What is Fluid mechanics: Definition and 757 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. M

    Fluid mechanics, why does the air flow faster over the wing?

    Why does the air flow faster over the wing? In my fluid mechanics course we used streamlines and a half body to show that the air flow faster over a half circle, but I do not understand why it does so.
  2. L

    Fluid Mechanics - Material derivative proofs

    Homework Statement l is an infintesimal material element of length. show that: Dl/Dt = l dot grad u where l is a smallelement that exists in the velocity field u. Consider its position at time t and t+dt The Attempt at a Solution have l(x,t) where x is representing all...
  3. B

    Fluid Mechanics - Floating Bodies

    Fluid Mechanics -- Floating Bodies Homework Statement A solid block with specific gravity 0.9 floats so that 75% of the body is submerged in water and the other 25% sits in an unknown fluid layered above the water. Find the specific gravity of the unknown fluid. density of water = 1000...
  4. J

    Is there a book(source) wich describes fluid mechanics from n-s equations?

    ¿Is there a book(source) which describes fluid mechanics from n-s equations? I mean that when i start to read a book on fluid mechanics I can see particular cases of compresible, incompresible, viscous... with easier equations than the navier stokes, but it is very confusing to me because I...
  5. N

    Can Suction Lift a 20 Meter Water Column Without Exceeding Its Tensile Strength?

    Homework Statement What suction (or negative pressure) is required to support a column of liquid 20 m high? Does this exceed the tensile strength of water? Homework Equations Bulk Modulus = (Change in Pressure/ (Change in Volume/Volume)) Pressure = Force / Area The Attempt at a...
  6. andrewkirk

    Problem with fluid mechanics part of GR derivation

    Hello all I am trying to teach myself general relativity and am working through the text 'a first course in general relativity' by Bernard F Schutz. So far I have made slow but consistent progress but I am perplexed by a couple of things in the fluid mechanics part where it derives the...
  7. U

    Fluid Mechanics Help: Questions Answered

    fluid mechanics... Hi,everyone. I'm doing the second of my mechanical engineering course and I've been doing fluid mechanics lately...I have some questions...could some ony please help me with them? 1.In Bernoulli's theorem,it basically states the if we have an ideal liquid (Newtonian)...
  8. D

    Fluid Mechanics - keeping water level constant

    Hello all,I am trying to construct this setup here: Don't mind the heat tape and microcontroller. I am concerned with the fluid dynamics of the system. When compressed air is applied, the water level in the evaporation chamber increase until it overflows into the tube that is exposed to...
  9. L

    Fluid mechanics : Barometer - slight confusion

    What would happen to the mercury in the column if a barometer is accelerated upwards? In static condition, acceleration is g. When the system moves upward with an acceleration a, effective acceleration = g + a. The air above the mercury in the trough will press it with higher force...
  10. L

    Fluid mechanics : Barometer - slight confusion.

    What would happen to the mercury in the column if a barometer is accelerated upwards? In static condition, acceleration is g. When the system moves upward with an acceleration a, effective acceleration = g + a. The air above the mercury in the trough will press it with higher force...
  11. I

    What Tank Shape Ensures Constant Height Change Rate in Fluid Mechanics?

    Homework Statement A liquid is to drain through a small exit port at the bottom of an axisymmetric tank that is open at the top. Find a tank shape such that the rate of change of the height of the free surface is constant (at least until the tank is almost empty). Assume that Bernoulli’s...
  12. A

    Fluid mechanics help mechanical engineering

    Fluid mechanics help! mechanical engineering Hi people! I have been doing some fluid questions and got stuck ont he following two; 1) A Casson plastic fluid is subjected to a shear force of 5.5 Pa. If the fluid obeys a law of the form T =1.5 +0.2^0.45u, determine the shear rate and...
  13. A

    Fluid mechanics help mechanical engineering

    Fluid mechanics help! mechanical engineering Hi all, I've answered a page of questions from a engineering textbook by mike tooley but I'm really struggling on these two questions. 1) A Casson plastic fluid is subjected to a shear force of 5.5 Pa. If the fluid obeys a law of the form T...
  14. H

    Fluid Mechanics : Ice cube melting and Surface Energy Que.

