# What is Hydrodynamics: Definition and 57 Discussions

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. ### I have a question about the air volume

Hello I need your help studying hydrodynamics. I have a question about the volume of air. Assuming incompressibility, non-viscosity, there is a coefficient of tube friction, and it moves in laminar flow... The Oulet stage Fan is installed, so air moves from top to bottom. The cross-sectional...
2. ### Misc. DIY RC Boat with Parallel Impeller

I'm not sure if you would call it a "Parallel Impeller," but the pics below should tell the story. I'm designing/3D printing my next RC boat from scratch, and I wanted to try something different from tried-and-true propeller and shaft system. Reasons? 1. Fun. 2. Using a "wet" brushless motor...
3. ### B Problem with understanding deriving Torricelli's law

We can derive it by using Bernoulli's equation ##p_0+h_0\rho g+\frac12 \rho {v_0}^2=p_1+h_1\rho g+\frac12 \rho {v_1}^2##, where ##v_0=0## is a velocity of a water surface and ##h_0## is its height. ##h_1## is a height of the outlet above the bottom of a tank the water is in. I am confused about...
4. ### B Why doesn't the Navier-Stokes equation have a solution?

Why the navier-stokes equation don't have a solution ?
5. ### B Hydrodynamics Effects: Are They the Same?

Are these hydrodynamic effects the same?

7. ### A Question about kinetic theory and hydrodynamics (in plasmas)

It is usual, in plasma physics, to combine the kinetic description for electron fluid and the hydrodynamic description for ion fluid, when studying the plasma properties or the dynamics of the electrostatic waves. I am wondering what are the physical meaning and limits of such an approach. Thanks.
8. ### A Relativistic Hydrodynamics Eqn for Perfect Fluid: Insight Needed

Hello. Could anyone help me with some insight in an extra term appearing in the motion equations of a relativistic fluid? I say extra term, because it's not present on the motion for a test particle, as it follows: Let's propose Minkowski space-time, the motion equations for a fluid with zero...
9. ### Classical Who said Lamb's Hydrodynamics is Dry?

Summary:: I remember seeing somewhere that people said Lamb's Hydrodynamics is so dry that the reader cannot see any water but drawn in a desert. But where did it come from ? I remember seeing somewhere that people said Lamb's Hydrodynamics is so dry that the reader cannot see any water but...
10. ### I Hydrodynamics - Wave of Translation

Hello guys! I am studying the hydrodynamics of a ship in shallow water. In deep water the ship creates 2 wave patterns, one transverse and another divergent, both making an angle of 19°28'. Also, the maximum velocity of a wave in shallow water is given by ##\sqrt{gh}## where h is the depth of...
11. ### A Thermal shock wave question from my hydrodynamics simulation

This is a fluid dynamic simulation. The top area has 100 degrees Celsius. The bottom area has 0 degrees Celsius. And both are filled with an ideal gas which is 1-atmosphere pressure. Two areas are connected through the left small line. Another part is blocked. So heat transfer can only happen...

13. ### Can I apply Bernoulli's equation to this situation?

Can Bernoulli's equation be applied between points 1 and 2, ignoring the another tank ?
14. ### Is Bernoulli's Equation related to the Conservation of Mechanical Energy?

So the Bernoulli's Equation.. My question : Are the terms on the left hand side equal to the total mechanical energy? So can I rewrite this equation as ?
15. ### Where Does River Water Go? - Numberphile

Tom Crawford on the mathematics of where river water goes when it hits the sea.
16. ### Relativistic hydrodynamics: gradient expansion

Hi everyone, I'm interested in relativistic anisotropic hydrodynamics and often a "gradient Expansion" is mentioned in articles, but not how this works exactly. I gathered that this is some kind of expansion of the energy-momentum tensor. Can someone explain to me how this expansion is set up...
17. ### A Lagrangian vs pseudo-Lagrangian vs Eulerian

I'm reading up a series of papers on hydrodynamical simulations for galaxies and cosmology. They keep mentioning things like "Lagrangian" or "pseudo-lagrangian" or "Eulerian". I tried looking it up on the internet, but the answers are either too broad and could mean a huge number of things in...
18. ### Non-mushroom-cloud hydrodynamics

Probably a silly question, but I'm curious because I want to draw some hard sci-fi based on it: if I shoot a nuke "ballistically" (viz., think of firing a cannon at a mountainside), upon detonation, what would be the smoke's/plasma's (?) profile? I guess it wouldn't be the famous mushroom...
19. ### I How is it that the SPH cubic spline kernel in normalized?

