# What is Fluid mechanics: Definition and 754 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. ### Aerodynamics: flow separation's effect on lift and drag

In aerodynamics, how does flow separation reduces the lift and drag of a wing at the same time?
2. ### Airbag Simulation using LS-DYNA: start from filled airbag

Hello! I'd like to model the impact of an object on an inflated air cushion (effectively an airbag) at rest in LS-DYNA, however all the tutorials I see start from a deflated airbag. I would like to skip this computation if possible to save computing time, since I would have to run the simulation...
3. ### I Static sphere with gravitating fluid

Hi The rotating bucket problem with a fluid is well known as a homework. For the fun i wanted to adapt it to the case of a massive non-rotating sphere surrounded by a fluid. However i don't know if the calculations i made are correct or don't make sense at all (even if the result lead to an...
4. ### Quantitative Risk Assessment Of buried crude Oil Pipelines

Currently, I am working on a project that necessitates a quantitative risk assessment (frequency analysis and consequence analysis) of buried crude oil pipelines, considering specific hazard scenarios. Most of the hazard analyses I have come across were conducted on gas pipelines, and there...
5. ### Time to empty gas cylinder (problem worked, but would like feedback)

Hi everyone I am trying to solve a specific problem. I already have an idea on how to solve it, but I hoped someone else could tell me if my general approach is somewhat sensible or not. So I would really appreciate some feedback. Situation: A long, narrow cylinder filled with gas that is at...
6. ### Fluid flow and elevation vs pressure

Hey guys! does anyone have a graph of the relationship between elevation change and pressure loss in pipes? I currently have experimental data of a negative gradient graph. know it's theoretically correct however, I just need supporting research for this - have tried finding everywhere but...
7. ### B The application of Newton's laws to fluid equilibrium

Hello respected members, I have been studying Sears and Zemansky's university physics, and I have encountered the following statement. I could not understand it well, so my question is: Why is fluid equilibrium based on Newton's first and third laws? Here is my try: - Newton's first law...
8. ### Programs Universities for Research in Dynamical Systems of Fluids

Hi everyone, (this is my first post so be gentle) I am currently getting my masters is mechanical engineering, was admitted to aero Ph.D. programs as Vtech, MSU, and Cinci last year but decided to get masters locally and apply to "better" schools (UofM) for next cycle with a better resume and...
9. ### What kind of pump can do this?

Hello -- I am working on a project where I need to recirculate a fluid which has a large quantity of glass spheres of say, 1mm diameter suspended in it, but without the pump crushing the spheres. I would appreciate any advice. To give a simple description of the desired function: it will be a...
10. ### A Why are the Navier-Stokes equations inconsistent in this case?

Consider the case of a one-dimensional incompressible, non-viscous fluid flowing down a vertical pipe under the influence of gravity. Since we assume the flow is constant along the cross section of the pipe from the one dimensional assumption, let us denote the velocity of the fluid down the...
11. ### Why is solid density used in this thermodynamics problem?

Callen asks us the following question in his famous textbook: I have answered as follows: However, I get the wrong answer and, in fact, the correct answer obtains from using ##\Delta P = -\rho_s g h##; that is, using the solid density for the change in pressure. Now why on earth should this...
12. ### Fluid Mechanics Force Body Diagrams

Let me start off by saying that I have found (or is given) all of these: ρ, Q, V1, V2, P1, P2, A1, A2 (V being the velocity here). So no problem with Bernoulli or the Continuity equation calculations. I am just struggling with drawing the FBD in order to evaluate the axial force, Fx I know we...
13. ### Engineering How Does Cup Anemometer Design Utilize Fluid Mechanics Principles?

First, this class uses Frank White's Fluid Mechanics textbook. This particular problem is taken straight from chapter 7, which is on "Flow Past Immersed Bodies" and is basically focused on external flow, geometry effects, and boundary-layer conditions. So I imagine that the problem makes use of...
14. ### I A specific case of an exception to Archimedes' Principle?

First post on this forum, hopefully in the correct category and conforming to forum rules. Will the object in below scenario move upwards, downwards or will it remain stationary? An object is submersed in a container 'A' which contains a fluid 'B' (e.g. water) The trapezium shaped object...
15. ### Does the discharge coefficient of an injector depend on the fluid?

The discharge coefficient is the ratio of the actual discharge to the ideal discharge and can be measured experimentally. If one were to experimentally measure the discharge coefficient using water, would this value be constant for all incompressible fluids? What does the discharge coefficient...
16. ### I How can I integrate variable velocity in fluid mechanics?

Do you know of any place where I can look up things about the momentum (linear momentum) in fluid mechanics? It's just that when I have a variable velocity and it has to be integrated, I don't quite understand how to do it. I have looked for videos and things and I can't find that they are...

48. ### Parabolic Pressure Distribution in a Jet

Assume the jet is straight but the radius of the jet varies over it's length (like a jet of water falling which narrows due to gravitational acceleration). Also ignore viscosity. A pressure gradient would be required to accelerate the fluid radially. Because during an expansion transformation...
49. ### Inertial Force in Fluid Mechanics

According to one explanation, the left hand acceleration terms of Navier Stokes equations are the called the inertial terms. If you were to balance forces on the fluid particle, they would have to be equal and opposite to the forces on the right hand side (pressure gradient, viscous, and body)...
50. ### Is this a valid way to calculate capillary force / pressure?

When figuring out the capillary pressure on a liquid in a tube of a certain cross-section, the typical approach is to consider the Young-Laplace pressure and the curvature etc. I was looking through some of my old notes and I had an equation for the capillary force: fc = γ cosθ dS/dx where γ...