    Q. 1. if a ice cube is placed in a container containing liq on which it is floating. then is it possible that after ice melts, water level rises in vessel in any particular case. 2.Does heat evolves when water rises in a capillary. and how much heat is evolved in height of liq in capillary...
  15. H

    Fluid Mechanics : Ice cube melting and Surface Energy Que.

    I have a que. if a ice cube is placed in a container containing liq on which it is floating. then is it possible that after ice melts, water level rises in vessel in any particular case. Does heat evolves when water rises in a capillary. and how much heat is evolved in height of liq in...
  16. G

    Fluid Mechanics: Power to Drive Flow in 1cm Diameter Pipe

    Homework Statement fluid is flowing upward through a 1cm diameter pipe at 0.15m/s find the necessary power per unit length to drive the flow through the pipe. Homework Equations tau= (viscosity)dU/dy flux of momentum out - flux of momentum in= forces acting on the CV (tau( downward)...
  17. F

    Pipe Flow Question - Fluid Mechanics

    Hi, literally trying on the off chance that someone could help me. basically doing an individual project in my third year at nottingham uni. Over the last 6 months I've built a pipe rig to measure the pressure drop over a test section. Now my tutor is a bit of an idiot, and said the way i...
  18. G

    Fluid mechanics :fluid in motion

    Homework Statement a vertical, 1cm-diameter jet of water impinges upon a bathroom scale such that the latter exhibits a reading of 5 kg. Estimate the volume flow rate of the jet. Homework Equations p=F/A Q(volume flow rate)=U*A(area where the jet of water is applied on) a=pi*r² F=mg...
  19. S

    Fluid mechanics of water in a pipe

    Hello All, I've frequented this forum for various purposes and this is the first time I've decided to post! Hopefully I can find the help or conformation I'm looking for. I may not have all the necessary info, but I feel this is basic enough that I should be able to come up with an...
  20. K

    Plotting Stream lines (Fluid Mechanics)

    Plotting Stream lines! (Fluid Mechanics) Homework Statement In this project you are required to investigate two types of potential flow solution: a. Flow over a vertical plate (flow is perpendicular to the plate i.e.  = 90) b. Flow over an inclined plate ( = 135). You are...
  21. I

    Fluid mechanics question on forces on a cone in a pressurized tank

    A plug in the bottom of the pressurized tank is conical in shape. The air pressure is 40kPa and the tank has a specific weight of 27kN/m^3. Determine the magnitude, direction, and line of action of the force exerted on the curved surface of the cone within the take due to the 40kpa pressure and...
  22. S

    Explain me concept (Fluid Mechanics)

    It has been told to me that atmosphere exert a pressure (known as atmospheric pressure) on the surface (I'll take water surface here). And as we go down into water (any fluid, but for instance I'm taking water) the pressure increases. And this increase in the pressure is independent of the shape...
  23. D

    Fluid Mechanics - statics/control volume

    Hi guys! here comes the question: I need some tips and guideness to make an attempt at it. I'm kind of confused if I am supose to use basic equations in integral form for control volume here and if so then how? If the reference material is water then a substance with a relative density...
  24. L

    Pressure Variation in a Tilted Fluid Column

    Homework Statement A 0.3 m long tube is filled with sterile solution of density 1037 kg m-3 and closed at the top. The tube is tilted at 40°. to the horizontal. The gauge pressure at the base of the tube is 3000 Pa. What is the gauge pressure at the top of the tube (in Pa)? Homework...
  25. J

    Fluid Mechanics - Estimating Reynolds number and flow rate.

    Homework Statement A pipe 0.15m in diameter has a roughness ratio (k/d) of 0.002 and carries water at a flow rate Q. Using the moody diagram, show that at high flow rates (where the friction factor is independent of reynolds number), the head loss per m length due to friction is approx...
  26. C

    Actual fluid mechanics used in CFD?

    I just recently graduated with my BS degrees in physics and applied math but am interested in switching my career path towards mechanical engineering. I honestly don't know much about CFD at all, so I was wondering how much of the fluid mechanics you learn in the ME classes is actually used in...
  27. B

    How Does Pipe Area Change Affect Fluid Velocity and Pressure?