Hi, (This is more of a math question but I thought Astronomy people would be more familiar with the equation and how it's used) So in Monaghan 1992 (http://adsabs.harvard.edu/abs/1992ARA&A..30..543M, bottom of pg 554) a cubic spline in three dimensions is defined. I tried to integrate it (using...
20. ### A Lattice Boltzmann simulation with arbitrary equilibrium func

Hi everyone, I plan to do a simulation of a Boltzmann equation with experimentally known scattering between two particles. Initially I intend to incorporate the scattering into the collision integral and use Lattice Boltzmann Equation (LBE) afterwards. But I only see LGBK (DnQb) which requires...
21. ### A problem about fluid mechanics

1. The problem statement, all variables and given/known d At what speed, the velocity head of water is equal to pressure head of 40 cm of Hg? (1) 10.32 m/s (2) 2.8 m/s (3) 5.6 m/s Homework Equations v^2/2g = p/rho*g (velocity head= pressure head). The Attempt at a Solution since pressure head...
22. ### Classical Need a Book on Hydrodynamics for Your Master's Degree in Physics?

I just started my master's degree in physics and one of the courses I've chosen is hydrodynamics. Since i have never done anything similar to this in my undergrad, i feel a bit lost and i would like to start with some sort of an introduction to the subject or fluid mechanics in general and work...
23. ### Python Why is my Hydrodynamics Simulation Code Producing a Noisy Signal?

Hi! I have this code which should simulate a sod shock tube like this: https://en.wikipedia.org/wiki/Sod_shock_tube But when i plot density versus distance I just get something like a noisy signal. Any idea where I am doing something wrong? from matplotlib import pyplot as plt import numpy as...
24. ### Will this pump work for my artificial irrigation system?

Hi all, I am designing an artificial rain system and was thinking about using http://www.dannermfg.com/Store/Products/Danner/PID-02720.aspx to power it. The goal of the system is to deliver roughly 1 gallon of water per hour to each of the 8 exit points (I will measure this by using a bucket...
25. L

### Can Ocean Waves on the Baja Peninsula Be Used to Generate Clean Electricity?

Hi. I assume at this point I'm supposed to introduce myself and pertinent interests. If so, then I'll be brief. I live on the Northwest coast of the Baja Peninsula in Mexico. My place faces the ocean. Every day good size waves pummel the beach. The exception is during our extreme low...
26. ### Relaxation time approximation and ideal hydrodynamics

Homework Statement please check attachment Homework Equations please check attachment The Attempt at a Solution since the deviation from f_0 to f is linear then we can write f=f_0 + C where C is some constant this should be enough to prove the first question (i think so) for the second...
27. ### Calculating Entrance Lengths in Hydrodynamics

Hi everybody, first of all, sorry for any grammatical mistakes, I am a non-native English speaker. So here is my concern, the dimensionless (hydrodynamic) entrance length is defined as: z+=zh/(Re*Dh) ,where zh is the hydrodynamic entrance length, Re is the Reynolds number, and dh is the...
28. ### The Role of Nonlinear Hydrodynamics in Ship Leaning & Capsizing

Can the nonlinear hydrodynamic be ignored in the process of a ship leaning slowly， and the ship capsized ultimately. Thanks！
29. ### Can you tell/give me any websites about ship hydrodynamics？

Can you tell/give me any websites about ship hydrodynamics？ Thanks！
30. ### Smoothed particle hydrodynamics

I wish to replicate the simulations and values obtained in the following paper but I do not know where to start my coding from. http://lasp.colorado.edu/~espoclass/ASTR_5835_2013_Files/2013_10_29_Canup.Moon.Icarus.2004.pdf How must I start the code? I am aware that I need to integrate the...
31. ### Another Hydrodynamics word problem

Homework Statement The pressure difference between the main pipeline and the throat of a venturri meter is 10.5 Pascals (Pa). The areas of the pipe and the constriction are 0.1 m^2 and 0.05 m^2 respectively. How many cubic meters per second are flowing in the pipe? The liquid in the pipe is...
32. ### Solving word problem in hydrodynamics

1. A circular hole 2 cm in diameter is cut in the side of a large stand pipe 10 m below the water level in the standpipe. Find: a. the velocity of the efflux b. the volume discharged per unit time[/b] 2. P + 1/2 pv^2 + pgh Q = A1 V1 = A2 V2 where = a = area v =...
33. ### I need some information about hydrodynamics

Hello, I need data (articles and books) about what connection there is between the speed (or the power) of a turbulent flow and the range of vibration frequencies that it can create on the body submerged in the flow. Thanks in advance.
34. ### Smoothed Particle Hydrodynamics discretization

Hi all, I want to use SPH discretization for my cooling rate but i don't know if its valid. So, this is the equation i want to discretize. L = (1/dT/dt) . ∫v(T) dT So, dT/dt = (1/L) . ∫v(T) dT dT/dt = (1/L). Ʃv(T) dT (with dT →0) The limits of the above integral are...
35. ### I'm not sure what the question is asking. What is v12 and v22?

