layer with Given Velocity Profile

    Homework Statement If the velocity v of the air in a boundary layer having a dynamic viscosity of 18x10-6 kg/ms is given in terms of the distance y from the surface by v = ay + by2 where a and b are constants, calculate the surface shear stress if at 1.5 mm from the surface the velocity is 75...
  35. Aniket13

    Area of common surface of two bubbles

    What will be the area of common surface of two identical bubbles of radius R , i know there common surface will be flat as the radius of curvature of comman surface will tends to Infinity , but how do i relate with area of flat surface I tried to use Energy = Surface tension * area And then...
  36. Pushoam

    Calculating water pressure in a horizontal pipe

    Homework Statement Homework EquationsThe Attempt at a Solution Calculating water pressure using in a horizontal pipe Applying Bernoulli principle, ## p_a + \frac 1 2 \rho gh_a + \frac 1 2 \rho v_a^2 = p_b + \frac 1 2 \rho gh_b + \frac 1 2 \rho v_b^2 ## ## h_a = h_b, v_b = \frac {...
  37. thepikminman

    Fluid Mechanics - Why? How? Why?

    Hi, I've been studying fluid mechanics for my mech. engineering degree for the past few months. Unlike my other subjects (mechanical analysis, thermodynamics, automated systems, mechanical vibrations), I can't seem to grasp the problem-solving technique. The annoying thing is, I find the...
  38. H

    Difficuilt and/or interesting problems in fluid mechanics

    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...
  39. Z

    Pressure drag acting on a sphere

    Homework Statement I am trying to show that the pressure drag acting on a sphere is 2πμaU by integrating around the surface of the sphere where U is the speed of the fluid the sphere is in, a is its radius, and μ is the viscosity. Homework Equations The pressure at a given position r can be...
  40. R

    Fluid mechanics/heat transfer - meaning of Nusselt number

    The Nusselt number represents the ratio of heat transfer by convection relative to conduction. At the onset of convection does this correspond to a Nusselt number of 1?
  41. U

    Fluid mechanics - Finding force point of application

    I get how to find vertical and horizontal forces on a submerged surface (vertical = weight of fluid and horizontal = force on vertical projection). I also get how to find the point of application for the horizontal force using a moment balance. But how do you determine the point of application...
  42. M

    Engineering Fluid Mechanics book that's pure integration/vector calculus

    Hello. The textbook that was assigned to my class is not a good fit for my professor. The textbook simplifies the basic force equations so that there are no general equations with integrals or vector calculus calculations. Can anybody recommend a Fluid Mechanics book or books that deal only...
  43. R

    Learning Radiometry, Photometry, Optics, Thermodynamics, ....

    Learning Radiometry, Photometry, Optics, Thermodynamics, Fluid Mechanics(Statics & Dynamics) with great resources. I'm looking for resources for understanding the topics above. I prefer video tutorials as opposed to books but I couldn't find any video resources on Photometry and Radiometry (I...
  44. P

    The formula for Thick-Edge Orifice

    Hi all, I have some problem in my research about the thick-edge orifice formula. I can't find the influence of orifice length to the discharge. I have found an online calculator for it but I can't find the formula derivation. Anybody can help me? Anybody have recommended literature? The...
  45. R

    Engineering Research in Fluid Mechanics for MS

    Hi Everyone, I am currently doing undergraduate program in mechanical engineering. I want to pursue masters after my B.Tech in the field of fluid mechanics and aerospace engineering.I want to know about the prospects of this field in the future research. Thanks in advance, Ritwik Kulkarni
  46. R

    What are the future research opportunities in impinging jets and related fields?

    Hi All, I am Ritwik from India and I am very interested in the area of fluid mechanics.Currently pursing B.Tech in Mechanical Engg. in IIT. I am currently doing my project in impinging jets. I want to explore and want to continue in the field for research in the graduate programmes. I want to...
  47. ramzerimar

    Courses Is CFD fluid mechanics + computer science?

    I'm having fluid dynamics classes right now and I'm enjoying it very much (much more than my solid mechanics classes, by the way). Also, I do like programming and computer science, and CFD looks like a very interesting field. I'm developing a real interest for it. One question for those who are...
  48. P

    Hardy Cross method with open loops

    Hi. I am using the Hardy Cross method to simulate the gas flow inside a multiple hearth furnace (as shown in figure A). Figure B is a representation of the furnace's body as a pipe network. The segment A-AH represents the actual hEarth's, while segments B-AI and C-AJ represent the exhaust ducts...
  49. O

    Classical Wilcox "Basic fluid mechanics"

    Hi, I was wondering if anybody has some experience with the mentioned book? I am to take a course in viscous flow and turbulence, and we are supposed to use White's "viscous fluid flow". I always like having a 2nd book, and I am considering Wilcox.
  50. MexChemE

    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...
Back
Top