    A circular pipe has a fall of 4m and narrows so that, at exit, its area is one quarter that at inlet. The pressure at inlet is 20kN/m^2 above atmospheric and at exit, where the velocity is 15m/s, the pressure is atmospheric. Calculate the inlet velocity and mass flow rate of water through the...
  28. T

    Fluid Mechanics (Gas through a pipe)

    Homework Statement Hot CO₂ gas enters a pipe at pressure P₁ and exits at atmospheric pressure (P₂ = 1 bar) and T₂ = 0°C. The pipe has a constant diameter D = 1 cm. The input temperature is T₁ = 100°C and the mass flow rate ṁ = 0.5 g/min. There is a significant change in mechanical energy due...
  29. D

    Fluid mechanics - u tube manometer

    dont have a picture to show, a solution is pumped through a pipe with an obstacle in it, to find the difference in the pressure on either side of the obstacle, a u tube manometer with mercury is fitted to it and a height difference of 19cm is measured. what is the pressure after the obstacle...
  30. U

    Fluid mechanics boundary layer solution

    Hello, I am looking for a reference which has solutions for the laminar flow boundary layer for the following scenario: circular cylinder, L>>d, length in direction of flow, with flat circular cap uniform laminar flow inviscid, incompressible fluid In other words, I would like the...
  31. P

    Fluid Mechanics - Venturimeter

    Homework Statement A horizontal venturimeter is used to measure the flow rate of an oil having density 940kgm-3 in a 16cm diameter pipe. The throat diameter of the venturimeter is 8cm with a discharge coefficient of 0.96. The pressure at inlet is 70kPa and it is required that the pressure at...
  32. M

    What is the Process for Determining Hydrostatic Forces in a Swimming Pool?

    Homework Statement Concider a 4 m long, 4 m wide and 1.5 m high aboveground swimming pool that is filled with water to the rim (completely). Determinate hydrostatic forces on each wall and distance of the line of actions of this force from the ground Homework Equations Hc = yc sin...
  33. P

    How Does Pipe Tapering Affect Pressure and Flow Rate in Fluid Dynamics?

    1. Water is flowing in a pipe from a tank to a nozzle. At some point (A) the pipe tapers from 160 mm diameter to 80 mm at point B over a certain length. Point A is 3 m above point B. The pressure at A is 100kPa and at B is 20kPa, both measured above the atmospheric pressure. The flow rate is...
  34. D

    Fluid Mechanics: Cross Sectional Area of Gas Tank?

    Homework Statement Gas pours into your gas tank at 5.3 gallons per minute. You can't see it, but the gas level inside the tank rises at 4.3 inches per minute. What is the cross sectional Area of the gas tank? Is this realistic? Homework Equations I'm not sure what shape the tank...
  35. M

    Advanced Fluid Mechanics Problems

    Is it possible to buy/download Shapiro, Ascher H., and Ain A. Sonin. Advanced Fluid Mechanics Problems. I can't find it http://mitocw.vocw.edu.vn/OcwWeb/Mechanical-Engineering/2-25Fall-2005/Assignments/index.htm
  36. R

    Why Do Velocity Components Depend on All Spatial Variables in Fluid Mechanics?

    HI I was a under a little confusion about vector field. Consider velocity field of fluid flow: V = u i + v j + w k here V is vector and consider a cap over i, j, k (since they represent x,y,z directions) now we know that u,v,w are functions of x,y,z,t. This is where i am confused...
  37. B

    How Many Truck Loads Are Needed to Transport Crushed Stone?

    Homework Statement A solid block of stone with a relative density of 4 is broken down and crushed into an average size of 20mm. if the stone originally had a volume of 50 m cubed, how many truck loads with a volume of 2 m cubed will it take to transport the crushed stone if 25L of the...
  38. R

    Recommend best book on fluid mechanics

    Hi I am going to take lectures on fluid mechanics in january. Which book would you recommend ? The book should be more theorotical in approach so as to clear concepts in detail. Thanx
  39. W

    Bernoulli's Equation and Fluid Mechanics?