Homework Statement A beaker contains a liquid of density ρ up to a height h (from the bottom), their is another layer of liquid of density 2ρ above it.(this is arrangement initially) also up to a height h. A hole is made in the upper part as well as in lower part such that the separation...
36. ### What is the total horizontal force on a constricted pipe with water flow?

(Hello everyone!) Homework Statement Water is gathered in a column of height h, above above a distributing pipe. The pipe then narrows from cross sectional area S1 to S2(S1>S2), after which, the fluid exits(as shown in the attached figure) Find the total horizontal force(in the direction of the...
37. ### Hydrodynamics : Calculate force exerted by fluid on Tube

Homework Statement A tube of uniform cross-section A is bent to form a circular arc of radius R, forming three quarters of a circle. A liquid of density \rho is forced through the tube with a linear speed v. Find the net force exerted by the liquid on the tube. 2. The attempt at a solution...
38. ### Hydrodynamics velocity and speed

For fluids in motion, how do I find speed using velocity and diameter or velocity and pressure? Like in a pipe or other cyllinder type thing
39. ### Hydrodynamics: Wavemaking resistance

Can somebody describe wave making resistance in terms of pressure distribution on a body (near or at a free surface)? Cheers, Simon
40. ### Help with smooth particles hydrodynamics

Hi, I've started to write a simulator for SPH, and I'm fallowing a paper on SPH simulation, The problem is that in that paper they show the formulas for computing force but they don't tell you on what vector do you need to apply this force. So here are the formulas for pressure, viscosity...
41. ### Re: Building a hydrodynamics water tunnel for surface water wheel testing.

I need to simulate the flow of a river, to do small scale hydrodynamics testing on a partially submerged water wheel / paddle wheel design. The typical water tunnel setup will not work, because we are interested in the flow near the surface. The water wheel is half in the water, and half out...
42. ### Cleaning chromatography columns and hydrodynamics

If you had to prove that your method for cleaning chromatography columns works and you had different sizes and shapes of columns, which one would you pick as a worst case to focus on? You have tall, skinny columns and short, fat columns, as well as different sizes. These are cylindrical glass...
43. ### Ballistics, hydrodynamics - tensile cavitation in tissue and fluids

I have made decent progress with my ballistics model, but I have run into trouble and I'm not quite sure how to solve it. This particular problem deals with penetration and tensile cavitation. Based on the Held equation for cavitation in jet penetration (still haven't found any sites discussing...
44. ### Hydrodynamics (related to the oil leak in the Gulf)

Ok here's a basic idea that I read somewhere else. See the attached image. Basically, its a pipe with inflatable "tires" surrounding it, that will be inserted into the well, and then the "tires" pumped full of hydrolic fluid. Hopefully capping the well, while still being able to retrieve oil...
45. ### Hydrodynamics: Pressure of water coming out of a glass

"What pressure do you need to get water to flow at 2 m/sec coming out of a hole?" Here is the visual of a container sitting on top of a glass of water with a hole poked through the bottom: http://i96.photobucket.com/albums/l168/synovial/fluids.jpg Given: A1, A2, V2, (y1-y2) Find: patm...
46. ### Hydrodynamics- rotational movement.

Hydrodynamics--- rotational movement. Hi,I am not sure whether my solution is correct. I am not an expert in this area either. Could anyone here help me to check my solution? Thank you If i hang a block like a cube in water. If we look from the top view, there will be two side A and two side...
47. ### Bubble Hydrodynamics: Find Numerical Solution to Air Bubble at 20m Depth

Diver at a depth of 20 m below the water breaths 1 liter of air. With what acceleration the air bubble begins to move against the surface ,how his speed varies with time and what is its volume at a depth of 5 m? The water temperature is 20° C. Part of a solution will be need to find numerically...
48. ### Hydrodynamics of structure formation

[9] arXiv:0809.2330 [pdf, other] Title: Hydrodynamics of structure formation in the early Universe Authors: C. H. Gibson (UCSD), T. M. Nieuwenhuizen (University of Amsterdam), R. E Schild (Harvard) Comments: 6 pages 4 figures. Additional information at this http URL Subjects...
49. ### Hydrodynamics: Meniscus Height in Thin and Wide Cylinders

If I have some water in a thin (on the order of micrometer or nanometer even) cylinder, a meniscus will form due to hydrodynamics and surface tension effects. There will be some characteristic height of the meniscus above the surface of the "bulk" water. Let's call this height "h". If I make...
50. ### Understanding the Navier-Stokes Equations for Smooth Particle Hydrodynamics

Hi, hope this is the right area. Also please excuse me completley ignoring the template, I don't think it's applicable for the problem. I'm an honours year student in a comp sci course and I've decided to do an implimentation of Smooth Particle Hydrodynamics in a 3d application as my topic...