    Water flows through a 0.30m radius pipe at the rate of 0.20m^2/s. The pressure in the pipe is atmospheric. The pipe slants downhill and feeds into a second pipe with a radius of 0.15m, positioned 0.60m lower. What is the gauge pressure in the second pipe? So, what I've figured from the...
  40. T

    Fluid Mechanics Problem: Evacuating a Tank with Vacuum Pump for Ideal Gas Air

    Homework Statement 6. A tank filled with air of initial density ρo=1.2 kg/m3 and initial pressure Po=100 kPa is to be evacuated by a vacuum pump. The tank volume is 1 m3 and the pump evacuates 0.0013 m3 of air per second regardless of the pressure. The process is isothermal and for an...
  41. M

    How does Boyles law apply to air in motion in a uniform tube?

    Homework Statement 1.a) the velocity components of a 3-d flow are u= \frac{ax}{x^2+y^2} v= \frac{ay}{x^2+y^2} \omega = c where a and c are arbitrary constants . show that the streamlines of this flow are helics x=acos(t) ; y=asin(t) ; x=a*c*t a. what is the...
  42. I

    Fluid Mechanics: 2 Conceptual Doubts Answered

    I had two conceptual doubts which are asked in the question. It would be good if anyone can answer the first one but my main query is the second one
  43. T

    Fluid Mechanics Internal Flow Question

    Hey all, I know that it is forbidden to post homework questions here, this is a question off a past exam, so I'm hope asking this is Kosher. A question says: "For a circular pipe of 6cm diameter, what is the expected pressure drop per unit length due to frictional losses, at a Reynolds...
  44. S

    Fluid mechanics - Bernoulli Ball

    sorry for the "bad" title, I couldn't think of anything else. We all have seen the experiment where you take a hair dryer and a ping-pong ball and the hair dryer blows the ball into the air and you can move and tilt the ball around... now, that is a very simplified version of my final...
  45. T

    Landau fluid mechanics- mathematical passage

    In the book about fluid-mechanics Landau in the first pages in the isentropic case from dw=\frac{dp}{\rho} deduces \nabla w=\frac{\nabla p}{\rho} but I can't understand... in its derivation dw and dp are material differential (dw=w(x+vdt,t+dt)-w(x,t)) in my view) so writing it...
  46. Saladsamurai

    Fluid Mechanics Question: erivation of Momentum EQ

    Fluid Mechanics Question::Derivation of Momentum EQ I have been doing some serious review of my FM. I am working my text from cover to cover in an attempt to solidify what I 'learned' in my 6-week summer FM class. What a load of crap that was. I am attempting to follow the text's derivation...
  47. S

    Fluid mechanics text that has the physics (or is it math) in it

    Hi, I'm taking a Fluid Mechanics course. The lecturer is very closely (letter to letter) following the book by Kundu and Cohen (https://www.amazon.com/dp/0123737354/?tag=pfamazon01-20). I think K&C has a bunch of isolated derivations with no examples or solved problems. The 'examples' they...
  48. Y

    Fluid Mechanics: pitot static tube/manometer system

    Homework Statement A water-filled manometer is connected to a Pitot-static tube to measure a nominal airspeed of 50 ft/s. It is assumed that a change in the manometer reading of 0.002 in. can be detected. What is the minimum deviation from the 50 ft/s airspeed that can be detected by this...
  49. W

    Fluid Mechanics Ideal Flow Problem

    Homework Statement Calculate flow velocity and magnitude at a point (2,-2) Sink at origin with strength 20 m2/s Vortex at (0,2) with strength 25 m2/s Uniform flow in +x with strength of 10 m/s The Attempt at a Solution \phi = \phi1 + \phi2 + \phi3 \phi1 = -Ux = -U r cos(\theta)...
  50. K

    Need help with fluid mechanics problem set by lecturer :[

    Note: Have been taught nothing about fluid mechanics yet, this task was set to help develop self learning skills, yet with some research I've carried out I'm still at a brick wall so i hope you don't mind helping me! Homework Statement Explain the phenomenon that causes a noticeable...
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